U.S. patent application number 11/940104 was filed with the patent office on 2008-03-13 for wire-bonded package with electrically insulating wire encapsulant and thermally conductive overmold.
Invention is credited to Constance L. Gettinger, J. Christopher JR. Matayabas.
Application Number | 20080061447 11/940104 |
Document ID | / |
Family ID | 33541337 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080061447 |
Kind Code |
A1 |
Matayabas; J. Christopher JR. ;
et al. |
March 13, 2008 |
WIRE-BONDED PACKAGE WITH ELECTRICALLY INSULATING WIRE ENCAPSULANT
AND THERMALLY CONDUCTIVE OVERMOLD
Abstract
The specification discloses an apparatus comprising a die
mounted on a substrate, the die being connected to the substrate by
a plurality of wires, and a mold cap encapsulating the die and the
plurality of wires, the mold cap comprising an electrically
insulating portion encapsulating the wires and at least a portion
of the die and a thermally conductive portion overmolded on the die
and the electrically insulating portion. Also disclosed is a
process comprising providing a die connected to a substrate by a
plurality of wires, encapsulating the wires and at least a portion
of the die in an electrically insulating material, and
encapsulating the die, the wires and the electrically insulating
material in a thermally conductive material. Other embodiments are
disclosed and claimed.
Inventors: |
Matayabas; J. Christopher JR.;
(Chandler, AZ) ; Gettinger; Constance L.;
(Chandler, AZ) |
Correspondence
Address: |
INTEL/BLAKELY
1279 OAKMEAD PARKWAY
SUNNYVALE
CA
94085-4040
US
|
Family ID: |
33541337 |
Appl. No.: |
11/940104 |
Filed: |
November 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10611549 |
Jun 30, 2003 |
|
|
|
11940104 |
Nov 14, 2007 |
|
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|
Current U.S.
Class: |
257/777 ;
257/E23.107; 257/E23.118; 257/E23.125; 257/E23.126 |
Current CPC
Class: |
H01L 2224/484 20130101;
H01L 2924/12042 20130101; H01L 2224/48091 20130101; H01L 2924/00014
20130101; H01L 2924/14 20130101; H01L 2224/05599 20130101; H01L
23/3737 20130101; H01L 2924/181 20130101; H01L 2924/00014 20130101;
H01L 2924/01013 20130101; H01L 2924/1461 20130101; H01L 2224/32145
20130101; H01L 2924/01006 20130101; H01L 2224/73204 20130101; H01L
2224/484 20130101; H01L 2224/85399 20130101; H01L 2224/73265
20130101; H01L 2924/181 20130101; H01L 24/48 20130101; H01L
2924/0103 20130101; H01L 2224/8592 20130101; H01L 2924/01079
20130101; H01L 2924/01047 20130101; H01L 2924/12042 20130101; H01L
2224/85399 20130101; H01L 2924/01029 20130101; H01L 2224/73265
20130101; H01L 2924/01074 20130101; H01L 23/3121 20130101; H01L
2224/48227 20130101; H01L 2924/00014 20130101; H01L 2924/01019
20130101; H01L 2224/16225 20130101; H01L 23/3135 20130101; H01L
2224/0401 20130101; H01L 2224/73265 20130101; H01L 2224/32225
20130101; H01L 2224/48091 20130101; H01L 2224/48227 20130101; H01L
2224/16225 20130101; H01L 2224/48227 20130101; H01L 2924/00014
20130101; H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L
2924/00 20130101; H01L 2224/05599 20130101; H01L 2924/00 20130101;
H01L 2224/32225 20130101; H01L 2224/32225 20130101; H01L 2224/32145
20130101; H01L 2924/00 20130101; H01L 2224/45099 20130101; H01L
2924/00012 20130101; H01L 2924/00014 20130101; H01L 2924/00
20130101; H01L 2924/1461 20130101; H01L 2224/73204 20130101 |
Class at
Publication: |
257/777 ;
257/E23.118 |
International
Class: |
H01L 23/29 20060101
H01L023/29 |
Claims
1. An apparatus comprising: a stack of dies mounted on a substrate,
the stack including a first die attached to the substrate and at
least one additional die stacked thereon; a plurality of wires
connecting at least one of the stacked dies to the substrate or to
another die in the stack; and a mold cap encapsulating the wires
and the stacked dies, the mold cap comprising an electrically
insulating portion encapsulating substantially all of the wires and
the entire stack of dies, and a thermally conductive portion
encapsulating substantially all the electrically insulating
portion.
2. The apparatus of claim 1 wherein at least one of the stacked
dies comprises an integrated circuit.
3. The apparatus of claim 1 wherein the first die is flip-chip
bonded to the substrate.
4. The apparatus of claim 1 wherein the electrically insulating
material comprises a curable resin, a crosslinker, a catalyst, and
a reinforcing filler.
5. The apparatus of claim 1 wherein the reinforcing filler
comprises silica, alumina, zinc oxide, talc, or combinations
thereof.
6. The apparatus of claim 1 wherein the resin comprises a curable
resin, a crosslinker, a catalyst, and a metal filler.
7. The apparatus of claim 6 wherein the metal filler comprises
aluminum, silver, copper, gold, or combinations or alloys
thereof.
8. The apparatus of claim 1, further comprising a heat dissipation
device attached to, and in thermal contact with, the thermally
conductive material.
9. An apparatus comprising: a stack of dies mounted on a substrate,
the stack including a first die attached to the substrate and at
least one additional die stacked thereon; a plurality of wires
connecting at least one of the stacked dies to the substrate or to
another die in the stack; and a mold cap encapsulating the wires
and the stacked dies, the mold cap comprising: an electrically
insulating portion encapsulating substantially all the wires and
the entire stack of dies, and a thermally conductive portion
encapsulating substantially all of the electrically insulating
portion.
10. The apparatus of claim 9 wherein at least one of the stacked
dies comprises an integrated circuit.
11. The apparatus of claim 9 wherein the first die is flip-chip
bonded to the substrate.
12. The apparatus of claim 9 wherein the electrically insulating
material comprises a curable resin, a crosslinker, a catalyst, and
a reinforcing filler.
13. The apparatus of claim 9 wherein the reinforcing filler
comprises silica, alumina, zinc oxide, talc, or combinations
thereof.
14. The apparatus of claim 9 wherein the resin comprises a curable
resin, a crosslinker, a catalyst, and a metal filler.
15. The apparatus of claim 14 wherein the metal filler comprises
aluminum, silver, copper, gold, or combinations or alloys
thereof.
16. The apparatus of claim 9, further comprising a heat dissipation
device attached to, and in thermal contact with, the thermally
conductive material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/611,549, filed 30 Jun. 2003, and claims priority
therefrom under 35 U.S.C. .sctn. 120. The priority application is
currently pending.
TECHNICAL FIELD
[0002] The present invention relates generally to semiconductor die
packaging and in particular, but not exclusively, to thermally
dissipative packaging of wire-bonded semiconductor dies.
BACKGROUND
[0003] FIG. 1 illustrates an encapsulated wire-bonded die 100. The
die 104 is bonded to a substrate 102 by a layer of adhesive 106,
and the die is connected to the substrate by a plurality of wires
108. The die 104 and the wires 108 are surrounded by a mold cap 110
that protects them from environmental contamination, mechanical
forces, and other elements which could damage them. Because the
mold cap 110 encapsulates and surrounds the wires 108, it cannot be
electrically conductive; if it were, it would cause a short circuit
between wires. Materials that are not electrically conductive are
generally also not thermally conductive, meaning that although the
mold cap 110 helps the wire-bonded assembly by protecting it from
environmental conditions, it also hinders the wire-bonded die by
preventing the escape of heat generated by the die. Where the
amount of power consumed by the die is small, the mold cap 110
allows sufficient heat transfer that the temperature of the die
does not increase enough to cause it any damage. As the amount of
power consumed by the die--and, consequently, the amount of heat
generated by the die--increases, the inability of the mold cap 110
to transfer significant amounts of heat away from the die leads to
large increases in the operating temperature of the die. If the die
temperature becomes too high, it could cause the die to malfunction
or fail completely.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Non-limiting and non-exhaustive embodiments of the present
invention are described with reference to the figures, which are
not to scale unless noted and wherein like reference numerals refer
to like parts throughout the various views unless otherwise
specified.
[0005] FIG. 1 is a side elevation of a prior art mold cap placed on
a wire-bonded die.
[0006] FIGS. 2A-2B are side elevations of embodiments of a mold cap
placed on a single wire-bonded die.
[0007] FIGS. 3A-3B are side elevation of alternative embodiments of
a mold cap placed on a single wire-bonded die.
[0008] FIGS. 4A-4B are side elevations of alternative embodiments
of a mold cap placed on stacked wire-bonded dies.
[0009] FIG. 5 is a side elevation of an embodiment of a mold cap
placed on wire-bonded dies stacked on a flip-chip bonded die.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0010] Embodiments of a system and method for thermally dissipative
packaging of wire-bonded semiconductor dies are described herein.
In the following description, numerous specific details are
described to provide a thorough understanding of embodiments of the
invention. One skilled in the relevant art will recognize, however,
that the invention can be practiced without one or more of the
specific details, or with other methods, components, materials,
etc. In other instances, well-known structures, materials, or
operations are not shown or described in detail to avoid obscuring
aspects of the invention.
[0011] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the present invention. Thus,
appearances of the phrases "in one embodiment" or "in an
embodiment" in this specification do not necessarily all refer to
the same embodiment. Furthermore, the particular features,
structures, or characteristics may be combined in any suitable
manner in one or more embodiments.
[0012] FIG. 2A illustrates an embodiment of an encapsulated
wire-bonded die 200. The wire-bonded die comprises a die 204 bonded
to a substrate 202 using a layer of adhesive 206. In one
embodiment, the die 204 comprises an integrated circuit, but in
other embodiments it may be something different such as an optical
die, microelectromechanical system (MEMS) die, etc. The die 204 is
connected to the substrate by a plurality of wires 208. After the
die 204 is attached to the substrate 202 and the wires 208 have
been connected, a mold cap 201 is placed over the die and wires.
The mold cap 201 includes an electrically insulating portion 210
and a thermally conductive portion 212. The electrically insulating
portion 210 is placed over the die 204 and the wires 108 to
encapsulate the wires and protect them from environmental
contamination, and to prevent the wires from moving and touching
each other. The electrically insulating portion covers
substantially the entire die 204, and is in contact with the
lateral surfaces 203 and the top surface 205 of the die. After the
electrically insulating portion 210 is in position, a thermally
conductive portion 212 is overmolded on top of the electrically
insulating portion 210.
[0013] In one embodiment, the electrically insulating portion
comprises a curable resin, a crosslinker, a catalyst, and a
reinforcing filler. A variety of polymeric resins can be used,
including epoxy, acrylate, bismaleimide, polyester, polyamide,
olefin, and their combinations. Typically, the resin includes
ceramic fillers for the purpose of increasing modulus, lowering
coefficient of thermal expansion (CTE) and improving mechanical
properties. Examples of suitable fillers include silica, alumina,
zinc oxide, talc, and the like or their combinations. In various
embodiments, the resin has melting point less than about
160.degree. C., typically between about 40 and 120.degree. C.
Optionally, other additives known in the art can be used, such as
demolding agents, adhesive modifiers, flow aids, colorants,
stabilizers, plasticizers, impact modifiers, flame retardants, and
other similar additives or combinations thereof.
[0014] In one embodiment where the electrically insulating portion
210 is made using a resin, it can be applied by processes known in
the art, such as dispensing (e.g., dam-and-fill), spraying, screen
printing, transfer molding, or injection molding. If desired, the
electrically insulating portion 210 may be partially or completely
cured prior to applying the thermally conductive portion 212. The
resin may be cured by thermal, UV, laser, microwave, or other
techniques known in the art, depending on the selection of
catalyst, resin, and crosslinker. It is preferred that the
electrically insulating portion be partially cured prior to
applying the overmolded thermally conductive portion 212, to
minimize its movement during overmolding yet provide good bonding
to the thermally conductive portion. Typically, complete cure of
the mold cap 201 is obtained by oven curing at elevated
temperatures after overmolding.
[0015] The thermally conductive portion 212 can be made of any
material that is readily moldable and has the appropriate thermal
conductivity for the application in which it will be used. In one
embodiment, the thermally conductive portion 212 comprises a
curable resin, a crosslinker, a catalyst, and a metal filler. A
wide variety of polymeric resins may be used including epoxy,
acrylate, bismaleimide, polyester, polyamide, olefin,
isocyanaurate, polyimide, and the like or combinations thereof. The
metal filler should have a bulk thermal conductivity greater than
about 100 W/m.degree. K and melting point greater than about
200.degree. C. Examples of suitable metal fillers include aluminum,
silver, copper, gold, and the like metals or their combinations and
alloys. The resin should have melting point less than about
160.degree. C., typically between about 40 and 120.degree. C.
Optionally, other additives known in the art may be used, such as
de-molding agents, adhesive modifiers, flow aids, colorants,
stabilizers, plastizers, impact modifiers, flame retardants, and
the like additives or their combinations.
[0016] In one particular embodiment, the thermally conductive
portion 212 is made of a material prepared by (1) dry blending in a
blender with a grinding blade and cooling to maintain the
temperature below 25.degree. C. 13.5 g of epoxylated
tetramethylbiphenol, 11.5 g of Bishenol F, 75 grams of silver
powder, 0.3 g of carnauba wax, 0.2 g of 3,4-epoxypropyl trimethoxy
silane, and 0.15 g of triphenyl phosphine; and (2) roll milling the
mixture at 110.degree. C. The resulting material is then ground and
pressed into a pellet. The material is observed to have a bulk
thermal conductivity of approximately 4.0 W/m.degree. K. As with
the electrically insulating portion 210, the thermally conductive
portion 212 can be applied by processes known in the art, such as
dispensing (e.g., dam-and-fill), screen printing, transfer molding,
or injection molding. Similarly, the thermally conductive portion
can be cured by thermal, UV, laser, microwave, or other techniques
known in the art, depending on the selection of catalyst, resin,
and crosslinker.
[0017] FIG. 2B illustrates an embodiment of an encapsulated
wire-bonded die 250. The encapsulated wire-bonded die 250 is
similar in construction to the encapsulated die 200. The primary
difference is that the encapsulated die 250 includes a heat
dissipation device 214 attached to, and in thermal contact with,
the exterior of the thermally conductive portion 212 of the mold
cap 201. With the addition of the heat dissipation device 214, the
ability to remove heat generated in the die is further enhanced. In
various embodiments the heat dissipation device 214 can comprise
fins, a heat sink, a vapor chamber, a heat plate and the like.
[0018] FIG. 3A illustrates an embodiment of an encapsulated
wire-bonded die 300. As with the encapsulated dies 200 and 250, the
encapsulated die 300 comprises a die 304 bonded to a substrate 302
using a layer of adhesive 306. In one embodiment the die 304
comprises an integrated circuit, but in other embodiments it may be
something different such as an optical die, microelectromechanical
system (MEMS) die, etc. The die is connected to the substrate by a
plurality of wires 308, and a mold cap 301 is placed over the die
and wires. Like the mold cap 201, the mold cap 301 includes an
electrically insulating portion 310 and a thermally conductive
portion 312. The mold cap 301, however, has a different
construction than the mold cap 201. In the mold cap 301, the
electrically insulating portion 310 is positioned only around the
perimeter of the die 304, such that it still encapsulates the wires
308 but only partially encapsulates the die 304. In other words,
the electrically insulating portion 310 covers the wires but is
only in contact with the sides 303 and a small portion near the
perimeter of the top 305 of the die. Once the electrically
insulating portion 310 is in place, the thermally conductive
portion 312 is overmolded on top of the die and the electrically
insulating portion. Once in place, the thermally conductive portion
is in direct contact with a large portion of the top surface 305 of
the die. This direct contact between the thermally conductive
portion and the die means that the mold cap 301 has greatly
enhanced heat transfer compared to the mold cap 201, since thermal
energy from large portions of the die 314 is more quickly
transferred through the mold cap because it no longer has to cross
an electrically insulating (and therefore thermally insulating)
portion.
[0019] The mold cap 301 can be made using the same electrically
insulating and thermally conductive materials discussed above in
connection with the mold cap 201. The techniques used to apply the
electrically insulating portion 310 and the thermally conductive
portion 312 are also as discussed above, except that in the
application of the insulating portion 310 the techniques must be
modified to allow the electrically insulating material to be placed
only around the sides 303 of the die and on a small portion of the
top 305, while still covering the wires 308.
[0020] FIG. 3B illustrates an embodiment of an encapsulated
wire-bonded die 350. The encapsulated wire-bonded die 350 is
similar in construction to the encapsulated die 300. The primary
difference is that the encapsulated die 350 includes a heat
dissipation device 314 attached to, and in thermal contact with,
the exterior of the thermally conductive portion 312. With the
thermally conductive portion 312 in direct contact with the die and
the addition of the heat dissipation device 314, the ability to
remove heat gene-rated by the die is further enhanced. In various
embodiments the heat dissipation device 314 can comprise fins, a
heat sink, a vapor chamber, a heat plate and the like.
[0021] FIG. 4A illustrates an embodiment of an encapsulated
wire-bonded die stack 400. The die stack comprises a first die 404
attached to a substrate 402 by a layer of adhesive 406. A second
die 408 is stacked on the first die 404, and a third die 410 is
stacked on the second die 408. In one embodiment the dies 402, 408
and 410 comprise integrated circuits, but in other embodiments they
may be something different such as an optical dies,
microelectromechanical system (MEMS) dies, etc, and they need not
all be the same type of die. All three dies 404, 408 and 410 are
connected to the substrate 402, or to one of the other dies in the
stack, by wires 412. After the dies 404, 408 and 410 are attached
to the substrate 402 and the wires 408 have been connected, a mold
cap 401 is placed over the die and wires. Like the mold cap 301,
the mold cap 401 includes an electrically insulating portion 410
and a thermally conductive portion 412, with the electrically
insulating portion 410 is positioned only around the perimeter of
the stacked dies 404, such that it completely encapsulates the
wires 412 and covers the sides 405 of the die 404, the sides 409 of
the die 408, and the sides 411 and a large part of the top 413 of
the third die 410. The electrically insulating portion 410 is only
in contact with the sides 403 and a small portion near the
perimeter of the top 405 of the die. Once the electrically
insulating portion 410 is in place, the thermally conductive
portion 412 is overmolded on top of the die and the electrically
insulating portion. Once in place, the thermally conductive portion
is in direct contact with a large portion of the top surface 405 of
the die.
[0022] FIG. 4B illustrates an embodiment of an encapsulated
wire-bonded die stack 450. The die stack is similar in construction
to the die stack of the encapsulated die stack 400. The primary
difference is in the positioning of the electrically insulating
portion 414 and the thermally conducting portion 416. Heat transfer
in stacked dies is more difficult than in single dies because in
stacked dies most of the dies in the stack have a limited area
through which heat can be transferred. For example, the second die
408 is sandwiched between the first die 404 and the third die 410,
and cannot transfer much heat to those dies. The second die is left
with only its sides 409 through which to transfer heat out of the
die. Because the heat transfer area is limited, it is very
desirable to have the thermally conductive portion 416 very close
to, or in direct contact with, the exposed surfaces of the die. In
the mold cap 451, the electrically insulating portion 414 is
deposited (e.g., by spraying) directly on the wires 412 and only
very thinly, if at all, around the dies. The thermally conducting
portion 416 is then overmolded onto the dies, the wires, and the
electrically insulating portion 414.
[0023] FIG. 5 illustrates an encapsulated mixed-bonding die stack
500. The die stack is a "mixed-bonding" stack because it comprises
dies bonded in different ways. The die stack comprised a first die
504 that is flip-chip bonded to the substrate, and a second die 506
and third die 508 wire-bonded to the first die 504. In one
embodiment the dies 504, 506 and 508 comprise integrated circuits,
but in other embodiments they may comprise something different such
as an optical dies, microelectromechanical system (MEMS) dies, etc,
and they need not all be the same type of die. The mold cap 501 is
configured with the electrically insulating portion 510 deposited
on the wires 514 and thinly on the dies, while thermally conductive
portion 512 is overmolded onto the dies, the wires, and the
electrically insulating portions. A mold cap such as mold cap 501,
or any of the other mold caps described herein can also be used
with other types of die packaging, for example wire-bonded PBGA,
multi-matrix array packaging (MMAP), and folded stack
packaging.
[0024] The above description of illustrated embodiments of the
invention, including what is described in the Abstract, is not
intended to be exhaustive or to limit the invention to the precise
forms disclosed. While specific embodiments of, and examples for,
the invention are described herein for illustrative purposes,
various equivalent modifications are possible within the scope of
the invention, as those skilled in the relevant art will recognize.
These modifications can be made to the invention in light of the
above detailed description.
[0025] The terms used in the following claims should not be
construed to limit the invention to the specific embodiments
disclosed in the specification and the claims. Rather, the scope of
the invention is to be determined entirely by the following claims,
which are to be construed in accordance with established doctrines
of claim interpretation.
* * * * *