U.S. patent application number 14/172664 was filed with the patent office on 2014-06-05 for electrical connector and method of making it.
This patent application is currently assigned to Neoconix, Inc.. The applicant listed for this patent is Neoconix, Inc.. Invention is credited to Dinesh Sundararajan Kalakkad, David Noel Light, Peter Tho Nguyen.
Application Number | 20140154893 14/172664 |
Document ID | / |
Family ID | 48524319 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140154893 |
Kind Code |
A1 |
Light; David Noel ; et
al. |
June 5, 2014 |
ELECTRICAL CONNECTOR AND METHOD OF MAKING IT
Abstract
The present invention is an electrical connector in which a
substrate (such as a printed circuit board or PCB) includes a
plurality of apertures (or vias) and some of those apertures are
filled with two materials to improve the characteristics of the
electrical interconnection. The preferred process of crating the
filled vias includes the steps of plating the vias with an
electrically-conductive material to create an
electrically-conductive path between portions of the substrate and
components associated with the substrate and partially filling the
apertures, then filling at least a portion of the apertures or vias
with a second or different filling material to seal at least apart
of the electrically conductive path through the plating. The second
filling material may be chosen to provide thermal compensation for
the connection.
Inventors: |
Light; David Noel; (Los
Gatos, CA) ; Kalakkad; Dinesh Sundararajan; (Palo
Alto, CA) ; Nguyen; Peter Tho; (San Jose,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Neoconix, Inc. |
Sunnyvale |
CA |
US |
|
|
Assignee: |
Neoconix, Inc.
Sunnyvale
CA
|
Family ID: |
48524319 |
Appl. No.: |
14/172664 |
Filed: |
February 4, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13310647 |
Dec 2, 2011 |
8641428 |
|
|
14172664 |
|
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Current U.S.
Class: |
439/66 ; 174/264;
29/852 |
Current CPC
Class: |
H05K 3/4092 20130101;
H01R 13/5219 20130101; H05K 1/0206 20130101; Y10T 29/49165
20150115; H05K 1/115 20130101; Y10T 29/49224 20150115; H01R 35/02
20130101; H05K 3/4069 20130101; H05K 2201/068 20130101 |
Class at
Publication: |
439/66 ; 174/264;
29/852 |
International
Class: |
H01R 35/02 20060101
H01R035/02; H05K 1/11 20060101 H05K001/11; H01R 13/52 20060101
H01R013/52 |
Claims
1.-23. (canceled)
24. An electrical connector comprising: a substrate having a first
surface and a second surface and carrying electrical contacts on at
least one surface and a plurality of apertures extending between
the first surface and the second surface, said electrical contacts
including an elastic portion; an electrically-conductive material
which extends through at least one of the plurality of apertures
and electrically couples the first surface and the second surface;
and an additional material in addition to the conductive material
which is included within at least one of the plurality of
apertures, said additional material sealing at least a portion of
the electrically-conductive material from exposure to the
environment outside the substrate, said additional material chosen
to have a coefficient of thermal expansion approximating the
coefficient of thermal expansion of at least one of the substrate
and the electrically-conductive material.
25. An electrical connector of the type described in claim 24
wherein the additional material is chosen to have a coefficient of
thermal expansion between the coefficient of thermal expansion of
the substrate and the coefficient of the electrically conductive
material.
26. An electrical connector of the type described in claim 24
wherein the additional material includes a thermosetting epoxy
material.
27. An electrical connector of the type described in claim 24
wherein the additional material is filled with silica
particles.
28. An electrical connector of the type described in claim 24
wherein the additional material is filled with a material with high
thermal conductivity.
29. An electrical connector of the type described in claim 24
wherein the additional material includes a fusible metal.
30. A method of making an electrical connector comprising the steps
of: providing a connector substrate with a plurality of apertures;
defining a plurality of electrically-conductive contacts on a flat
sheet of conductive material, forming the flat sheet into a
three-dimensional form with a plurality of elastic electrical
contacts, attaching the three-dimensional conductive sheet with a
plurality of electrical contacts to the substrate and singulating
the electrical contacts; providing an electrically-conductive path
through at least one of the apertures and attaching at least one of
the electrical contacts to the electrically-conductive path through
the substrate; choosing an additional material which has a
coefficient of thermal expansion approximating the coefficient of
thermal expansion of at least one of the substrate, the electrical
contact and the electrically-conductive path; and inserting the
chosen additional material into the aperture to protect the
electrically-conductive path by providing a sealing of at least
part of the electrically-conductive path.
31. A method including the steps of claim 30 wherein the step of
filling includes the step of choosing a fill material with a
characteristic based on at least one characteristic of the
substrate.
32. A method including the steps of claim 30 wherein the step of
filling includes the step of choosing a fill material with a
characteristic based on at least one characteristic of the
electrically conductive path.
33. A method including the steps of claim 30 wherein the step of
filling includes the step of choosing a fill material with a
characteristic based on at least one characteristic of at least one
of the substrate, the electrical contact and the electrically
conductive path through the substrate.
34. A method including the steps of claim 30 wherein the step of
choosing a fill material includes the step of choosing a material
with a suitable amount of silica included therein to provide the
desired coefficient of thermal expansion.
35. An electrical connector comprising: a substrate including an
insulating body, at least one mounting surface and a plurality of
apertures extending at least partially through the substrate; a set
of electrical contacts carried on the mounting surface of the
substrate and at least some of the electrical contacts being
proximate at least some of the apertures, the electrical contacts
including at least one elastic spring contact; a first conductive
material within at least some of the apertures and in contact with
at least one of the electrical contacts providing an electrical
path coupling the one electrical contact with a second surface of
the substrate, said first conductive material only partially
filling the apertures into which the first conductive material is
within; and a second material in the same aperture in which the
first conductive material has been inserted, said second material
covering at least part of the first conductive material and filling
at least part of the aperture, said second material having a
coefficient of thermal expansion which approximates the coefficient
of thermal expansion of at least one of the substrate and the first
conductive material.
36. An electrical connector of the type described in claim 35
wherein the substrate has a second mounting surface comprising
mounting pads for at least one chosen from solderballs and surface
mount attachments, where at least one of the mounting pads is
electrically connected to at least one of the electrical
contacts.
37. An electrical connector of the type described in claim 35
wherein the second material comprises a thermosetting epoxy.
38. An electrical connector of the type described in claim 35
wherein the second material has a coefficient of thermal expansion
which has been chosen based on the coefficient of thermal expansion
of the first material.
39. An electrical connector comprising: a substrate having a first
surface and a second surface and carrying electrical contacts on
both surfaces and a plurality of apertures extending between the
first surface and the second surface, said electrical contacts
including an elastic portion; an electrically-conductive material
which extends through at least one of the plurality of apertures
and electrically couples the first surface and the second surface;
and an additional material in addition to the conductive material
which is included within each of the plurality of apertures, said
additional material sealing the apertures to prevent ingress of
fluid materials through the apertures; a sealing mechanism around
the perimeter of at least the connector first surface, said sealing
mechanism comprising a compliant material, said sealing mechanism
providing a fluid ingress-inhibiting seal around the perimeter of
the connector area containing the electrical contacts when
compressed against a mating surface of an electrical component,
such as a printed circuit board.
40. An electrical connector of the type described in claim 39
wherein the sealing mechanism comprises an O-ring.
41. An electrical connector of the type described in claim 39
wherein the sealing mechanism results from the use of a compliant
coverlay material on the connector surface.
42. An electrical connector of the type described in claim 41
wherein the compliant coverlay material is comprised of an
elastomer.
43. An electrical connector of the type described in claim 41
wherein the compliant coverlay material is comprised of a closed
cell foam.
44. An electrical connector of the type described in claim 41
wherein the compliant coverlay material is comprised of an open
cell foam which deters ingress of liquid when sufficiently
compressed.
45. An electrical connector of the type described in claim 39
wherein a sealing mechanism is included on both surfaces of the
connector.
46. An electrical connector comprising: a substrate including an
insulating body, at least one mounting surface and a plurality of
apertures extending at least partially through the substrate; a set
of electrical contacts carried on the mounting surface of the
substrate and at least some of the electrical contacts being
adjacent to or on top of at least some of the apertures, the
electrical contacts including at least one elastic spring contact;
a first conductive material within at least some of the apertures
and in contact with at least one of the electrical contacts
providing an electrical path coupling the one electrical contact
with a second surface of the substrate, said first conductive
material only partially filling the apertures into which the first
conductive material is within; and a second material in the same
aperture in which the first conductive material has been inserted,
said second material covering completely filling the apertures; and
a sealing mechanism around at least the perimeter of at least the
connector first surface, said sealing mechanism comprising a
compliant material, said sealing mechanism providing a seal which
inhibits the ingress of liquids from around the perimeter of the
connector area containing the electrical contacts when compressed
against a mating surface of an electrical component, such as a
printed circuit board.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to an improved electrical
connector and method of making it. More specifically, the present
invention relates to an electrical connector comprising elastic
contacts on an insulating substrate, in which vias or holes in the
insulating substrate are filled to provide a better connector
performance and improved ease of manufacturing.
[0003] 2. Background Art
[0004] Electrical connectors are an important component of many
electronic devices. As the devices become smaller, the
functionality is increasing, requiring increasing numbers of
electrical interconnections between components. In order to enable
system miniaturization, the electrical connectors must become
smaller, yet they are required to handle increasing power and
signal loads and to operate at faster speeds. It is necessary in
many applications to provide a low-cost, high reliability
electrical interconnection on an extremely small scale to allow for
an increasing number of components to be interconnected. As the
operating frequencies and data transfer rates of the electronic
system increases, there is an increased need for high speed signal
integrity through the connector.
[0005] Various electrical connectors have been proposed in the
prior art. Examples of such electrical connector (electrical
interconnection) is shown in Neoconix' prior patents such as U.S.
Pat. No. 7,113,408.
[0006] Conventional electrical connectors present challenges in
terms of their size, cost, and operating speed. A conventional
connector has a substantial size and a significant cost to
manufacture, especially when the connector includes many electrical
contacts. Such connectors also must operate at speeds which are
increasing without losing data as a result of the electrical
connections. Power handling requirements are also increasing.
Conventional connectors are limited in power handling capability,
and can overheat when power load exceeds their capability. These
conventional connectors are typically lacking in their ability to
dissipate heat or to conduct heat away from the mating
components.
[0007] Further, many electrical connectors utilize precious metal
surface finishes, such as gold, to prevent corrosion. These
materials are costly. As a result there is a desire to use smaller
connections (to take up less space and to use less precious
material), and to minimize the surface area which must be finished
with the precious metals.
[0008] Electronic devices and particularly portable electronic
devices are susceptible to corrosion and degradation from liquids
or gases from the environment that penetrate the system. Electrical
connectors typically have a high density of electrical
interconnections, and it is difficult to shield these from the
environment while maintaining connector separability. In contrast,
interconnections on a packaged semiconductor can be over-molded or
under-filled to protect the interconnections from moisture, water,
or gas ingress. Hence, the electrical connector tends to be a
highly susceptible component from the perspective of water ingress
or damage from corrosive environments.
[0009] Accordingly, it will be apparent that the prior art
electrical connectors have limitations and undesirable
characteristics.
SUMMARY OF THE INVENTION
[0010] The present invention overcomes the limitations and
disadvantages of the prior art electrical connectors and methods of
making them.
[0011] The present invention is an improved electrical connector
and method of making it in which the electrical connector may have
dense interconnections, and which provides high reliability
interconnections, low resistance and high current carrying
capacity, improved thermal dissipation, reduced precious metal
usage during fabrication, and thin electrical conductors while
providing improved protection for the electrical interconnections.
This method and connector will allow for smaller scale
interconnections and greater reliability of the interconnection
while providing improved signal integrity at high frequency and an
economical electrical connector to manufacture.
[0012] Other objects and advantages of the present invention will
be apparent to those skilled in the relevant art in view of the
following description of the preferred embodiment and the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates one form of prior art electrical
connector in an enlarged, cut-away or sectional view;
[0014] FIG. 2 illustrates one form of an electrical connector of
the present invention in an enlarged, cut-away or sectional
view;
[0015] FIG. 3 illustrates a second form of prior art electrical
connector in a cut-away or sectional view;
[0016] FIG. 4 illustrates a second form of an electrical connector
of the present invention in a cut-away or sectional view;
[0017] FIG. 5 illustrates portions of the electrical connector of
FIG. 2 or 4 as one example of manufacturing progression using the
method of the present invention;
[0018] FIG. 6 is a flow chart illustrating one process for making
the electrical connector of the present invention;
[0019] FIG. 7 is a cross-sectional view of an electrical connector
which illustrates other uses for the present invention on
multilayer printed circuit structures containing blind and/or
buried interconnections; and
[0020] FIGS. 8a, 8b, 8c and 8d illustrate applications for the use
of the present invention to create a sealed electrical connector,
where FIG. 8c is a front view of a contact pad array on a PCB to
which an electrical connector (or interposer), shown in perspective
view of FIG. 8a, would mate, FIG. 8b is an enlarged perspective
view from a different angle of a portion of the electrical
connector (interposer) of FIG. 8a, showing details of its contact
array and FIG. 8d is a cross-sectional view depicting one
application of that electrical connector.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] FIG. 1 is an enlarged and cross-sectional view of a portion
of an electrical connector 10 of the prior art, such as is
described in U.S. Pat. No. 7,113,408 owned by assignee of the
present invention, Neoconix. The electrical connector as shown in
this view the electrical connector 10 has a substrate 12 a
plurality of electrical contacts 14 mounted on a top surface 12a of
the substrate 12 and a plurality of contacts 16 mounted on a bottom
surface 12b of the substrate 12. The electrical contacts 14 and 16
are typically formed from an initially flat sheet of conductive
material which has been formed into a three-dimensional shape in a
batch process (as described in U.S. Pat. No. 7,758,351, owned by
the assignee of the present invention), with the sheet of
electrical contacts then secured to the substrate 12 in a single
operation, then singulated in a conventional process (such as a
chemical etching process).
[0022] The substrate 12 is typically non-conducting and made
starting with a printed circuit board (PCB) material such as a
sheet of copper-clad FR4. The substrate 12 as shown in this FIG. 1
includes a plurality of through holes 18 which are formed in a
conventional manner. The through holes 18 (which are also sometimes
referred to as apertures or vias and may extend completely through
the substrate 12 or only partially through the substrate 18,
terminating at an intermediate layer of the substrate 18) are
plated in a conventional manner to provide an electrically
conductive via 18a through the substrate 12. The copper cladding
and plating material also provides conductor portions 12c, 12d on
the top and bottom surfaces 12a, 12b to provide an
electrically-conductive path on these surfaces of the substrate 12
to electrically couple selected electrical contacts 14, 16. 12c and
12d are electrically connected to the plated via which provides a
conductive path between 12 c and 12 d.
[0023] The plated through holes are typically formed through a
drilling process followed by a process to make the hole walls
electrically conductive, after which the hole walls are plated
through a chemical or electrochemical process which allows for the
wall of the electrically conductive via 18a to be of a controlled
thickness to provide sufficient conductivity and reliability. The
standard through hole or via 18 with plating 18a of the prior art
electrical connectors is thus not filled completely, but only
around the periphery of the cylindrical opening, having a hollow or
open center portion, represented by the reference numeral 18c.
[0024] FIG. 2 illustrates an electrical connector 10' of the
present invention which is a modified version of the connector 10
of FIG. 1. In this view, the connector 10' includes a substrate 12
with a plurality of through holes 18 and a plurality of electrical
contacts 14 mounted to the top surface 12a of the substrate 12 and
a plurality of electrical contacts 16 mounted to the lower or
bottom surface 12b of the substrate 12. A first conductive material
(a plating material) is shown applied to the aperture to provide
the plating layer 18a as an electrical connection with selected
electrical contacts 14, leaving a cylinder-shaped opening within
the aperture 18. A fill material 18b substantially fills the
cylinder-shaped void, providing a covering and sealing material
over at least a portion of the plating material 18a within the
aperture 18.
[0025] The preferred fill material 18b for many applications of the
present invention is thermosetting epoxy, a plastic material.
However, other materials can be used to advantage in the present
invention including other thermo-setting materials (such as
acrylic, polyimide, or Bakelite) or thermoplastic material (such as
PMMA, thermoplastic polyimide, or LCP). Other materials which could
be used to advantage as the fill material 18b in the present
invention include solder mask, fluoropolymers, and other polymers
and blends of polymers. The via fill material 18b also can be a
composite polymeric material including particulate or fiber filler
materials such as glass fibers, alumina, silicon carbide, magnesium
oxide, or silicon dioxide (silica) particles to control thermal
expansion or to increase thermal conductivity, where silica is
particularly useful in mixtures to achieve a desired coefficient of
thermal expansion. The via fill material also can include
conductive fillers such as silver flake or metal particles
including gold, copper and/or silver to improve conductivity and/or
reliability. In yet some other applications, a via fill material
can be an electrically conductive material--a metal such as copper
or an alloy such as solder. The filler could include copper which
has been plated sufficiently to completely fill the via. The solder
filler could be created by printing solder paste into the vias,
then reflowing to create a solder via fill.
[0026] The via fill material 18b can provide a mechanical
strengthening of the electrical connection provided by the plated
via. This via fill material reduces the stress on the via plating
layer 18a during electrical connector operation, including reducing
stress during thermal cycling or during activation of the
electrical connector (for example, from flexing of the electrical
connection structure or from expansion and contraction of the
substrate 12). The present invention also contemplates that the via
fill material might provide a sealed connector in some
applications, including with a separate seal such as an o-ring, If
desired. A sealed connector provided by (or in conjunction with)
the via fill material can protect the sensitive electronic
components inside of an electronic device from gases and liquids
which might erode or corrode the electronic components and reduce
the effectiveness and the useful life of the electronic system.
[0027] The via fill material 18b may be chosen based on the
application under consideration. In some cases, it is desirable to
have a coefficient of thermal expansion which is selected based on
the coefficient of the plating material (approximately equal to
that of the plating material). In other applications, it is
desirable to have a coefficient of thermal expansion which is
approximately the same as the coefficient of thermal expansion of
the substrate. In still others, it is desirable to have a
coefficient of thermal expansion which is approximately the average
of the coefficients of thermal expansion of the plating material
and the substrate.
[0028] The via fill material 18b might be thermally conductive in
other applications. This can be accomplished by using thermally
conductive fillers in the via fill material, such as metals (for
example copper) and certain ceramic materials (for example boron
nitride, aluminum nitride, or aluminum oxide). Using a thermally
conductive fill material would improve the heat transfer through
the electrical connector 10' and reduce the heat retained at the
electrical interconnections or transferred to the mating
components, which may be heat sensitive. This can effectively
increase the current carrying capacity of the connector, and as a
result may reduce the number of high power interconnections
required and/or improve the reliability of the system.
[0029] The via fill material 18b might be electrically conductive
in certain other applications. This can be accomplished by
including a metal (such as copper, silver, or gold) or a metallic
alloy (such as solder) within the fill material. This type of
material can reduce the electrical resistance through the
electrical connector 10', enabling high current carrying
capability. This increased current carrying capacity can reduce the
number of connector contacts ("pins" or "positions") required to
provide sufficient power to a device or system element. This can
also reduce the heat generation due to resistive heating and can
also improve signal integrity.
[0030] Because the elastic contacts commonly require surface
finishing with a precious metal such as gold, to ensure low contact
resistance and prevent corrosion, and the surface finishing
frequently occurs subsequent to attachment of the contacts to the
substrate, the via or plated through hole will typically
incidentally be plated with the precious metal, increasing gold
usage. The via fill material prevents the walls of the via from
being plated with the precious metal, hence reducing precious metal
usage and therefore fabrication cost.
[0031] In a connector structure where all of the vias are filled,
the connector structure may be sealed from side to side and
prevents moisture or water ingress through the connector structure.
By sealing the perimeter of the connector to another component or
element of the electronic system, a watertight connector can be
achieved. This is a significant advantage, for example, for battery
connectors for cell phones, where the battery side of the connector
may have significantly higher likelihood of exposure to water than
the electronic components within the main body of the phone
housing. The sealed connector would prevent water ingress from the
battery side of the connector into the main body of the phone,
where sensitive electronic devices inside including semiconductor
devices such as processor chips, memory chips, and logic chips
reside.
[0032] The present invention is related to electrical connectors in
general and is not limited to electrical connectors having a
plurality of spring contacts on the top and bottom of the
electrical connector, and it is not limited to a connector having
electrical contacts on both top and bottom portions of the
connector. So, in place of one set of the electrical contacts, an
array of surface mount pads could be employed. In the alternative,
the contacts could be a ball grid array (BGA), if desired, FIG. 3
illustrates the use of a ball grid array (BGA) contacts 19 in the
electrical connector 10 of the prior art. The electrical connector
10 includes the substrate 12 with its top surface 12a and its
bottom surface 12b, with a plurality of spring electrical contacts
14 on the top surface 12a. The substrate 12 includes a plurality of
through holes or vias 18 with plating 18a on the vias or through
holes, leaving a void or open space 18c within the vias 18. A grid
array of balls 19 is mounted to the bottom surface 12b in a
conventional manner of soldering the balls in place. However, since
the solder would wick into the apertures if the balls were located
over a via 18 with its open void 18c or in close proximity thereto,
these balls 19 must be spaced from the open vias 18 of this
electrical connector 10.
[0033] FIG. 4 illustrates the electrical connector 10' of the
present invention with such an array of electrically conductive
balls 19 mounted to the lower surface 12b of the substrate 12. The
apertures or vias 18 through the substrate 12 have been plated with
a plating material 18a and the rest of the aperture has been filled
with the fill material 18b. The fill material 18b prevents the
solder from wicking into the hole, allowing the placement of a
solder ball 19 over an aperture or in close proximity thereto.
[0034] FIG. 5 illustrates the substrate of the electrical connector
of the present invention as it progresses through one typical
manufacturing process, up to but not including the attachment of
the sheet of elastic contacts to the substrate. Many variations on
this manufacturing process can be made and additional steps can be
inserted if desired for particular applications. In step 1, a
copper clad FR4 printed circuit board substrate 12e is shown as the
starting material, with layers 12f of copper on top and bottom of
the insulating material 12g. In step 2, a substrate 12h is shown
after the apertures or vias 18 (sometimes called through holes)
have been formed, preferably using a drilling process. At step 3 a
substrate 12i is shown after the seeding and plating process has
formed plated paths 18a through at least some of the vias 18, but
leaving the open region or void 18c within the aperture 18 adjacent
to the plating 18a. At step 4, a substrate 12j is shown with fill
material 18b inserted into the void 18c of step 3. At step 5, the
fill material 18b is cured and shrinks and the surfaces (top and
bottom, as desired) may be cleaned mechanically or chemically to
remove residual material such as resin from the surface of the fill
material 18b. At step 6, the substrate 12m now has undergone
circuit formation through the use of a "print and etch" process.
Portions of the conductive material at 12n have been removed to
provide the circuit in the desired interconnection in a well known
manner.
[0035] Of course, it will be understood that many variations to
this process are possible without departing from the spirit of the
present invention. So, for example, if the fill material 18b does
not substantially shrink during the cure process, planarization may
be necessary (e.g., by mechanical abrasion) so that the hole fill
18b surfaces have the desired relationship to the surface of the
substrate. If the fill material shrinks too much, then an
additional fill step might be desired to bring the level of the
fill material to the desired level. If it is desired to have the
fill material 18b recessed from the surface of the substrate--for
example, to prevent interference with the movement of the spring
contacts), the surface of the substrate can be plated with copper
in selected locations.
[0036] FIG. 6 illustrates the steps of one preferred process for
making the electrical connector of the present invention. The
process begins with the substrate 12 at step 100, with the
preferred substrate being printed circuit board with copper
cladding. At step 110 the apertures or vias 18 are formed,
preferably using a drilling process. This drilling process could
include mechanical drilling, laser drilling, plasma drilling, or
other means of hole making. Next at step 120, the apertures 18 are
seeded and plated using conventional methods, forming vias 18 with
a conductive coat 18a and a cylinder-shaped openings 18c. The
cylinder-shaped openings 18c in the vias 18 are filled using a
second material at the step 130. This fill process can be
accomplished by several means, including screen printing, stencil
printing, and dispensing. Screen printing can be done from one side
or from both sides of the substrate and with or without vacuum
assist to help pull the fill material into the vias. In many
applications it is preferred to use a single-sided screen printing
using vacuum assist to ensure complete filling of the apertures 18
(where the plating does not fill the via or aperture). Of course,
there are other ways to insert the fill material within the voids,
including dispensing it and stencil printing it. After the fill
material is positioned within the aperture, the preferred method of
filling the voids involves heating the fill material to cure it, if
it is a thermoset polymer or filled thermoset polymer, or to reflow
it if it is a solder paste or thermoplastic polymer, to permanently
fill the voids. It is also possible to cure the fill material with
ultraviolet (UV) radiation, if a UV curable polymer is used as the
fill material. The cure processes stabilizes and solidifies the
fill material. The surface of the processed substrate 12 is then
cleaned at step 140, preferably using a plasma cleaning process,
although a chemical or mechanical cleaning are also possible. Now,
the fill material may be in an acceptable position as a result of
this processing or it may require planarization. If the fill
material protrudes above the surface of the plated, copper clad
substrate, a planarization operation will likely be required, such
as abrasive sanding, brushing, plasma etching, or polishing, to
flatten the fill material so it is coplanar with or slightly
recessed from the surface of the copper. If the fill material
shrinks substantially during curing, it may be recessed from the
surface of the plated, copper clad substrate. It is possible a
second via filling process may be required to fully fill the via.
At the step 150 printing and etching is done to provide a surface
with the appropriate conductive attachments. Alternatively, a
pattern plating process or semi-additive circuit formation process
can be used to provide the appropriate conductive attachments. Then
at step 160 the elastic contacts are attached to the conductive
attachments, preferably by positioning the sheet of elastic
contacts in the proper location, bonding and interconnecting the
sheet of electrical contacts, then singulating the contacts.
[0037] Finally, if some further finishing of the surface of the
fill material is required or desired, it may be done, such as
adding a metallization layer on top of the fill material (which can
be accomplished through plating or other suitable methods).
[0038] FIG. 7 illustrates a variation on the present invention
wherein the electrical connector includes a multilayer printed
circuit board (PCB). This electrical connector 10'' includes a PCB
or substrate 12'' having multiple conductive lawyers separated by
insulating layers made in a conventional, known manner. The
substrate 12'' has its top surface 12a and its bottom surface 12b
each having electrical contacts 14, 16 mounted thereon. As shown in
this view, there is a blind via 50 and a buried via 60 illustrated
in this view, where the blind via 50 is beneath a connection plate
and the buried via is between two internal conductive layer s 60c,
60d of the substrate 12''. The filling of the blind via 50 includes
a conductive material 50a and a second material 50b which fills the
rest of the hole (the void). The filling of the buried via 60
includes a conductive material 60a and a second material 60b
filling the void of this via. While the filling of the blind vias
on the outer layers of the substrate provides the advantages listed
above, the filling of the buried via is optional and depends on the
circuit layout and the nature of the multilayer printed circuit
board fabrication process.
[0039] FIG. 8a is a perspective view of an electrical connector (or
interposer) 240 which provides interconnections including
board-to-board or flex-to-board electrical interconnections. A
plurality of electrical spring contacts 250 are arranged in an
array on the electrical connector (interposer) 240, where the
electrical spring contacts 250 are preferably the spring contacts
of the type sold by Neoconix under its PCBeam trademark and
described in its issued patents. A seal 260 surrounds the array of
electrical contacts 250, with the seal 260 being a conventional
o-ring or other suitable seal. The seal 260 could also be comprised
of the coverlay material 270, where the coverlay in this instance
would be substantially compliant, such as an elastomeric material
like silicone. When the electrical connector (interposer) 240 is
mated to and compressed against the substrate, the seal 260 forms a
watertight barrier to fluid penetration. Not shown in this view are
the filled vias, which also contribute to forming the watertight
connector by preventing water ingress or egress through the
vias.
[0040] FIG. 8b shows the detail of a portion of the electrical
connector (interposer) 240 with some of the electrical spring
contacts 250 which are mounted such that their base portion is
located under a coverlay 270. Spring contacts 250 are located in
openings 280 in the coverlay 270. Not shown in this view are the
filled vias of the present invention which cooperate with the other
structures to assist in prevention of moisture or water penetration
while protecting the electrical interconnections provided by
plating of the vias.
[0041] FIG. 8c shows a mating substrate 200 having a 6.times.5
array of contact pads 210 arranged on a PCB or flex circuit
substrate 215. An optional copper seal ring 220 surrounds the
contact pads 210. The contact pads 210 are electrically connected
by internal vias to electronic circuits on and/or within the
substrate. The copper seal ring 220 helps provide a seal by
providing a raised surface which compresses against compliant seal
on the electrical connector 240 of FIGS. 8a and 8b, such as an
o-ring or other compliant member, during actuation of the connector
to the substrate 215. The seal formed between the substrate and the
connector outside of the contact array, in conjunction with filled
vias in the connector interposer, restricts the passage of fluids,
such as water or moisture, protecting the electrical
connections.
[0042] FIG. 8d shows one representative example of the electrical
connector (or interposer) 240 to form a watertight electrical
interconnection to the inside of a sealed electronic system 290
surrounded by a housing, 360. A seal 260 surrounds the contact
array and is compressed between the electrical connector (or
interposer) 240 and the mating printed circuit substrate 200,
and/or the housing. The filled vias 310 prevent water ingress
through the connector (interposer) 240, and electrically
interconnect electrical contacts 250 on a first surface 340 of the
electrical connector (or interposer) 240 to electrical contacts 320
on a second surface 350 of the connector (or interposer) 240. An
electrical interconnection is made between the electrical contacts
250 on the first surface 340 of the connector (interposer) 240 and
mating pads (not shown) on the printed circuit substrate 200. On
the second surface 350 of the connector (interposer) 240,
electrical interconnections are made between the electrical
contacts 320 and a device 300, such as a battery, power supply, or
antenna, located outside of the sealed electronic system 290, and
thus potentially exposed to the outside environment 330.
[0043] Many modifications and alterations of the preferred
embodiment described above are possible without departing from the
spirit of the present invention. For example, the filled via can be
created using a plating or etching process to create a copper or
other metal post or pillar on the surface of a carrier sheet, and
this post can be inserted into a hole in the non-conductive
substrate material to create the solid or filled via. Further, some
of the features of the present invention can be used to advantage
without the corresponding use of other features. For example, the
use of an abrasion of the fill of the vias may be desirable in some
instances and not required in other instances. Accordingly, the
foregoing description of the preferred embodiment should be
considered as merely illustrative of the principles of the present
invention and not in limitation thereof, as the claims which follow
are the sole definitions of the present invention.
* * * * *