Title of Invention

METHOD FOR THE FABRICATION OF ELECTRICAL CONTACTS

Abstract A method for the fabrication of electrical contacts 700 using metal forming, masking etching, and soldering techniques is presented. The method produces a plurality of specialized electrical contacts 700, capable of use in an interposer, or other device, including non-permanent or permanent electrical connections providing contact wipe, soft spring rates, durability, and significant amounts of travel.
Full Text METHOD FOR THE FABRICATION OF ELECTRICAL CONTACTS
FIELD OF THE INVENTION
This invention relates generally to the field of electrical contacts and more
specifically to methods for the fabrication of electrical contacts.
BACKGROUND OF THE INVENTION
Existing electrical contact designs include interposers constructed from
elastomeric material and interposers constructed from balls of wire. Both of these
solutions have limitations inherent in their design. Current elastomeric materials are
unable to sustain adequate contact spring force over time and temperature and have a
small range of working heights. Interposers constructed from balls of wire are fragile,
prone to unravel, often require costly inspection, and provide a limited amount of contact
travel.
SUMMARY OF THE INVENTION
A method for the fabrication of electrical contacts using metal forming, masking
etching, and soldering techniques is presented. The method produces a plurality of
specialized electrical contacts, capable of use in an interposer, or other device, including
non-permanent or permanent electrical connections providing contact wipe, soft spring
rates, durability, and significant amounts of travel.
Other aspects and advantages of the present invention will become apparent from
the following detailed description, taken in conjunction with the accompanying drawings,
illustrating by way of example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of an embodiment of a substrate including an array
of holes according to the present invention.
Figure 2 is a close-up perspective view of an embodiment of one of the substrate
holes from Figure 1 according to the present invention.
Figure 3 is a perspective view of an embodiment of the structure of Figure 2 after
through plating and etching according to the present invention.
Figure 4 is a perspective view of an embodiment of the structure of Figure 3 with
the addition of a molded dome according to the present invention.
Figure 5 is a perspective view of an embodiment of the structure of Figure 4 after
the dome has been metal plated according to the present invention.
Figure 6 is a perspective view of an embodiment of the structure of Figure 5 after
the addition of a mask layer according to the present invention.
Figure 7 is a perspective view of an embodiment of the structure of Figure 6 after
the metal layer has been etched away in all areas not covered by the mask layer according
to the present invention.
Figure 8 is a perspective view of an embodiment of the structure of Figure 7 after
the mask layer has been removed according to the present invention.
Figure 9 is a perspective view of an embodiment of the structure of Figure 8 after
the dome has been dissolved according to the present invention.
Figure 10 is a top view of an embodiment of the final micro-spider contact
structure from Figure 9 according to the present invention.
Figure 11 is a perspective view of an embodiment of an array of clockwise micro-
spiders according to the present invention.
Figure 12 is a cross-section view of an embodiment of a micro-spider interposer
according to the present invention.
Figures 13A and 13B are cross-section views of embodiments of single micro-
spider interposer pairs according to the present invention.
Figure 14 is a view of an embodiment of a single clockwise micro-spider and a
single micro stop according to the present invention.
Figure 15 is a cross-section view of an embodiment of the structure from Figure
14 according to the present invention.
Figure 16 is a flowchart of a method of creating micro-spider contacts according
to the present invention.
Figure 17 is a perspective view of an embodiment of a three-legged micro-spider.
Figure 18 is a perspective view of an embodiment of a plurality of three-legged
micro-spiders on a substrate according to the present invention.
Figure 19 is a cross-section view of an embodiment of a micro-spider/ball grid
array interposer according to the present invention.
DETAILED DESCRIPTION
Figure 1 is a perspective view of an embodiment of a substrate including an array
of holes according to the present invention. A quantity of holes or vias 102 is created in a
substrate 100. In an example embodiment of the present invention the holes may be
drilled into a printed circuit board (PCB) substrate. In an example embodiment of the
present invention using a PCB substrate, metal pads may be placed on the substrate
surrounding the planned locations of the holes before the holes are drilled. Other
methods of creating the holes, such as etching, and other substrate materials, such as
ceramics, may be used within the scope of the present invention. The quantity of holes
102 does not need to form a regular array shown in Figure 1. In other embodiments of
the present invention, the holes may be irregularly spaced as desired for any particular
design. The PCB substrate material is commonly fiberglass, however other materials may
be used within the scope of the present invention.
Figure 2 is a close-up perspective view of an embodiment of one of the substrate
holes from Figure 1 according to the present invention. A hole 102 in a substrate 100 is
shown here.
Figure 3 is a perspective view of an embodiment of the structure of Figure 2 after
through-plating and etching according to the present invention. After through-plating, the
hole 102 has a ring of metal plating 300 surrounding the hole 102 and through the hole
102 to the opposite side of the substrate 100. While the areas of metal plating 300 in this
embodiment are circular in shape, other shapes of the areas of metal 300 will work
equally well within the scope of the present invention. For example, in some
embodiments of the present invention, the area of metal 300 may be elliptical, square,
rectangular, or other, more complex shapes. While copper is a preferred metal for the
metal plating, other example embodiments of the present invention may use other
materials for the plating.
Figure 4 is a perspective view of an embodiment of the structure of Figure 3 with
the addition of a molded dome according to the present invention. A molded dome 400 is
added to at least some of the through-plated holes 102. Molded domes 400 may be added
to none, some, or all of the through-plated holes 102 on each side of the substrate 100. In
an example embodiment of the present invention, molded domes 400 are added to both
sides of the substrate 100 to create a dual micro-spider interposer. A specialized
electrical contact created pursuant to the present invention is referred herein to as a micro-
spider contact, or simply as a micro-spider. In an alternate embodiment of the present
invention, molded domes 400 are added to only one side of the substrate 100 to create a
micro-spider/ball grid array (BGA) ball interposer.
Figure 5 is a perspective view of an embodiment of the structure of Figure 4 after
the dome has been metal plated according to the present invention. The metal plated
dome 500 of Figure 5 may include copper or other metal elements or compositions
according to design requirements.
Figure 6 is a perspective view of an embodiment of the structure of Figure 5 after
the addition of a mask layer according to the present invention. A mask layer 600 in the
shape of a clockwise micro-spider has now been added over the metal plated dome 500.
The mask layer may comprise photoresist and be applied by any number of methods. The
photoresist may be exposed and developed to produce the mask layer 600 in the shape of
micro-spiders.
Figure 7 is a perspective view of an embodiment of the structure of Figure 6 after
the metal layer has been etched away in all areas not covered by the mask layer according
to the present invention. An etched micro-spider 700, covered with the mask layer 600, is
seen in place over the molded dome 400 on the substrate 100.
Figure 8 is a perspective view of an embodiment of the structure of Figure 7 after
the mask layer 600 has been removed from the micro-spider 700.
Figure 9 is a perspective view of an embodiment of the structure of Figure 8 after
the dome has been dissolved according to the present invention. The molded dome 400
may be preferably dissolved by any chemicals (or other etching method) capable of
completely removing the dome material without damaging the micro-spider 700, plating
300, hole 102, or substrate 100.
Figure 10 is a top view of an embodiment of the micro-spider contact
structure from Figure 9 according to the present invention. A single clockwise micro-
spider 700 is shown over a through-hole 102 surrounded by metal plating 300 on a
substrate 100. At this point the micro-spider may undergo further processing such as
additional metal plating if desired. Also note that in other embodiments of the present
invention counter-clockwise micro-spiders may be produced as desired. For example, it
may be advantageous to design a large array of micro-spiders such that substantially
equal numbers of clockwise and counter-clockwise micro-spiders are created. Such a
design may reduce the rotational torque that would occur in an array of only clockwise or
only counter-clockwise micro-spiders. Since the micro-spiders each rotate slightly,
creating a wiping action on the contact during use, each micro-spider causes a small
amount of torque on the device as it is connected.
The resulting micro-spiders are described further in a U.S. patent application,
Serial No.__________, "Electrical Contact", filed concurrently with the present
application, and incorporated herein by reference. Another method for the fabrication of
micro-spiders is described further in a U.S. patent application, Serial No.__________,
"Method for the Fabrication of Electrical Contacts", filed concurrently with the present
application, and incorporated herein by reference.
Figure 11 is a perspective view of an embodiment of an array of clockwise micro-
spiders 700 shown over a substrate 100 according to the present invention. As disclosed
above, in some embodiments of the present invention, it may be desired to alternate
clockwise and counter-clockwise micro-spiders, for example in a checkerboard pattern.
Figure 12 is a cross-section view of an embodiment of a micro-spider interposer
according to the present invention. In this example embodiment of the present invention
micro-spiders are constructed on both sides of the substrate 100. Connecting each pair of
micro-spiders 700 is a through-plated hole 102. The metal 300 surrounding each hole
may be seen connecting to individual micro-spiders. While this example embodiment
comprises clockwise micro-spiders 700 on the top of the substrate 100, and counter-
clockwise micro-spiders 700 on the bottom of the substrate 100 other configurations are
possible within the scope of the present invention.
Figures 13 A and 13B are cross-section views of embodiments of single micro-
spider interposer pairs according to the present invention. In Figure 13A a counter-
clockwise micro-spider 700 is shown on the top of the substrate 100, and a clockwise
micro-spider 700 is shown on the bottom of the substrate 100. The pair of micro-spiders
700 are electrically connected by a through-plated hole 102 and the metal 300
surrounding the hole. In Figure 13B a clockwise micro-spider 700 is shown on the top of
the substrate 100, and a counter-clockwise micro-spider 700 is shown on the bottom of
the substrate 100. The pair of micro-spiders 700 are electrically connected by a through-
plated hole 102 and the metal 300 surrounding the hole.
Figure 14 is a perspective view of an embodiment of a single clockwise micro-
spider 700 electrically connected to the metal 300 surrounding a hole 102 in the substrate
100 next to a micro stop 1400 in accordance to the present invention. The micro stop
1400 may be constructed using processes similar to standard printed circuit board
processes, to create an elevated stop configured to prevent over-compression of the
micro-spiders 700 during use. The height of the micro stop 1400 preferably enables
compression and contact wiping action of the micro-spiders 700 while preventing over-
compression that would physically damage the micro-spiders 700.
Figure 15 is a cross-section view of an embodiment of the structure from Figure
14 according to the present invention. In this example embodiment of the present
invention a micro-spider interposer including a pair of micro stops 1400 is shown in
cross-section view. The clockwise micro-spider 700 on top of the substrate 100 is
electrically connected to the counter-clockwise micro-spider 700 on the bottom of the
substrate through the metal 300 surrounding the through-plated hole 102 in the substrate
100.
Figure 16 is a flowchart of a method of creating micro-spider contacts according
to the present invention. In a step 1602, a plurality of holes 102 are created in a substrate
100. In a step 1604, the holes 102 are through-plated and etched. In a step 1606, molded
domes are created over the through-plated holes 102. In a step 1608, the substrate 100
with the holes 102 covered by molded domes is metal-plated. In a step 1610, a mask
layer in the configuration of micro-spiders is created over the metal-plated domes. In a
step 1612, the metal-plating is etched away in all the places not covered by the mask
layer. In a step 1614, the mask layer is removed. In a step 1616, the domes are dissolved
or etched away leaving the finished micro-spiders. If desired, the micro-spiders may be
metal-plated again with one or more additional metals, such as nickel or gold, at this point
in the process. In an optional step 1618, ball grid array (BGA) balls are placed on the
through-plated holes 102 on a side of the substrate 100 opposite to the micro-spiders 700.
In such an embodiment of the present invention, micro-spiders 700 are placed on one side
of the substrate 100 and BGA balls 1900 are placed on the other side of the substrate 100
producing a micro-spider/BGA interposer.
Figure 17 is a perspective view of an embodiment of a three-legged micro-spider
according to the present invention. A three-legged micro-spider 1700 is shown connected
to the metal 300 surrounding a through-plated hole 102 in a substrate 100. Micro-spiders
may be constructed with any number of legs (greater than one) as desired by an intended
use, within the scope of the present invention.
Figure 18 is a perspective view of an embodiment of a plurality of three-legged
micro-spiders on a substrate according to the present invention. Figure 18 shows an array
of three-legged micro-spiders 1700 on a substrate 100. While this figure shows a regular
array of micro-spiders 1700, other embodiments of the present invention may use an
irregular array of micro-spiders 1700 as desired by the intended use of the plurality of
micro-spiders 1700.
In a specific example embodiment of the present invention, micro-spiders 700 are
preferably constructed on a first side of the substrate 100 and ball grid array balls 1900
are preferably constructed on a second side of the substrate 100, creating an interposer for
use in non-permanently attaching electronic devices such as a multi-chip module (MCM)
to a circuit board. Figure 19 is a cross-sectional view of such an embodiment. The
example embodiment of the present invention shown in Figure 19 illustrates a plurality of
micro-spiders 700 constructed on a first side of a substrate and ball grid array (BGA)
balls 1900 placed on a second side of a substrate 100, connected together by through-
plated holes 102 surrounded by areas of metal 104 contacting the micro-spiders 300. This
example embodiment of the present invention may be employed as an interposer for use
in non-permanently attaching electronic devices, such as a MCM, to a circuit board, while
the interposer is attached to the circuit board by the BGA balls 1900. This example
embodiment of the present invention may be fabricated using the process described in
connection with Figure 16 including optional step 1618.
WE CLAIM
1. A method for the fabrication of electrical contacts, comprising the steps of:
a) through-plating a plurality of vias 102 in a substrate 100;
b) creating domes 400 over at least some of said through-plated vias 102;
c) first metal plating said domes 400;
d) masking said domes 400;
e) etching away said first metal plating on said domes 400 in areas not covered by
said mask creating a plurality of electrical contacts 700, wherein said electrical
contacts 700 include spiraling legs configured to create a wiping action on metal
pads when compressed; and
f) dissolving said domes 400.
2. The method for the fabrication of electrical contacts of claim 1, wherein said substrate
includes metal pads 300 surrounding substantially all locations of said vias 102
before said vias 102 are created in said substrate 100.
3. The method for the fabrication of electrical contacts of claim 1, further comprising the
step of:
g) second metal plating said electrical contacts 700 after said step of first metal
plating.
4. The method for the fabrication of electrical contacts of claim 3, wherein said second
metal plating includes gold.
5. The method for the fabrication of electrical contacts of claim 3, wherein said second
metal plating includes nickel and gold.
6. The method for the fabrication of electrical contacts of claim 1, wherein said first
metal plating is copper.
7. The method for the fabrication of electrical contacts of claim 1, wherein said substrate
100 is a printed circuit board substrate 100.
8. The method for the fabrication of electrical contacts of claim 1, wherein at least some
of said electrical contacts 700 are on opposite sides of said substrate 100.
9. The method for the fabrication of electrical contacts of claim 1, further comprising the
step of:
g) adding a plurality of ball grid array balls 1900 to said through-plated holes 102 on
a side of said substrate 100 opposite to said electrical contacts 700.
10. The method for the fabrication of electrical contacts of claim 1, further comprising the
step of:
i) forming at least one micro stop 1400 on said substrate 100.

A method for the fabrication of electrical contacts 700 using metal forming,
masking etching, and soldering techniques is presented. The method produces a plurality
of specialized electrical contacts 700, capable of use in an interposer, or other device,
including non-permanent or permanent electrical connections providing contact wipe, soft
spring rates, durability, and significant amounts of travel.

Documents:

375-CAL-2002-(22-03-2012)-CORRESPONDENCE.pdf

375-CAL-2002-(22-03-2012)-PA-CERTIFIED COPIES.pdf

375-cal-2002-abstract.pdf

375-cal-2002-claims.pdf

375-CAL-2002-CORRESPONDENCE.pdf

375-cal-2002-description (complete).pdf

375-cal-2002-drawings.pdf

375-cal-2002-examination report.pdf

375-cal-2002-form 1.pdf

375-cal-2002-form 13.pdf

375-cal-2002-form 19.pdf

375-cal-2002-form 2.pdf

375-cal-2002-form 26.pdf

375-cal-2002-form 3.pdf

375-cal-2002-form 5.pdf

375-CAL-2002-FORM-27.pdf

375-CAL-2002-OTHERS.pdf

375-cal-2002-reply to examination report.pdf

375-cal-2002-specification.pdf

375-cal-2002-translated copy of priority document.pdf


Patent Number 239968
Indian Patent Application Number 375/CAL/2002
PG Journal Number 16/2010
Publication Date 16-Apr-2010
Grant Date 16-Apr-2010
Date of Filing 17-Jun-2002
Name of Patentee HEWLETT-PACKARD COMPANY
Applicant Address 3000 HANOVER STREET, PALO ALTO, CALIFORNIA
Inventors:
# Inventor's Name Inventor's Address
1 BRADLEY E. 737 HINSDALE DRIVE FT. COLLINS, CO 80526
2 WHITE JOSEPH M. 1228 WALNUT STREET WINDSOR, CO 80550
PCT International Classification Number H01B 13/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 09/917093 2001-07-27 U.S.A.