U.S. patent application number 11/483279 was filed with the patent office on 2006-11-09 for kinetic spray application of coatings onto covered materials.
This patent application is currently assigned to Delphi Corporation. Invention is credited to George Albert Drew, Daniel William Gorkiewicz, John R. Smith, Martin Stier, Thomas Hubert Van Steenkiste.
Application Number | 20060251823 11/483279 |
Document ID | / |
Family ID | 33303061 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060251823 |
Kind Code |
A1 |
Van Steenkiste; Thomas Hubert ;
et al. |
November 9, 2006 |
Kinetic spray application of coatings onto covered materials
Abstract
Disclosed is a process for applying a kinetic spray coating of
powder particles onto a substrate covered in a plastic-type
material without first removing the plastic-type material. In one
use of the process a mask is used to enable a single kinetic spray
pass to both remove the plastic covering and bind particles having
average nominal diameters of from 60 to 250 microns to the
underlying substrate. In another use of the process the particles
have an average nominal diameter of from 250 to 1400 microns and
the use of a mask is optional because the particles can penetrate
the plastic material and bind directly to the substrate. The
process finds special use in forming electrical connections or
solderable pads anywhere along the length of a flexible
circuit.
Inventors: |
Van Steenkiste; Thomas Hubert;
(Ray, MI) ; Gorkiewicz; Daniel William;
(Washington, MI) ; Smith; John R.; (Birmingham,
MI) ; Stier; Martin; (Werne, DE) ; Drew;
George Albert; (Warren, OH) |
Correspondence
Address: |
DELPHI TECHNOLOGIES, INC.
M/C 480-410-202
PO BOX 5052
TROY
MI
48007
US
|
Assignee: |
Delphi Corporation
|
Family ID: |
33303061 |
Appl. No.: |
11/483279 |
Filed: |
July 7, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10812861 |
Mar 30, 2004 |
|
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11483279 |
Jul 7, 2006 |
|
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60462022 |
Apr 11, 2003 |
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Current U.S.
Class: |
427/446 |
Current CPC
Class: |
H05K 3/28 20130101; H05K
1/118 20130101; H05K 3/102 20130101; C23C 24/04 20130101; H05K
2203/1344 20130101; H05K 2203/1189 20130101; H05K 3/24
20130101 |
Class at
Publication: |
427/446 |
International
Class: |
B05D 1/08 20060101
B05D001/08 |
Claims
1. A method of kinetic spray coating a substrate covered by a
plastic-type material comprising the steps of: a) providing
particles of a material to be sprayed having an average nominal
diameter of from 60 to 250 microns; b) providing a supersonic
nozzle having a converging region connected to a diverging region
through a throat; c) providing a substrate material covered by a
plastic-type material and positioned opposite the nozzle; d)
providing a mask having at least one opening therein, pressing the
mask against the plastic-type material; e) directing a flow of a
heated main gas through the nozzle; and f) kinetic spraying the
particles by entraining the particles in the flow of the heated
main gas and accelerating the particles to a velocity sufficient to
result in the particles passing through the opening in the mask and
removing the plastic-type material and then adhering to the
substrate material upon impact.
2. The method as recited in claim 1, wherein the particles comprise
either tin, tin alloys, aluminum, aluminum alloys, silver, silver
alloys, gold, gold alloys, lead, lead alloys, zinc, zinc alloys, or
a mixture thereof.
3. The method as recited in claim 1, wherein the substrate material
comprises at least one electrical conductor material.
4. The method as recited in claim 1, wherein the substrate material
comprises a flexible electrical circuit.
5. The method as recited in claim 1, wherein step c) comprises
positioning the substrate material at a distance of from 1.2 to 10
centimeters from an exit end of the nozzle.
6. The method as recited in claim 1, wherein step d) comprises
providing a mask comprising an upper mask and a lower mask and
sandwiching the substrate material between the upper and lower
masks.
7. The method as recited in claim 1, wherein step d) comprises
providing a mask formed from steel, stainless steel, ceramic, a
metal, or a mixture thereof.
8. The method as recited in claim 1, wherein step f) comprises
entraining the particles in the flow of the gas at a point in the
diverging region.
9. The method as recited in claim 1, wherein step f) comprises
accelerating the particles to a velocity of from 100 to 1200 meters
per second.
10. The method as recited in claim 1, wherein the substrate
material and the nozzle are moved relative to each other at a
traverse speed of from 70 to 260 millimeters per second.
11. The method as recited in claim 1, wherein step e) comprises
providing a heated main gas having a temperature of from about 315
to 710 degrees Celsius.
12. A method of kinetic spray coating a substrate covered by a
plastic-type material comprising the steps of: a) providing
particles of a material to be sprayed having an average nominal
diameter of from 250 to 1400 microns; b) providing a supersonic
nozzle having a converging region connected to a diverging region
through a throat; c) providing a substrate material covered by a
plastic-type material and positioned opposite the nozzle; d)
directing a flow of a heated main gas through the nozzle; and e)
kinetic spraying the particles by entraining the particles in the
flow of the heated main gas and accelerating the particles to a
velocity sufficient to result in the particles passing through the
plastic-type material and adhering to the substrate material upon
impact.
13. The method as recited in claim 12, wherein the particles
comprise either tin, tin alloys, aluminum, aluminum alloys, silver,
silver alloys, gold, gold alloys, lead, lead alloys, zinc, zinc
alloys, or a mixture thereof.
14. The method as recited in claim 12, wherein the substrate
material comprises at least one electrical conductor material.
15. The method as recited in claim 12, wherein the substrate
material comprises a flexible electrical circuit.
16. The method as recited in claim 12, wherein step c) comprises
positioning the substrate material at a distance of from 3.5 to 15
centimeters from an exit end of the nozzle.
17. The method as recited in claim 12, wherein step e) comprises
entraining the particles in the flow of the gas at a point in the
diverging region.
18. The method as recited in claim 12, wherein step e) comprises
accelerating the particles to a velocity of from 100 to 1200 meters
per second.
19. The method as recited in claim 12, wherein the substrate
material and the nozzle are moved relative to each other at a
traverse speed of from 70 to 260 millimeters per second.
20. The method as recited in claim 12, wherein step d) comprises
providing a heated main gas having a temperature of from about 315
to 710 degrees Celsius.
21. The method as recited in claim 12, further comprising providing
a mask having at least one opening therein and positioned between
the nozzle and the substrate material and directing the particles
through the opening.
22. The method as recited in claim 21, wherein the mask is formed
from steel, stainless steel, ceramic, a metal, or a mixture
thereof.
23. The method as recited in claim 12, wherein step e) comprises
kinetic spraying the particles in a single pass.
24. The method as recited in claim 12, wherein the particles have
an average nominal diameter of from greater than 250 microns to
1400 microns.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/462,022, filed Apr. 11, 2003.
TECHNICAL FIELD
[0002] The present invention is generally directed toward a method
for applying a kinetic spray coating to a substrate that is covered
in a plastic-type material without prior removal of the
plastic-type cover material. More specifically, the present
invention finds use in the kinetic spray application of coating
material through a plastic over-layer onto underlying electrical
contacts in flexible electrical circuitry.
INCORPORATION BY REFERENCE
[0003] The present invention comprises an improved use for the
kinetic spray process as generally described in U.S. Pat. Nos.
6,139,913, 6,283,386 and the articles by Van Steenkiste, et al.
entitled "Kinetic Spray Coatings" published in Surface and Coatings
Technology Volume III, Pages 62-72, Jan. 10, 1999, and "Aluminum
coatings via kinetic spray with relatively large powder particles",
published in Surface and Coatings Technology 154, pp. 237-252,
2002, all of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0004] A new technique for producing coatings on a wide variety of
substrate surfaces by kinetic spray, or cold gas dynamic spray, was
recently reported in two articles by T. H. Van Steenkiste et al.
The first was entitled "Kinetic Spray Coatings," published in
Surface and Coatings Technology, vol. 111, pages 62-71, Jan. 10,
1999 and the second was entitled "Aluminum coatings via kinetic
spray with relatively large powder particles", published in Surface
and Coatings Technology 154, pp. 237-252, 2002. The articles
discuss producing continuous layer coatings having high adhesion,
low oxide content and low thermal stress. The articles describe
coatings being produced by entraining metal powders in an
accelerated gas stream, through a converging-diverging de Laval
type nozzle and projecting them against a target substrate surface.
The particles are accelerated in the high velocity gas stream by
the drag effect. The gas used can be any of a variety of gases
including air, nitrogen, argon, neon or helium. It was found that
the particles that formed the coating did not melt or thermally
soften prior to impingement onto the substrate. It is theorized
that the particles adhere to the substrate when their kinetic
energy is converted to a sufficient level of thermal and mechanical
deformation upon striking the substrate. Thus, it is believed that
the particle velocity must exceed a critical velocity and be high
enough to exceed the yield stress of the particle to permit it to
adhere when it strikes the substrate. It was found that the
deposition efficiency of a given particle mixture was increased as
the inlet gas temperature was increased. Increasing the inlet gas
temperature decreases its density and thus increases its velocity.
The velocity varies approximately as the square root of the inlet
gas temperature. The actual mechanism of bonding of the particles
to the substrate surface is not fully known at this time. The
critical velocity is dependent on the material of the particle and
the material of the substrate. Once an initial layer of particles
has been formed on a substrate subsequent particles bind not only
in the voids between previous particles bound to the substrate but
also engage in particle to particle bonds. The bonding process is
not due to melting of the particles in the main gas stream because
the temperature of the particles is always below their melting
temperature.
[0005] Kinetic spray technology would greatly reduce the cost of
manufacturing if it could be used to coat materials covered by
plastic-type material without requiring prior removal of the
plastic material. One area of special concern is flexible
electrical circuitry. In these systems electrical conductors,
typically ribbon wire, are covered in a plastic-type coating to
protect them and to electrically isolate them from each other.
Other plastic covered substrates of interest include ceramics. In
the present specification and claims the term plastic-type material
is meant to designate not only true plastics but also
polyurethanes, polymers, nylons, rubbers, and elastomers. These
coverings are relatively soft compared to the metals and ceramics
that typically make up the underlying substrate. As mentioned, one
common manufacturing environment that could benefit from the
technology is the flexible circuit wiring area. This wiring is the
typical plastic covered ribbon type wiring found in computers,
automobiles and other electrical systems. Currently, when one
desires to manufacture an electrical connection point or solderable
pad somewhere along the flexible circuit it is necessary to remove
the outer plastic covering in some manner prior to making the
connection. Typically, this is done by laser ablation, using a
punch wheel, or milling. The exposed wiring is then cleaned and
finally, electroplated. These steps are very time consuming,
require a large manufacturing footprint, and generate waste
problems. It would be advantageous to develop a method for applying
a kinetic spray coating onto a surface that is covered in a
plastic-type material without requiring prior removal of the
plastic-type material. The kinetic sprayed coating can serve as an
electrical contact or solder point.
SUMMARY OF THE INVENTION
[0006] In one embodiment, the present invention is a method of
kinetic spray coating a substrate covered by a plastic-type
material comprising the steps of: providing particles of a material
to be sprayed having an average nominal diameter of from 60 to 250
microns; providing a supersonic nozzle having a converging region
connected to a diverging region through a throat; providing a
substrate material covered by a plastic-type material and
positioned opposite the nozzle; providing a mask having at least
one opening therein, pressing the mask against the plastic-type
material; directing a flow of a heated main gas through the nozzle;
and entraining the particles in the flow of the heated main gas and
accelerating the particles to a velocity sufficient to result in
the particles passing through the opening in the mask and removing
the plastic-type material and then adhering to the substrate
material upon impact.
[0007] In another embodiment, the present invention is a method of
kinetic spray coating a substrate covered by a plastic-type
material comprising the steps of: providing particles of a material
to be sprayed having an average nominal diameter of from 250 to
1400 microns; providing a supersonic nozzle having a converging
region connected to a diverging region through a throat; providing
a substrate material covered by a plastic-type material and
positioned opposite the nozzle; directing a flow of a heated main
gas through the nozzle; and entraining the particles in the flow of
the heated main gas and accelerating the particles to a velocity
sufficient to result in the particles passing through the
plastic-type material and adhering to the substrate material upon
impact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention will now be described, by way of
example, with reference to the accompanying drawings, in which:
[0009] FIG. 1 is a generally schematic layout illustrating a
kinetic spray system for performing the method of the present
invention;
[0010] FIG. 2 is an enlarged cross-sectional view of one embodiment
of a kinetic spray nozzle used in the system;
[0011] FIG. 3 is a schematic diagram of one embodiment of the
present invention;
[0012] FIG. 4 is scanning electron photo-micrograph of a
cross-section through a flexible circuit sprayed in accordance with
one embodiment of the invention;
[0013] FIG. 5 is a schematic of another embodiment of the present
invention;
[0014] FIG. 6 is a scanning electron photo-micrograph of a flexible
circuit kinetically sprayed in accordance with the embodiment
illustrated in FIG. 5; and
[0015] FIG. 7 is another scanning electron photo-micrograph of a
flexible circuit kinetically sprayed in accordance with the
embodiment illustrated in FIG. 5.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0016] Referring first to FIG. 1, a kinetic spray system according
to the present invention is generally shown at 10. System 10
includes an enclosure 12 in which a support table 14 or other
support means is located. A mounting panel 16 fixed to the table 14
supports a work holder 18 capable of movement in three dimensions
and able to support a suitable covered substrate to be coated. The
work holder 18 is preferably designed to move a substrate relative
to a nozzle 34 of the system 10, thereby controlling where the
powder material is deposited on the substrate. In other
embodiments, workholder 18 can be stationary and designed to feed a
substrate past the nozzle 34, as described below. The enclosure 12
includes surrounding walls having at least one air inlet, not
shown, and an air outlet 20 connected by a suitable exhaust conduit
22 to a dust collector, not shown. During coating operations, the
dust collector continually draws air from the enclosure 12 and
collects any dust or particles contained in the exhaust air for
subsequent disposal.
[0017] The spray system 10 further includes a gas compressor 24
capable of supplying gas pressure up to 3.4 MPa (500 psi) to a high
pressure gas ballast tank 26. The gas ballast tank 26 is connected
through a line 28 to both a powder feeder 30 and a separate gas
heater 32. The gas heater 32 supplies high pressure heated gas, the
main gas described below, to a kinetic spray nozzle 34. The
pressure of the main gas generally is set at from 150 to 500 psi,
more preferably from 300 to 400 psi. The powder feeder 30 mixes
particles of a spray powder with unheated gas at a lower pressure
and supplies the mixture to a supplemental inlet line 48 of the
nozzle 34. As discussed below, the powder feeder 30 is a low
pressure feeder. Preferably the particles are fed at a rate of from
0.2 to 10 grams per second to the nozzle 34, more preferably at a
rate of from 0.2 to 4 grams per second. A computer control 35
operates to control the pressure of gas supplied to the gas heater
32, the temperature of the heated main gas exiting the gas heater
32, and the pressure of the gas supplied to the powder feeder
30.
[0018] The particles used in the present invention are preferably
either electrically conductive materials or solderable materials
including: tin, tin alloys, especially tin silver alloys, aluminum,
aluminum alloys, silver, silver alloys, gold, gold alloys, lead,
lead alloys, zinc, zinc alloys, and mixtures of these materials. In
one embodiment, the powders preferably have nominal average
particle diameters of from 60 to 250 microns and more preferably
from 177 to 250 microns. In another embodiment, the particles
powders preferably have nominal average particle sizes of from 250
to 1400 microns and more preferably from 600 to 1400 microns.
Depending on the particles or combination of particles chosen the
main gas temperature may range from 315 to 710 degrees Celsius.
With aluminum and its alloys the temperature preferably is around
315.degree. C., while the other materials preferably are sprayed at
a main gas temperature of from 400 to 710.degree. C. Mixtures of
the materials may be sprayed at from 315 to 710.degree. C. It will
be recognized by those of skill in the art that the temperature of
the particles in the gas stream will vary depending on the particle
size and the main gas temperature. The main gas temperature is
defined as the temperature of heated high-pressure gas at the inlet
to the nozzle 54. Since the particles are never heated to their
melting point, even upon impact, there is no change in the solid
phase of the original particles due to transfer of kinetic and
thermal energy, and therefore no change in their original physical
properties. The particles are always at a temperature below the
main gas temperature. The particles exiting the nozzle 34 are
directed toward a surface of a substrate to coat it.
[0019] FIG. 2 is a cross-sectional view of one embodiment of the
nozzle 34 and its connections to the gas heater 32 and the powder
feeder 30. This embodiment is a low pressure nozzle 34 that is
connected to a low pressure powder feeder 30. A main gas passage 36
connects the gas heater 32 to the nozzle 34. Passage 36 connects
with a premix chamber 38 that directs gas through a flow
straightener 40 and into a chamber 42. Temperature and pressure of
the heated main gas are monitored by a gas inlet temperature
thermocouple 44 in the passage 36 and a pressure sensor 46
connected to the chamber 42. The main gas has a temperature that is
always insufficient to cause melting in the nozzle 34 of any
particles being sprayed. With this nozzle 34 the main gas
temperature generally ranges from 315 to 710.degree. C. The main
gas temperature can be well above the melt temperature of the
particles. Main gas temperatures that are 5 to 7 fold above the
melt temperature of the particles have been used in the present
system 10. What is necessary is that the temperature and exposure
time to the main gas be selected such that the particles do not
melt in the nozzle 34. The temperature of the main gas decreases
rapidly as it travels through the nozzle 34. In fact, the
temperature of the main gas measured as it exits the nozzle 34 is
often at or below room temperature even when its initial
temperature is above 530.degree. C.
[0020] Chamber 42 is in communication with a de Laval type
supersonic nozzle 54. The nozzle 54 has a central axis 52 and an
entrance cone 56 that decreases in diameter to a throat 58. The
entrance cone 56 forms a converging region of the nozzle 54.
Downstream of the throat 58 is an exit end 60 and a diverging
region is defined between the throat 58 and the exit end 60. The
largest diameter of the entrance cone 56 may range from 10 to 6
millimeters, with 7.5 millimeters being preferred. The entrance
cone 56 narrows to the throat 58. The throat 58 may have a diameter
of from 3.5 to 1.5 millimeters, with from 3 to 2 millimeters being
preferred. The diverging region of the nozzle 54 from downstream of
the throat 58 to the exit end 60 may have a variety of shapes, but
in a preferred embodiment it has a rectangular cross-sectional
shape. At the exit end 60 the nozzle 54 preferably has a
rectangular shape with a long dimension of from 8 to 14 millimeters
by a short dimension of from 2 to 6 millimeters.
[0021] In use of this nozzle 54 a mixture of unheated low pressure
gas and coating powder is fed from the powder feeder 30 through one
of a plurality of supplemental inlet lines 48 each of which is
connected to a powder injector tube 50 comprising a tube having a
predetermined inner diameter. For simplicity the actual connections
between the powder feeder 30 and the inlet lines 48 are not shown.
The injector tubes 50 supply the particles to the nozzle 54 in the
diverging region downstream from the throat 58, which is a region
of reduced pressure. The length of the nozzle 54 from the throat 58
to the exit end can vary widely and typically ranges from 80 to 400
millimeters.
[0022] As would be understood by one of ordinary skill in the art
the number of injector tubes 50, the angle of their entry relative
to the central axis 52 and their position downstream from the
throat 58 can vary depending on any of a number of parameters. In
FIG. 2 ten injector tubes 50 are show, but the number can be as low
as one and as high as the available room of the diverging region.
Preferably, the number of injector tubes 50 is from 1 to 3 and more
preferably only 1. The angle of their entry relative to the central
axis 52 can be any that ensures that the particles are directed
toward the exit end 60, basically from 1 to about 90 degrees. It
has been found that an angle of 45 degrees relative to central axis
52 works well. An inner diameter of the injector tube 50 can vary
between 0.4 to 3.0 millimeters. The use of multiple injector tubes
50 permits one to easily modify the system 10. One can rapidly
change particles by turning off a first powder feeder 30 connected
to a first injector tube 50 and the turning on a second powder
feeder 30 connected to a second injector tube 50. Such a rapid
change over is not easily accomplished with a single powder feeder
30 system. For simplicity only one powder feeder 30 is shown in
FIG. 1, however, as would be understood by one of ordinary skill in
the art, the system 10 could include a plurality of powder feeders
30. The system 10 also permits one to mix a number of powders in a
single injection cycle by having a plurality of powder feeders 30
and injector tubes 50 functioning simultaneously. An operator can
also run a plurality of particle populations, each having a
different average nominal diameter, with the larger population
being injected closer to the throat 58 relative to the smaller size
particle populations and still get efficient deposition. The system
10 permits an operator to better optimize the deposition efficiency
of a particle or mixture of particles. For example, it is known
that harder materials have a higher critical velocity, therefore in
a mixture of particles the harder particles could be introduced at
a point closer to the throat 58 thereby giving a longer
acceleration time.
[0023] Using the nozzle 54 one can use much lower pressures to
inject the powder when the injection takes place after the throat
58. All that is required is that it exceed the main gas pressure at
the point of injection. The main gas pressure at 2.5 centimeters
past the throat 58 can vary from about 14 to 40 pounds per square
inch (psi). Preferably the injection takes place at from 1.2 to 5.0
centimeters, and more preferably from 1.7 to 3.8 centimeters beyond
the throat 58. Preferably the pressure of the powder injection is
from 20 to 60 psi above the pressure of the main gas at the
injection point and more preferably from 30 to 50 psi above the
main gas pressure at the point of injection. The nozzle 54 produces
an exit velocity of the entrained particles of from 100 meters per
second to as high as 1200 meters per second.
[0024] In the present invention it is preferred that the nozzle 34
be at an angle of from 0 to 20 degrees relative to a line drawn
normal to the plane of the surface being coated, more preferably at
an angle of from 0 to 5 degrees relative to the normal line.
Preferably the work holder 18 moves the substrate past the nozzle
34 at a traverse speed of from 70 to 260 millimeters per second
depending on the size of the particles as discussed below. It is
preferred that the exit end 60 of the nozzle 54 have a standoff
distance from the surface to be coated of from 2.5 to 15
centimeters, again depending on particle size as discussed
below.
[0025] As discussed above, in one embodiment the particles used
have a nominal average diameter of from 250 to 1400 microns and
more preferably from 600 to 1400 microns. In this embodiment the
particles are large enough that a single particle sprayed per the
invention can bind to an underlying substrate and provide an
electrical path from the substrate through the overlying plastic
layer. Particles of this size can be directly sprayed through the
plastic onto the substrate. A schematic diagram of this is shown in
FIG. 3. A cross-section of a flexible circuit is generally shown at
80. Flexible circuit 80 includes an overlayer of a plastic 82 and
an underlayer of plastic 84 with a plurality of ribbon conductors
86 embedded between them. Particles having a nominal average
diameter of from 250 to 1400 microns are shown at 88. Particles 88
bind to the conductors 86 and form an electrical path through the
overlaying plastic 82.
[0026] FIG. 4 is a scanning electron photo-micrograph of a
cross-section through a flexible circuit 90 kinetically sprayed in
accordance with the present invention. The particles were a 100%
tin particle population having an average nominal diameter of 400
to 850 microns. The spray parameters were as follows: a powder
pressure of 140 psi., powder feed rate of 2 grams/second, main gas
temperature of 705.degree. C., injection was at 2.5 centimeters
past a throat of 2.8 millimeters, stand-off distance was 3.7
centimeters, and the nozzle 54 had a diverging region length of 280
millimeters with an exit end 60 of 5 by 12.5 millimeters. Flexible
circuit 90 includes a plurality of ribbon conductors 92 covered in
the plastic. Single tin particles 94 sprayed according to the
present invention form an electrical path from the conductor 92
through the plastic layer. These tin particles 94 can serve as
electrical contact points or solder points as the situation
requires.
[0027] In the embodiment, described above, wherein the particles
have an average nominal size of from 250 to 1400 microns one can
adjust the traverse rate and stand-off distance to ensure that
there is no electrical shorting between conductors 92. Thus, from a
technical stand point the invention can be carried out without use
of a mask. From an aesthetic stand point, however, it may be
desirable to use a mask to avoid having any particles in the area
between adjacent conductors 92. The mask material can be any of the
well known compositions including: steel, stainless steel, ceramic,
and metals. This embodiment permits previously unobtainable
results. In a single high speed pass one can selectively coat
conductors 92 through a plastic layer to form electrical contact
points or solder points. If the kinetic spray is applied near an
end of the flexible circuit 90 the end can simply be bent over to
form a contact that can be inserted into a connector.
[0028] In Table 1 below the preferred spray parameters are listed
for a series of particle sizes in the range of from 250 to 1400
microns when using a 100% tin particle powder and a nozzle 54
having a throat 58 diameter of 2.8 millimeters, a diverging region
length of 280 millimeters and an exit end 60 having dimensions of 5
millimeters by 12.5 millimeters. TABLE-US-00001 TABLE 1 Main gas
Powder feed Stand-off Traverse rate Particle size temperature rate
distance millimeters/ microns .degree. C. grams/second centimeters
second 250 to 600 480 to 600 0.3 to 3 10 to 15 75 to 150 600 to
1400 420 to 710 0.3 to 3 3.5 to 10 150 to 260
[0029] Using the 100% tin particle powder after the nozzle 54 is
modified to have a diverging region length of 85 millimeters and an
exit end 60 having dimensions of 2 millimeters by 10 millimeters
and the particle size is from 250 to 425 microns it is preferred
that the parameters be changed as shown in Table 2, below.
TABLE-US-00002 TABLE 2 Main gas Powder feed Stand-off Traverse rate
Particle size temperature rate distance millimeters/ microns
.degree. C. grams/second centimeters second 250 to 425 480 to 600
0.3 to 3 3.5 to 5 90 to 125
[0030] When using particles having an average nominal diameter of
from 60 to 250 microns it was found that the process needed to be
changed. These particles are too small for a single particle to
create an electrical path from the conductor 92 through the plastic
layer. It was found that for particles of this size the spray
parameters needed to be changed and that a mask is necessary to
eliminate potential electrical shorting between adjacent conductors
92. Using the kinetic spray process it is possible to in a single
step to remove the plastic overlay and bind a sufficient density of
particles to create a contact or solder point while preventing
cross flow between adjacent conductors 92.
[0031] FIG. 5 is a schematic diagram of the present invention as
modified for particles having a size of from 60 to 250 microns. The
flexible electrical circuit includes a plastic overlayer 112 and a
plastic underlayer 114 with conductors 116 embedded between them.
As discussed a mask is necessary and further more a two part mask
is required. The mask includes an upper mask 118 having a cutout
120 with a desired shape and a lower mask 122 preferably having a
projection 126 having a shape that mirrors that of the cutout 120.
The upper and lower masks 118, 122 are held against each other with
sufficient pressure to cause some distortion of the plastic layers
112, 114 to ensure a tight seal. Although not shown the masks 118,
122 could be modified so either the upper or the lower includes a
ridge matching the cutout with the other mask being flat. Such a
design would also permit a tight seal between the two masks and
some distortion of the plastic layers 112, 114. Using the two part
mask the kinetic spray parameters can be more aggressive and
surprisingly it has been found that the initial particles strike
with sufficient force to completely remove the plastic overlayer
112 and subsequent particles bind directly to the conductor 116.
The mask material can be any of the well known compositions
including: steel, stainless steel, ceramic, and a metal.
[0032] The preferred parameter setting for particle sizes in the
range of from 177 to 250 microns when using a 100% tin particle
powder and a nozzle 54 having a throat 58 diameter of 2.8
millimeters, a diverging region length of 280 millimeters and an
exit end 60 having dimensions of 5 millimeters by 12.5 millimeters
are shown in Table 3 below. In addition, the preferred settings
when using the 100% tin particle powder after the nozzle 54 is
modified to have a diverging region length of 85 millimeters and an
exit end 60 having dimensions of 2 millimeters by 10 millimeters
and the particle size is from 60 to 250 microns are shown in Table
3 below. TABLE-US-00003 TABLE 3 Main gas Powder feed Stand-off
Traverse rate Particle size temperature rate distance millimeters/
microns .degree. C. grams/second centimeters second 60 to 250 480
to 600 0.5 to 2 1.2 to 3.0 75 to 90 (short nozzle) 177 to 250 480
to 600 0.5 to 2 10 to 15 75 to 150 (long nozzle)
[0033] Using these parameters one is able to spray complex patterns
with a high degree of precision and very rapidly unlike prior
methods. Examples are shown in FIGS. 6 and 7. In FIG. 7 a mask
having a circular cutout 120 was used with a nozzle 54 having a
rectangular exit end 60. The flexible circuit is shown at 129 and
the kinetic sprayed pattern at 130. The pattern 130 has a clean
well defined edge and a high density with no overspray on the
circuit. The mask was used at a traverse rate of either 75
millimeters per second or 112 millimeters per second and then the
contact resistance was tested at a series of points within the
pattern 130 at a series of applied mechanical loads. It was found
that at all points within the pattern 130 using applied loads of
from 20 to 100 grams the contact resistance was from 4 to 1.8
milliOhms. This is within the range that is measured when the tin
particles are sprayed directly onto bare copper wire. Thus, the
results demonstrate that the spray parameters enable the system 10
to remove the plastic overlayer 112 and bind the particles directly
to the conductor 116 at a high rate of speed. In FIG. 7 the cutout
120 was a series of slots to match the spacing of conductors in a
flexible circuit 140. The spray pattern 142 has a high density of
particles and clean well defined edges with no overspray.
[0034] The foregoing invention has been described in accordance
with the relevant legal standards, thus the description is
exemplary rather than limiting in nature. Variations and
modifications to the disclosed embodiment may become apparent to
those skilled in the art and do come within the scope of the
invention. Accordingly, the scope of legal protection afforded this
invention can only be determined by studying the following
claims.
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