U.S. patent application number 15/539534 was filed with the patent office on 2017-12-21 for sensor for detecting electrically conductive and/or polarizable particles, sensor system, method for operating a sensor, method for producing a sensor of this type and use of a sensor of this type.
This patent application is currently assigned to HERAEUS SENSOR TECHNOLOGY GMBH. The applicant listed for this patent is HERAEUS SENSOR TECHNOLOGY GMBH. Invention is credited to Tim ASMUS, Stefan DIETMANN, Martin KUNZ, Karlheinz WIENAND.
Application Number | 20170363530 15/539534 |
Document ID | / |
Family ID | 54884003 |
Filed Date | 2017-12-21 |
United States Patent
Application |
20170363530 |
Kind Code |
A1 |
ASMUS; Tim ; et al. |
December 21, 2017 |
SENSOR FOR DETECTING ELECTRICALLY CONDUCTIVE AND/OR POLARIZABLE
PARTICLES, SENSOR SYSTEM, METHOD FOR OPERATING A SENSOR, METHOD FOR
PRODUCING A SENSOR OF THIS TYPE AND USE OF A SENSOR OF THIS
TYPE
Abstract
A sensor for detecting electrically conductive and/or
polarizable particles, in particular for detecting soot particles,
includes a substrate and at least two electrode layers, a first
electrode layer and at least one second electrode layer. Which is
arranged between the substrate and the first electrode layer. At
least one insulation layer is formed between the first electrode
layer and the at least one second electrode layer and at least one
opening is formed in both the first electrode layer and the at
least one insulation layer. At least some sections of the opening
in the first electrode layer and of the opening in the insulation
layer are arranged one above the other, such that at least one
passage is formed to the second electrode layer.
Inventors: |
ASMUS; Tim;
(Allendorf-Winnen, DE) ; WIENAND; Karlheinz;
(Aschaffenburg, DE) ; DIETMANN; Stefan; (Alzenau,
DE) ; KUNZ; Martin; (Waldbronn, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HERAEUS SENSOR TECHNOLOGY GMBH |
Hanau |
|
DE |
|
|
Assignee: |
HERAEUS SENSOR TECHNOLOGY
GMBH
Hanau
DE
|
Family ID: |
54884003 |
Appl. No.: |
15/539534 |
Filed: |
December 23, 2015 |
PCT Filed: |
December 23, 2015 |
PCT NO: |
PCT/EP2015/081100 |
371 Date: |
June 23, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 2560/05 20130101;
F02D 41/222 20130101; G01N 2015/0046 20130101; F01N 11/007
20130101; F01N 13/008 20130101; G01N 27/226 20130101; G01N 27/043
20130101; F02D 41/1494 20130101; B32B 2457/00 20130101; F01N
2560/20 20130101; B32B 37/18 20130101; G01N 27/07 20130101; B32B
38/10 20130101; F02B 1/04 20130101; F02B 3/06 20130101; G01N
15/0656 20130101; F02D 41/1466 20130101 |
International
Class: |
G01N 15/06 20060101
G01N015/06; F01N 11/00 20060101 F01N011/00; F02D 41/14 20060101
F02D041/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2014 |
DE |
10 2014 119 484.5 |
Claims
1.-43. (canceled)
44. A sensor for detecting soot particles, the soot particles being
electrically conductive or polarizable, the sensor comprising:
substrate, a first electrode layer and a second electrode layer,
the second electrode layer arranged between the substrate and the
first electrode layer; a first insulation layer disposed between
the first electrode layer and the second electrode layer; a first
opening disposed in the first electrode layer and a second opening
disposed in the first insulation layer; wherein the first opening
and the second opening are aligned to form a first passage to the
second electrode layer.
45. The sensor as claimed in claim 44, further comprising a second
insulation layer and a third electrode layer, the second insulation
layer disposed between the first electrode layer and the third
electrode layer, a third opening disposed in the third electrode
layer and a fourth opening disposed in the second insulation layer,
and wherein the third opening and the fourth opening are aligned to
form a passage extension to the first passage to the second
electrode layer.
46. The sensor as claimed in claim 44, wherein the first opening is
distal from a peripheral region of the first electrode layer and
the second opening is distal from a peripheral region of the first
insulation layer, and wherein the third opening is distal from a
peripheral region of the third electrode layer and the fourth
opening is distal from a peripheral region of the second insulation
layer.
47. The sensor as claimed in claim 45, wherein the first electrode
layer, the second electrode layer, or the third electrode layer
comprises a metal, a metal alloy, a high-temperature-resistant
metal, a high-temperature-resistant alloy, a platinum metal, or an
alloy of a metal of the platinum metals.
48. The sensor as claimed in claim 45, wherein the first electrode
layer comprises a first material selected from the group of a
metal, a metal alloy, a high-temperature-resistant metal, a
high-temperature-resistant alloy, a platinum metal, or an alloy of
platinum metals, wherein the second electrode comprises a second
material selected from the group of a metal, a metal alloy, a
high-temperature-resistant metal, a high-temperature-resistant
alloy, a platinum metal, or an alloy of platinum metals, wherein
the third electrode comprises a third material selected from the
group of a metal, a metal alloy, a high-temperature-resistant
metal, a high-temperature-resistant alloy, a platinum metal, or an
alloy of platinum metals, and wherein the second material has a
higher etching resistance than the first material or the third
material.
49. The sensor as claimed in claim 44, further comprising a
covering layer disposed on a side of the first electrode layer, the
side of the first electrode layer facing away from the first
insulation layer, the covering layer comprising ceramic, a glass, a
metal oxide, or a combination thereof.
50. The sensor as claimed in claim 45, further comprising a
covering layer disposed on a side of the third electrode layer, the
side of the third electrode layer facing away from the first
insulation layer, the covering layer comprising ceramic, a glass, a
metal oxide, or a combination thereof, wherein the first passage is
a blind hole, wherein a portion of the second electrode layer is a
bottom of the blind hole, and wherein the blind hole extends
through the first insulation layer, the first electrode layer, the
second insulation layer, the third electrode layer, or the covering
layer.
51. The sensor as claimed in claim 50, wherein the blind hole has a
square cross section with a surface area in a range of 3.times.3
.mu.m.sup.2-150.times.150 .mu.m.sup.2, a range of 10.times.10
.mu.m.sup.2-100.times.100 .mu.m.sup.2, a range of 15.times.15
.mu.m.sup.2-50.times.50 .mu.m.sup.2, or 20.times.20
.mu.m.sup.2.
52. The sensor as claimed in claim 44, further comprising a fifth
opening disposed in the first electrode layer and a sixth opening
disposed in the first insulation layer, wherein the fifth opening
and the sixth opening are aligned to form a second passage to the
second electrode layer, wherein the first passage is a first blind
hole having a first cross-sectional area, wherein the second
passage is a second blind hole having a second cross-sectional
area, and wherein the first cross-sectional area is larger than the
second cross-sectional area.
53. The sensor as claimed in claim 45, wherein the first passage,
the passage extension, or a combination of the first passage and
the passage extension comprises a meandering shape or a spiral
shape.
54. The sensor as claimed in claim 53, further comprising a
covering layer disposed on a side of the third electrode layer, the
side of the third electrode layer facing away from the first
insulation layer, the covering layer comprising ceramic, a glass, a
metal oxide, or a combination thereof, wherein the first passage is
a blind hole, wherein a portion of the second electrode layer is a
bottom of the blind hole, and wherein the blind hole extends
through the first insulation layer, the first electrode layer, the
second insulation layer, the third electrode layer, or the covering
layer.
55. The sensor as claimed in claim 45, further comprising a
covering layer disposed on a side of the third electrode layer, the
side of the third electrode layer facing away from the first
insulation layer, the covering layer comprising ceramic, a glass, a
metal oxide, or a combination thereof, wherein the first electrode
layer comprises a first electrical contact area, wherein the second
electrode layer comprises a second electrical contact area, wherein
the third electrode layer comprises a third electrical contact
area, wherein the first electrical contact area is connected to the
first electrode layer, the second electrical contact area is
connected to the second electrode layer, the third electrical
contact area is connected to the third electrode layer, wherein the
second electrical contact area is not overlayed by the first
insulation layer and the first electrode layer, wherein the first
electrical contact area is not overlayed by the second insulation
layer and the third electrode layer, wherein the third electrical
contact area is not overlayed by a covering layer, and wherein each
electrical contact area is connected to a terminal pad.
56. The sensor as claimed in claim 55, wherein the first electrode
layer, the second electrode layer, or the third electrode layer
comprises a strip conductor loop, strip conductor loop being a
heating coil, a temperature-sensitive layer, a shielding electrode,
or a combination thereof, wherein the first electrode layer, the
second electrode layer, or the third electrode layer comprising the
strip conductor loop comprises further a fourth electrical contact
area not overlayed by one of the insulation layers or an electrode
layer, and wherein the fourth electrical contact area is connected
to the terminal pad.
57. A sensor system comprising: the sensor of claim 45, and a
controller or a control circuit, the controller or the control
circuit for operating the sensor in a measuring mode, in a cleaning
mode, in a monitoring mode, or a combination thereof.
58. A method for controlling the sensor as claimed in claim 45, the
method comprising the step of: operating the sensor in a measuring
mode, in a cleaning mode, in a monitoring mode, or a combination
thereof.
59. A method of making a sensor for detecting soot particles, the
soot particles being electrically conductive or polarizable, the
sensor comprising a substrate; a first electrode layer and a second
electrode layer, the second electrode layer arranged between the
substrate and the first electrode layer; a first insulation layer
disposed between the first electrode layer and the second electrode
layer; a second insulation layer and a third electrode layer, a
third opening disposed in the third electrode layer and a fourth
opening disposed in the second insulation layer, and wherein the
third opening and the fourth opening are aligned to form a passage
extension to the first passage to the second electrode layer, the
method comprising the steps of: laminating the first electrode
layer, the second electrode layer, the third electrode, the first
insulation layer, and the second insulation layer to form a
laminate, the first insulation layer being disposed between the
first electrode layer and the second electrode layer, the second
insulation layer disposed between the first electrode layer and the
third electrode layer, subsequently forming a passage through the
first electrode layer, the third electrode layer, the first
insulation layer, and the second insulation layer, ending the
passage to have a bottom formed by a portion of the second
electrode layer.
60. The method as claimed in claim 59, wherein the passage is
formed as a blind hole by etching, plasma-ion etching, or
successive etching adapted to each layer being etched.
61. The method as claimed in claim 60, wherein the passage is
formed as a blind hole or as an elongate depression by etching,
plasma-ion etching, or successive etching adapted to each layer
being etched, and wherein the first insulation layer or the second
insulation layer is etching-resistant layer, the blind hole or a
portion of the elongate depression being formed in the insulation
layer by a conditioning process with phase conversion of the first
insulation layer or the second insulation layer.
62. The method as claimed in claim 59, wherein the passage is
formed as a blind hole, a subportion of the blind hole, an elongate
depression, or a subportion of the elongate depression by
irradiation, wherein irradiation is performed with electromagnetic
waves, charged particles, or electrons, wherein a radiation source,
a wavelength, a pulse frequency of a radiation, or energy of the
charged particles being adapted individually to each layer being
irradiated.
63. A method of making a sensor for detecting soot particles, the
soot particles being electrically conductive or polarizable, the
sensor comprising a substrate; a first electrode layer and a second
electrode layer, the second electrode layer arranged between the
substrate and the first electrode layer; a first insulation layer
disposed between the first electrode layer and the second electrode
layer; a second insulation layer and a third electrode layer, a
third opening disposed in the third electrode layer and a fourth
opening disposed in the second insulation layer, and wherein the
third opening and the fourth opening are aligned to form a passage
extension to the first passage to the second electrode layer, the
method comprising the steps of: laminating the first electrode
layer, the second electrode layer, the third electrode, the first
insulation layer, and the second insulation layer to form a
laminate, the first insulation layer being disposed between the
first electrode layer and the second electrode layer, the second
insulation layer disposed between the first electrode layer and the
third electrode layer, wherein the first electrode layer, the
second electrode layer, the third electrode, the first insulation
layer, or the second insulation layer are structured by a lift-off
process, an ink-jet process, a stamping process one over the other
forming a passage to the second electrode layer.
64. A method of using the sensor of claim 45, the method comprising
the step of: directing a flow (a) of the soot particles to not
impinge perpendicularly on a plane (x, y) of the third
electrode.
65. A method of using the sensor of claim 56, the method comprising
the step of: detecting electrically conductive or polarizable
particles, and adjusting an angle .alpha. between a normal (z) to a
plane (x, y) of the first electrode layer and a direction of a flow
(a) of the particles is 1 degree or more, 10 degrees or more, or 30
degrees or more.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention is directed to a sensor for detecting
electrically conductive and/or polarizable particles, in particular
for detecting soot particles. The invention is also directed to a
sensor system, to a method for operating a sensor, to a method for
producing a sensor for detecting electrically conductive and/or
polarizable particles and to a use of a sensor of this type.
2. Discussion of the Related Art
[0002] The prior art discloses sensors comprising a sensor carrier,
with electrodes and heating structures being arranged on this
sensor carrier in a planar arrangement. In a detecting mode of
operation, polarizable and/or electrically conductive particles are
deposited on this planar arrangement. The deposited particles bring
about a reduction in the resistance between the electrodes, this
drop in the resistance being used as a measure of the mass of
deposited particles. When a predefined threshold value with respect
to the resistance is reached, the sensor arrangement is heated by
the heating structures, so that the deposited particles are burned
and, after the cleaning process, the sensor can be used for a
further detection cycle.
[0003] DE 10 2005 029 219 A1 gives a description of a sensor for
detecting particles in an exhaust-gas flow of internal combustion
engines, the electrode, heater and temperature-sensor structures
having been applied to a sensor carrier in a planar arrangement.
One disadvantage of this sensor arrangement is that the electrodes
to be bridged have a necessary minimum length in order to be able
to arrive at an acceptable sensitivity range when measuring
conductive or polarizable particles, such as for example soot.
However, a certain size of the sensor component is necessary for
this, in order to be able to arrange the minimum length for the
electrodes to be bridged. This is accompanied by corresponding cost
disadvantages in the production of these sensor components.
[0004] The invention is based on the object of providing a
further-developed sensor for detecting electrically conductive
and/or polarizable particles, in particular for detecting soot
particles, the sensor being minimized with regard to its size, so
that the aforementioned disadvantages can be overcome.
[0005] The object of the present invention is also to provide a
sensor system, a method for operating a sensor and a method for
producing a sensor of this type.
SUMMARY OF THE INVENTION
[0006] This object is achieved according to the invention by a
sensor for detecting electrically conductive and/or polarizable
particles, in particular for detecting soot particles.
[0007] The invention is based on the idea of providing a sensor for
detecting electrically conductive and/or polarizable particles, in
particular for detecting soot particles, comprising a substrate and
at least two electrode layers, a first electrode layer and at least
a second electrode layer, which is arranged between the substrate
and the first electrode layer, being arranged, at least one
insulation layer being formed between the first electrode layer and
the at least a second electrode layer and at least one opening
being respectively formed in the first electrode layer and in the
at least one insulation layer, the opening in the first electrode
layer and the opening in the insulation layer being arranged at
least in certain portions one over the other in such a way that at
least one passage to the second electrode layer is formed.
[0008] A sensor is preferably provided, comprising a substrate, a
first electrode layer, a second electrode layer, which is arranged
between the substrate and the first electrode layer, a first
insulation layer being formed between the first electrode layer and
the second electrode layer, at least a third electrode layer being
formed between the first insulation layer and the first electrode
layer, and at least a second insulation layer being formed between
the at least third electrode layer and the first electrode layer,
at least one opening being respectively formed in the first
electrode layer, in the at least second insulation layer, in the at
least third electrode layer and in the first insulation layer, the
opening in the first electrode layer, the opening in the at least
second insulation layer, the opening in the at least third
electrode layer and the opening in the insulation layer being
arranged at least in certain portions one over the other in such a
way that at least one passage to the second electrode layer is
formed.
[0009] In other words, a sensor is made available, a first and a
second electrode layer being arranged horizontally one over the
other and a first insulation layer, optionally at least a third
electrode layer and optionally at least a second insulation layer
being formed between these two electrode layers. In order to form a
passage to the second electrode layer, so that particles to be
detected, in particular soot particles, can reach the second
electrode layer with the aid of the passage, both the first and
third electrode layers and the first and second insulation layers
respectively have at least one opening, the opening in the first
and third electrode layers and the opening in the first and second
insulation layers being arranged at least in certain portions one
over the other, so that the passage is formed or can be formed.
[0010] Particles can accordingly reach the second electrode layer
by way of at least one passage only from one side of the sensor, to
be specific from the side of the sensor that is made to be the
closest to the first electrode layer. The electrically conductive
and/or polarizable particles accordingly lie on a portion of the
second electrode layer.
[0011] The sensor according to the invention may for example
comprise at least three electrode layers and at least two
insulation layers, an insulation layer preferably always being
formed between two electrode layers.
[0012] An insulation layer may also consist of two or more
sublayers, which may be arranged next to one another and/or one
over the other. Two or more sublayers of an insulation layer may
consist of different materials and/or comprise different
materials.
[0013] An electrode layer may also consist of two or more
sublayers, which may be arranged next to one another and/or one
over the other. Two or more sublayers of an electrode layer may
consist of different materials and/or comprise different
materials.
[0014] It is possible that the sensor comprises more than three
electrode layers and more than two insulation layers, also in this
situation an insulation layer preferably always being formed
between two electrode layers. From now on, the expression "at least
third electrode layer" should be understood as meaning that a
fourth and/or fifth and/or sixth and/or seventh and/or eighth
and/or ninth and/or tenth electrode layer may also be intended
instead of the stated third electrode layer.
[0015] From now on, the expression "at least second insulation
layer" should be understood as meaning that a third and/or fourth
and/or fifth and/or sixth and/or seventh and/or eighth and/or ninth
insulation layer may also be intended instead of the stated second
insulation layer.
[0016] The sensor according to the invention may in other words
comprise a laminate which comprises at least three electrode layers
and at least two insulation layers. The electrode layer closest to
the substrate is referred to as the second electrode layer, the
electrode layer at the maximum distance from the substrate is
referred to as the first electrode layer. Between the first
electrode layer and the second electrode layer there is for example
at least a third electrode layer, at least one insulation layer
being respectively formed between two electrode layers.
[0017] The electrode layers are arranged one over the other, in
particular in layers one over the other, the electrode layers being
respectively kept at a distance from one another by means of the
insulation layers. In other words, the electrode layers do not lie
in one plane.
[0018] Preferably, the opening in the first electrode layer is
formed at a distance from the peripheral region of the first
electrode layer, the opening in the optionally at least second
insulation layer is formed at a distance from the peripheral region
of the second insulation layer, the opening in the optionally at
least third electrode layer is formed at a distance from the
peripheral region of the third electrode layer and the opening in
the first insulation layer is formed at a distance from the
peripheral region of the first insulation layer. The openings are
accordingly preferably not formed in a peripheral position, or not
formed at the side peripheries of the layers concerned.
[0019] The first electrode layer and the optionally third electrode
layer are insulated from one another by the second insulation layer
located in between. The optionally third electrode layer and the
second electrode layer are insulated from one another by the first
insulation layer located in between. Such a structure allows a very
sensitive sensor of a smaller overall size in comparison with
sensors of the prior art to be formed.
[0020] The second electrode layer, formed for example with a flat
extent, is indirectly or directly connected to the substrate. An
indirect connection of the second electrode layer to the substrate
may take place for example by means of a bonding agent, in
particular a bonding agent layer. The bonding agent may also be
formed in an insular manner between the substrate and the second
electrode layer. For example, a drop-like formation of the bonding
agent/the bonding agent layer is possible. A bonding agent layer
may be formed between the second electrode layer and the
substrate.
[0021] The bonding agent, in particular the bonding agent layer,
may for example consist of an aluminum oxide (Al.sub.2O.sub.3) or a
silicon dioxide (SiO.sub.2) or a ceramic or a glass or any desired
combinations thereof. The bonding agent layer is preferably formed
very thin, and consequently only has a small thickness.
[0022] The first insulation layer and/or the at least second
insulation layer may have a thickness of 0.1 to 50 .mu.m, in
particular of 1.0 .mu.m to 40 .mu.m, in particular of 5.0 .mu.m to
30 .mu.m, in particular of 7.5 .mu.m to 20 .mu.m, in particular of
8 .mu.m to 12 .mu.m. With the aid of the thickness of the
insulation layer(s), the distance of one electrode layer from
another electrode layer is set. The sensitivity of the sensor can
be increased by reducing the distance between the, for example
flat-extending, electrode layers, located one over the other. The
smaller the thickness of the insulation layer is formed, the more
sensitive the sensor is made.
[0023] It is also possible that the thickness(es) of the electrode
layers and/or the thickness(es) of the insulation layer(s) of a
substrate vary.
[0024] The insulation layer(s) may be formed from aluminum oxide
(Al.sub.2O.sub.3) or silicon dioxide (SiO.sub.2) or magnesium oxide
(MgO) or silicon nitride (Si.sub.2N.sub.4) or glass or ceramic or
any desired combinations thereof.
[0025] Preferably, the first insulation layer laterally encloses
the second electrode layer. In other words, the first insulation
layer can cover the side faces of the second electrode layer in
such a way that the second electrode layer is laterally insulated.
For example, the at least second insulation layer laterally
encloses the at least third electrode layer. In other words, the
second insulation layer can cover the side faces of the third
electrode layer in such a way that the third electrode layer is
laterally insulated.
[0026] The first electrode layer and/or the second electrode layer
and/or the optionally at least third electrode layer is formed from
a conductive material, in particular from metal or an alloy, in
particular from a high-temperature-resistant metal or a
high-temperature-resistant alloy, particularly preferably from a
platinum metal or from an alloy of a platinum metal. The elements
of the platinum metals are palladium (Pd), platinum (Pt), rhodium
(Rh), osmium (Os), iridium (Ir) and ruthenium (Rh). Nonprecious
metals such as nickel (Ni) or nonprecious metal alloys such as
nickel/chromium or nickel/iron may also be used.
[0027] It is possible that at least one electrode layer is formed
from a conductive ceramic or a mixture of metal and ceramic. For
example, at least one electrode layer may be formed from a mixture
of platinum grains (Pt) and aluminum oxide grains
(Al.sub.2O.sub.3). It is also possible that at least one electrode
layer comprises silicon carbide (SiC) or is formed from silicon
carbide (SiC). The stated materials and metals or alloys of these
metals are particularly high-temperature-resistant and are
accordingly suitable for the forming of a sensor element that can
be used for detecting soot particles in an exhaust-gas flow of
internal combustion engines.
[0028] In a further embodiment of the invention, the second
electrode layer is formed from a conductive material, in particular
from a metal or an alloy, that has a higher etching resistance than
the conductive material, in particular the metal or the alloy, of
the first electrode layer. This has the advantage that the second
electrode layer can be formed in a production process as a layer
stopping the etching process. In other words, a second electrode
layer formed in this way can determine the depth to be etched of a
passage that is for example to be introduced into the sensor
structure.
[0029] On the side of the first electrode layer that is facing away
from the first insulation layer there may be formed at least one
covering layer, which is formed in particular from ceramic and/or
glass and/or metal oxide. In other words, the covering layer is
formed on a side of the first electrode layer that is opposite from
the first insulation layer. The covering layer may serve as a
diffusion barrier and additionally reduces an evaporation of the
first electrode layer at high temperatures, which in an exhaust-gas
flow for example may be up to 850.degree. C.
[0030] The at least one covering layer may laterally enclose the
first electrode layer. In a further embodiment of the invention,
the covering layer may additionally laterally enclose the at least
second insulation layer. In a further embodiment of the invention,
the covering layer may additionally laterally enclose the at least
second insulation layer and the at least third electrode layer.
[0031] It is possible that at least one covering layer does not
completely cover the uppermost electrode layer, in particular the
first electrode layer. In other words it is possible that at least
one covering layer only covers certain portions of the uppermost
electrode layer, in particular the first electrode layer. If the
uppermost electrode layer is formed as a heating layer, it is
possible that only the portions of the heating loop/heating coil
are covered by the at least one covering layer.
[0032] In a further embodiment of the invention, the at least one
covering layer may additionally laterally enclose the at least
second insulation layer and the at least third electrode layer and
the first insulation layer. In other words, both the side faces of
the first electrode layer and the side faces of the insulation
layers and electrode layers arranged thereunder may be covered by
at least one covering layer. It is also conceivable that the
covering layer additionally laterally encloses the second electrode
layer. The lateral enclosing part or lateral enclosing region of
the covering layer may accordingly reach from the first electrode
layer to the second electrode layer. This brings about a lateral
insulation of the first electrode layer and/or of the insulation
layers and/or of the at least third electrode layer and/or of the
second electrode layer.
[0033] On the side of the first electrode layer that is facing away
from the first insulation layer or on the side of the covering
layer that is facing away from the first electrode layer there may
be additionally formed at least one porous filter layer. With the
aid of a porous filter layer of this type, large particle parts can
be kept away from the arrangement of at least two, in particular at
least three, electrode layers arranged one over the other. The pore
sizes of the filter layer may be for example >1 .mu.m.
Particularly preferably, the pore size is formed in a range from 20
.mu.m to 30 .mu.m. The porous filter layer may for example be
formed from a ceramic material. It is also conceivable that the
porous filter layer is formed from an aluminum oxide foam. With the
aid of the filter layer, which also covers the at least one passage
to the second electrode layer, the large particles, in particular
soot particles, that disturb the measurement can be kept away from
the at least one passage, so that such particles cannot cause a
short circuit.
[0034] The at least one passage to the second electrode layer may
for example be formed as a blind hole, a portion of the second
electrode layer being formed as the bottom of the blind hole and
the blind hole extending at least over the first insulation layer,
over the optionally at least third electrode layer, over the
optionally at least second insulation layer and over the first
electrode layer. If the sensor has a covering layer, the blind hole
also extends over this covering layer. In other words, not only the
first electrode layer but also the optionally at least second
insulation layer, the optionally at least third electrode layer and
the first insulation layer and the covering layer then have an
opening, these openings being arranged one over the other in such a
way that they form a blind hole, the bottom of which is formed by a
portion of the second electrode layer. The bottom of the blind hole
may for example be formed on the upper side of the second electrode
layer that is facing the first insulation layer. It is also
conceivable that the second electrode layer has a depression that
forms the bottom of the blind hole.
[0035] The opening cross section of the blind hole is formed by the
peripheral portions of the first electrode layer, of the at least
second insulation layer, of the at least third electrode layer and
of the first insulation layer and, if there is one, of the covering
layer that bound the openings. The opening cross section of the at
least one blind hole may be round or square or rectangular or
lenticular or honeycomb-shaped or polygonal or triangular or
hexagonal. Other types of design, in particular free forms, are
also conceivable.
[0036] For example, it is possible that the blind hole has a square
cross section with a surface area of 3.times.3 .mu.m.sup.2 to
150.times.150 .mu.m.sup.2, in particular of 10.times.10 .mu.m.sup.2
to 100.times.100 .mu.m.sup.2, in particular of 15.times.15
.mu.m.sup.2 to 50.times.50 .mu.m.sup.2, in particular of
20.times.20 .mu.m.sup.2.
[0037] In a development of the invention, the sensor may have a
multiplicity of passages, in particular blind holes, these blind
holes being formed as already described. It is also conceivable
that at least two passages, in particular at least two blind holes,
have different cross sections, in particular different sizes of
cross section, so that a sensor array with a number of zones can be
formed, in which a number of measuring cells with blind-hole cross
sections of different sizes can be used. Parallel detection of
electrically conductive and/or polarizable particles, in particular
of soot particles, allows additional items of information
concerning the size of the particles or the size distribution of
the particles to be obtained.
[0038] In a further embodiment of the invention, the openings in
the first insulation layer, in the optionally at least third
electrode layer, in the optionally at least second insulation
layer, and in the first electrode layer may be respectively formed
in a linear form or respectively formed in a meandering manner or
respectively formed in a grid form or respectively formed in a
spiral form. In other words, an opening in the first insulation
layer, an opening in the optionally at least third electrode layer,
an opening in the optionally at least second insulation layer, and
an opening in the first electrode layer are respectively formed in
a linear form or respectively formed in a meandering manner or
respectively formed in a spiral form or respectively formed in a
grid form. The openings in the individual layers are preferably
formed similarly, so that a passage can be formed. The openings do
not necessarily have to have exactly coinciding cross sections or
exactly coinciding sizes of cross section. It is possible that,
beginning from the second electrode layer, the cross sections of
the openings respectively become greater in the direction of the
first electrode layer. The basic forms of the openings are
preferably formed similarly, so that all of the openings are formed
either in a linear form or in a meandering manner or in a spiral
form or in a grid form.
[0039] In a further embodiment of the invention it is possible that
the sensor has a number of passages that are formed in a linear
form and/or a meandering manner and/or a spiral form and/or a grid
form.
[0040] If the second electrode layer has the form of a meander or
the form of a loop, the at least one passage of the sensor is
formed in such a way that the passage does not end in a gap or an
opening in the form of the meander or the form of the loop. The at
least one passage of the sensor is formed in such a way that a
portion of the second electrode layer forms the bottom of the
passage.
[0041] It is also possible that the at least one passage is formed
as an elongate depression, a portion of the second electrode layer
being formed as the bottom of the elongate depression and the
elongate depression extending at least over the first insulation
layer, over the optionally at least third electrode layer, over the
optionally at least second insulation layer, and over the first
electrode layer and over a/the optionally formed covering
layer.
[0042] The elongate depression may also be referred to as a trench
and/or groove and/or channel.
[0043] In a further embodiment of the invention it is possible that
the sensor comprises both at least one passage in the form of a
blind hole, which is formed as round and/or square and/or
rectangular and/or lenticular and/or honeycomb-shaped and/or
polygonal and/or triangular and/or hexagonal, and at least one
passage in the form of an elongate depression, which is formed in a
linear form and/or a meandering manner and/or in a spiral form
and/or in a grid form.
[0044] In a further embodiment of the invention, the first
electrode layer, the optionally at least second insulation layer,
the optionally at least third electrode layer and the first
insulation layer are respectively formed as porous, the at least
one opening in the first electrode layer, the at least one opening
in the optionally at least second insulation layer, the at least
one opening in the optionally at least third electrode layer, and
the at least one opening in the first insulation layer respectively
being formed by at least one pore, the pore in the first insulation
layer, the pore in the at least third electrode layer, the pore in
the at least second insulation layer and the pore in the first
electrode layer being arranged at least in certain portions one
over the other in such a way that the at least one passage to the
second electrode layer is formed. In other words, it is possible to
dispense with an active or subsequent structuring of the passages,
the first and at least third electrode layer and the first and at
least second insulation layer being formed as permeable to the
medium to be measured.
[0045] This can be made possible for example by a porous or
granular structure of the layers. Both the electrode layers and the
insulation layers can be produced by sintering together individual
particles, with pores or voids for the medium to be measured being
formed while they are being sintered together. The second electrode
layer is preferably formed as non-porous. Accordingly, at least one
passage that allows access to the second electrode layer for a
particle that is to be measured or detected must be formed,
extending from the side of the first electrode layer that is facing
away from the first insulation layer to the side of the second
electrode layer that is facing the insulation layer as a result of
the one-over-the-other arrangement of pores in the electrode
layers, in particular the first and the optionally at least third
electrode layer, and in the insulation layers. If the sensor has a
covering layer, this covering layer is also preferably to be formed
as porous in such a way that a pore in the covering layer, a pore
in the first electrode layer, a pore in the second insulation
layer, a pore in the third electrode layer and a pore in the first
insulation layer form a passage to the second electrode layer.
[0046] The pore size distribution and their number in the first and
optionally third electrode layer and/or the first and optionally
second insulation layer and/or the covering layer(s) can be
optimized with regard to the measuring or detecting tasks to be
carried out.
[0047] The first and/or third electrode layer and/or the first
and/or second insulation layer and, if there is one, the at least
one covering layer may have portions with different pore sizes in
such a way that a sensor array with a number of zones of different
pore sizes is formed. Parallel detection with portions of layers of
different pore sizes allows a "fingerprint" of the medium that is
to be analyzed or detected to be measured. Accordingly, further
items of information concerning the size of the particles to be
measured or the size distribution of the particles to be measured
can be obtained.
[0048] The first electrode layer, the second electrode layer and
the optionally at least third electrode layer respectively have an
electrical contacting area that are free from sensor layers
arranged over the respective electrode layers and are or can in
each case be connected to a terminal pad. The electrode layers are
connected or can be connected to terminal pads in such a way that
they are insulated from one another. For each electrode layer there
is formed at least one electrical contacting area, which is exposed
in the region of the terminal pads for the electrical contacting.
The electrical contacting area of the first electrode layer is free
from a possible covering layer and free from a passive porous
filter layer. In other words, above the electrical contacting area
of the first electrode layer there is neither a portion of the
covering layer nor a portion of the filter layer.
[0049] The electrical contacting area of the second or at least
third electrode layer is free from insulation layers, free from
electrode layers, and also free from a possibly formed covering
layer and free from a passive porous filter layer.
[0050] In other words, on the electrical contacting area of the
second or at least third electrode layer there is neither a portion
of an insulation layer nor a portion of an electrode layer, nor a
portion of the passive porous filter layer.
[0051] In a further embodiment of the invention, the first
electrode layer and/or the second electrode layer and/or the at
least third electrode layer has strip conductor loops in such a way
that the first electrode layer and/or the second electrode layer
and/or the at least third electrode layer is formed as a heating
coil and/or as a temperature-sensitive layer and/or as a shielding
electrode. The first electrode layer and/or the second electrode
layer and/or the at least third electrode layer has at least one
additional electrical contacting area that is free from sensor
layers arranged over the electrode layer, that is to say the first
and/or the second and/or the at least third electrode layer, and is
connected or can be connected to an additional terminal pad. In
other words, the first electrode layer and/or the second electrode
layer and/or the at least third electrode layer has two electrical
contacting areas, both electrical contacting areas being free from
sensor layers arranged over the electrode layer.
[0052] The formation of two electrical contacting areas on an
electrode layer is necessary whenever this electrode layer is
formed as a heating coil and/or temperature-sensitive layer and/or
as a shielding electrode. Preferably, the second and/or the at
least third electrode layer has at least two electrical contacting
areas. The second and/or the at least third electrode layer is
preferably formed not only as a heating coil but also as a
temperature-sensitive layer and as a shielding electrode. By
appropriate electrical contacting of the electrical contacting
area, the electrode layer can either heat or act as a
temperature-sensitive layer or shielding electrode. Such a
formation of the electrode areas allows compact sensors to be
provided, since one electrode layer can assume a number of
functions. Accordingly, no separate heating coil layers and/or
temperature-sensitive layers and/or shielding electrode layers are
necessary.
[0053] During the heating of at least one electrode layer, measured
particles or particles located in a passage of the sensor may for
example be burned away or burned off.
[0054] To sum up, it can be stated that a very accurately measuring
sensor can be made available as a result of the structure according
to the invention. The forming of a/a number of thin insulation
layers allows the sensitivity of the sensor to be increased
significantly.
[0055] Furthermore, the sensor according to the invention can be
made much smaller than known sensors. The formation of the sensor
in a three-dimensional space allows a number of electrode layers
and/or a number of insulation layers to be built as a smaller
sensor. Furthermore, significantly more units can be formed on a
substrate or a wafer during the production of the sensor. This
structure is consequently accompanied by a considerable cost
advantage in comparison with normally planar-constructed
structures.
[0056] A further advantage of the sensor according to the invention
is that the cross sections of the passages can be dimensioned in
such a way that specific particles of specific sizes cannot enter
the passages. It is also possible that the cross sections of a
number of passages can be of different sizes, so that only specific
particles of corresponding particle sizes are allowed access into
individual passages.
[0057] The sensor according to the invention may be used for
detecting particles in gases. The sensor according to the invention
may be used for detecting particles in liquids. The sensor
according to the invention may be used for detecting particles in
gases and liquids or gas-liquid mixtures. When the sensor is used
for detecting particles in liquids, it is not always possible
however to burn off or burn away the particles.
[0058] In the case of known sensors, the sensors are arranged in
one plane and engage in one another. In the case of the present
sensor, it is not necessary for the electrode structures to engage
in one another, since the individual electrode layers are formed at
a distance from one another as a result of the formation of
insulation layers between the electrode layers. The electrode
layers of the sensor according to the invention are not connected
to one another, but lie one over the other, separated by at least
one insulation layer. There is a "non continuous loop" between at
least a first electrode layer and at least a second electrode
layer. The at least two electrode layers are not twisted together
or entwined. At least two electrode layers can only be electrically
connected to one another by a soot particle located in at least one
passage.
[0059] With the aid of at least three formed electrode layers, it
is possible during a measurement of particles for example to deduce
the particle size or to detect the particle size. If a particle
bridges only two electrode layers arranged one over the other, the
size of the particle is smaller than a particle that bridges more
than two electrode layers. Different formations of the thickness of
the insulation layers also allow the size of the particles to be
deduced.
[0060] According to an independent aspect, the invention relates to
a sensor system, comprising at least one sensor according to the
invention and at least one controller, in particular at least one
control circuit, which is formed in such a way that the sensor can
be operated in a measuring mode and/or in a cleaning mode and/or in
a monitoring mode.
[0061] The sensor according to the invention and/or the sensor
system according to the invention may have at least one auxiliary
electrode. Between an auxiliary electrode and an electrode layer
and/or between an auxiliary electrode and a component of the sensor
system, in particular the sensor housing, there may be applied such
an electrical potential that the particles to be measured are
electrically attracted or sucked in by the sensor and/or the sensor
system. Preferably, such a voltage is applied to the at least one
auxiliary electrode and to at least one electrode layer that
particles, in particular soot particles, are "sucked into" the at
least one passage.
[0062] The sensor according to the invention is preferably arranged
in a sensor housing. The sensor housing may for example have an
elongate tube form. The sensor system according to the invention
may accordingly also comprise a sensor housing.
[0063] Preferably, the sensor and/or the sensor in the sensor
housing and/or the sensor housing is formed and/or arranged in such
a way that the sensor, in particular the uppermost layer of the
sensor, or the layer of the sensor that is arranged furthest away
from the substrate, is arranged obliquely in relation to the
direction of flow of the fluid. The flow in this case does not
impinge perpendicularly on the plane of the electrode layers.
Preferably, the angle .alpha. between the normal to the plane of
the first electrode layer and the direction of flow of the
particles is at least 1 degree, preferably at least 10 degrees,
particularly preferably at least 30 degrees. Also preferred is an
arrangement of the sensor in which the angle .beta. between the
direction of flow of the particles and the longitudinal axis of for
example elongate depressions lies between 20 and 90 degrees. In
this embodiment, the particles to be detected more easily enter the
passages, in particular blind holes or elongate depressions, in the
sensor, and thereby increase the sensitivity.
[0064] The controller, in particular the control circuit, is
preferably formed in such a way that the electrode layers of the
sensor are interconnected with one another. Such voltages may be
applied to the electrode layers or individual electrode layers that
the sensor can be operated in a measuring mode and/or in a cleaning
mode and/or in a monitoring mode.
[0065] According to an independent aspect, the invention relates to
a method for controlling a sensor according to the invention and/or
a sensor system according to the invention.
[0066] The method according to the invention allows the sensor to
be operated according to choice in a measuring mode and/or in a
cleaning mode and/or in a monitoring mode.
[0067] In the measuring mode, a change in the electrical resistance
between the electrode layers or between at least two electrode
layers of the sensor and/or a change in the capacitances of the
electrode layers can be measured.
[0068] With the aid of the method according to the invention,
particles can be detected or measured on the basis of a measured
change in resistance between the electrode layers and/or by a
measurement of the change in impedance and/or by a measurement of
the capacitance of the electrode layer(s). Preferably, a change in
resistance between the electrode layers is measured.
[0069] In the measuring mode, an electrical resistance measurement,
that is to say a measurement on the resistive principle, may be
carried out. This involves measuring the electrical resistance
between two electrode layers, the electrical resistance decreasing
if a particle, in particular a soot particle, bridges at least two
electrode layers, which act as electrical conductors.
[0070] It applies in principle in the measuring mode that, by
applying different voltages to the electrode layers, different
properties of the particles to be measured, in particular soot
particles, can be detected. For example, the particle size and/or
the particle diameter and/or the electrical charging and/or the
polarizability of the particle can be determined.
[0071] If at least one electrode layer is also used or can be
connected as a heating coil or heating layer, an electrical
resistance measurement may additionally serve the purpose of
determining the point in time of the activation of the heating coil
or heating layer. The activation of the heating coil or heating
layer corresponds to a cleaning mode to be carried out.
[0072] Preferably, a decrease in the electrical resistance between
at least two electrode layers indicates that particles, in
particular soot particles, have been deposited on or between the
electrodes (electrode layers). As soon as the electrical resistance
reaches a lower threshold value, the activation of the heating coil
or heating layer takes place. The particles are in other words
burned off. With an increasing number of burnt-off particles or
burnt-off particle volume, the electrical resistance increases. The
burning off is preferably carried out for such a time until an
upper electrical resistance value is measured. Reaching an upper
electrical resistance value is taken as an indication of a
regenerated or cleaned sensor. A new measuring cycle can
subsequently begin or be carried out.
[0073] Alternatively or in addition, it is possible to measure a
change in the capacitances of the electrode layers. An increasing
loading of the arrangement of electrode layers leads to an increase
in the capacitance of the electrode layers. The arrangement of
particles, in particular soot particles, in at least one passage of
the sensor leads to a charge transfer or a change in the
permittivity (s), which leads to an increase in the capacitance
(C). In principle: C=(.epsilon..times.A)/d, where A stands for the
active electrode area of the electrode layer and d stands for the
distance between two electrode layers.
[0074] The measuring of the capacitance may be carried out by way
of example by: [0075] determining the rate of voltage increase with
a constant current and/or [0076] applying a voltage and determining
the charging current and/or [0077] applying an AC voltage and
measuring the current profile and/or [0078] determining the
resonant frequency by means of an LC oscillating circuit.
[0079] The described measurement of the change in the capacitances
of the electrode layers may also be carried out in connection with
a monitoring mode to be carried out.
[0080] According to OBD (on-board diagnosis) regulations, all parts
and components that are relevant to exhaust gas must be checked for
their function. The functional check is to be carried out for
example directly after starting a motor vehicle.
[0081] For example, at least one electrode layer may be destroyed,
this being accompanied by a reduction in the active electrode area
A. Since the active electrode area A is directly proportional to
capacitance C, the measured capacitance C of a destroyed electrode
layer decreases.
[0082] In the monitoring mode, it is alternatively or additionally
possible to form the electrode layers as conductor circuits. The
conductor circuits may be formed as closed or open conductor
circuits, which can be closed on demand, for example by a switch.
It is also possible to close the electrode layers by way of at
least one switch to form at least one conductor circuit, it being
checked in the monitoring mode whether a test current is flowing
through the at least one conductor circuit. If an electrode layer
has a crack or is damaged or destroyed, no test current would
flow.
[0083] According to an independent aspect, the invention relates to
a method for producing a sensor for detecting electrically
conductive and/or polarizable particles, in particular a method for
producing a described sensor according to the invention.
[0084] The method comprises that a laminate with a first electrode
layer, a second electrode layer, a first insulation layer, which is
arranged between the first electrode layer and the second electrode
layer, optionally at least a third electrode layer, which is
arranged between the first insulation layer and the first electrode
layer, and optionally at least a second insulation layer, which is
arranged between the third electrode layer and the first electrode
layer, is produced, at least one passage that extends over the
first electrode layer, the optionally at least second insulation
layer, the optionally at least third electrode layer, and the first
insulation layer being subsequently introduced into the laminate,
the bottom of the passage being formed by a portion of the second
electrode layer.
[0085] The method is also based on the idea of producing a laminate
which comprises at least three electrode layers and two insulation
layers, in order to introduce at least one passage into this
laminate. The passage serves as access to the second electrode
layer for the particles to be detected, in particular soot
particles.
[0086] The production of the laminate and/or of the individual
layers of the laminate may take place by a thin-film technique or a
thick-film technique or a combination of these techniques. As part
of a thin-film technique to be applied, a vapor depositing process
or preferably a cathode sputtering process may be chosen. As part
of a thick-film process, a screen-printing process is conceivable
in particular.
[0087] At least one insulation layer and/or at least one covering
layer, which is formed on the side of the first electrode layer
that is facing away from the first insulation layer, may be formed
by a chemical vapor deposition (CVD process) or a plasma-enhanced
chemical vapor deposition (PECVD process).
[0088] The first insulation layer may be produced in such a way
that it laterally encloses the second electrode layer. An
optionally present covering layer may likewise be produced in such
a way that it laterally encloses the first electrode layer and/or
the at least second insulation layer and/or the at least third
electrode layer and/or the first insulation layer and/or the second
electrode layer. Accordingly, both at least one of the insulation
layers and at least one/the covering layer may form an additional
lateral enclosure.
[0089] The passage may for example be formed as a blind hole or as
an elongate depression, the at least one blind hole or a subportion
of the blind hole or the at least one elongate depression or a
subportion of the elongate depression being introduced into the
laminate by at least one removing or etching process, in particular
by a plasma-ion etching process, or by a number of successively
carried out removing or etching processes which is adapted to the
layer of the laminate that is respectively to be etched or to be
removed.
[0090] In other words, a blind hole or an elongate depression may
be introduced into the laminate in such a way that, for example for
each layer to be penetrated or to be etched or to be removed, a
process that is optimum for this layer is used, and consequently a
number of etching or removing steps that are to be successively
carried out are carried out.
[0091] It is also conceivable that the blind hole or a subportion
of the blind hole or the elongate depression or a subportion of the
elongate depression may be made in a chemical etching process from
the liquid or vapor phase. The first electrode layer preferably
consists of a metal, in particular a platinum layer, which is
relatively easy to etch through or to etch.
[0092] In one possible embodiment of the method according to the
invention it is possible that the etching process stops at the
second electrode layer if the second electrode layer is produced
from a material that is more resistant to etching in comparison
with the first and third electrode layers and with the insulation
layers. If the laminate or the sensor comprises an additional
covering layer, the second electrode layer also comprises a
material that is more resistant to etching in comparison with this
covering layer. For example, the second electrode layer is produced
from a platinum-titanium alloy (Pt/Ti). It is also conceivable that
the second electrode layer consists of a layer filled with metal
oxides.
[0093] In a further embodiment of the method according to the
invention it is possible that the first insulation layer and/or the
at least second insulation layer is formed as a layer stopping the
etching process and, in a further step, a subportion of the blind
hole or a subportion of the elongate depression is introduced into
the first insulation layer and/or the at least second insulation
layer by a conditioning process or a conditioning step with phase
conversion of the first insulation layer and/or the at least second
insulation layer.
[0094] In a further embodiment of the method according to the
invention it is possible that the at least one passage and/or a
passage is formed as a blind hole or as an elongate depression and
this blind hole or the at least one blind hole or a subportion of
the blind hole or this elongate depression or the at least one
elongate depression or a subportion of the elongate depression is
introduced into the laminate by a process of irradiating with
electromagnetic waves or charged particles (electrons), the
radiation source and/or the wavelength and/or the pulse frequency
of the radiation being adapted to the layer of the laminate that is
respectively to be machined.
[0095] It is preferably possible that the at least one passage
and/or a passage is formed as a blind hole or as an elongate
depression and this blind hole or the at least one blind hole or a
subportion of the blind hole or this elongate depression or the at
least one elongate depression or a subportion of the elongate
depression is introduced into the laminate by a laser machining
process, in particular by means of an ultrashort pulse laser, the
laser source and/or the wavelength and/or the pulse frequency of
the laser and/or the energy of the charged particles and/or the
species of the charged particles being adapted to the layer of the
laminate that is respectively to be machined. Particularly
preferably, an ultrashort pulse laser is a femto laser or a pico
laser.
[0096] One possibility for producing the passage that is formed as
a blind hole or as an elongate depression is consequently the
partial removal of the laminate by means of a laser. Laser sources
with different wavelengths and/or pulse frequencies that are
respectively made to suit the material to be removed can be used.
Such a procedure has the advantage that, by making them suit the
material of the layer that is to be removed, the respectively
individual laser machining steps can be carried out quickly, so
that overall an improved introduction of passages and/or blind
holes and/or elongate depressions into the laminate is obtained.
The use of an ultrashort pulse laser proves to be particularly
advantageous.
[0097] Apart from electromagnetic radiation, charged or uncharged
particles can however also be used for removing the electrode
layers and/or insulation layers. Thus, apart from electron beams,
other charged or uncharged particles can also be used for the
ablation. This may be carried out with or without masks that
contain the structural information to be transferred.
[0098] In a further embodiment of the method according to the
invention it is possible that, when producing the laminate, the
first insulation layer and/or the at least second insulation layer
is created over the full surface area, in particular by a
screen-printing process or spraying-on process or immersion process
or spin-coating process, between the second electrode area and the
at least third electrode area or between the at least third
electrode area and the first electrode area and, in a subsequent
method step, at least a portion of the first insulation layer
and/or of the at least second insulation layer is removed, in
particular by structured dissolving or etching or burning out, in
such a way that the passage is formed in the sensor.
[0099] Such a method corresponds to the lost mold principle.
Accordingly, it is possible, especially in the case of thermally
stable materials, to perform structuring by the lost mold
principle. A lost mold serves for creating a passage from the first
electrode layer to the second electrode layer. The at least one
insulation layer or insulating layer is created between the
electrode layers from a thermally stable material, a portion of
this insulation layer preferably being removed by dissolving or
etching or burning out after the application of the first electrode
layer. As a result of this, the first electrode layer located
thereover is also removed. If a covering layer is formed, the
portion of the covering layer that is located over the removed
portion of the insulation layer is also removed by the dissolving
or etching or burning out of the portion of the insulation
layer.
[0100] Preferably, after the introduction of a passage and/or a
blind hole and/or an elongate depression into the laminate, at
least one passive porous filter layer is applied on the covering
layer. The passive porous filter layer is formed for example by an
aluminum oxide foam. This is also formed over the at least one
passage or over the at least one blind hole or over the at least
one elongate depression.
[0101] In a further independent aspect, the invention relates to a
method that serves for producing a sensor for detecting
electrically conductive particles and/or polarizable particles.
[0102] A laminate with a first electrode layer, a second electrode
layer, a first insulation layer, which is arranged between the
first electrode layer and the second electrode layer, at least a
third electrode layer, which is arranged between the first
insulation layer and the first electrode layer, and at least a
second insulation layer, which is arranged between the third
electrode layer and the first electrode layer, is produced, the
first insulation layer, the at least third electrode layer, the at
least second insulation layer and the first electrode layer being
formed as porous layers. The pores in the first and third electrode
layer and the first and second insulation layer are set in such a
way that at least one pore in the first electrode layer, at least
one pore in the at least second insulation layer, at least one pore
in the at least third electrode layer and at least one pore in the
first insulation layer are arranged at least in certain portions
one over the other, so that at least one passage to the second
electrode layer is produced.
[0103] If the sensor has a covering layer, this covering layer is
also applied to the first electrode layer with a pore size and
porosity, at least one pore in the covering layer being arranged at
least in certain portions over a pore in the first electrode layer,
over a pore in the at least second insulation layer, over a pore in
the at least third electrode layer and a pore in the first
insulation layer in such a way that, starting from the covering
layer, at least one passage to the second electrode layer is
formed. A passive porous filter layer may finally be applied to the
covering layer.
[0104] In a further independent aspect, a method for producing a
sensor for detecting electrically conductive particles and/or
polarizable particles is provided, a laminate with a first
electrode layer, a second electrode layer, at least a first
insulation layer, which is arranged between the first electrode
layer and the second electrode layer, optionally at least a third
electrode layer, which is arranged between the first insulation
layer and the first electrode layer, and optionally at least a
second insulation layer, which is arranged between the third
electrode layer and the first electrode layer, being produced, the
first insulation layer, the at least third electrode layer, the at
least second insulation layer and the first electrode layer being
structured, in particular created by a lift-off process and/or an
ink-jet process and/or in a stamping process, in such a way that,
as a result of the structured application of the individual layers
one over the other, a passage to the second electrode layer is
formed.
[0105] In other words, already during the production of the
insulation layer(s) and/or the first and/or third electrode layer,
such a structure that has openings or clearances is produced, a
number of openings that are arranged at least in certain portions
one over the other forming at least one passage to the second
electrode layer. If the sensor has a covering layer, this covering
layer may also be applied in an already structured form to the
first electrode layer.
[0106] In the case of all of the described processes for producing
a sensor for detecting electrically conductive and/or polarizable
particles, it is necessary that an electrical contacting area is
respectively formed in the first electrode layer and/or in the
second electrode layer and/or in the optionally at least third
electrode layer. This is achieved by portions of the first
electrode layer and/or of the second electrode layer and/or of the
optionally at least third electrode layer being kept free from
sensor layers arranged over the respective electrode layers. This
may take place on the one hand by the electrical contacting areas
being produced by removing and/or etching away and/or lasering away
sensor layers arranged thereover. It is also conceivable that the
insulation layers and/or the electrode layers and/or the covering
layer(s) are applied to one another in a structured form, so that
the electrical contacting areas are already kept free during the
production of the individual sensor layers.
[0107] As an alternative or in addition, it is possible that at
least the insulation layers, preferably all of the layers, of the
laminate of the sensor are produced by means of an HTCC (high
temperature cofired ceramics) process. The insulation layers are
produced by combining powder, for example ceramic powder, metal
powder, aluminum oxide powder and glass powder, and also an amount
of binder and solvent, which together form a homogeneous liquid
mass. This mass is applied to a film strip, so that green sheets
are formed. The drying of the green sheets subsequently takes
place. The dried green sheets may be cut and/or punched and/or
shaped, in particular provided with openings. Subsequently, the
green sheets may for example be rolled up and transported for
further processing.
[0108] The electrode layers may for example be produced on the
green sheet by printing, in particular by screen printing or
stencil printing, from metal pastes. Alternatively, thin metal
films may be produced and correspondingly prestructured.
[0109] Once the various substrate, electrode and insulation layers
have been created, the green sheets are arranged in the desired
sequence and positioned in exact register one over the other,
pressed and joined together by thermal treatment. The binder may be
of an organic or inorganic nature and during the thermal treatment
either turns into a stable material or combusts or evaporates. The
particles thereby fuse firmly to one another by melting and/or
sintering processes during the thermal treatment. In this way, the
three-dimensional structure of the sensor is formed or
produced.
[0110] In a further embodiment of the invention it is conceivable
that, when producing the laminate, the electrical contacting areas
are covered with the aid of stencils, so that the electrical
contacting areas cannot be coated with other sensor layers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0111] The invention is explained in more detail below on the basis
of exemplary embodiments with reference to the accompanying
schematic drawings, in which:
[0112] FIGS. 1a-c show sectional representations of various
embodiments of sensors for detecting electrically conductive and/or
polarizable particles;
[0113] FIG. 2 shows a perspective plan view of a sensor according
to the invention;
[0114] FIG. 3 shows a possible formation of a second electrode
layer;
[0115] FIG. 4 shows a sectional representation of a further
embodiment of a sensor for detecting electrically conductive and/or
polarizable particles;
[0116] FIG. 5 shows a sectional representation of a further
embodiment of a sensor for detecting electrically conductive and/or
polarizable particles which comprises at least three electrode
layers;
[0117] FIGS. 6a-f show representations of various embodiments of
openings;
[0118] FIGS. 7a+b show representation of a possible arrangement of
a sensor in a fluid flow;
[0119] FIGS. 8a+b show representations of various cross sections or
cross-sectional profiles of passages;
[0120] FIG. 9 shows a sectional representation of undercuts in
insulation layers or set-back insulation layers; and
[0121] FIGS. 10a-d show exploded representations of various
embodiments of a sensor according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0122] The same reference numerals are used below for parts that
are the same and parts that act in the same way.
[0123] FIG. 1 a shows in a sectional representation a sensor 10 for
detecting electrically conductive and/or polarizable particles, in
particular for detecting soot particles. The sensor 10 comprises a
substrate 11, a first electrode layer 12 and a second electrode
layer 13, which is arranged between the substrate 11 and the first
electrode layer 12. An insulation layer 14 is formed between the
first electrode layer 12 and the second electrode layer 13. At
least one opening is respectively formed in the first electrode
layer 12 and in the insulation layer 14, the opening 15 in the
first electrode layer 12 and the opening 16 in the insulation layer
14 being arranged one over the other, so that a passage 17 to the
second electrode layer 13 is formed.
[0124] For the purposes of a high-temperature application, the
substrate 11 is formed for example from aluminum oxide
(Al.sub.2O.sub.3) or magnesium oxide (MgO) or from a titanate or
from steatite.
[0125] The second electrode layer 13 is connected to the substrate
11 indirectly by way of a bonding agent layer 18. The bonding agent
layer 18 may be for example very thinly formed aluminum oxide
(Al.sub.2O.sub.3) or silicon dioxide (SiO.sub.2).
[0126] In the exemplary embodiment, the first electrode layer 12 is
formed by a platinum layer. In the example shown, the second
electrode layer 13 consists of a platinum-titanium alloy (Pt--Ti).
The platinum-titanium alloy of the second electrode layer 13 is a
layer that is more resistant to etching in comparison with the
first electrode layer 12.
[0127] The distance between the first electrode layer 12 and the
second electrode layer 13 is formed by the thickness d of the
insulation layer 14. The thickness d of the insulation layer may be
0.5 .mu.m to 50 .mu.m. In the present case, the thickness d of the
insulation layer is 10 .mu.m. The sensitivity of the sensor 10
according to the invention can be increased by reducing the
distance between the first electrode layer 12 and the second
electrode layer 13, and consequently by reducing the thickness d of
the insulation layer 14.
[0128] The insulation layer 14 covers the second electrode layer 13
on the side face 19 shown, so that the second electrode layer 13 is
laterally enclosed and insulated.
[0129] The passage 17 is formed as a blind hole, a portion of the
second electrode layer 13 being formed as the bottom 28 of the
blind hole. The blind hole or the passage 17 extends over the
insulation layer 14 and over the first electrode layer 13. The
passage 17 is in other words formed by the openings 15 and 16
arranged one over the other. In the embodiment shown, the openings
15 and 16 are not formed peripherally.
[0130] A soot particle 30 can enter the passage 17. In FIG. 1a, the
particle 30 is lying on the bottom 28 of the blind hole, and
consequently on a side 31 of the second electrode layer 13.
However, the particle 30 is not touching the first electrode layer
12 in the peripheral region 32, which bounds the opening 15. As a
result of the particle 30 being deposited on the bottom 28 and
touching the second electrode layer 13 on the side 31, the
electrical resistance is reduced. This drop in the resistance is
used as a measure of the accumulated mass of particles. When a
predefined threshold value with respect to the resistance is
reached, the sensor 10 is heated, so that the deposited particle 30
is burned and, after being burned free, the sensor 10 can detect
electrically conductive and/or polarizable particles in a next
detection cycle.
[0131] FIG. 1b likewise shows in a sectional representation a
sensor 10 for detecting electrically conductive and/or polarizable
particles, in particular for detecting soot particles. Likewise
shown are a first electrode layer 12 and a second electrode layer
13, which is arranged between the substrate 11 and the first
electrode layer 12. An insulation layer 14 is formed between the
first electrode layer 12 and the second electrode layer 13. With
respect to the properties and the design of the openings 15 and 16,
reference is made to the explanations in connection with the
embodiment according to FIG. 1a.
[0132] A covering layer 21, which is for example formed from
ceramic and/or glass and/or metal oxide, is formed on the side 20
of the first electrode layer 12 that is facing away from the
insulation layer 14. The covering layer 21 encloses the side face
22 of the first electrode layer 12, the side face 23 of the
insulation layer 14 and the side face 19 of the second electrode
layer 13. The covering layer 21 consequently covers the side faces
19, 22 and 23, so that the first electrode layer 12, the second
electrode layer 13 and the insulation layer 14 are laterally
insulated. The covering layer 21 consequently comprises an upper
portion 24, which is formed on the side 20 of the first electrode
layer 12, and a side portion 25, which serves for the lateral
insulation of the sensor 10.
[0133] FIG. 1c shows in a sectional representation a sensor 10 for
detecting electrically conductive and/or polarizable particles, in
particular for detecting soot particles. The sensor 10 comprises a
substrate 11, a first electrode layer 12 and a second electrode
layer 13, which is arranged between the substrate 11 and the first
electrode layer 12. An insulation layer 14 is formed between the
first electrode layer 12 and the second electrode layer 13. At
least one opening is respectively formed in the first electrode
layer 12 and in the insulation layer 14, the opening 15 in the
first electrode layer 12 and the opening 16 in the insulation layer
14 being arranged one over the other, so that a passage 17 to the
second electrode layer 13 is formed.
[0134] For the purposes of a high-temperature application, the
substrate 11 is formed for example from aluminum oxide
(Al.sub.2O.sub.3) or magnesium oxide (MgO) or from a titanate or
from steatite.
[0135] The second electrode layer 13 is connected to the substrate
11 indirectly by way of a bonding agent layer 18. The bonding agent
layer 18 may be for example very thinly formed aluminum oxide
(Al.sub.2O.sub.3) or silicon dioxide (SiO.sub.2).
[0136] In the exemplary embodiment, the first electrode layer 12 is
formed by a platinum layer. In the example shown, the second
electrode layer 13 consists of a platinum-titanium alloy (Pt--Ti).
The platinum-titanium alloy of the second electrode layer 13 is a
layer that is more resistant to etching in comparison with the
first electrode layer 12.
[0137] The insulation layer 14 consists of a thermally stable
material with a high insulation resistance. For example, the
insulation layer 14 may be formed from aluminum oxide
(Al.sub.2O.sub.3) or silicon dioxide (SiO.sub.2) or magnesium oxide
(MgO) or silicon nitride (Si.sub.3N.sub.4) or glass.
[0138] The distance between the first electrode layer 12 and the
second electrode layer 13 is formed by the thickness d of the
insulation layer 14. The thickness d of the insulation layer may be
0.5 .mu.m to 50 .mu.m. In the present case, the thickness d of the
insulation layer is 10 .mu.m. The sensitivity of the sensor 10
according to the invention can be increased by reducing the
distance between the first electrode layer 12 and the second
electrode layer 13, and consequently by reducing the thickness d of
the insulation layer 14.
[0139] A covering layer 21, which is for example formed from
ceramic and/or glass and/or metal oxide, is formed on the side 20
of the first electrode layer 12 that is facing away from the
insulation layer 14. The covering layer 21 encloses the side face
22 of the first electrode layer 12, the side face 23 of the
insulation layer 14 and the side face 19 of the second electrode
layer 13. The covering layer 21 consequently covers the side faces
19, 22 and 23, so that the first electrode layer 12, the second
electrode layer 13 and the insulation layer 14 are laterally
insulated. The covering layer 21 consequently comprises an upper
portion 24, which is formed on the side 20 of the first electrode
layer 12, and a side portion 25, which serves for the lateral
insulation of the sensor 10.
[0140] In a further embodiment of the invention it is conceivable
that the covering layer 21 also laterally encloses the substrate
11.
[0141] A porous filter layer 27 is formed on the side 26 of the
covering layer 21 that is facing away from the first electrode
layer 12. The sensitivity of the sensor 10 is increased as a result
of the formation of this passive porous filter or protective layer
27 which is facing the medium that is to be detected with regard to
electrically conductive and/or polarizable particles, since larger
particles or constituents that could disturb the measurement or
detection are kept away from the first electrode layer 12 and the
second electrode layer 13. Since the passage 17 is covered by the
porous filter layer 27, particles can still penetrate through the
pores in the porous filter layer 27, but short-circuits caused by
large penetrated particles can be avoided as a result of the porous
filter layer 27.
[0142] The passage 17 is formed as a blind hole, a portion of the
second electrode layer 13 being formed as the bottom 28 of the
blind hole. The blind hole or the passage 17 extends over the
insulation layer 14, the first electrode layer 13 and over the
covering layer 21. For this purpose, the covering layer 21 also has
an opening 29. In other words, the passage 17 is formed by the
openings 29, 15 and 16 arranged one over the other.
[0143] As a result of the choice of materials for the individual
layers and the insulation of the individual layers from one
another, the sensor 10 shown is suitable for a high-temperature
application of up to for example 850.degree. C. The sensor 10 can
accordingly be used as a soot particle sensor in the exhaust-gas
flow of an internal combustion engine.
[0144] After penetrating through the porous filter layer 27, a soot
particle 30 can enter the passage 17. In FIG. 1c, the particle 30
lies on the bottom 28 of the blind hole, and consequently on a side
31 of the second electrode layer 13. However, the particle is not
touching the first electrode layer 12 in the peripheral region 32,
which bounds the opening 15. As a result of the particle 30 being
deposited on the bottom 28 and touching the second electrode layer
13 on the side 31, the electrical resistance is reduced. This drop
in the resistance is used as a measure of the accumulated mass of
particles. When a predefined threshold value with respect to the
resistance is reached, the sensor 10 is heated, so that the
deposited particle 30 is burned and, after being burned free, the
sensor 10 can detect electrically conductive and/or polarizable
particles in a next detection cycle.
[0145] FIG. 2 shows a perspective view of a sensor 10. The sensor
has nine passages 17. For better illustration, the porous filter
layer 27 is not shown in FIG. 2. The upper portion 24 of the
covering layer 21 and also the side portion 25 of the covering
layer 21 can be seen. The bottoms 28 of the passages 17 are formed
by portions of the second electrode layer 13. The nine passages 17
have a square cross section, it being possible for the square cross
section to have a surface area of 15.times.15 .mu.m.sup.2 to
50.times.50 .mu.m.sup.2.
[0146] The first electrode layer 12 has an electrical contacting
area 33. The second electrode layer 13 likewise has an electrical
contacting area 34. The two electrical contacting areas 33 and 34
are free from sensor layers arranged over the respective electrode
layers 12 and 13. The electrical contacting areas 33 and 34 are or
can in each case be connected to a terminal pad (not shown).
[0147] The second electrode layer 13 has an additional electrical
contacting area 35, which is likewise free from sensor layers
arranged over the electrode layer 13. This additional electrical
contacting area 35 may be connected to an additional terminal pad.
The additional electrical contacting area 35 is necessary to allow
the second electrode layer 13 to be used as a heating coil or as a
temperature-sensitive layer or as a shielding electrode. Depending
on the contacting assignment (see FIG. 3) of the electrical
contacting areas 34 and 35, the second electrode layer 13 may
either heat and burn the particle 30 or detect the particle 30.
[0148] To be able to use an electrode layer, here the second
electrode layer 13, as a heating coil and/or temperature-sensitive
layer and/or shielding electrode, the second electrode layer 13 has
a small number of strip conductor loops 36.
[0149] In FIG. 4, a further embodiment of a possible sensor 10 is
shown. The first electrode layer 12 and the insulation layer 14 are
respectively formed as porous, the at least one opening 15 in the
first electrode layer 12 and the at least one opening 16 in the
insulation layer 14 respectively being formed by at least one pore,
the pore 41 in the insulation layer 14 and the pore 40 in the first
electrode layer 12 being arranged at least in certain portions one
over the other in such a way that the at least one passage 17 to
the second electrode layer 13 is formed. In other words, it is
possible to dispense with an active or subsequent structuring of
the passages, the first electrode layer 12 and the insulation layer
14 being formed as permeable to the medium to be measured. The
passages 17 are represented in FIG. 4 with the aid of the vertical
arrows.
[0150] The passages 17 may be formed by a porous or granular
structure of the two layers 12 and 14. Both the first electrode
layer 12 and the insulation layer 14 can be produced by sintering
together individual particles, with pores 40 and 41 or voids for
the medium to be measured being formed while they are being
sintered together. Accordingly, a passage 17 that allows access to
the second electrode layer 13 for a particle 30 that is to be
measured or detected must be formed, extending from the side 20 of
the first electrode layer 12 that is facing away from the
insulation layer 14 to the side 31 of the second electrode layer 13
that is facing the insulation layer 14 as a result of the
one-over-the-other arrangement of pores 40 and 41 in the first
electrode layer 12 and in the insulation layer 14.
[0151] In the example shown, the second electrode layer 13 is
completely enclosed on the side face 19 by the porous insulation
layer 14. The second electrode layer 13 is accordingly covered on
the side 31 and on the side faces 19 by the porous insulation layer
14. The porous first electrode layer 12 on the other hand encloses
the porous insulation layer 14 on the side face 23 and on the side
37 facing away from the second electrode layer 13. The insulation
layer 14 is accordingly covered on the side 37 and on the side
faces 23 by the first electrode layer 12.
[0152] If this sensor 10 has a covering layer, this covering layer
is also to be formed as porous in such a way that a pore in the
covering layer, a pore 40 in the first electrode layer 12 and a
pore 41 in the insulation layer 14 form a passage 17 to the second
electrode layer 13.
[0153] In FIG. 5, a section through a sensor 10 for detecting
electrically conductive and/or polarizable particles, in particular
for detecting soot particles, is shown. The sensor 10 can in
principle be used for detecting particles in gases and in liquids.
The sensor 10 comprises a substrate 11, a first electrode layer 12,
a second electrode layer 13, which is arranged between the
substrate 11 and the first electrode layer 12, a first insulation
layer 14 being formed between the first electrode layer 12 and the
second electrode layer 13.
[0154] At least a third electrode layer 50 is formed between the
first insulation layer 14 and the first electrode layer 12, at
least a second insulation layer 60 being formed between the third
electrode layer 50 and the first electrode layer 12.
[0155] According to sensor 10 of FIG. 5, therefore at least three
electrode layers 12, 13, 50 and at least two insulation layers 14,
60 are formed. The first electrode layer 12 is in this case the
electrode layer that is arranged furthest away from the substrate
11. The second electrode layer 13 on the other hand is connected
directly to the substrate 11. It is possible that the second
electrode layer 13 is connected indirectly to the substrate 11,
preferably by means of a bonding agent layer.
[0156] In the embodiment according to FIG. 5, a fourth electrode
layer 51 is also formed and also a third insulation layer 61. The
sensor 10 consequently comprises altogether four electrode layers,
to be specific the first electrode layer 12, the second electrode
layer 13, and also the third electrode layer 50 and the fourth
electrode layer 51. Insulation layers are respectively formed
between the electrode layers (12, 13, 50, 51), to be specific the
first insulation layer 14, the second insulation layer 60 and also
the third insulation layer 61. The sensor 10 also comprises a
covering layer 21, which is formed on the side of the first
electrode layer 12 that is facing away from the substrate 11.
[0157] At least one opening 15, 16, 70, 71, 72, 73 is respectively
formed in the first electrode layer 12, in the third insulation
layer 61, in the fourth electrode layer 51, in the second
insulation layer 60, in the third electrode layer 50 and in the
first insulation layer 14. The covering layer 21 also has an
opening 29. The opening 15 in the first electrode layer 12, the
opening 73 in the third insulation layer 61, the opening 72 in the
fourth electrode layer 51, the opening 71 in the second insulation
layer 60, the opening 70 in the third electrode layer 50 and the
opening 16 in the first insulation layer 14 are arranged at least
in certain portions one over the other in such a way that at least
one passage 17 to the second electrode layer 13 is formed.
[0158] The distance between the electrode layers 12, 13, 50 and 51
is formed by the thickness of the insulation layers 14, 60 and 61.
The thickness of the insulation layers 14, 60 and 61 may be 0.1
.mu.m to 50 .mu.m. The sensitivity of the sensor 10 according to
the invention can be increased by reducing the distance between the
electrode layers 12, 13, 50 and 51, and consequently by reducing
the thickness of the insulation layers 14, 60 and 61.
[0159] The passage 17 is formed as a blind hole, a portion of the
second electrode layer 13 being formed as the bottom 28 of the
blind hole. The blind hole or the passage 17 extends over the first
insulation layer 14, the third electrode layer 50, the second
insulation layer 60, the fourth electrode layer 51, the third
insulation layer 61, the first electrode layer 12 and over the
covering layer 21. In other words, the passage 17 is formed by the
openings 16, 70, 71, 72, 73, 15 and 29 arranged over one another.
In the embodiment shown, the openings 16, 70, 71, 72, 73, 15 and 29
are not formed peripherally. A perspective section through a
passage 17 is shown.
[0160] A small soot particle 30 for example can enter the passage
17. In FIG. 5, the particle 30 is lying on the bottom 28 of the
blind hole, and consequently on a side 31 of the second electrode
layer 13. The particle 30 is also touching the third electrode
layer 50. If the determination of particles is performed on the
basis of the resistive principle, the resistance between the second
electrode layer 13 and the third electrode layer 50 is measured,
this resistance decreasing if the particle 30 bridges the two
electrode layers 13 and 50. The size of the particle 30 is
consequently relatively small.
[0161] The soot particle 30' has also entered the passage 17. The
particle 30' is lying on the bottom 28 of the blind hole, and
consequently on the side 31 of the second electrode layer. The
particle 30' is also touching the third electrode layer 50, the
fourth electrode layer 51 and also the first electrode layer 12.
The particle 30' consequently bridges a number of electrode layers,
in the example shown all of the electrode layers 12, 13, 50 and 51,
so that the particle 30' is detected as a particle that is larger
in comparison with the particle 30.
[0162] By applying different voltages to the electrode layers 12,
13, 50 and 51, different particle properties, in particular
different soot properties, such as for example the diameter and/or
the size of the (soot) particle and/or the charging of the (soot)
particle and/or the polarizability of the (soot) particle, can be
measured.
[0163] Various embodiments of openings 80 are shown in FIGS. 6a to
6f. The openings 80 may be formed both in insulation layers 14, 60
and 61 and in electrode layers 12, 50 and 51. Accordingly, the
openings 80 that are shown may be an arrangement of openings 15 in
a first electrode layer 12, openings 16 in a first insulation layer
14, openings 70 in a third electrode layer 50, openings 71 in a
second insulation layer 60, openings 72 in a fourth electrode layer
51 and also openings 73 in a third insulation layer 61.
[0164] Preferably, the openings 80 in a laminate of the sensor 10
are formed similarly. The individual layers 12, 14, 21, 50, 51, 60
and 61 are arranged one over the other in such a way that the
openings 15, 16, 29, 70, 71, 72 and 73 form passages 17. As a
result of the openings shown in FIGS. 6a to 6d, elongate
depressions 17' and 17'' are respectively formed.
[0165] In FIG. 6a, linear openings 80 are formed, the openings 80
being formed parallel to one another and all pointing in the same
predominant direction.
[0166] In FIG. 6b, a layer of the sensor 10 is subdivided into a
first portion 45 and a second portion 46. All of the openings 80,
80' shown are formed as linear clearances, with both the openings
80 in the first portion 45 being formed parallel to one another,
and the openings 80' in the second portion 46 being formed parallel
to one another. The openings 80 in the first portion 45 run
parallel in the horizontal direction or parallel to the width b of
the sensor layer, whereas the openings 80' in the second portion 46
run parallel in the vertical direction or parallel to the length l
of the sensor layer. The openings 80' in the second portion 46 run
in a perpendicular direction in relation to the openings 80 in the
first portion 45.
[0167] In FIG. 6c, likewise a number of openings 80, 80', 80'' are
shown in the form of elongate clearances. In a central portion 47,
a number of linear openings 80' running in the vertical direction
are shown, in the example shown eight openings, which are formed
parallel to the length l of the sensor layer. These openings are
surrounded by further openings 80, 80'', forming a frame-like
portion 48. First openings 80'' are in this case formed parallel to
the openings 80' of the central portion 47. Further openings 80 are
formed perpendicularly in relation to the openings 80, 80''. The
openings 80'' are of different lengths, so that the layer of the
sensor 10 can be formed with a largest possible number of openings
80.
[0168] In FIG. 6d, a sensor layer with an elongate through-opening
80 is shown, the opening 80 running in a meandering manner.
[0169] In FIG. 6e, a further sensor layer with a number of
vertically running openings 80' and a number of horizontally
running openings 80 is shown. The vertical openings 80' and the
horizontal openings 80 form a grid structure.
[0170] Apart from rectangular grid structures, other angular
arrangements can also be produced, or geometries in which the grid
or network structure has round, circular or oval shapes.
Furthermore, corresponding combinations of the structures, which
may be regular, periodic or irregular, can be created.
[0171] In FIG. 6f, a sensor layer with an elongate through-opening
80 is shown, the opening 80 running spirally. Apart from
rectangular geometries, circular, oval geometries or combinations
thereof can also be produced.
[0172] In each case a number of layers, which respectively have
openings 80, 80', 80'' according to an embodiment of FIG. 6a, 6b,
6c, 6d, 6e or 6f, are arranged in layers one over the other, so
that passages in the form of elongate depressions 17' and 17'' are
respectively formed in a sensor.
[0173] As shown in FIG. 7a, a sensor 10 is introduced into a fluid
flow in such a way that the direction of flow a of the particles
does not impinge perpendicularly on the plane (x, y) of the
electrode layers. The angle .alpha. between the normal (z) to the
plane (x, y) of the first electrode layer and the direction of flow
of the particles is in this case at least 1 degree, preferably at
least 10 degrees, particularly preferably at least 30 degrees. The
particles can consequently be guided more easily into the elongate
depressions 17', 17'', and consequently more easily to the walls of
the openings of the electrode layers 12, 50, 51 formed therein.
[0174] In FIG. 7b, a sensor 10 has thus been introduced into a
fluid flow in such a way that the angle .beta. between the
direction of flow a of the particles and the longitudinal axis x of
the elongate depressions lies between 20 and 90 degrees.
[0175] In FIGS. 8a and 8b, a cross section which is taken
perpendicularly to the sensor 10, that is to say beginning from the
uppermost insulation or covering layer 21 to the substrate 11, is
respectively shown. The sensors 10 of FIGS. 8a and 8b have four
electrode layers, to be specific a first electrode layer 12, a
second electrode layer 13 and also a third electrode layer 50 and a
fourth electrode layer 51. Also formed are three insulation layers,
to be specific a first insulation layer 14, a second insulation
layer 60 and also a third insulation layer 61.
[0176] In the sensor 10 according to FIG. 8a, the cross-sectional
profiles of two passages in the form of elongate depressions 17',
17'' are shown. The left passage 17' has a V-shaped cross section
or a V-shaped cross-sectional profile. The right passage 17'' on
the other hand has a U-shaped cross section or a U-shaped
cross-sectional profile. The sizes of the openings or cross
sections of the openings decrease from the covering layer 21 in the
direction of the second electrode layer 13. The cross sections of
the openings 29, 15, 73, 72, 71, 70 and 16 become increasingly
smaller from the first cross section of an opening 29 in the
direction of the lowermost cross-sectional opening 16.
[0177] With the aid of the V-shaped and U-shaped cross-sectional
profiles, the measurements of round particles are improved.
[0178] In FIG. 8b it is also shown that the passages 17', 17'' can
have different widths. The left passage 17' has a width B1. The
right passage 17'' shown has a width B2. B1 is greater than B2. As
a result of passages 17', 17'' formed with different widths,
size-specific measurements of the particles 30 can be carried
out.
[0179] In FIG. 9, undercuts in insulation layers 14, 21, 60, 61 or
set-back insulation layers 14, 21, 60, 61 are shown in cross
section. In the case of round particles, the formation of level or
smooth passage surfaces is unfavorable. The measurement of round
particles can be improved by the formation of undercuts or set-back
insulation layers.
[0180] The left passage 17' shown has a first insulation layer 14,
a second insulation layer 60 and also a third insulation layer 61
and a covering layer 21, which also serves as an insulation layer.
The insulation layers 14, 60, 61 and 21 have undercuts or
clearances 90. The size of the openings 16, 71, 73 and 29 in the
insulation layers 14, 60, 61 and 21 are consequently greater than
the openings 70, 72 and 15 in the electrode layers 12, 50 and 51
that are respectively formed over and under the insulation layers
14, 60, 61 and 21.
[0181] This also applies in connection with the passage 17'' shown
on the right. In this case, the insulation layers 14, 16, 61 and 21
are formed as set-back in comparison with the electrode layers 50,
51 and 12. The openings 16, 71 or 73 in an insulation layer 14, 60
or 61 is formed larger in each case than an opening 70, 72 or 15
formed thereover in an electrode layer 50, 51 or 12 arranged over
the respective insulation layer. Since the cross-sectional profile
of the right passage 17'' is formed in a V-shaped manner and the
openings in all the layers 21, 12, 61, 51, 60, 50 and 14 become
smaller in the direction of the substrate 11, the openings 16, 71,
73 and 29 in the insulation layers 14, 60, 61 and 21 are not of
coinciding sizes.
[0182] It should be pointed out in connection with the sensors 10
shown in FIGS. 5, 8a, 8b and 9 that it is possible that only two
uppermost electrode layers have to be made accessible within a
passage. In other words, in a method, preferably according to the
invention, a passage 17, 17', 17'' that is merely formed with
respect to the uppermost electrode layers 12 and 51 may be formed
in a sensor 10.
[0183] It is also possible that a sensor 10 comprises a number of
passages 17, 17', 17'', at least a first passage merely reaching as
far as the fourth electrode layer 51. The fourth electrode layer 51
or the second insulation layer 60 forms the bottom of this passage
formed.
[0184] A second passage reaches as far as the third electrode layer
50. The third electrode layer 50 or the first insulation layer 14
forms the bottom of the passage formed. A third passage reaches as
far as the second electrode layer 13. The second electrode layer 13
forms the bottom of the passage formed.
[0185] This embodiment can be carried out or can be formed
independently of the features of the sensors 10 shown in FIGS. 5,
8a, 8b and 9.
[0186] The exploded representations of FIGS. 10a to 10d illustrate
that a number of openings can be formed in a number of layers of
the sensor 10, the layers being arranged one over the other in such
a way that the openings are also formed one over the other, so that
passages 17, 17' and 17'' can be formed.
[0187] The sensors 10 shown comprise a substrate 11, a second
electrode layer 13 arranged thereupon, a first electrode layer 12
and also a first insulation layer 14, which is arranged between the
first electrode layer 12 and the second electrode layer 13. A first
covering layer 21 and also a second covering layer 42 are formed on
the first electrode layer 12. The first electrode layer 13 does not
have an arrangement of openings for the forming of passages (see
FIG. 10a).
[0188] Gaps 95 are formed within the second electrode layer 13. The
first insulation layer 14 is arranged on the second electrode layer
13 in such a way that the openings 16 in the first insulation layer
14 are not arranged above the gaps 95.
[0189] On the other hand, the first electrode layer 12 is arranged
in such a way that the openings 15 in the first electrode layer 12
are arranged above the openings 16 in the first insulation layer
14. With the aid of the openings 15 in the first electrode layer 12
and the openings 16 in the first insulation layer 14, passages 17
are formed, the side 31 of the first electrode layer 13 serving as
the bottom 28 of the passages, in particular of blind holes and/or
elongate depressions 17', 17''.
[0190] In FIG. 10b, the arrangement of the openings 15 and 16 in
relation to one another is shown in an enlarged representation. It
can be seen that a first portion 45 and a second portion 46 with
openings 15 and 16 are respectively formed both in the first
insulation layer 14 and in the first electrode layer 12. The
openings 15 and 16 arranged one over the other form in each case
blind-hole-like passages 17.
[0191] Also in FIG. 10c, a first portion 45 and a second portion 46
are respectively formed in the first insulation layer 14 and also
in the first electrode layer 12. Elongate openings 15, 16 are
respectively formed in the portions 45 and 46, the elongate
openings 15 and 16 being oriented in the same directions.
[0192] According to the representation of FIG. 10d it is possible
that the elongate openings 15 and 16 can also be aligned
perpendicularly in relation to the orientations shown in FIG.
10c.
[0193] It is pointed out that some of the sensors 10 shown (FIGS.
1a-1c, FIG. 4, FIG. 5, FIGS. 8a-b and FIG. 9) are in each case only
shown as a detail. The measurement of the particles preferably
takes place only in the passages 17, 17', 17'' and not on side
edges/side faces of the sensor and not on side faces/side edges of
the sensor layers.
[0194] It is also possible that, in a further embodiment of the
invention, all of the sensors 10 shown do not have an upper
insulation layer/covering layer 21 and/or do not have a filter
layer 27. If sensors 10 do not have an upper insulation
layer/covering layer 21 and/or do not have a filter layer 27, large
particles have no influence on the signal or on the measurement
result.
[0195] With regard to a possible production process in connection
with the sensors 10 according to the invention of FIGS. 1a-c, 2, 4,
5, 8a-b, 9 and FIGS. 10a-d, reference is made to the production
possibilities already described, in particular to etching processes
and/or laser machining processes.
[0196] At this stage it should be pointed out that all of the
elements and components described above in connection with the
embodiments according to FIGS. 1a to 10d are essential to the
invention on their own or in any combination, in particular the
details that are shown in the drawings.
LIST OF DESIGNATIONS
[0197] 10 Sensor [0198] 11 Substrate [0199] 12 First electrode
layer [0200] 13 Second electrode layer [0201] 14 First insulation
layer [0202] 15 Opening in first electrode layer [0203] 16 Opening
in first insulation layer [0204] 17 Passage [0205] 17', 17''
Elongate depression [0206] 18 Bonding agent layer [0207] 19 Side
face of second electrode layer [0208] 20 Side of the first
electrode layer [0209] 21 Covering layer [0210] 22 Side face of
first electrode layer [0211] 23 Side face of insulation layer
[0212] 24 Upper portion of covering layer [0213] 25 Side portion of
covering layer [0214] 26 Side of covering layer [0215] 27 Porous
filter layer [0216] 28 Bottom [0217] 29 Opening in covering layer
[0218] 30, 30' Particle [0219] 31 Side of second electrode layer
[0220] 32 Peripheral region of first electrode layer [0221] 33
Electrical contacting area of first electrode layer [0222] 34
Electrical contacting area of second electrode layer [0223] 35
Additional electrical contacting area of second electrode layer
[0224] 36 Strip conductor loop [0225] 37 Side of insulation layer
[0226] 40 Pore in first electrode layer [0227] 41 Pore in
insulation layer [0228] 42 Second covering layer [0229] 45 First
portion [0230] 46 Second portion [0231] 47 Central portion [0232]
48 Frame-like portion [0233] 50 Third electrode layer [0234] 51
Fourth electrode layer [0235] 60 Second insulation layer [0236] 61
Third insulation layer [0237] 70 Opening in third electrode layer
[0238] 71 Opening in second insulation layer [0239] 72 Opening in
fourth electrode layer [0240] 73 Opening in third insulation layer
[0241] 80, 80', 80'' Opening [0242] 90 Undercut [0243] 95 Gap
[0244] a Direction of flow [0245] b Width of sensor layer [0246] l
Length of sensor layer [0247] B1 Width of passage [0248] B2 Width
of passage [0249] d Thickness of insulation layer [0250] x
Longitudinal axis of the elongate depressions [0251] .alpha. Angle
between the normal to the electrode plane and the direction of flow
[0252] .beta. Angle between the longitudinal axis and the direction
of flow
* * * * *