U.S. patent application number 12/084958 was filed with the patent office on 2009-11-12 for jetting apparatus and method of improving the performance of a jetting apparatus.
This patent application is currently assigned to MYDATA AUTOMATION AB. Invention is credited to William Holm, Johan Kronstedt, Hakan Sandell.
Application Number | 20090278875 12/084958 |
Document ID | / |
Family ID | 37709751 |
Filed Date | 2009-11-12 |
United States Patent
Application |
20090278875 |
Kind Code |
A1 |
Holm; William ; et
al. |
November 12, 2009 |
Jetting Apparatus and Method of Improving the Performance of a
Jetting Apparatus
Abstract
The present invention is generally related to a jetting device
for jetting droplets of viscous medium onto a substrate, said
jetting device comprising an ejector element for performing the
jetting process and a jetting outlet through which said droplets
are jetted. In particular, the invention is related to a method, a
measuring device, a jetting device, and a viscous medium container
for use in such a jetting device for measuring or monitoring a
level or volume of viscous medium during a jetting process and/or
measuring electrical properties of the viscous medium to determine
characteristics of the medium.
Inventors: |
Holm; William; (Alvsjo,
SE) ; Sandell; Hakan; (Taby, SE) ; Kronstedt;
Johan; (Sollentuna, SE) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
MYDATA AUTOMATION AB
Bromma
SE
|
Family ID: |
37709751 |
Appl. No.: |
12/084958 |
Filed: |
November 14, 2006 |
PCT Filed: |
November 14, 2006 |
PCT NO: |
PCT/EP2006/010922 |
371 Date: |
May 14, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60735898 |
Nov 14, 2005 |
|
|
|
Current U.S.
Class: |
347/10 ;
347/104 |
Current CPC
Class: |
B23K 3/082 20130101;
B05B 7/0408 20130101; B05C 5/022 20130101; B05B 17/0623 20130101;
B05C 11/1034 20130101; B23K 3/0623 20130101; B05C 5/0225 20130101;
B05B 17/06 20130101; B05B 7/0483 20130101 |
Class at
Publication: |
347/10 ;
347/104 |
International
Class: |
B41J 29/38 20060101
B41J029/38; B41J 2/01 20060101 B41J002/01 |
Claims
1-33. (canceled)
34. A method for a jetting device for jetting droplets of viscous
medium onto a substrate, said jetting device comprising an ejector
element for performing the jetting process and a jetting outlet
through which said droplets are jetted, said method comprising the
steps of: generating at least one electromagnetic signal in a
detachable viscous medium container mounted in said jetting device,
wherein a magnetic element is provided in or adjacent to said
viscous medium container such that a magnetic field is generated in
said viscous medium container, said magnetic element being movable
as a response of a change of quantity of said viscous medium in
said viscous medium container; measuring a response signal to said
generated electromagnetic signal in said viscous medium container
including: detecting said generated magnetic field in said viscous
medium container; and producing at least one signal being
proportional to a present quantity of viscous medium in said
viscous medium container; determining a level of viscous medium in
said viscous medium container using said response signal; providing
a first conductive element in a passage between said container and
an ejector chamber of said ejector element such that said first
conductive element is in contact with said viscous medium;
providing a second conductive element in a passage between said
container and an ejector chamber of said ejector element such that
said second conductive element is in contact with said viscous
medium; applying an electrical current between said at least one
first conducting element and said at least one second conducting
element; and measuring an impedance of the viscous medium in said
passage between said container and said ejector chamber to the
applied electrical current.
35. A method for a jetting device for jetting droplets of viscous
medium onto a substrate, said jetting device comprising an ejector
element for performing the jetting process and a jetting outlet
through which said droplets are jetted, said method comprising the
steps of: generating at least one electromagnetic signal in a
detachable viscous medium container mounted in said jetting device,
wherein a magnetic element is provided in or adjacent to said
viscous medium container such that a magnetic field is generated in
said viscous medium container, said magnetic element being movable
as a response of a change of quantity of said viscous medium in
said viscous medium container; measuring a response signal to said
generated electromagnetic signal in said viscous medium container
including: detecting said generated magnetic field in said viscous
medium container; and producing at least one signal being
proportional to a present quantity of viscous medium in said
viscous medium container; determining a level of viscous medium in
said viscous medium container using said response signal; providing
at least one first conducting element in said viscous medium
container; providing at least one second conducting element in said
viscous medium container; applying an electrical current between
said at least one first conducting element and said at least one
second conducting element; and measuring an impedance of the
viscous medium in said viscous medium container to the applied
electrical current.
36. The method according to claim 35, wherein the step of providing
conducting elements in said viscous medium container comprises the
steps of: arranging a first longitudinal conductive strip at an
inner wall of said viscous medium container in a longitudinal
direction; arranging a second longitudinal conductive strip at an
inner wall of said viscous medium container in said longitudinal
direction substantially parallel to said first conductive strip;
connecting said first conductive strip to a signal generator and a
signal processing unit; and connecting said second conductive strip
to said signal generator.
37. The method according to claim 35, wherein the step of providing
conducting elements in said viscous medium container comprises the
steps of: arranging a first array of conductive elements at an
inner wall of said viscous medium container in a longitudinal
direction, said elements of said first array being arranged in a
line and electrically separated from each other; arranging a second
array of conductive elements at an inner wall of said viscous
medium container in said longitudinal direction substantially
parallel with said first array, said elements of said second array
being arranged in a line and electrically separated from each
other; connecting said elements of said first array to a signal
generator and a signal processing unit; and connecting said
elements of said second array to said signal generator.
38. The method according to claim 34, wherein the step of measuring
a response signal comprises the steps of: detecting a hall effect
caused by said generated magnetic field being proportional to a
quantity of viscous medium in said viscous medium container; and
producing at least one signal being proportional to a present
quantity of viscous medium in said viscous medium container using
said detected hall effect.
39. The method according to claim 38, wherein said step of
determining a level of viscous medium in said viscous medium
container comprises the steps of: combining at least one signal
from one or more of said hall effect sensors to determine a
position of said magnetic element in said viscous medium container;
and determining a level of viscous medium in said viscous medium
container using said position determination of the magnetic
element.
40. The method according to claim 34, further comprising the step
of arranging said magnetic element in a plunger arranged to be
positioned in said viscous medium container and adapted to apply a
press on said viscous medium of said viscous medium container
during a jetting operation.
41. The method according to claim 34, wherein said applied current
comprises at least one current waveform including a DC component,
wherein the step of determining a level of viscous medium in said
viscous medium container comprises the steps of: measuring the
resistive component of said impedance, said resistive component of
said impedance being proportional to level of viscous medium in
said viscous medium container; and determining the level of viscous
medium in said viscous medium container using said resistive
component.
42. The method according to claim 34, wherein said applied current
comprises at least one current waveform including an AC component,
further comprising the steps of: measuring a reactive or a
capacitive component of said impedance over a predetermined
frequency range; determining a complex impedance using said
resistive component and said reactive or capacitive component of
said impedance; and using said complex impedance and/or said
reactive or capacitive component of said impedance to determine
characteristic features of said viscous medium.
43. The method according to claim 34, further comprising the step
of: determining electrical properties of said viscous medium, said
electrical properties including permittivity, loss factor, or
dielectric constant.
44. The method according to claim 34, wherein said characteristic
features includes a degree of oxidation of particles in said
viscous medium, or content of lead.
45. A measuring device for a jetting device for jetting droplets of
viscous medium onto a substrate, said jetting device comprising an
ejector element for performing the jetting process and a jetting
outlet through which said droplets are jetted, said measuring
device comprising: signal generating circuit adapted to generate an
electromagnetic signal in a detachable viscous medium container
mounted in said jetting device, said signal generating circuit
comprising a magnetic element adapted to be arranged in or adjacent
to said viscous medium container and to generate a magnetic field
in said viscous medium container, said magnetic element being
movable as a response of a change of quantity of said viscous
medium in said viscous medium container; signal measuring circuit
adapted to measure a response signal to said generated
electromagnetic signal in said viscous medium container, wherein
said signal measuring circuit is adapted to: detect said generated
magnetic field in said viscous medium container, and produce at
least one signal being proportional to a present quantity of
viscous medium in said viscous medium container; and a signal
processing circuit connected to said signal measuring circuit and
being adapted to determine a level of viscous medium in said
viscous medium container using said response signal, said signal
processing circuit being connectable to: at least one first
conducting element arranged in a passage between said container and
an ejector chamber of said ejector element; and at least one second
conducting element arranged in said in a passage between said
container and an ejector chamber of said ejector element; wherein
said signal generating circuit is adapted to apply an electrical
current between said at least one first conducting element and said
at least one second conducting element; and wherein said signal
measuring circuit including an impedance measuring circuit adapted
to measure an impedance of the viscous medium in said passage
between said container and said ejector chamber to the applied
electrical current.
46. A measuring device for a jetting device for jetting droplets of
viscous medium onto a substrate, said jetting device comprising an
ejector element for performing the jetting process and a jetting
outlet through which said droplets are jetted, said measuring
device comprising: signal generating circuit adapted to generate an
electromagnetic signal in a detachable viscous medium container
mounted in said jetting device, said signal generating circuit
comprising a magnetic element adapted to be arranged in or adjacent
to said viscous medium container and to generate a magnetic field
in said viscous medium container, said magnetic element being
movable as a response of a change of quantity of said viscous
medium in said viscous medium container; signal measuring circuit
adapted to measure a response signal to said generated
electromagnetic signal in said viscous medium container, wherein
said signal measuring circuit is adapted to: detect said generated
magnetic field in said viscous medium container, and produce at
least one signal being proportional to a present quantity of
viscous medium in said viscous medium container; and wherein said
signal generating circuit further comprises a signal generator
connectable to: at least one first conducting element adapted to be
arranged in said viscous medium container; at least one second
conducting element adapted to be arranged in said viscous medium
container; wherein said signal generator is, when connected to said
conductive elements, adapted to apply an electrical current between
said at least one first conducting element and said at least one
second conducting element; and wherein said signal measuring
circuit includes an impedance measuring circuit adapted to measure
an impedance of the viscous medium in said viscous medium container
to the applied electrical current.
47. The measuring device according to claim 46, wherein said at
least one first conducting element is a first longitudinal
conductive strip adapted to be arranged at an inner wall of said
viscous medium container in a longitudinal direction and connected
to said signal generator and said signal processing circuit; said
at least one second conducting element is a second longitudinal
conductive strip adapted to be arranged at an inner wall of said
viscous medium container in said longitudinal direction
substantially parallel to said first conductive strip and connected
to said signal generator.
48. The measuring device according to claim 46, wherein said at
least one first conducting element is a first array of conductive
elements adapted to be arranged at an inner wall of said viscous
medium container in a longitudinal direction, said elements of said
first array being arranged in a line and electrically separated
from each other and connected to said signal generator and said
signal processing circuit; said at least one second conducting
element is a second array of conductive elements adapted to be
arranged at an inner wall of said viscous medium container in said
longitudinal direction substantially parallel to said first
conductive array, said elements of said second array being arranged
in a line and electrically separated from each other and connected
to said signal generator.
49. The measuring device according to claim 45, wherein said signal
measuring circuit comprises an array of hall effect sensors adapted
to be arranged in a longitudinal direction parallel with said
viscous medium container, said hall effect sensors being adapted
to: detect a hall effect caused by said generated magnetic field
being proportional to a quantity of viscous medium in said viscous
medium container; and produce at least one signal being
proportional to a present quantity of viscous medium in said
viscous medium container using said detected hall effect.
50. The measuring device according to claim 49, wherein said signal
processing circuit is adapted to: combine a signal from one or more
of said hall effect sensors to determine a position of said
magnetic element in said viscous medium container; and determine a
level of viscous medium in said viscous medium container using said
position determination of the magnetic element.
51. The measuring device according to claim 45, wherein said
magnetic element is arranged in a plunger arranged to be positioned
in said viscous medium container and adapted to apply press on said
viscous medium of said viscous medium container during a jetting
operation.
52. The measuring device according to claim 45, wherein said signal
generator is adapted to apply an electrical current comprising at
least one current waveform including a DC component; wherein said
impedance measuring circuit is adapted to measure the resistive
component of said impedance, said resistive component of said
impedance being proportional to level of viscous medium in said
viscous medium container; and wherein said signal processing
circuit is adapted to determine the level of viscous medium in said
viscous medium container using said resistive component.
53. The measuring device according to claim 45, wherein said signal
generator is adapted to apply an electrical current comprising at
least one current waveform including an AC component; wherein said
impedance measuring circuit is adapted to measure a reactive or a
capacitive component of said impedance over a predetermined
frequency range; wherein said impedance measuring circuit is
adapted to determine a complex impedance using said resistive
component and said reactive or capacitive component of said
impedance; and wherein analyzing circuit connected to said
impedance measuring circuit is adapted to use said complex
impedance and/or said reactive or capacitive component of said
impedance to determine characteristic features of said viscous
medium.
54. The measuring device according to claim 45, wherein said signal
processing circuit is adapted to determine electrical properties of
said viscous medium, said electrical properties including
permittivity, loss factor, or dielectric constant.
55. The measuring device according to claim 45, wherein said
characteristic features includes a degree of oxidation of particles
in said viscous medium, or content of lead.
56. A jetting device for jetting droplets of viscous medium onto a
substrate, said jetting device comprising an ejector element for
performing the jetting process and a jetting outlet through which
said droplets are jetted, said jetting device further comprising a
measuring device in accordance with claim 45.
57. A viscous medium container for holding a viscous medium adapted
to be attached in a jetting device for jetting droplets of said
viscous medium onto a substrate, said jetting device comprising an
ejector element for performing the jetting process and a jetting
outlet through which said droplets are jetted, said viscous medium
container comprising: at least one first conducting element
arranged at an inner wall; at least one second conducting element
arranged at an inner wall; and wherein said viscous medium
container is adapted to comprise an electrically conducting
plunger, which plunger is adapted to apply press on said viscous
medium of said viscous medium container during a jetting operation,
and wherein said plunger is arranged to short-circuit said at least
one first conducting element and said at least one second
conducting element; and wherein said at least one first conducting
element and said at least one second conducting element is
connectable to a signal processing circuit adapted to, at detection
of current flowing between said at least one first conducting
element and said at least one second conducting element, determine
the level of viscous medium in said viscous medium container using
a short-circuiting position of said plunger.
58. The viscous medium container according to claim 57, wherein
said at least one first conducting element is a first longitudinal
conductive strip arranged at an inner wall of said viscous medium
container in a longitudinal direction substantially parallel to
said first conductive strip and connectable to said signal
generator and said signal processing circuit; and said at least one
second conducting element is a second longitudinal conductive strip
arranged at an inner wall of said viscous medium container in said
longitudinal direction and connectable to said signal
generator.
59. The viscous medium container according to claim 57, wherein
said at least one first conducting element is a first array of
conductive elements arranged at an inner wall of said viscous
medium container in a longitudinal direction, said elements of said
first array being arranged in a line and electrically separated
from each other and connectable to said signal generator and said
signal processing circuit; said at least one second conducting
element is a second array of conductive elements arranged at an
inner wall of said viscous medium container in said longitudinal
direction substantially parallel to said first conductive array,
said elements of said second array being arranged in a line and
electrically separated from each other and connectable to said
signal generator.
60. A computer program product, directly loadable into an internal
memory of a measuring device, comprising software code portions for
causing said measuring device to perform steps in accordance with
claim 34.
Description
TECHNICAL FIELD
[0001] The present application refers to systems for applying
viscous mediums onto substrates using jet printing within the field
of electronics production. More specifically, the invention relates
to a method of improving the performance of a jetting device, and a
device for jetting droplets of viscous medium onto a substrate.
BACKGROUND
[0002] Systems, devices and methods for jetting droplets of viscous
medium, e.g. solder paste or glue, onto a sub-strate, e.g. an
electronic circuit board, are known in the art. See for instance
patent publications U.S. Pat. No. 6,450,416 B1, US 2002/0043570 A1,
US 2002/0047052 A1, US 2002/0014602 A1, US 2002/0015780 A1, US
2004/0118935 A1, US 2004/0217193 A1, US 2004/0262824 A1, US
2005/0092774 A1, US 2005/0167519 A1, WO 2005/048678, which are
incorporated herein by reference.
[0003] In the MY500 Jet Printer provided by Mydata automation AB, a
system for jetting viscous medium comprises a jet printing machine,
a solder paste container for containing solder paste to be jetted,
a residue receptacle for holding residue and surplus of solder
paste resulting from the jetting process, an ejector element for
performing the actual jetting of the solder paste, and a holder
matable with the jet printing machine. The ejector comprises a
feeder in the form of a feed screw, which is powered by a stepper
motor arranged in the holder matable via interface means of the
stepper motor and the ejector.
[0004] The throughput is an essential factor in the manufacturing
of electronic circuit boards. This has lead to, inter alia, a
desire of increasing the speed at which a substrate is provided
with viscous medium and a desire to eliminate or, at least
minimize, interruptions or breaks during the production process. A
way to improve the throughput or manufacturing speed of electronic
circuit boards is to eliminate or reduce the need for operator
interventions due to, inter alia, interruptions in the jet printing
process. Such interruptions may be caused by shortage of solder
paste. Accordingly, it is of high importance for the production
speed to obtain a reliable and accurate measure of the solder paste
quantity remaining in the solder paste tube. Today, this may be
performed by so called "dead counting", i.e. the number of ejected
droplets is counted. However, this is impaired with problems. For
example, the accuracy is low due to counting errors caused by
difficulties of estimating the quantity of solder paste in the
droplets or due to the fact that information regarding the quantity
of solder paste contained in the solder paste tube may be
erroneous. An alternative way of measuring the solder paste level
in a solder paste tube is to arrange inductive transducers or
sensors at a predetermined level at the tube, which deliver a
signal when the solder paste has reached the level that the solder
paste is about to run out. This method is associated with
drawbacks, for example, that the operator of the jetting device is
not provided with any information regarding the solder paste
quantity during a jet printing process until the solder paste is
about to ran out.
[0005] In addition, the high quality requirements of the electronic
industry and the detrimental consequences of errors appearing in
circuit boards has led to an arising interest in means for
monitoring and/or determining characteristic features or parameters
of the solder paste, for example, with respect to quality including
oxidation degree of the solder pellets, solder paste type,
remaining shelf-life, etc. during a jet printing operation as well
as before a jet printing operation is initiated when the solder
paste tube is mounted in the jet printing device.
[0006] Hence, a need exists for improved jetting methods and
devices.
[0007] Further, there is a need within the art of jet printing of
improved and more reliable methods and devices for measuring and/or
monitoring the solder paste consumption during a jet printing
process.
SUMMARY OF THE INVENTION
[0008] Thus, an object of the present invention is to provide an
improved jetting method and device.
[0009] Another object of the present invention is to improve the
performance of a device for jetting droplets of viscous medium onto
a substrate.
[0010] A further object of the present invention is to provide
improved and more reliable methods and devices for measuring and/or
monitoring the solder paste consumption during a jet printing
process.
[0011] These and other objects are achieved according to the
present invention by providing a method and an apparatus having the
features defined in the independent claims. Preferred embodiments
are defined in the dependent claims.
[0012] According to an aspect of the present invention, there is
provided a method for a jetting device for jetting droplets of
viscous medium onto a substrate, the jetting device comprising an
ejector element for performing the jetting process and a jetting
outlet through which the droplets are jetted. The method comprises
the steps of: generating at least one electromagnetic signal in a
detachable viscous medium container mounted in the jetting device;
measuring a response signal to the generated electromagnetic signal
in the viscous medium container; and determining a level of viscous
medium in the viscous medium container using the response
signal.
[0013] According to a second aspect of the present invention, there
is provided a measuring device for a jetting device for jetting
droplets of viscous medium onto a substrate, the jetting device
comprising an ejector element for performing the jetting process
and a jetting outlet through which the droplets are jetted. The
measuring device comprises: a signal generating circuit adapted to
generate an electromagnetic signal in a detachable viscous medium
container mounted in the jetting device; and signal measuring
circuit adapted to measure a response signal to the generated
electromagnetic signal in the viscous medium container and signal
processing circuit connected to the signal measuring circuit and
being adapted to determine a level of viscous medium in the viscous
medium container using the response signal.
[0014] According to third aspect of the present invention, there is
provided a jetting device for jetting droplets of viscous medium
onto a substrate, the jetting device comprising an ejector element
for performing the jetting process and a jetting outlet through
which the droplets are jetted, the jetting device further
comprising a measuring device in accordance with the second aspect
of the present invention.
[0015] According to a fourth aspect of the present invention, there
is provided a viscous medium container for holding a viscous medium
adapted to attached in a jetting device for jetting droplets of the
viscous medium onto a substrate, the jetting device comprising an
ejector element for performing the jetting process and a jetting
outlet through which the droplets are jetted. The viscous medium
container comprises: at least one first conducting element arranged
at an inner wall of the container; at least one second conducting
element arranged at an inner wall; the first conducting element and
the second conducting element being connectable to a measuring
device in accordance with the second aspect of the present
invention.
[0016] According to a further aspect of the present invention,
there is provided a computer program product, directly loadable
into an internal memory of a measuring device, comprising software
code portions for causing the measuring device to perform steps of
the method in accordance with first aspect of the invention.
[0017] Hence, the present invention is based on the idea of
utilizing electromagnetical signals and/or fields applied in the
viscous medium container, e.g. a solder paste tube, measuring a
response of the viscous medium to the applied signals and/or
fields, and determining the present level, volume, or filling
degree of the viscous medium in the container using this response.
Thereby, it is possible to continuously monitor and measure the
volume or level of viscous medium held by the container during a
jet printing process. This can be used to keep a user updated of
the current level of viscous medium and the remaining volume of
viscous medium and, thus, the jet printing process be improved, for
example, in that interruption of the process can be predicted
and/or adapted to the product production flow.
[0018] For the purposes of this application, it is to be noted that
the term "viscous medium" should be inter-preted as solder paste,
flux, adhesive, conductive adhe-sive, or any other kind of medium
used in connection with mounting components on a substrate,
conductive ink, resistive paste, or the like; that the term
"deposit" refers to a connected amount of viscous medium applied at
a position on a substrate as a result of one or more jetted
droplets; and that the term "substrate" should be interpreted as a
printed circuit board (PCB), a substrate for ball grid arrays
(BGA), chip scale packages (CSP), quad flat packages (QFP), wafers,
flip-chips, or the like.
[0019] It is also to be noted that the term "jetting" should be
interpreted as a non-contact dispensing process that utilizes a
fluid jet to form and shoot droplets of a viscous medium from a jet
nozzle onto a substrate, as compared to a contact dispensing
process, such as "fluid wetting.
[0020] In the following description, embodiments of jetting systems
and methods will be described which comprise a jetting machine,
viscous medium ejectors, viscous medium containers, residue
receptacles, and holders. The term "ejector" refers to the element
for actuating the actual jetting of viscous medium droplets;
"container" refers to the element in which viscous medium is stored
before and supplied from during jetting and is in fluid
communica-tion with the ejector; "receptacle" refers to a container
for receiving and holding surplus or residue viscous medium, for
instance surplus viscous medium transported from the outlet of the
ejector by means of pressurized air; and "holder" refers to a
holding frame having mechanical and electrical interface with the
jetting machine and holds the ejector, container and receptacle,
thus forming an aggregate unit or assembly in conjunction with the
ejector, container and receptacle, which in the following
description sometimes will be referred to as a "cassette"; and
"jetting machine" refers to the framework into which the unit or
assembly is mounted. The jetting machine comprises means for
holding, positioning and providing trigger signals for the
cassettes during the jetting operation, and also means for holding
and transporting the substrates onto which viscous medium is to be
applied. The jetting machine further comprises software and
inspection means for controlling and monitoring the entire viscous
medium application process. However, unless the interaction between
the jetting machine and the other elements or the cassette is
described, the term jetting machine or jetting apparatus will in
the following often refer to the entire system, including the
elements referred to above.
[0021] In one aspect of the invention, the volume of viscous medium
held by the container can be measured by providing the plunger
provided at the end of the container opposite an outlet end with
magnetic properties. Then, the movement of the plunger within the
container, indicative of the viscous medium volume and filling
degree, can be monitored using external measuring equipment
including the signal measuring circuit and the signal processing
circuit. Arranging a permanent magnet in the plunger, for instance
a ferrite magnet, can provide the magnetic properties.
Alternatively, the plunger material could be a polymer filled with
magnetic particles. Many types of non-contact measurement methods
could be adapted to perform the task of measuring the viscous
medium volume.
[0022] In one embodiment, an array of hall effect sensor is
arranged in proximity to the container. The sensors detect the
magnetic field generated by the magnetic plunger in the viscous
medium and deliver a current at detection of a field. As the
plunger moves within the container, indicative of a viscous medium
volume and filling degree, only the sensors that detect a magnet
field within the viscous medium will deliver the current. Thus, by
combining signals from one or more of the sensors, the position of
the plunger can be determined and thereby the level of the viscous
medium in the container.
[0023] Furthermore, in other exemplifying embodiments for measuring
the amount of viscous medium in the containers, the viscous medium
containers per se are provided with conduction paths within the
actual container. Thus, the conduction paths are essentially
arranged to be in electrical contact with the viscous medium such
that electrical properties of the medium can be measured. Thereby,
measuring the impedance in the viscous medium content can monitor
the amount or filling degree of the viscous medium contained in the
container. A change in the impedance level, or in fact the DC
component, can be calculated and converted into a corresponding
change in the volume of viscous medium. It should be noted that the
conduction paths within the container could be in the form of
conduction points in contact with the viscous medium, while other
or major portions of the conductions paths can be located in
portions of the container where there is no contact with the
viscous medium.
[0024] Also, the provision of conduction paths or points within the
viscous medium container, provides the possibility to determine the
permittivity, the loss factor or dielectric constant of the viscous
medium through impedance measurements and other characteristics of
the viscous medium, for example, with respect to quality, remaining
shelf-life, etc, can be monitored. For instance, the viscous medium
could have a limited useful life, i.e. that the quality of the
viscous medium deteriorates over time due to, inter alia, oxidation
of the solder particles in solder paste. Furthermore, by conducting
impedance measurements over a predetermined frequency range it is
possible to obtain a "fingerprint" of the viscous medium which may
be used to identify a certain type of viscous medium, for example,
a solder paste having a certain quality or produced by a certain
manufacturer. It is thereby also possible to, for example, verify
that a solder paste container actually contains the indicated
solder paste.
[0025] In a further embodiment of the present invention,
measurement probes are arranged in a passage between the container
and an ejector chamber of the ejector element, for example, between
the container and a feed screw essentially to be in electrical
contact with the viscous medium such that electrical properties of
the medium can be measured. This provides the possibility to
monitor other characteristics of the viscous medium. This may be
combined with the magnetic plunger to provide the possibility to
monitor the volume, or level, of the viscous medium by means of the
detection of the magnetic field in the container and the electrical
properties of the viscous medium by means of the impedance
measurements in the passage between the container and the ejector
chamber.
[0026] According to a further embodiment, the plunger is made
electrically conducting and may short-circuit conduction paths or
points arranged in the container. Thereby, it is possible to
determine the level of the viscous medium within the container.
This may be combined with measurement probes arranged in passages
between the container and the ejection chamber of the ejector
element, for example, between the container and the feed screw or
in the ejection chamber such that electrical properties of the
medium and the level of the viscous medium within the container can
be measured.
[0027] As realized by the person skilled in the art, steps of the
methods of the present invention, as well as preferred embodiment
thereof, are suitable to realize as a computer program or a
computer readable medium.
[0028] The features that characterize the invention, both as to
organization and to method of operation, together with further
objects and advantages thereof, will be better understood from the
following description used in conjunction with the accompanying
drawings. It is to be expressly understood that the drawings is for
the purpose of illustration and description and is not intended as
a definition of the limits of the invention. These and other
objects attained, and advantages offered, by the present invention
will become more fully apparent as the description that now follows
is read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES OF DRAWINGS
[0029] FIG. 1 is a perspective view showing the general outline of
a machine for application of solder paste comprising a jetting
device according to the present invention;
[0030] FIG. 2 is a general block diagram of the measuring device
according to the present invention for measuring a level or volume
of solder paste in a solder paste container and/or measure
electrical properties of the solder paste to determine
characteristics of the solder paste;
[0031] FIG. 3 is an embodiment of a viscous medium container
according to the present invention;
[0032] FIG. 4 is an embodiment of a viscous medium container
arranged in holder to be attached in a jetting apparatus according
to the invention;
[0033] FIG. 5 is a schematic cross-sectional view of a solder paste
container connected to a measuring device according to an
embodiment of the present invention;
[0034] FIG. 6 is a schematic cross-sectional view of a solder paste
container connected to a measuring device according to another
embodiment of the present invention;
[0035] FIG. 7 is a schematic cross-sectional view of a solder paste
according to a further embodiment of the present invention;
[0036] FIG. 8 is a schematic cross-sectional view of a solder paste
container connected to a measuring device according to yet another
embodiment of the present invention;
[0037] FIG. 9 is a perspective view a jetting apparatus according
to the present invention connected to a work station; and
[0038] FIG. 10 is a schematic cross-sectional view of a solder
paste container connected to a measuring device according to a
further embodiment of the present invention.
DESCRIPTION OF EXEMPLARY EMBODIMENT
[0039] FIG. 1 illustrates the general outline of a preferred
embodiment of an apparatus 1 for providing a substrate 2 with
deposits by dispensing droplets of a viscous medium onto the
substrate 2, for example, jetting, in accordance with the present
invention. For ease of description, the viscous medium will
hereinafter be referred to as solder paste, which is one of the
alternatives defined above. For the same reason, the substrate will
be referred to as an electric circuit board and the gas will be
referred to as air. In this embodiment, the jetting apparatus 1 is
of a type comprising an X-beam 3 and an X-wagon 4, which is
connected to the X-beam 3 via an X-rail and is movable in a
reciprocating way along the X-rail. The X-beam, in turn, is movably
connected to a Y-rail 17, the X-beam 3 thereby being movable to the
X-rail 16. The Y-rail 17 is rigidly mounted in the jetting
apparatus 1. Generally, the movements are provided by linear motors
(not shown).
[0040] Furthermore, the jetting apparatus 1 comprises an internal
conveyor 17 for carrying the board 2 through the jetting apparatus
1, and a locking device for locking the board 2 when jetting is to
take place.
[0041] A docking device is attached to the X-wagon 4 for enabling
releasable mounting of an assembly 5 at the docking device 8. The
assembly 5 is arranged for dispensing droplets of solder paste,
i.e. jetting, which impact and form deposits on the board 2. The
jetting apparatus 1 also comprises a vision device, e.g. a camera
15. The camera 15 is used for determining the position and rotation
of the board 2 and for checking the result of the dispensing
process by viewing the deposits on the board 2.
[0042] Additionally, the jetting apparatus 1 comprises a vacuum
ejector (not shown in FIG. 1) arranged on the X-wagon 4, and a
source of compressed air (not shown). The vacuum ejector, as well
as the source of compressed air, is in communication with the
docking device 8 via air conduit interface means, which are
connectable to com-plementary air conduit interface means, of the
docking device.
[0043] As understood by those skilled in the art, the jetting
apparatus comprises a control unit (not explicitly shown in FIG. 1)
for executing software running the apparatus and for controlling
functions of a measuring device according to the present
invention.
[0044] Briefly, the jetting apparatus works as follows. The board 2
is fed into the jetting apparatus 1 by means of the conveyor 18,
upon which the board 2 is placed. When the board 2 is in the
correct position under the X-wagon 4, the board 2 is fixed with the
aid of the locking device. By means of the camera, fiducially
markers are located, which markers are prearranged on the surface
of the board 2 and used to determine the precise position thereof.
Then, by moving the X-wagon over the board 2 in a predetermined
(pre-programmed) pattern and operating the jetting assembly 5 at
predetermined locations, solder paste is applied on the board 2 at
the desired locations.
[0045] In FIG. 2, a general block diagram of the measuring device
20 (which will be described in more detail with reference to FIGS.
3-8) according to the present invention for measuring a level or
volume of solder paste in a solder paste container 21 attached in
the jetting apparatus 1 and/or measure electrical properties of the
solder paste to determine characteristics of the solder paste is
shown.
[0046] The measuring device 20 comprises a signal generating
circuit 22 adapted to generate an electromagnetic signal in a
solder paste container 21 when attached in a container holder, see
FIG. 4. Moreover, the measuring device 20 comprises a signal
measuring circuit 23 adapted to measure response signals to the
generated electromagnetic signal in solder paste container 21,
which signal measuring circuit may include signal measuring sensors
(see FIG. 5), and a signal processing circuit 24 connected to the
signal measuring circuit 23 adapted to determine a level of solder
paste in the container and/or characteristics such as electrical
properties of the solder paste using the response signals. The
measuring device 20 may be controlled of; a control unit (not
shown) of the jetting apparatus 1. Alternatively, the measuring
device 20 may include logic for executing measuring functions,
which logic may be arranged in the circuits of the measuring device
20. Furthermore, the measuring device 20 includes a memory circuit
25, which memory circuit can be arranged in the circuits of the
measuring device 20, for example, in the signal processing circuit
24. Alternatively, the memory circuit may be arranged in the
control unit of the jetting apparatus 1. The memory circuit 25 may
include a random access memory (RAM) and/or a non-volatile memory
such as a read-only memory (ROM). For example, information related
to the solder level paste measuring and solder paste
characteristics can be stored in the memory circuit 25.
[0047] With reference to FIGS. 3 and 4, an embodiment of a viscous
medium container, which for ease of description, hereinafter will
be referred to as solder paste container will be discussed. In FIG.
3, a solder paste container 31 intended for use in a jetting
system, e.g. the jetting apparatus shown in FIG. 1, comprises an
outlet 32 for providing the viscous medium to an ejector, or the
like. At the other end of the container, i.e. opposite the outlet
end, a plunger 33 or membrane is provided. Thereby, the solder
paste content in the container 31 is held between the plunger 33 at
one end and the outlet 32 at the other end. Thus, a surface of the
plunger 33 is in contact with the solder paste and the medium is
held in a voidless condition. During the jetting of droplets, and
the corresponding emptying of the container of solder paste, the
plunger 33 is moved in a direction towards the outlet 32 such that
the voidless condition may be maintained when the amount of solder
paste held by the container 31 is decreased during the jetting
process. In FIG. 4, the container 31 is shown mounted in a
container holder 34, which is adapted for attachment in the jetting
apparatus.
[0048] Now, an aspect of the present invention will be discussed
with reference to FIG. 5 showing a schematic cross-sectional view
of a solder paste container. A solder paste medium container 51
intended for use in a jetting system, e.g. the jetting apparatus
shown in FIG. 1, is provided with a plunger 53 with magnetic
properties that generates a magnetic field in the container 51. The
volume of solder paste held by the container 51 can be measured by
monitoring the movement of the plunger 53 within the container 51
which is indicative of the solder paste volume and filling degree,
i.e. monitoring the change of the magnetic field by means of the
signal measuring circuit 23 shown in FIG. 2. Arranging a permanent
magnet in the plunger, for instance a ferrite magnet, can provide
the magnetic properties. Alternatively, the plunger material could
be a polymer filled with magnetic particles.
[0049] According to one embodiment of the present invention, the
signal measuring circuit 23 comprises an array of hall effect
sensor elements 54 arranged in proximity of the container 51. The
sensor elements 54 are arranged according to a longitudinal line
and are preferable mounted parallel with a longitudinal axis of the
container 51. For example, the sensor array 54 may be arranged at
the holder 34 shown in FIG. 4. Each sensor element 54 is connected
to the signal processing circuit 24 including a combining circuit
(not shown) adapted to combine currents from respective sensor
element 54 to determine a position of the magnetic element 53 in
solder paste container 51 and adapted to determine a level of
solder paste in the container 51 using the position determination
of the magnetic element 53.
[0050] With reference now to FIG. 6, another embodiment of the
present invention will be described. A solder paste container 61 is
provided with first and second conductive elements 62a, 62b at an
inner wall of the container 61, which conductive elements 62a, 62b
are connectable to signal generator 64 of the signal generating
circuit 22, see FIG. 2, and a signal measuring circuit 65 and a
signal processing circuit 66. In one embodiment, the solder paste
container 61 is provided with the conductive elements, e.g.
conductive strips, per se. The signal measuring circuit 65
comprises resistive elements 67 connected to an amplifier 68 and an
analog-to-digital converter 69.
[0051] Thus, the conduction paths are essentially arranged to be in
electrical contact with the viscous medium, e.g. solder paste, such
that electrical properties of the medium can be measured. Thereby,
the amount or filling degree of the viscous medium contained in the
container can be monitored by measuring the impedance in the solder
paste content. According to this embodiment, the signal generator
64 applies a current via the first conductive element 62a and the
resulting impedance is measured by the signal measuring circuit 65
via the second conductive element 62b. A change in the DC-impedance
level can be calculated and converted into a corresponding change
in the volume of solder paste.
[0052] It should be noted that the conduction paths within the
container could be in the form of conduction points in contact with
the solder paste, while other or major portions of the conductions
paths can be located in portions of the container where there is no
contact with the viscous medium.
[0053] Also, the provision of conduction paths or points within the
solder paste container, provides the possibility to monitor other
characteristics of the solder paste by measuring the impedance and
calculating electrical properties of the viscous medium, e.g. the
solder paste. For instance, the solder paste could have a limited
useful life, i.e. that the quality of the solder paste deteriorates
over time. Then, conduction paths in the container can be used for
determining electrical properties of the viscous medium that would
be indicative of whether the solder paste has passed its
best-before date. For instance, the permittivity, the loss factor
or dielectric constant of the viscous medium can be determined
through DC- and AC-impedance measurements, i.e. complex impedance
measurements. The impedance measurement are conducted over a
predetermined frequency range, for example, in a range of 0-1 MHz
or in a range of 0-500 KHz.
[0054] In one embodiment, the signal generating circuit 64 includes
a signal generator adapted to generate DC and/or AC current
waveforms over a predetermined frequency range which are delivered
into the solder paste via conducting elements arranged within the
container 61. For example, voltages of in range of about 0.5-50 V
at a frequency range of about 0-1 MHz can be used. In another
embodiment, voltages of in range of about 10-20 V at a frequency
range of about 0-500 KHz can be used.
[0055] In FIG. 7, an embodiment of the solder paste container
provided with conducting points is shown. A first array of
conducting points 72a and a second array of conducting points 72b
are arranged at an inner wall of the solder paste container 71. The
first and second arrays 72a and 72b are, as the conductive strips
shown in FIG. 6, connectable to a signal generator of the signal
generating circuit 22, see FIG. 2, and a signal measuring circuit
and a signal processing circuit.
[0056] With reference now to FIG. 8, a further embodiment of the
present invention will be discussed. A first and a second
measurement probe 82a and 82b are arranged in a passage 83 between
the container and the ejection chamber of the ejector element, for
example, between the container and the feed screw of an ejector
element 87 essentially to be in electrical contact with the solder
paste such that electrical properties of the paste can be measured.
Alternatively, the probes 82a and 82b may be arranged in the
ejection chamber or in a passage between the feed screw and the
ejection chamber.
[0057] The first and second measurement probes 82a and 82b are
connected: to a signal generator 84 of the signal generating
circuit 22, see FIG. 2, and a signal measuring circuit 85 and a
signal processing circuit 86. The signal measuring circuit 85
comprises resistive elements 90 connected to an amplifier 88 and an
analog-to-digital converter 89. According to this embodiment, the
signal generator 84 applies a current via the first conductive
element 82a and the resulting impedance is measured by the signal
measuring circuit 85 via the second conductive element 82b. For
example, voltages of in range of about 0.5-50 V at a frequency
range of about 0-1 MHz can be used. In another embodiment, voltages
of in range of about 10-20 V at a frequency range of about 0-500
KHz can be used.
[0058] This provides the possibility to monitor other
characteristics of the solder paste such as the electrical
properties of the solder paste by means of the complex impedance
measurements in the passage between the container and the ejection
chamber of the ejector element, for example, between the container
and the feed screw. Furthermore, in order to determine or measure
the level of solder paste in the container 81, a plunger 93 with
magnetic properties that generates a magnetic field in the
container 81 is provided. The volume of solder paste held by the
container 81 can thus, as described above, be measured by
monitoring the movement of the plunger 93 within the container 81
which is indicative of the solder paste volume and filling degree,
i.e. monitoring the change of the magnetic field by means of the
signal measuring circuit 85. Arranging a permanent magnet in the
plunger, for instance a ferrite magnet, can provide the magnetic
properties. Alternatively, the plunger material could be a polymer
filled with magnetic particles. The signal measuring circuit 85
comprises an array of hall effect sensor elements 94 arranged in
proximity of the container 81. The sensor elements 54 are arranged
according to a longitudinal line and are preferable mounted
parallel with a longitudinal axis of the container 81. For example,
the sensor array 94 may be arranged at the holder 34 shown in FIG.
4. Each sensor element 94 is connected to the signal processing
circuit 86 including a combining circuit (not shown) adapted to
combine currents from respective sensor element 94 to determine a
position of the magnetic element 93 in solder paste container 81
and adapted to determine a level of solder paste in the container
81 using the position determination of the magnetic element.
Consequently, this embodiment provide the possibility to monitor
both the volume, or level, of the solder paste in the solder paste
container 81 by means of the detection of the magnetic field in the
container 81 and characteristics of the solder paste such as the
electrical properties, e.g. permittivity and dielectric constant,
of the solder paste by means of the complex impedance measurements
in the passage 83 between the container and the ejection chamber of
the ejector element, for example, between the container and the
feed screw.
[0059] In another embodiment of the present invention, the
measurement probes are arranged in the passages between the
container and the ejection chamber of the ejector element, for
example, between the container and the feed screw for measuring
electrical properties of the solder paste such as permittivity or
dielectric constant and the container is provided with conduction
paths as described above for measuring a DC-impedance level to
determine the solder paste level in the container. The measurement
device described with reference to FIG. 6 can be used with minor
adaptations as the person skilled within the art easily
realizes.
[0060] Thus, it is possible to monitor both the volume, or level,
of the solder paste in the solder paste container by means of the
detection of the DC-impedance level in the container and
characteristics of the solder paste such as the electrical
properties, e.g. permittivity and dielectric constant, of the
solder paste by means of the complex impedance measurements in
passage between the container and the ejection chamber of the
ejector element, for example, between the container and the feed
screw.
[0061] In FIG. 9, a jetting apparatus in accordance with the
present invention, for example a jetting apparatus as shown in FIG.
1, including any one of the embodiments for measuring the level of
solder paste and/or electrical properties of the solder paste in
order to determine characteristics of the solder paste described
above and an external work station connectable to the jetting
apparatus is shown. The work station 102 is comprises a display
screen or monitor 104 for presenting information for a user by
means of a graphical user interface (GUI) such as a level or volume
of viscous medium in the viscous medium container and
characteristics of the viscous medium, and input devices 106, for
example, a keyboard and a mouse, which enable a user to, for
example, input information and commands. An operator of the jetting
can thus be presented with information regarding, for example, a
remaining amount of viscous medium, estimated time remaining at
current jetting droplet ejection rate until the container in the
jetting apparatus has to be replaced, etc. The external work
station 102 may communicate with the jetting apparatus 1 via a
physical connection such as, for example, an USB connection or
wirelessly by means of a number of different technologies including
short range communication links including BLUETOOTH, or other types
of short-range wireless connections such as Infrared.
[0062] Referring now to FIG. 10, a further embodiment of the
present invention will be discussed. A plunger 113 arranged in a
solder paste container 111 is provided with first conductive
elements 112a and the container 111 is provided with a second
conductive element 112b at an inner wall of the container 111,
which conductive elements 112a, 112b are connectable to signal
generator 114 of the signal generating circuit 22, see FIG. 2, and
a signal measuring circuit 115 and a signal processing circuit 116.
In one embodiment, the solder paste container 111 is provided with
the conductive element, e.g. conductive strips, per se. The signal
measuring circuit 115 comprises resistive elements 117 connected to
an amplifier 118 and an analog-to-digital converter 119.
[0063] Thus, the conductive elements are essentially arranged to be
in electrical contact with the viscous medium, e.g. solder paste,
such that electrical properties of the medium can be measured.
Thereby, the amount or filling degree of the viscous medium
contained in the container can be monitored by measuring the
impedance in the solder paste content. According to this
embodiment, the signal generator 114 applies a current via the
first conductive element 112a arranged in the plunger 113 and the
resulting impedance is measured by the signal measuring circuit 115
via the second conductive element 112b. A change in the
DC-impedance level can be calculated and converted into a
corresponding change in the volume of solder paste.
[0064] It should be noted that the conduction path within the
container could be in the form of conduction points in contact with
the solder paste, while other or major portions of the conductions
path can be located in portions of the container where there is no
contact with the viscous medium.
[0065] Also, the provision of conduction paths or points within the
solder paste container, provides the possibility to monitor other
characteristics of the solder paste by measuring the impedance and
calculating electrical properties of the viscous medium, e.g. the
solder paste. For instance, the solder paste could have a limited
useful life, i.e. that the quality of the solder paste deteriorates
over time. Then, conduction paths in the container can be used for
determining electrical properties of the viscous medium that would
be indicative of whether the solder paste has passed its
best-before date. For instance, the permittivity, the loss factor
or dielectric constant of the viscous medium can be determined
through DC- and AC-impedance measurements, i.e. complex impedance
measurements. The impedance measurement are conducted over a
predetermined frequency range, for example, in a range of 0-1 MHz
or in a range of 0-500 KHz.
[0066] As the person skilled within the easily realizes, there are
a number of conceivable alternative embodiments, for example, the
second conductive element 112b may be arranged in a passage between
the container 113 and the ejection chamber of the ejector element
87, for example, between the container and the feed screw of an
ejector element 87.
[0067] In one embodiment, the signal generating circuit 64 includes
a signal generator adapted to generate DC and/or AC current
waveforms over a predetermined frequency range which are delivered
into the solder paste via conducting elements arranged within the
container 61. For example, voltages of in range of about 0.5-50 V
at a frequency range of about 0-1 MHz can be used. In another
embodiment, voltages of in range of about 10-20 V at a frequency
range of about 0-500 KHz can be used.
[0068] The preceding specific embodiments are illustrative of the
practice of the invention. It is to be understood, therefore, that
other expedients known to those of skill in the art or disclosed
herein may be employed without departing from the invention as
defined by the appended claims. It is therefore understood that the
invention may be practiced otherwise than is specifically described
without departing from the scope of the present invention.
* * * * *