U.S. patent application number 15/576203 was filed with the patent office on 2018-05-24 for method to produce electrically isolated or insulated areas in a metal, and a product comprising such area.
This patent application is currently assigned to Metalmembranes.com B.V.. The applicant listed for this patent is Metalmembranes.com B.V.. Invention is credited to Johannes Kuipers, Sybrandus Jacob Metz, Hans Hendrik Wolters.
Application Number | 20180142373 15/576203 |
Document ID | / |
Family ID | 56567654 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180142373 |
Kind Code |
A1 |
Metz; Sybrandus Jacob ; et
al. |
May 24, 2018 |
METHOD TO PRODUCE ELECTRICALLY ISOLATED OR INSULATED AREAS IN A
METAL, AND A PRODUCT COMPRISING SUCH AREA
Abstract
The present specification relates to a method to produce
electrically isolated or insulated areas in a metal, and a product
comprising such area. The method according to the invention
comprising the steps of: providing a metallic structure; performing
a plasma electrolytic oxidation and/or anodization process such
that an oxide layer is achieved on an area of the metallic
structure; and electrically isolating a part of the metallic
structure by removing part of the metallic structure and/or
connecting a further metallic structure to the metallic structure
with the oxide layer.
Inventors: |
Metz; Sybrandus Jacob;
(Heerenveen, NL) ; Wolters; Hans Hendrik;
(Leeuwarden, NL) ; Kuipers; Johannes; (Leeuwarden,
NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Metalmembranes.com B.V. |
Leeuwarden |
|
NL |
|
|
Assignee: |
Metalmembranes.com B.V.
Leeuwarden
NL
|
Family ID: |
56567654 |
Appl. No.: |
15/576203 |
Filed: |
May 25, 2016 |
PCT Filed: |
May 25, 2016 |
PCT NO: |
PCT/NL2016/050372 |
371 Date: |
November 21, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 11/20 20130101;
C25D 11/026 20130101; C25D 11/022 20130101; C25F 3/04 20130101 |
International
Class: |
C25D 11/02 20060101
C25D011/02; C25D 11/20 20060101 C25D011/20; C25F 3/04 20060101
C25F003/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 26, 2015 |
NL |
2014857 |
Claims
1. A method to produce an electrically isolated area in a metal,
comprising the steps of: providing a metallic structure; performing
a plasma electrolytic oxidation and/or anodization process such
that an oxide layer is achieved on an area of the metallic
structure; and electrically isolating a part of the metallic
structure by removing part of the metallic structure and/or
connecting a further metallic structure to the metallic structure
with the oxide layer.
2. The method according to claim 1, further comprising the step of
masking parts of the metallic structure and performing the plasma
electrolytic oxidation and/or anodization such that an oxide layer
is achieved on an unmasked area of the metallic structure.
3. The method according to claim 1, wherein removing part of the
metallic structure is performed after performing the plasma
electrolytic oxidation process and/or anodization process.
4. The method according to claim 3, wherein removing part of the
metallic structure comprises performing an etching process.
5. The method according to claim 4, wherein the etching process
comprises an electrochemical etching process.
6. The method according to claim 4, wherein the etching process
comprises the step of automatically stopping the etching when
reaching the oxide layer.
7. The method according to claim 1, further comprising the step of
providing non-conductive material to the removed part or parts of
the metallic structure.
8. The method according to claim 1, further comprising the step of
increasing the stability and/or strength of the metallic structure
by providing a stability layer on the oxide layer of the metallic
structure after performing the plasma electrolytic oxidation and/or
anodization process.
9. The method according to claim 8, wherein the stability layer
comprises non-conductive material.
10. The method according to claim 8, wherein providing a stability
layer comprises providing a layer with a thickness in the range of
10 to 100 .mu.m, preferably in the range of 20 to 75 .mu.m, and
most preferably with a thickness of about 50 .mu.m.
11. The method according to claim 8, further comprising the step of
removing the stability layer.
12. The method according to one claim 1, further comprising the
step of providing a third metallic structure connecting the other
metallic structures together.
13. The method to claim 1, wherein at least one of the metallic
structures is of a different material.
14. A product comprising an electrically isolated area that is
produced with a method according to claim 1.
15. The product according to claim 14, wherein the product is a
computing device and the area is part of an antenna.
16. The product according to claim 14, wherein the metallic
structures of the product comprise a tubular shape, a metallic mesh
structure on the metallic structure, or a wire shape.
17. The product according to claim 15, wherein the metallic
structures of the product comprise a tubular shape, a metallic mesh
structure on the metallic structure, or a wire shape.
18. The method according to claim 2, wherein removing part of the
metallic structure is performed after performing the plasma
electrolytic oxidation process and/or anodization process.
19. The method according to claim 18, wherein removing part of the
metallic structure comprises performing an etching process.
20. The method according to claim 19, wherein the etching process
comprises an electrochemical etching process.
21. The method according to claim 20, wherein the etching process
comprises the step of automatically stopping the etching when
reaching the oxide layer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present specification is a National Phase Entry of
International Application No. PCT/NL2016/050372 filed 25 May 2016
and entitled "Method to produce electrically isolated or insulated
areas in a metal, and a product comprising such area" which,
itself, claims priority to NL 2014857 filed 26 May 2015 and
entitled "Method to produce electrically isolated or insulated
areas in a metal, and a product comprising such area," each of
which are incorporated by reference herein in their entireties.
FIELD
[0002] The present specification relates to a method to produce
electrically isolated or insulated areas in a metal. Such areas are
used in various applications, including electronic devices. More
specifically, the method according to the present specification
relates to forming metal structures that have an electrically
isolated area that is connected by non-conductive part(s). In this
context isolating and insulating both describe the electrical
separation of an area from other parts and can be used alternately
in the context of the present specification.
BACKGROUND
[0003] A problem with conventional electronic devices, including
computing devices such as mobile phones, tablets, computers,
laptops etc., that use an antenna is that the devices often cover
the antenna with a housing, thereby increasing the risk of
hindering communication and/or producing noise.
SUMMARY
[0004] The present specification has for its object to improve
conventional products having an electrically isolated area.
[0005] This object is achieved with the method to produce
electrically isolated areas in a metal, the method comprising the
steps of:
providing a metallic structure; performing a plasma electrolytic
oxidation and/or anodization process such that an oxide layer is
achieved on an area of the metallic structure; and electrically
isolating a part of the metallic structure by removing part of the
metallic structure and/or connecting a further metallic structure
to the metallic structure with the oxide layer.
[0006] The treated structure can be used in various applications,
including electronic devices. More specifically, the method
according to the present specification relates to forming metal
structures that have an electrically isolated area that is
connected by non-conductive part(s). Such structure can
advantageously be used as an antenna or antenna part, such as an RF
antenna. Such antenna that is produced involving the method
according to the present specification enables improved
communication having less noise, for example.
[0007] In embodiments according to the present specification the
ceramic layer has a thickness in the range of 5-300 .mu.m,
preferably 10-200 .mu.tm, more preferably 15-150 .mu.m and most
preferably a thickness is about 100 .mu.m.
[0008] By providing the ceramic layer with a sufficient thickness
the stability and strength of the heater is improved. Furthermore,
the insulation is increased, enabling control of heat transfer
and/or heat production. The thickness of the ceramic layer is
adapted to the desired characteristics. This flexibility during
production provides a further advantage of the system according to
the present specification.
[0009] In embodiments according to the present specification, the
ceramic layer is provided on or at the conductor with plasma
electrolytic oxidation (PEO).
[0010] Principles of a PEO process are disclosed in WO 2011/010914
and are included by reference herein. In embodiments, the element
is made from an aluminium material, or other suitable material,
such as titanium, on which a porous metal oxide layer, such as
aluminium oxide or titanium oxide, is grown with plasma
electrolytic oxidation. In this embodiment of the present
specification the metal oxide layer is provided on a side of the
metal layer involving a plasma oxidation process, more specifically
a plasma electrolytic oxidation process. By performing a plasma
electrolytic oxidation process on the first metal layer locally the
electric brake down potential of the oxide film on the metal layer
is exceeded and discharges occur. Such discharges lead to a type of
local plasma reactors, resulting in a growing oxide. This builds
the desired structure for the membrane layer. The plasma
electrolytic oxidation process creates very fine pores in the metal
layer, thereby forming an oxide layer that contains small pores.
This method provides a ceramic layer that can be made efficiently.
Surprisingly, also the pore sizes of this ceramic layer can be
controlled more effectively and the desired characteristics for
such ceramic layer can be achieved more accurately. A further
advantage of the method according to the present specification is
that it enables the manufacturing of ceramic material in a modular
way. Optionally, this enables providing complicated
three-dimensional shapes of the desired element.
[0011] Plasma electrolytic oxidation enables that a relatively
thick aluminium, titanium or other suitable metal layer is grown
from the metal (>130 .mu.m) by oxidizing (part of) the metal to
metal oxide. Especially the use of titanium provides good results.
The resulting layer is a porous, flexible and elastic metal oxide
ceramic. Plasma electrolytic oxidation (>350 550 V) requires
much higher voltage compared to standard anodizing (15-21 V). At
this high voltage, micro discharge arcs appear on the surface of
the aluminium, or other material, and cause the growth of the thick
(metal) oxide layer. Results have shown that a ceramic layer can be
achieved on an aluminium foil of about 13 .mu.m thickness, with a
flexible and elastic ceramic layer. One of the advantageous effects
of using plasma electrolytic oxidation to provide the ceramic layer
is that due to the growth of the layer from the metal during
oxidation the adherence of the ceramic layer to the metal is
excellent.
[0012] Alternative manufacturing methods for producing an
electrically isolated area in a metal include sintering or spark
plasma sintering, oxidation of the surface layer of the metal by
heating in oxygen rich environment, anodizing, and plasma spraying.
Also, it would be possible to deposit an aluminium, or other
material, coating on the conductor of the heater element, for
example with arc spraying, and to oxidize the deposited material to
an oxide with plasma electrolytic oxidation.
[0013] As an alternative to PEO, or in combination therewith, an
anodization process may be applied to provide a ceramic layer.
Typically, anodization takes place at a voltage that from 1 to 300
V DC, although most fall in the range of 15 to 21 V. Higher
voltages are typically required for thicker coatings formed in
sulfuric and organic acid. Typically, the current that is applied
is in the range from 30 to 300 amperes/meter.sup.2.
[0014] The resulting ceramic layer may have pores with a diameter
in the range of 1-150 nm in diameter on the interface of the
metal/ceramic layer and pores with a diameter in the range of 50 nm
to 5 .mu.m on the outside. The ceramic layer thickness can range
from under 0.5 .mu.m up to 150 .mu.m for architectural
applications.
[0015] In embodiments of the present specification the method
comprises the step of electrically isolating a part of the metallic
structure by removing part of the metallic structure. This provides
separate parts/elements in the metallic structure that are
electrically isolated.
[0016] Alternatively, or in combination therewith, the method in
another embodiment of the present specification comprises the step
of connecting a further metallic structure to the metallic
structure with the oxide layer. Because of the process conditions,
involving high temperatures and pressure, the metal oxide layer
melts during plasma oxidation and solidifies again during cooling.
Provided the further metallic structure is positioned closed to the
metallic structure the oxide layers of the respective structure
will solidify together, thereby connecting the metallic structures,
while preferably electrically isolating the metallic
structures.
[0017] In embodiments of the present specification the method
further comprises the step of masking parts of the metallic
structure and performing the plasma electrolytic oxidation and/or
anodization such that an oxide layer is achieved on an unmasked
area of the metallic structure. This provides an effective method
to provide a structure or an isolating structure to the metallic
structure.
[0018] Removing part of the metallic structure may be performed
after performing the plasma electrolytic oxidation process. This
enables effective oxidation. In embodiments, removing part of the
metallic structure comprises performing an etching process, for
example chemical etching or electrochemical etching.
[0019] In embodiments the etching involves electrochemical
etching.
[0020] Electrochemical etching, also referred to as electrochemical
machining (ECM) and, in embodiments, including jet electrochemical
machining (JET-ECM), allows for a precise, fast and reproducible
local removal of material of the first metal layer. Surprisingly,
in this etching process it was found that etching the first metal
layer does not significantly influence the metal oxide layer. In
fact, the metal oxide layer remains substantially intact whereas
the metal is locally etched away. This enables an efficient and
effective manufacturing of a product comprising an electrically
isolated area, for example. Performing the removing step after
producing the oxide layer further improves the electric isolation
of the respective area. For example, this may prevent or reduce
undesired bulging and/or oxidation to the sides in a transversal
direction. This improves the quality of the resulting product.
Also, this may further reduce the noise disturbance. As a further
advantage the etching process that is applied may automatically
stop when reaching the oxide layer. This improves the isolation
that is effectively provided.
[0021] In embodiments the method further comprises the step of
providing non-conductive material to the removed areas of the
metallic structures.
[0022] The use of non-conductive material further improves the
quality of the resulting product. In embodiments according to the
present specification the method further comprises the step of
increasing the stability and/or strength of the metallic structure
by providing a stability layer on the oxide layer of the metallic
structure after performing the plasma electrolytic oxidation and/or
anodization process.
[0023] By providing a stability layer the strength and stability of
the metallic structure is significantly improved. This improves the
etching performance. In embodiments, the stability layer comprises
non-conductive material, for example an epoxy.
[0024] In embodiments with a stability layer, the stability layer
is provided with a thickness in the range of 10 to 100 .mu.m,
preferably in the range of 20 to 75 .mu.m, and most preferably with
a thickness of about 50 .mu.m. It was shown that such thickness
improves stability and strength thereby enabling or improving
possibilities for further processing, such as electrochemical
etching.
[0025] In embodiments according to the present specification the
method further comprises the step of removing the stability
layer.
[0026] Optionally, the stability layer is removed after performing
the etching process. This may depend on the actual use or
application of the product.
[0027] In further embodiments of the present specification the
method further comprises the step of providing a third metallic
structure connecting the other metallic structures together. In
embodiments, such third metallic structure will connect the two
other metallic structures together in a plasma oxidation process.
Optionally, at least one of the two, three of further metallic
structures is of a different material. For example, in one of the
embodiments the third metallic structure is a sacrificial metallic
structure that can be used to connect the other metallic
structures. An example of such embodiment is the use of a titanium
structure as third, sacrificial structure for connecting two
aluminum structures. In a further example, metallic structures of
aluminum, magnesium and titanium are connected together.
[0028] The present specification also relates to a product
according to the present specification, with the product comprising
an electrically isolated area that is produced with a method as
described earlier.
[0029] The product provides the same effects and advantages as
described for the method.
[0030] In embodiments, such product is a computing device, such as
mobile phones, tablets, computers, laptops etc., and the area is
part of an antenna. In embodiments, the effects of undesired noise
in the communication can be significantly reduced. The product may
have different shapes or configurations. For example, the metallic
structures of the product may comprise a tubular shape, a metallic
mesh structure on the metallic structure, or a wire shape.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Further advantages, features and details of the present
specification are elucidated on the basis of preferred embodiments
thereof wherein reference is made to the accompanying drawings, in
which:
[0032] FIG. 1 shows a cell and metal that is subjected to plasma
oxidation according to the present specification;
[0033] FIG. 2 shows a cross section of the product resulting from
the method according to the present specification;
[0034] FIG. 3 shows a top view of the product shown in FIG. 2;
[0035] FIG. 4 shows a process according to an embodiment of the
present specification with a stability layer; and
[0036] FIG. 5A-D shows different embodiments of the present
specification with two or more metallic structures.
DETAILED DESCRIPTION
[0037] A piece of metal 2 (FIG. 1) is subjected to plasma oxidation
to create an oxide layer 4 on a metal plate. In order to make a
ceramic layer on one side of the metal and on a particular region,
the metal is placed in a plasma electrolytic oxidation cell 6 as
shown in FIG. 1.
[0038] The metal plate 2 preferably aluminum is connected to an
anode. Alternative materials titanium, magnesium or other so called
valve metals can also be used. The synthetic material 8 shown in
the figure can be a hard plastic which can be compressed against
another hard plastic with in between a metal plate 2 and a rubber
10 for sealing. This synthetic material 8 acts as a masking
material to form plasma electrolytic oxide 4 at unmasked areas 12.
Different kind of shapes can be used to mask the metal plate 2.
[0039] The rubber material 10 seals the cell and masks the metal 2.
The synthetic material 8 also acts as a mask. In such a cell 6 as
described here only the part 12 which is not masked is treated
through plasma electrolytic oxidation. Plasma electrolytic
oxidation (PEO) or micro arc oxidation creates a non-conductive
metal oxide layer 4 on the metal plate 2. Different properties,
like color of the layer, can be adjusted by choosing different
electrolytes for the PEO process. Electrolytes that can be used
contain KOH (potassium hydroxide) in a concentration range 0-10
g/l, and Na.sub.2SiO.sub.3 5H.sub.2O concentration range 0-10 g/l,
for example. It is known from literature that these electrolytes or
mixtures of these electrolytes can give a good PEO layer on
Aluminum. Also other salts can be used like Na.sub.2AlO.sub.2 or
Na.sub.2SiF.sub.6 (NaPO.sub.3).sub.6, potassium borate
K.sub.2B.sub.4O.sub.7, or sodium borate Na.sub.2B.sub.4O. It will
be understood that other alternatives could also be envisaged in
accordance with the present specification.
[0040] In an illustrated embodiment of the present specification
the structure of the metal element 2 comprises a thin plate or
sheet of titanium, aluminium, or any other valve metal, such as
magnesium, zirconium, zinc, niobium, vanadium, hafnium, tantalum,
molybdenum, tungsten, antimony, bismuth, or an alloy of one or more
of the preceding metals. Plate or sheet 2 is coated on the other
side through plasma electrolytic oxidation. Plasma electrolytic
oxidation is done by placing titanium plate or sheet 2 in an
electrolyte. For example, the electrolyte comprises 15 g/l
(NaPO.sub.3).sub.6 and 8 g/l Na.sub.2SiO.sub.3.5H.sub.2O. The
electrolyte is maintained at a temperature of 25.degree. C. through
cooling. Plate or sheet 2 is used as an anode and placed in a
container containing the electrolyte. Around plate or sheet 2 a
stainless steel cathode 12 is positioned. A current density is
maintained between the plate or sheet and cathode 22 of about 0.15
A/cm.sup.2. The current is applied in a pulsed mode of about 1000
Hz. The current increases rapidly to about 500 Volt between the
plate or sheet and cathode 22. This creates a plasma electrolytic
oxidation process on anode plate or sheet 2 and creates ceramic
layer 4. It will be understood that process parameters may depend
on the structure of the plate or sheet and/or the dimensions
thereof.
[0041] After the PEO process a ceramic layer 4 is obtained with a
layer thickness that depends on the treatment time. In order to
obtain parts 14 which are electrically isolated from the metal 2,
the metal 14 remaining attached to the ceramic layer 4 has to be
removed. There are many methods which can remove the metal.
Electrochemical machining is very effective in removing the metal
14 under the oxide layer 4.
[0042] After the plasma oxidation treatment the metal plate was
transferred to an etch cell. In this cell the metal was etched via
electrochemical machining. The plate was mounted in this cell with
the metal side facing the cathode. This cathode consists partly of
a metal and a plastic. The metal shape of the cathode determines
the shape and dimensions which will be etched in the metal plate. A
pulsed electric field is applied between the cathode and the anode
(metal plate with on the other side the metal oxide layer). A
highly conductive electrolytic flow was provided between the anode
and the cathode. The potential difference between the anode and the
cathode was in the beginning 1-15 Volts and increased gradually
during the etching. The potential increases sharply when the metal
is etched away and reaches the metal oxide layer. Then the process
was stopped. The current density was kept at a value of about 250
kA/m.sup.2. This process results in a metal plate with on one side
a metal oxide layer and a structure etched in the metal. Fluids can
be filtrated through the open structure in the metal. The metal
oxide layer can be supported during filtration by a metal plate
and/or a (paper) filter that is optionally provided in between the
metal oxide layer and the metal plate. Because the surface
roughness of the metal oxide layer is high the permeate water can
flow easily away to the sides and can be separated from the feed
water. This filtration configuration also allows for high
filtration pressures over 5 bars.
[0043] Tests have shown that a combination of the PEO process with
electrochemical machining achieves a high quality product, for
example with very accurate removal of the metal at the desired
spots.
[0044] After performing the plasma oxidation (PEO) step, or if the
process is performed at lower potentials after the anodization
step, part of the metal 14 can be removed from the other side by
electrochemical machining, for example. The advantage of
electrochemical machining is that the process stops when it reaches
the non-conductive ceramic layer 4. The formed opening can be
filled with a non-conductive polymer 16 or other substances. By
doing so, electrically isolated areas 18 are created.
[0045] A cross section of a product 20 formed this way is shown in
FIG. 2. A top view of product 20 may look like as shown in FIG.
3.
[0046] In embodiments according to the present specification
manufacturing process 102 (FIG. 4) starts with providing metal
plate of sheet 104. With a PEO process, or alternatively an
anodization process, ceramic layer 106 is provided on one side of
metal element 104. Stability layer 108 may be provided on and/or in
ceramic layer 106 to improve stability and strength of element 104
with ceramic layer 106. In the illustrated embodiment stability
layer 108 is from epoxy. In the next step an ECM process is
performed that provides grooves, holes or openings 110 from the
other side of element 104. The ECM process is stopped as grooves,
holes or openings 110 reach ceramic layer 106. Optionally, grooves,
holes or openings 110 are filled with non-conductive material 112,
for example epoxy. Also optionally, stability later 108 can be
removed from ceramic layer 106.
[0047] In connecting method 202 according to an embodiment of the
present specification (FIG. 5A) metallic structure 204 is connected
to second metallic structure 206 with plasma electrolytic oxidation
bonding metallic structures 204, 206 together with the oxide
layers. In embodiments, the connection is made such that metallic
structures 204, 206 are electrically isolated. Optionally, in an
alternative method 208 (FIG. 5B) two metallic structures 210, 212
are connected with sacrificial third metallic structure 214. For
example, the respective materials for metallic structures 210, 212
and 214 are aluminum, magnesium and titanium. Alternatively, middle
structure 214 is of titanium and the other structures 210, 212 are
of aluminum.
[0048] The structures can be shaped as plates or sheets.
Alternatively, other shapes are possible. For example, in process
216 (FIG. 5C) two tubular metallic structures 218, 220 are
connected. Such shape may act as antenna, for example. In a further
process 222 (FIG. 5D) of the present specification mesh 224 (or
alternatively a wire) is connected to plate/sheet 226 (or
alternatively a wire). Also, two or more wires may be connected. It
will be understood that also other embodiments, shapes or
configurations can be envisaged in accordance with the present
specification.
[0049] All different kind of shapes can be made on the metal by
plasma electrolytic oxidation and masking the metal during plasma
oxidation and removing the metal after plasma oxidation by
electrochemical machining and filling the cavity with a
nonconductive material.
[0050] The present specification is by no means limited to the
above described preferred embodiments thereof. The rights sought
are defined by the following claims, within the scope of which many
modifications can be envisaged.
* * * * *