U.S. patent application number 11/237049 was filed with the patent office on 2006-02-02 for loc semiconductor assembled with room temperature adhesive.
Invention is credited to Warren M. Farnworth, Ford B. Grigg.
Application Number | 20060022314 11/237049 |
Document ID | / |
Family ID | 25438175 |
Filed Date | 2006-02-02 |
United States Patent
Application |
20060022314 |
Kind Code |
A1 |
Grigg; Ford B. ; et
al. |
February 2, 2006 |
LOC semiconductor assembled with room temperature adhesive
Abstract
A semiconductor device assembly having a lead frame and a
semiconductor die configured to be attached to each other is
disclosed. An adhesive is applied at room temperature through a
stencil to the lead frame. The semiconductor die is urged against
the adhesive to effect the attachment between the semiconductor
device and the lead frame. The adhesive preferably is from about 75
percent to about 95 percent isobutyl acetal diphenol copolymer and
from about 25 percent to about 5 percent, respectively, of titanium
oxide.
Inventors: |
Grigg; Ford B.; (Meridian,
ID) ; Farnworth; Warren M.; (Nampa, ID) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
25438175 |
Appl. No.: |
11/237049 |
Filed: |
September 27, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10035078 |
Dec 28, 2001 |
|
|
|
11237049 |
Sep 27, 2005 |
|
|
|
09569216 |
May 11, 2000 |
6337511 |
|
|
10035078 |
Dec 28, 2001 |
|
|
|
09176967 |
Oct 22, 1998 |
6248611 |
|
|
09569216 |
May 11, 2000 |
|
|
|
08916977 |
Aug 14, 1997 |
5840598 |
|
|
09176967 |
Oct 22, 1998 |
|
|
|
Current U.S.
Class: |
257/666 ;
257/673; 257/E23.039; 257/E23.04 |
Current CPC
Class: |
H01L 2224/4826 20130101;
H01L 2224/92147 20130101; H01L 24/32 20130101; H01L 2924/01006
20130101; Y10T 428/24207 20150115; H01L 24/27 20130101; H01L 24/28
20130101; H01L 2224/48247 20130101; H01L 2224/8385 20130101; H01L
2924/01074 20130101; H01L 2924/12044 20130101; H01L 2224/48091
20130101; H01L 2924/01005 20130101; H01L 2924/078 20130101; H01L
2224/4824 20130101; H01L 23/49513 20130101; H01L 2224/48465
20130101; H01L 24/743 20130101; H01L 2224/743 20130101; H01L
2224/83101 20130101; H01L 2924/01033 20130101; H01L 2924/01013
20130101; H01L 23/4951 20130101; H01L 24/48 20130101; H01L
2224/83192 20130101; H01L 2224/92247 20130101; H01L 2224/32245
20130101; H01L 24/83 20130101; H01L 2924/01082 20130101; H01L 24/29
20130101; H01L 2224/73215 20130101; H01L 2924/00014 20130101; H01L
2224/32014 20130101; H01L 2224/48 20130101; H01L 2224/92 20130101;
H01L 2924/07802 20130101; H01L 2224/92 20130101; H01L 2224/83
20130101; H01L 2224/85 20130101; H01L 2224/48091 20130101; H01L
2924/00014 20130101; H01L 2224/48091 20130101; H01L 2924/00014
20130101; H01L 2224/73215 20130101; H01L 2224/32245 20130101; H01L
2224/4826 20130101; H01L 2924/00012 20130101; H01L 2224/48465
20130101; H01L 2224/48247 20130101; H01L 2924/00 20130101; H01L
2224/83192 20130101; H01L 2224/32245 20130101; H01L 2224/83192
20130101; H01L 2224/83101 20130101; H01L 2924/00 20130101; H01L
2224/48465 20130101; H01L 2224/4826 20130101; H01L 2924/00
20130101; H01L 2224/48465 20130101; H01L 2224/4824 20130101; H01L
2924/00 20130101; H01L 2224/48465 20130101; H01L 2224/48091
20130101; H01L 2924/00 20130101; H01L 2224/4824 20130101; H01L
2224/48465 20130101; H01L 2924/00 20130101; H01L 2224/4826
20130101; H01L 2224/48465 20130101; H01L 2924/00 20130101; H01L
2924/00014 20130101; H01L 2224/45099 20130101; H01L 2924/00014
20130101; H01L 2224/05599 20130101; H01L 2924/00014 20130101; H01L
2224/85399 20130101; H01L 2924/00014 20130101; H01L 2224/45015
20130101; H01L 2924/207 20130101; H01L 2224/73215 20130101; H01L
2224/32245 20130101; H01L 2224/4826 20130101; H01L 2224/48
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
257/666 ;
257/673 |
International
Class: |
H01L 23/495 20060101
H01L023/495 |
Claims
1. In combination, adhesive and a semiconductor die, the adhesive
used for attaching a portion of the semiconductor die to portion of
a lead frame having a plurality of lead fingers thereon, at least
one lead finger of said plurality of lead fingers having an
attaching surface, the a semiconductor die having a surface having
at least one bond pad thereon for connection to at least one lead
finger of the plurality of lead fingers of the lead frame
comprising: a nonconductive substantially tacky compliant polymer
adhesive to be applied at room temperature to at least one of the
attaching surface of the at least one lead finger and a portion of
the surface of the semiconductor die for connecting the at least
one bond pad of the semiconductor die to the at least one lead
finger of the plurality of lead fingers of the lead frame, the
nonconductive polymer adhesive including a first material from a
group of copolymers that includes isobutyl compounds and a second
material that is from a group of metal oxides.
2. The combination of claim 1 wherein a first portion of said
nonconductive polymer adhesive is isobutyl acetal diphenol
copolymer.
3. The combination of claim 1 wherein said nonconductive polymer
adhesive includes said first material from a group of copolymers
that includes isobutyl acetal diphenol copolymer and said second
material that is from said group of metal oxides that includes
titanium dioxide.
4. The combination of claim 3 wherein said nonconductive polymer
adhesive has from about 75 percent to about 95 percent by weight of
said isobutyl acetal diphenol copolymer and from about 25 percent
to about 5 percent by weight, respectively, of said titanium
dioxide.
5. The combination of an adhesive and a semiconductor die
comprising: a nonconductive substantially tacky compliant polymer
adhesive to be applied at room temperature to at least one
attaching surface of at least one lead finger and a portion of a
surface of the semiconductor die for connecting at least one bond
pad of the semiconductor die to at least one lead finger of a
plurality of lead fingers of a lead frame, the nonconductive
polymer adhesive including a first material from a group of
copolymers that includes isobutyl compounds and a second material
that is from a group of metal oxides.
6. The combination of claim 5, wherein a first portion of said
nonconductive polymer adhesive is isobutyl acetal diphenol
copolymer.
7. The combination of claim 5, wherein said nonconductive polymer
adhesive includes said first material from said group of copolymers
that includes isobutyl acetal diphenol copolymer and said second
material that is from said group of metal oxides that includes
titanium dioxide.
8. The combination of claim 7, wherein said nonconductive polymer
adhesive has from about 75 percent to about 95 percent by weight of
said isobutyl acetal diphenol copolymer and from about 25 percent
to about 5 percent by weight, respectively, of said titanium
dioxide.
9. A semiconductor device comprising: a lead of a lead frame having
at least one attaching surface thereon; a semiconductor die having
an active surface having at least one bond pad thereon for
electrical connection to the lead of the lead frame; and a
nonconductive polymer adhesive which includes a first material from
a group of copolymers that includes isobutyl acetal diphenol
copolymer and a second material that is from a group of metal
oxides that includes titanium dioxide, said nonconductive polymer
adhesive being applied to one of said attaching surface of the lead
and a portion of the active surface of said semiconductor die for
compression therebetween to connect said semiconductor device to
said lead of the lead frame.
10. A device comprising: a lead frame having an attaching surface
thereon; a semiconductor die having a bond pad on a surface
thereof; and an adhesive that includes from about 75 percent to
about 95 percent of isobutyl acetal diphenol copolymer and from
about 25 percent to about 5 percent, respectively, of titanium
dioxide, said adhesive being applied to one of said attaching
surface of said lead frame and the bond pad of said semiconductor
die for compression therebetween to Electrically connect said at
least one bond pad of said semiconductor die to said attaching
surface of said lead frame.
11. A device comprising: a lead frame having a plurality of
attaching surfaces thereon; a semiconductor die having a surface
having a plurality of bond pads thereon for connection to said lead
frame; and a nonconductive polymer adhesive which includes a first
material from a group of copolymers that includes isobutyl acetal
diphenol copolymer and a second material that is from a group of
metal oxides that includes titanium dioxide, said nonconductive
polymer adhesive being applied to one of said attaching surfaces of
said lead frame and said surface of said semiconductor die for
compression therebetween to connect said active surface of said
semiconductor die to said attaching surfaces of said lead
frame.
12. An assembly comprising: a lead frame having an attaching
surface; a semiconductor die having bond pads on a surface thereof
for connection to said lead frame; and an adhesive that includes
from about 75 percent to about 95 percent of isobutyl acetal
diphenol copolymer and from about 25 percent to about 5 percent,
respectively, of titanium dioxide, said adhesive being applied to
one of said attaching surface of said lead frame and said
semiconductor die for compression therebetween to connect said
surface of said semiconductor device to said attaching surface of
said lead frame.
13. An assembly of a semiconductor device and a lead frame having a
plurality of lead fingers thereon, at least one lead finger of said
plurality of lead fingers having an attaching surface and having a
semiconductor die having a surface having at least one bond pad
thereon for connection to said at least one lead finger of said
plurality of lead fingers of said lead frame, the assembly
comprising: a polymer adhesive that is tacky and compliant at room
temperature, said polymer adhesive applied to one of said attaching
surface of said at least one lead finger of said plurality of lead
fingers of said lead frame and a portion of said surface of said
semiconductor die to electrically connect said at least one bond
pad of said semiconductor die to said at least one lead finger of
said plurality of lead fingers of said lead frame, said polymer
adhesive including a first material from a group of copolymers
including isobutyl compounds and a second material from a group
including metal oxides.
14. The assembly of claim 13, wherein a first portion of said
polymer adhesive is isobutyl acetal diphenol copolymer.
15. The assembly of claim 13, wherein said polymer adhesive
includes said first material from a group of copolymers that
includes isobutyl acetal diphenol copolymer and said second
material that is from said group of metal oxides that includes
titanium dioxide.
16. The assembly of claim 15, wherein said polymer adhesive has
from about 75 percent to about 95 percent by weight of said
isobutyl acetal diphenol copolymer and from about 25 percent to
about 5 percent by weight, respectively, of said titanium
dioxide.
17. An assembly of at least one semiconductor device and a lead
frame having a plurality of lead fingers thereon, at least one lead
finger of said plurality of lead fingers having an attaching
surface and having a semiconductor die having a surface for
connection to said at least one lead finger of said plurality of
lead fingers of said lead frame, the assembly comprising: an
adhesive that is tacky and compliant at room temperature, said
adhesive applied to one of said attaching surface of said at least
one lead finger of said plurality of lead fingers of said lead
frame and a portion of said surface of said semiconductor die to
connect said semiconductor die to said at least one lead finger of
said plurality of lead fingers of said lead frame, said adhesive
including a first material from a group of copolymers including
isobutyl compounds and a second material from a group including
metal oxides.
18. The assembly of claim 17, wherein a first portion of said
adhesive is isobutyl acetal diphenol copolymer.
19. The assembly of claim 17, wherein said adhesive includes said
first material from a group of copolymers that includes isobutyl
acetal diphenol copolymer and said second material that is from
said group of metal oxides that includes titanium dioxide.
20. The assembly of claim 15, wherein said adhesive has from about
75 percent to about 95 percent by weight of said isobutyl acetal
diphenol copolymer and from about 25 percent to about 5 percent by
weight, respectively, of said titanium dioxide
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
10/035,078, filed Dec. 28, 2001, pending, which is a continuation
of application Ser. No. 09/569,216, filed May 11, 2000, now U.S.
Pat. No. 6,337,511, issued Jan. 8, 2002, which is a divisional of
application Ser. No. 09/176,967, filed Oct. 22, 1998, now U.S. Pat.
No. 6,248,611, issued Jun. 19, 2001, which is a continuation of
application Ser. No. 08/916,977, filed Aug. 14, 1997, now U.S. Pat.
No. 5,840,598, issued Nov. 24, 1998.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to the manufacture of semiconductor
device assemblies and, more particularly, to methods of assembly of
semiconductor devices using room temperature adhesives and to the
assembled semiconductor device and lead frame using room
temperature adhesives.
[0004] 2. State of the Art
[0005] To manufacture a semiconductor device assembly, a
semiconductor device, typically called a die or chip, is typically
attached to a lead frame. A lead frame is a structure having a
plurality of leads, bus bars, or other connecting structure to be
electrically connected with the semiconductor device. In a
conventional lead frame, the lead frame includes a die paddle to
which the semiconductor device is attached and a plurality of leads
extending inwardly to surround the periphery of a semiconductor
device mounted on the die paddle. Subsequently, a plurality of wire
bonds are made to connect the bond pads on the active surface of
the semiconductor device to the ends of the leads extending around
the periphery of the semiconductor device. In a leads-over-chip
type lead frame (LOC lead frame), the lead frame is formed having
no die paddle and having a plurality of leads which extends over
the active surface of the semiconductor device being secured
thereto to support the semiconductor device, with a plurality of
wire bonds being formed between the bond pads on the active surface
of the semiconductor device and the ends of the leads of the lead
frame.
[0006] A conventional lead frame or LOC lead frame may serve other
functions. That is, it may assist in heat dissipation during
manufacture, increase the structural strength of the assembled
semiconductor device as well as provide convenient locations to
make electrical connections.
[0007] In order to attach the semiconductor device to the lead
frame, different adhesives and adhesively coated tapes have been
suggested. For example, U.S. Pat. No. 5,304,582 (Ogawa) shows use
of adhesive tape with different adhesives on opposite sides for
attaching a die to a lead frame. U.S. Pat. No. 5,548,160 (Corbett
et al.) discloses use of adhesives including adhesives that have a
core.
[0008] Typically, in attaching an LOC lead frame to a semiconductor
device, a double-coated adhesive tape is applied between the active
surface of the semiconductor device and the lead frame. The
adhesive tape is typically an insulating carrier with a polymer
adhesive on both sides to mechanically interconnect the lead frame
and the semiconductor device. The tape composition and the amount
of polymer adhesive used on the tape varies with the size of the
semiconductor device. It is desired to use the least amount of
adhesively coated tape to attach a semiconductor device to a lead
frame to attempt to minimize problems. Too much polymer adhesive
added to the tape can cause a coefficient of thermal expansion
mismatch between the lead frame, the polymer adhesive and the
semiconductor device which can contribute to the failure of the
packaged device. Reducing the size of the tape to enhance
performance may involve reprocessing the tape at some increased
cost and at some difficulty for the smaller sizes.
[0009] If an adhesive, as opposed to an adhesively coated tape, is
used to attach the semiconductor device to the lead frame, the
quantity of adhesive must be carefully controlled in the dispensing
process. The bond time for the adhesive is recognized to be
difficult to control and can vary greatly with variations in
adhesive viscosity, adhesive application temperature and amount of
adhesive used. Further, adhesive can bleed from under the lead
finger and interfere with the attachment of other lead fingers of
the lead frame. Also, use of an adhesive (at elevated temperatures)
may also lead to a nonuniform bond line between the semiconductor
device and the lead frame. That is, the semiconductor device is not
generally in alignment with the lead frame, causing different
spacings to be present between the lead fingers and the bond pads
on the active surface of the semiconductor device, thereby
affecting wire bonding operations. Additionally, uneven application
of adhesive or non-uniform adhesive viscosity can lead to tilting
of the semiconductor device relative to the lead frame. An uneven
or tilted relationship has been determined to be a factor that
reduces semiconductor device assembly quality and leads to
failures. U.S. Pat. No. 5,548,160 (Corbett et al.).
[0010] Therefore, an adhesive with better qualities suitable for
direct bonding of the semiconductor device to the lead fingers of a
lead frame is desirable.
BRIEF SUMMARY OF THE INVENTION
[0011] A semiconductor device assembly is formed by joining a lead
frame and a semiconductor device. The lead frame includes a
plurality of lead fingers, each lead finger having a lower
attaching surface for adhesive attachment to portions of the active
surface of a semiconductor device.
[0012] A non-conductive polymer adhesive is selected from the group
of adhesives that is tacky and compliant at room temperature,
easily applied to a substrate, such as through the use of a
stencil, and easily cured to a predetermined degree. The
non-conductive polymer is applied at room temperature, either to
the lower surface of the lead fingers of the lead frame or to
portions of the active surface of the semiconductor device for
compression therebetween. The lead fingers are connected by wire
bonds to the bond pads on the active surface of the semiconductor
device.
[0013] The adhesive preferably has a first copolymer material
selected from the group of copolymers that includes isobutyl
compounds and a second material that is from a group of metal
oxides that includes titanium dioxide. Preferably, the first
material is isobutyl acetal diphenol copolymer. More preferably,
the second material is titanium dioxide.
[0014] In a preferred composition, the adhesive has about 75
percent to about 95 percent of isobutyl acetal diphenol copolymer
and, respectively, from about 25 percent to about 5 percent of
titanium dioxide.
[0015] Methods of assembling the semiconductor device assembly
include providing a lead frame and a semiconductor device. A
non-conductive polymer adhesive is selected from the group that is
tacky and compliant at room temperature and is applicable to a
substrate through a stencil. The adhesive is applied to one of the
semiconductor devices and a surface of the lead frame at room
temperature. The lead frame and the semiconductor device are urged
together at room temperature to attach the semiconductor device to
the lead frame and with electrical connections between the lead
fingers of the lead frame and the bond pads on the active surface
of the semiconductor device made by wire bonds extending
therebetween.
[0016] In the preferred methods of assembly, the adhesive may be
from the groups of adhesives as described hereinbefore.
[0017] In an alternate configuration, a stencil is provided with
the adhesive, at room temperature, applied to either a surface of
each lead finger of the lead frame or portions of the active
surface of the semiconductor device. The lead frame and the
semiconductor device are thereafter positioned relative to each
other and urged together to effect attachment and electrical
connection, if desired.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0018] In the drawings which illustrate what are regarded as the
best modes and preferred embodiments for carrying out the
invention:
[0019] FIG. 1 is a perspective simplified illustration of a
semiconductor device assembly of the invention;
[0020] FIG. 2 is a perspective simplified illustration of a
semiconductor device assembly of the invention with a stencil for
applying adhesive;
[0021] FIG. 3 is a cross-sectional depiction of portions of a
semiconductor device of the invention; and
[0022] FIG. 4 is a cross-sectional depiction of portions of a
semiconductor device assembly of the invention with the
semiconductor device and the lead frame in contact.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Referring to drawing FIG. 1, a semiconductor device assembly
10 includes a lead frame 12 having a plurality of lead fingers 14
thereon. The lead frame 12 is one of a plurality that is connected
in end-to-end fashion, thereby forming a strip or roll of lead
frames. That is, lead frame 12 is positioned between a preceding
frame 16 and a following frame 18. The lead frame 12 as well as the
preceding frame 16 and following frame 18 are driven or moved
through a manufacturing environment by an appropriate drive or
indexing system that engages the apertures 20 formed in the
opposite edges or rails 22 and 24. At a convenient time, the lead
frames 12, 16 and 18 are separated one from the other and the
opposite edges or rails 22 and 24 are removed so that each frame
with a semiconductor device attached thereto becomes a separate and
useable semiconductor device assembly.
[0024] Each lead frame 12 is formed having a plurality of lead
fingers 14, each lead finger 14 having a lower surface, i.e., an
undersurface or attaching surface 26. In some instances, the bond
pads 36 of the semiconductor device 34 may include bumps thereon to
mate with each of the lead fingers 14 of the lead frame 12.
[0025] As illustrated in drawing FIG. 1, the semiconductor device
34 is any suitable semiconductor device configured for attachment
to the lead frame 12. The semiconductor device 34 has portions,
bond pads 36, on the active surface thereof configured for
electrical connection to the lead fingers 14 of a lead frame 12. As
illustrated, the semiconductor device 34 has a plurality of bond
pads 36 thereon, all suitably positioned so that, upon proper
positioning of the semiconductor device 34 with respect to the lead
fingers of a lead frame, the bond pads 36 are available for further
connection. The semiconductor device 34 may also have additional
bond pads thereon.
[0026] Adhesive 40 is used to attach the lead frame 12 and the
semiconductor device 34 together. As shown in FIG. 1, the adhesive
40 may be applied in a line or in a plurality of beads positioned
for effecting attachment of the semiconductor device 34 to the
attaching surface 26 of the lead fingers 14 of the lead frame
12.
[0027] In operation, the adhesive 40 is preferably applied to an
attaching surface 26 of the lead fingers 14 of the lead frame 12.
That is, the adhesive 40 is positioned on the attaching surface by
any appropriate nozzle, roller, glue gun tip or the like. Upon
urging the semiconductor device 34 and the lead frame 12 together,
the adhesive 40 is compressed and spread horizontally to effect an
attachment. Since the adhesive is preferably at room temperature,
viscosity and flow is typically constant throughout the adhesive.
In turn, the risk of an uneven relationship between the
semiconductor device and the lead frame is reduced as the
semiconductor device and lead frame are assembled. Further,
application at room temperature of the adhesive reduces heat
induced failures in the semiconductor device and lead frame
assembly arising during the assembly operations.
[0028] As illustrated in drawing FIG. 2, the lead frame 60 is the
same as lead frame 12. The lead frame 60 is positioned to pass
relative to a stencil 62. That is, a drive or indexing means (not
shown) urges the lead frame 60 as well as the preceding frame 64
and the following frame 66 to move past the stencil 62. A source 67
of adhesive 68 is illustrated separate from the stencil 62 for
clarity. In normal use, the stencil 62 is positioned so that
adhesive 68 from the source 67 is urged through the apertures 70 of
the stencil 62 (by, for example, a piston) and onto the underside
or attaching surface 72 of the lead frame 60. The stencil 62 may be
configured with any desired pattern of apertures for deposition of
adhesive 68 on an attaching surface 72 of the lead frame 60. Of
course, the adhesive may also be deposited on the active surface 73
of the semiconductor device 76.
[0029] The source 67 with stencil 62 and adhesive 68 may move up
and down relative to the attaching surface 72 to apply the adhesive
68 thereto. An anvil block 74 may be positioned opposite the
stencil 62 so that the lead frames 60, 64 and 66 are all properly
supported upon movement of the stencil 62 in close proximity and
upon operation of the source 67 to urge the adhesive 68 outwardly
to and in contact with the attaching surface 72. A similar anvil
block may be positioned so that the lead frame 60 is supported upon
movement of the semiconductor device 76 into contact with the
adhesive on the attaching surface 72 of the lead frame 60 and
further upon compression of the adhesive 68 as the active surface
73 of the semiconductor device 76 is urged toward the attaching
surface 72 of the lead frame 60. As the active surface 73 of the
semiconductor device 76 comes into contact with the attaching
surface 72, bond pads 78, 80 and 82 located on the active surface
73 of the semiconductor device 76 are positioned to effect
electrical connection with corresponding lead fingers 60' of the
lead frame 60 as desired using wire bonds.
[0030] Referring to drawing FIG. 3, a semiconductor device 34 is
illustrated in relation to the lead fingers 14 of a lead frame 12
having adhesive 40 applied to the attaching surfaces 26
thereof.
[0031] Referring to drawing FIG. 4, a semiconductor device 34 is
illustrated having the active surface 35 thereof secured to the
attaching surfaces 26 of the lead fingers 14 of a lead frame 12
(not shown) by the adhesive 40 located therebetween. As previously
stated, the adhesive 40 may be applied to either the active surface
35 of the semiconductor device 34 or the attaching surfaces 26 of
the lead fingers 14 of a lead frame 12. The lead fingers 14 and the
semiconductor device 34 are pressed into contact with the adhesive
40, which is subsequently cured. Also illustrated, wire bonds 100
extend between and electrically connect the lead fingers 14 with
the bond pads 36 on the active surface 35 of the semiconductor
device 34.
[0032] The adhesives 40 and 68 are non-conductive polymers selected
from that group or class of adhesives that is tacky and compliant
at room temperature and is at the same time applicable at room
temperature to a substrate through a stencil such as stencil 70.
The adhesives 40 and 68 preferably have a first copolymer that is
from the group of copolymers that includes isobutyl compounds and
is specifically isobutyl acetal diphenol copolymer. The adhesive
also contains a second material which is from a group of metal
oxides that includes titanium dioxide. The preferred adhesive has
from about 75 percent by weight or volume to about 95 percent by
weight or volume of isobutyl acetal diphenol copolymer and
respectively from about 25 percent to about 5 percent by weight or
volume of titanium dioxide. The amounts of the two constituents may
vary somewhat from those stated so long as the resulting
composition has the requisite tackiness and compliancy to be
suitable to secure a semiconductor device and a lead frame at room
temperature.
[0033] A suitable adhesive is available from International
Microelectronics Research Corporation of Nampa, Id. under the
product designation EXP/NCBP-4143-33 and is also known as
NON-CONDUCTIVE BUMP POLYMER 4243-33 (hereinafter referred to as the
BUMP POLYMER). The BUMP POLYMER is particularly suitable because it
may be applied at or near room temperature so that assembly can be
effected at room temperature. Room temperature is generally deemed
to be between 60.degree. Fahrenheit (F.) and 85.degree. F. and may
range from as low as 50.degree. F. to as high as 95.degree. F.
[0034] To manufacture the desired semiconductor devices, the user
provides the necessary lead frames in frame-by-frame sequence. Each
lead frame has an attaching surface and connectors associated
therewith. Semiconductor devices are also provided in a
piece-by-piece sequence, each to be attached to an appropriate lead
frame. Each semiconductor device has bond pads thereon configured
for electrical connection to the lead fingers of its respective
lead" frame.
[0035] A non-conductive polymer adhesive from the group that is
tacky and compliant at room temperature and is applicable through a
stencil is selected and applied at room temperature to one of the
semiconductor device and the attaching surface of the lead frame
and preferably the attaching surface. The semiconductor device and
the attaching surface are urged together to effect a desired
connection between the active surface of the semiconductor device
and the lead frame. Desirably, the adhesive selected is the
isobutyl acetal diphenol copolymer with titanium dioxide as
hereinbefore described. In a preferred method, the adhesive is
urged through the stencil as it is applied to the attaching surface
of the lead frame or the active surface of the semiconductor
device.
[0036] As previously stated, wire bonds are used to form the
electrical connections between the ends of the lead fingers of the
lead frame and the bond pads on the active surface of the
semiconductor device.
[0037] Those skilled in the art will appreciate that modifications
may be made to the illustrated embodiment and the disclosed methods
without departing from the spirit or principles of the invention
and are not intended to limit the scope of the following
claims.
* * * * *