U.S. patent application number 12/028848 was filed with the patent office on 2009-08-13 for polymer and solder pillars for connecting chip and carrier.
Invention is credited to Timothy H. Daubenspeck, Jeffrey P. Gambino, Christopher D. Muzzy, Wolfgang Sauter, Timothy D. Sulliwan.
Application Number | 20090200663 12/028848 |
Document ID | / |
Family ID | 40938203 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090200663 |
Kind Code |
A1 |
Daubenspeck; Timothy H. ; et
al. |
August 13, 2009 |
POLYMER AND SOLDER PILLARS FOR CONNECTING CHIP AND CARRIER
Abstract
A method of connecting chips to chip carriers, ceramic packages,
etc. (package substrates) forms smaller than usual first solder
balls and polymer pillars on the surface of a semiconductor chip
and applies adhesive to the distal ends of the polymer pillars. The
method also forms second solder balls, which are similar in size to
the first solder balls, on the corresponding surface of the package
substrate to which the chip will be attached. Then, the method
positions the surface of the semiconductor chip next to the
corresponding surface of the package substrate. The adhesive bonds
the distal ends of the polymer pillars to the corresponding surface
of the package substrate. The method heats the first solder balls
and the second solder balls to join the first solder balls and the
second solder balls into solder pillars.
Inventors: |
Daubenspeck; Timothy H.;
(Colchester, VT) ; Gambino; Jeffrey P.; (Westford,
VT) ; Muzzy; Christopher D.; (Burlington, VT)
; Sauter; Wolfgang; (Richmond, VT) ; Sulliwan;
Timothy D.; (Underhill, VT) |
Correspondence
Address: |
FREDERICK W. GIBB, III;Gibb Intellectual Property Law Firm, LLC
2568-A RIVA ROAD, SUITE 304
ANNAPOLIS
MD
21401
US
|
Family ID: |
40938203 |
Appl. No.: |
12/028848 |
Filed: |
February 11, 2008 |
Current U.S.
Class: |
257/737 ;
257/E21.511; 257/E23.068; 438/118; 438/125 |
Current CPC
Class: |
H01L 24/11 20130101;
H01L 2224/06505 20130101; H01L 2224/17051 20130101; H05K 2201/0379
20130101; H01L 2224/1403 20130101; H01L 2224/14 20130101; H01L
2224/1319 20130101; H01L 2224/1329 20130101; H01L 2924/14 20130101;
H01L 2224/81193 20130101; H05K 3/3436 20130101; H01L 24/81
20130101; H01L 2924/00013 20130101; H01L 23/49811 20130101; H01L
24/90 20130101; H01L 2924/01013 20130101; H01L 2224/81139 20130101;
H01L 2224/133 20130101; H01L 2224/83194 20130101; H01L 2224/14505
20130101; H01L 2224/13082 20130101; H01L 2224/81191 20130101; H01L
2924/01033 20130101; H05K 3/303 20130101; H01L 24/14 20130101; H01L
24/17 20130101; H01L 2224/11822 20130101; H01L 2924/01082 20130101;
Y02P 70/613 20151101; H01L 2224/131 20130101; H01L 2224/0401
20130101; H01L 2924/01074 20130101; H01L 2224/838 20130101; H01L
24/83 20130101; H01L 2924/014 20130101; H05K 2201/10674 20130101;
H05K 2201/2036 20130101; H01L 2224/16 20130101; H01L 23/49816
20130101; H01L 2924/01076 20130101; Y02P 70/50 20151101; H01L
2224/83191 20130101; H01L 2924/01022 20130101; H01L 2224/81801
20130101; H01L 2224/0603 20130101; H01L 2924/12044 20130101; H01L
24/16 20130101; H01L 2224/1319 20130101; H01L 2924/00014 20130101;
H01L 2224/133 20130101; H01L 2924/00014 20130101; H01L 2224/1329
20130101; H01L 2924/00014 20130101; H01L 2224/131 20130101; H01L
2924/014 20130101; H01L 2924/00013 20130101; H01L 2224/13099
20130101; H01L 2924/3512 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
257/737 ;
438/125; 438/118; 257/E23.068; 257/E21.511 |
International
Class: |
H01L 23/498 20060101
H01L023/498; H01L 21/60 20060101 H01L021/60 |
Claims
1. A structure comprising: a semiconductor chip; a package
substrate connected to said semiconductor chip; polymer pillars
positioned between and connecting said semiconductor chip and said
package substrate; and solder pillars positioned between and
connecting said semiconductor chip and said package substrate.
2. The structure according to claim 1, all the limitations of which
are incorporated herein by reference, wherein said solder pillars
have a shape and a size similar to that of said polymer
pillars.
3. The structure according to claim 1, all the limitations of which
are incorporated herein by reference, wherein said solder pillars
and said polymer pillars each have a first dimension between said
semiconductor chip and said package substrate that is at least 2
times a second dimension that is perpendicular to said first
dimension.
4. The structure according to claim 1, all the limitations of which
are incorporated herein by reference, wherein said solder pillars
provide greater physical support between said semiconductor chip
and said package substrate relative to said solder pillars.
5. The structure according to claim 1, all the limitations of which
are incorporated herein by reference, wherein said solder pillars
lack lead.
6. A structure comprising: a semiconductor chip; a package
substrate connected to said semiconductor chip; polymer pillars
positioned between and connecting said semiconductor chip and said
package substrate; and solder pillars positioned between and
connecting said semiconductor chip and said package substrate,
wherein said polymer pillars comprise optical transmission media
adapted to transmit optical signals between said semiconductor chip
and said package substrate, wherein said solder pillars comprise
electrical transmission media adapted to transmit electrical
signals between said semiconductor chip and said package substrate,
and wherein said solder pillars comprise two joined solder
balls.
7. The structure according to claim 6, all the limitations of which
are incorporated herein by reference, wherein said solder pillars
have a shape and a size similar to that of said polymer
pillars.
8. The structure according to claim 6, all the limitations of which
are incorporated herein by reference, wherein said solder pillars
and said polymer pillars each have a first dimension between said
semiconductor chip and said package substrate that is at least 2
times a second dimension that is perpendicular to said first
dimension.
9. The structure according to claim 6, all the limitations of which
are incorporated herein by reference, wherein said solder pillars
provide greater physical support between said semiconductor chip
and said package substrate relative to said solder pillars.
10. The structure according to claim 6, all the limitations of
which are incorporated herein by reference, wherein said solder
pillars lack lead.
11. A method comprising: forming first solder balls on a surface of
a semiconductor chip; forming polymer pillars on said surface of
said semiconductor chip; forming second solder balls on a
corresponding surface of a package substrate; positioning said
surface of said semiconductor chip next to said corresponding
surface of said package substrate such that said polymer pillars
contact said corresponding surface of said package substrate and
such that said first solder balls contact corresponding ones of
said second solder balls; and heating said first solder balls and
said second solder balls to join said first solder balls and said
second solder balls into solder pillars.
12. The method according to claim 11, all the limitations of which
are incorporated herein by reference, wherein said polymer pillars
extend further from said surface of said semiconductor chip than
said first solder balls.
13. The method according to claim 11, all the limitations of which
are incorporated herein by reference, wherein combined diameters of
said first solder balls and said second solder balls is equal to or
greater than a dimension that said polymer pillars extend from said
surface of said semiconductor chip.
14. The method according to claim 11, all the limitations of which
are incorporated herein by reference, wherein said polymer pillars
maintain relative positions of said surface of said integrated
circuit chip and said corresponding surface of said package
substrate during said heating of said first solder balls and said
second solder balls.
15. The method according to claim 11, all the limitations of which
are incorporated herein by reference, wherein said heating
comprises heating to a temperature at least equal to a melting
point of said first solder balls and said second solder balls.
16. A method comprising: forming first solder balls on a surface of
a semiconductor chip; forming polymer pillars on said surface of
said semiconductor chip; applying adhesive to distal ends of said
polymer pillars, wherein said distal ends comprise ends of said
polymer pillars that are furthest away said surface of said
semiconductor chip; forming second solder balls on a corresponding
surface of a package substrate; positioning said surface of said
semiconductor chip next to said corresponding surface of said
package substrate such that said distal ends of said polymer
pillars contact said corresponding surface of said package
substrate and such that said first solder balls contact
corresponding ones of said second solder balls, wherein said
adhesive bonds said distal ends of said polymer pillars to said
corresponding surface of said package substrate; and heating said
first solder balls and said second solder balls to join said first
solder balls and said second solder balls into solder pillars.
17. The method according to claim 16, all the limitations of which
are incorporated herein by reference, wherein said polymer pillars
extend further from said surface of said semiconductor chip than
said first solder balls to an extent such that said applying of
said adhesive to said distal ends of said polymer pillars is
performed without applying adhesive to said first solder balls.
18. The method according to claim 16, all the limitations of which
are incorporated herein by reference, wherein combined diameters of
said first solder balls and said second solder balls is equal to or
greater than a dimension that said polymer pillars extend from said
surface of said semiconductor chip.
19. The method according to claim 16, all the limitations of which
are incorporated herein by reference, wherein said polymer pillars
maintain relative positions of said surface of said integrated
circuit chip and said corresponding surface of said package
substrate during said heating of said first solder balls and said
second solder balls.
20. The method according to claim 16, all the limitations of which
are incorporated herein by reference, wherein said heating
comprises heating to a temperature at least equal to a melting
point of said first solder balls and said second solder balls.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The embodiments of the invention generally relate to methods
of connecting chips to chip carriers, ceramic packages, etc.
(package substrates) and to a method that forms smaller than usual
first solder balls and polymer pillars on the surface of a
semiconductor chip and forms second solder balls on the
corresponding surface of the package substrate to which the chip
will be attached. The method heats the first solder balls and the
second solder balls to join the first solder balls and the second
solder balls into solder pillars.
[0003] 2. Description of the Related Art
[0004] In conventional systems, solder balls are used to join chips
to the package. However, it is becoming increasingly difficult to
ensure solder ball reliability due to the following trends: smaller
solder ball size (for higher I/O density); larger chip size;
plastic packaging (with larger coefficient of thermal expansion
(CTE) than ceramic packages); and the use of Pb-free solder (with
higher reflow temperature and higher modulus than Pb-containing
solder). The coefficient of thermal expansion mismatch between the
chip and the package can result in high stress in the solder
joints, which can cause cracks and eventually device failure.
SUMMARY
[0005] In view of the foregoing, an embodiment of the invention
provides a method of connecting chips to chip carriers, ceramic
packages, etc. (package substrates) that forms smaller than usual
first solder balls and polymer pillars on the surface of a
semiconductor chip. The method applies adhesive to the distal ends
of the polymer pillars.
[0006] The polymer pillars extend further from the surface of the
semiconductor chip than the first solder balls to an extent such
that the applying of the adhesive to the distal ends of the polymer
pillars is performed without applying adhesive to the first solder
balls.
[0007] The method also forms second solder balls, which are similar
in size to the first solder balls, on the corresponding surface of
the package substrate to which the chip will be attached. Then, the
method positions the surface of the semiconductor chip next to the
corresponding surface of the package substrate such that the distal
ends of the polymer pillars contact the corresponding surface of
the package substrate and such that the first solder balls contact
corresponding ones of the second solder balls.
[0008] The combined diameters of the first solder balls and the
second solder balls is equal to or greater than a dimension that
the polymer pillars extend from the surface of the semiconductor
chip. Thus, when the polymer pillars contact the surface of the
substrate, the first solder balls are pushed against the second
solder balls and the solder balls make very good contact with each
other. The method heats the first solder balls and the second
solder balls to join the first solder balls and the second solder
balls into solder pillars. The heating process heats the first and
second solder balls to a temperature at least equal to a melting
point of the first solder balls and the second solder balls (the
heating process reflows the solder). After the solder cools below
its melting point, the resulting solder structure forms as solder
pillars.
[0009] The adhesive bonds the distal ends of the polymer pillars to
the corresponding surface of the package substrate. Thus, because
they are firmly attached between the chip and the substrate, the
polymer pillars maintain relative positions of the surface of the
integrated circuit chip and the corresponding surface of the
package substrate during the heating of the first solder balls and
the second solder balls.
[0010] The first and second solder balls (which can be lead-free
solder) are approximately the same size on the substrate and on the
chip, but are only approximately one-half the exterior size
(approximately one quarter of the volume) of a standard C4
(controlled collapsible chip connection) solder balls. The C4
solder balls are conventionally only formed on the chip when
forming connections to the substrate.
[0011] After the heating process (reflow), the two smaller solder
balls would be expected to have somewhere between 1/2 and 1/4 the
volume of solder contained in the single conventional C4 bump
(because each smaller solder ball has only approximately one
quarter of the volume of a standard C4 solder ball). Thus, during
reflow, the two smaller solder balls would be expected to collapse
as occurs conventionally with the C4 solder balls. However, the
height of the polymer pillars controls the stand-off distance
between the chip surface and the corresponding substrate surface,
which prevents the solder from collapsing into a spherical shape.
Because of the presence of the polymer pillars, the solder balls
join to form a solder pillar, whose shape is determined by a
combination of the solder volume, the sizes of the back level
metalization (BLM) and substrate pads, and the polymer pillar
height. Further, the solder pillars provide greater physical
support between the semiconductor chip and the package substrate
relative to the solder pillars. By observing the resulting
structure, it sometimes can be seen that the solder pillars
actually comprise two joined solder balls.
[0012] The foregoing process produces a unique structure that
comprises polymer pillars and solder pillars positioned between and
connecting the semiconductor chip and the package substrate. The
solder pillars have a shape and a size similar to that of the
polymer pillars. However, the polymer pillars comprise optical
transmission media (adapted to transmit optical signals between the
semiconductor chip and the package substrate) while the solder
pillars comprise electrical transmission media (adapted to transmit
electrical signals between the semiconductor chip and the package
substrate).
[0013] As described above, these solder and polymer pillars are
elongated structures, as contrasted with the conventional rounded
C4 solder balls (used conventionally to connect the chip and the
substrate). Thus, the height (first dimension) of the solder
pillars and the polymer pillars between the semiconductor chip and
the package substrate is at least 2 times their width (second
dimension that is perpendicular to the first dimension).
[0014] These and other aspects of the embodiments of the invention
will be better appreciated and understood when considered in
conjunction with the following description and the accompanying
drawings. It should be understood, however, that the following
descriptions, while indicating preferred embodiments of the
invention and numerous specific details thereof, are given by way
of illustration and not of limitation. Many changes and
modifications may be made within the scope of the embodiments of
the invention without departing from the spirit thereof, and the
embodiments of the invention include all such modifications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The embodiments of the invention will be better understood
from the following detailed description with reference to the
drawings, in which:
[0016] FIG. 1 illustrates a schematic diagram of an integrated
circuit assembly;
[0017] FIG. 2 illustrates a schematic diagram of an integrated
circuit assembly;
[0018] FIG. 3 illustrates a schematic diagram of an integrated
circuit assembly;
[0019] FIG. 4 illustrates a schematic diagram of an integrated
circuit assembly;
[0020] FIG. 5 illustrates a schematic diagram of an integrated
circuit assembly;
[0021] FIG. 6 illustrates a schematic diagram of an integrated
circuit assembly;
[0022] FIG. 7 illustrates a schematic diagram of an integrated
circuit assembly;
[0023] FIG. 8 illustrates a schematic diagram of an integrated
circuit assembly;
[0024] FIG. 9 illustrates a schematic diagram of an integrated
circuit assembly;
[0025] FIG. 10 illustrates a schematic diagram of an integrated
circuit assembly; and
[0026] FIG. 11 illustrates a schematic diagram of an integrated
circuit assembly.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0027] The embodiments of the invention and the various features
and advantageous details thereof are explained more fully with
reference to the non-limiting embodiments that are illustrated in
the accompanying drawings and detailed in the following
description. It should be noted that the features illustrated in
the drawings are not necessarily drawn to scale. Descriptions of
well-known components and processing techniques are omitted so as
to not unnecessarily obscure the embodiments of the invention. The
examples used herein are intended merely to facilitate an
understanding of ways in which the embodiments of the invention may
be practiced and to further enable those of skill in the art to
practice the embodiments of the invention. Accordingly, the
examples should not be construed as limiting the scope of the
embodiments of the invention.
[0028] One solution to relieving stress in solder connections is to
use elongated solder connections. For example, elongated solder
connections can be formed by joining the chip to the package at the
solder reflow temperature, mechanically separating the chip from
the package to elongate the solder, and then cooling the solder in
the "stretched state". This process provides an elongated solder
connection for improved reliability; however, this process is
difficult to implement in manufacturing.
[0029] Hence, an effective process for making elongated solder
connections would be useful. It would also be advantageous to form
electrical and optical I/Os on the same chip, which would be useful
for connections between, for example, stacked chips or connections
from the chip to the package. For example, U.S. Patent Publication
2006/0104566 to Bakir et al. (the complete disclosure of which is
incorporated herein by reference) uses polymer pillars for the
optical inputs/outputs and solder balls for the electrical
inputs/outputs.
[0030] However, when polymer pillars are used in combination with
rounded solder ball connections, the polymer pillars should be
taller than the solder balls (to allow dipping into an adhesive).
For example, as shown in FIG. 1, a semiconductor chip 102 includes
contact pads 104 upon which solder balls 106 are formed. These
solder balls form electrical input/output connections. In addition,
the structure includes polymer pillars 108 that form optical
input/output connections. For a detailed description of how such
structures are formed, and the materials and processing for
creating such structures, reference is made to the previously
mentioned U.S. Patent Publication 2006/0104566, and such
explanation is not repeated herein.
[0031] As shown in FIG. 1, the polymer pillars 108 are taller than
the solder balls 106 by a measure labeled T1 in FIG. 1. In FIG. 2,
the distal ends of the polymer pillars 108 are dipped into an
adhesive 202, which results in the distal ends of the polymer
pillars 108 being covered with adhesive 202 as shown in FIG. 3.
Then, as shown in FIG. 4, the chip 102 can be positioned adjacent
to a package substrate 404 such that the solder balls 106 make
contact with pads 402 on the package substrate 404 and such that
the polymer pillars 180 become attached to the package substrate
404 by means of the adhesive 202.
[0032] The height difference between the solder balls 106 and the
polymer pillars 108, discussed above, (Ti) allows the polymer
pillars 108 to be dipped into an adhesive 202, as shown in FIG. 2,
without having the adhesive 202 contact the solder balls 106.
Therefore, it is desirable to maintain a gap (shown as item 204 in
FIG. 2) between the solder balls 106 and the adhesive 202, to
prevent the solder balls 106 from becoming contaminated with the
adhesive 202.
[0033] If the height difference T1 is too small, the solder balls
may be contaminated by the adhesive 202 and may not form good
connections with the pads 402. If the height difference T1 is too
great, the solder balls may not be large enough to make contact
with the bond pad 402. It is difficult to ensure that the solder
balls 106 make contact to the bond pads 402 on the substrate
because, if the solder balls 106 are too small, they may not reach
the bond pads 402. To the contrary, if the solder balls 106 are too
large, no gap 204 may be present and the solder balls may be
covered with adhesive 202. This adhesive 202 can interfere with the
ability of the solder balls 106 to bond with the pads 402.
[0034] In view of these issues, the processing sequence shown in
FIGS. 5-9 is utilized to form a new structure and ensure that the
electrical connections between the chip 102 and the package
substrate 404 are formed properly. More specifically, as shown in
FIGS. 5-9, a method is disclosed that creates a new structure and
which properly forms electrical connections when both electrical
and optical connections are utilized between semiconductor chips
and packaging substrates.
[0035] More specifically, FIG. 5 illustrates a similar structure to
that shown in FIG. 1; however, in FIG. 5, rather than using the
full-size solder balls 106, the structure in FIG. 5 utilizes
smaller solder balls 506. This increases the height difference to a
measure shown as T2 which is greater than the height difference T1
shown in FIG. 1. For example, the smaller solder balls 506 could be
approximately one-half to three-quarters of the height (H1, which
is shown in FIG. 10 and discussed below) of the polymer pillars
108, which would allow T2 to be approximately one-quarter to
one-half the height of the polymer pillar (H1).
[0036] Thus, in FIG. 6, the method applies adhesive 202 to the
distal ends of the polymer pillars 108 (the distal ends are the
ends of the polymer pillars 108 that are furthest away the surface
of the semiconductor chip 102 opposite the ends that are connected
to the semiconductor chip 102). This allows in the tips of the
polymer pillars 108 be coated in adhesive 202 as shown in FIG.
7.
[0037] The polymer pillars 108 extend further from the surface of
the semiconductor chip 102 than the first solder balls 506 to an
extent such that the applying of the adhesive to the distal ends of
the polymer pillars 108 is performed without applying adhesive to
the first solder balls 506. In other words, the greater height
difference T2 produces a larger gap 604 (when compared to gap 204
shown in FIG. 2) and provides a much greater margin for error than
did the smaller height difference T1. The larger gap 604
substantially reduces the chance of the smaller solder balls 506
becoming contaminated with the adhesive 202, which increases yield
and decreases waste.
[0038] In order to ensure that a good electrical connection is
formed, the method also forms second solder balls 802, which are
similar in size to the first solder balls 506, on the bond pads 402
of the corresponding surface of the package substrate 404 to which
the chip 102 will be attached. Then, the method positions the
surface of the semiconductor chip 102 next to the corresponding
surface of the package substrate 404 such that the distal ends of
the polymer pillars 108 contact the corresponding surface of the
package substrate 404 and such that the first solder balls 506
contact corresponding ones of the second solder balls 802.
[0039] The combined diameters of the first solder balls 506 and the
second solder balls 802 is equal to or greater than a dimension
that the polymer pillars 108 extend from the surface of the
semiconductor chip 102. Thus, when the polymer pillars 108 contact
the surface of the substrate 404, the first solder balls 506 are
pushed against the second solder balls 802 and the solder balls
make very good contact with each other.
[0040] The method heats the first solder balls 506 and the second
solder balls 802 to join the first solder balls 506 and the second
solder balls 802 into solder pillars 902, as shown in FIG. 9. The
heating process heats the first and second solder balls 802 to a
temperature at least equal to a melting point of the first solder
balls 506 and the second solder balls 802 (the heating process
reflows the solder). After the solder cools below its melting
point, the resulting solder structure forms as solder pillars
902.
[0041] The adhesive 202 bonds the distal ends of the polymer
pillars 108 to the corresponding surface of the package substrate
404. Thus, because they are firmly attached between the chip 102
and the substrate 404 by the adhesive 202, the polymer pillars 108
maintain the relative positions of the surface of the integrated
circuit chip 102 and the corresponding surface of the package
substrate 404 during the heating of the first solder balls 506 and
the second solder balls 802. This prevents the first and second
solder balls 506, 802 from collapsing into a larger ball shape and,
instead, forces the solder balls 506, 802 to take an elongated
pillar-like shape upon cooling.
[0042] The first and second solder balls 802 (which can be
lead-free solder) are approximately the same size on the substrate
404 and on the chip 102, but are only approximately one-half the
exterior size (approximately one quarter of the volume) of the C4
solder balls that would be required if the processing shown in
FIGS. 1-4 were being performed. As shown above, in FIGS. 1-4, the
C4 solder balls are conventionally only formed on the chip 102 when
forming connections to the substrate 404.
[0043] After the heating process (reflow), the two smaller solder
balls would be expected to have somewhere between 1/2 and 1/4 the
volume of solder contained in the single C4 bump used in FIG. 1-4
(because each smaller solder ball has only approximately one
quarter of the volume of a standard C4 solder ball shown in FIG.
1-4). Thus, during reflow, the two smaller solder balls would be
expected to collapse as occurs conventionally with the C4 solder
balls.
[0044] However, the height of the polymer pillars 108 controls the
stand-off distance between the chip 102 surface and the
corresponding substrate 404 surface, which prevents the solder
balls 506, 802 from collapsing into a spherical shape. Because of
the presence of the polymer pillars 108, the solder balls 506, 802
join to form the solder pillar 902, whose shape is determined by a
combination of the solder volume, the sizes of the substrate 404
pads, and the polymer pillar 108 height.
[0045] As described above, the solder and polymer pillars 108, 902
are elongated structures, as contrasted with the conventional
rounded C4 solder balls 106 (used conventionally to connect the
chip 102 and the substrate 404). Because they are elongated, the
height (first dimension H1) of the solder pillars 902 and the
polymer pillars 108 between the semiconductor chip 102 and the
package substrate 404 is approximately at least 2 times their width
(second dimension W2 that is perpendicular to the first dimension)
as shown in FIG. 10. To the contrary, the height (first dimension
H1) of the solder balls 106 between the semiconductor chip 102 and
the package substrate 404 is about the same as their width (second
dimension W1 that is perpendicular to the first dimension) as also
shown in FIG. 10. The measures H1, W1, and W2 shown in FIG. 10 are
only approximate relative measures and the pillars are not all
exactly the same size, but are all similarly elongated. Thus, the
solder pillars 902 are elongated, as contrasted with the rounded
solder balls 106 shown in FIGS. 1-4.
[0046] Further, the solder pillars 902 provide greater physical
support between the semiconductor chip 102 and the package
substrate 404 relative to the solder pillars 902. The solder
pillars 902 can have a somewhat uneven elongated shape. For
example, by observing some embodiments of the resulting structure,
it sometimes can be seen that the solder pillars 902 actually
comprise two joined solder balls, as shown in FIG. 11.
[0047] The foregoing process produces a unique structure that
comprises polymer pillars 108 and solder pillars 902 positioned
between and connecting the semiconductor chip 102 and the package
substrate 404. The solder pillars 902 have a shape and a size
similar to that of the polymer pillars 108. However, the polymer
pillars 108 comprise optical transmission media (adapted to
transmit optical signals between the semiconductor chip 102 and the
package substrate 404) while the solder pillars 902 comprise
electrical transmission media (adapted to transmit electrical
signals between the semiconductor chip 102 and the package
substrate 404).
[0048] With the foregoing method shown in FIGS. 5-9, the larger gap
604 substantially reduces the chance of the smaller solder balls
506 becoming contaminated with the adhesive 202, which increases
yield and decreases waste; yet, when the polymer pillars 108
contact the surface of the substrate 404, the first solder balls
506 are pushed against the second solder balls 802 and the solder
balls make very good contact with each other, which increases yield
and reliability. Therefore, the process and structure discussed
above produces a new structure and increases yield and
reliability.
[0049] The foregoing description of the specific embodiments will
so fully reveal the modify and/or adapt for various applications
such specific embodiments without departing from the generic
concept, and, therefore, such adaptations and modifications should
and are intended to be comprehended within the meaning and range of
equivalents of the disclosed embodiments. It is to be understood
that the phraseology or terminology employed herein is for the
purpose of description and not of limitation. Therefore, while the
embodiments of the invention have been described in terms of
preferred embodiments, those skilled in the art will recognize that
the embodiments of the invention can be practiced with modification
within the spirit and scope of the appended claims.
* * * * *