U.S. patent application number 11/501600 was filed with the patent office on 2006-11-30 for semiconductor device modules, semiconductor devices, and microelectronic devices.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Teck Kheng Lee.
Application Number | 20060267171 11/501600 |
Document ID | / |
Family ID | 32590087 |
Filed Date | 2006-11-30 |
United States Patent
Application |
20060267171 |
Kind Code |
A1 |
Lee; Teck Kheng |
November 30, 2006 |
Semiconductor device modules, semiconductor devices, and
microelectronic devices
Abstract
Supports (40) of microelectronic devices (10) are provided with
underfill apertures (60) which facilitate filling underfill gaps
(70) with underfill material (74). The underfill aperture may have
a longer first dimension (62) and a shorter second dimension (64).
In some embodiments, a method of filling the underfill gap (70)
employs a removable stencil (80). If so desired, a stencil (80) can
be used to fill multiple underfill gaps through multiple underfill
apertures in a single pass.
Inventors: |
Lee; Teck Kheng; (Singapore,
SG) |
Correspondence
Address: |
PERKINS COIE LLP;PATENT-SEA
PO BOX 1247
SEATTLE
WA
98111-1247
US
|
Assignee: |
Micron Technology, Inc.
Boise
ID
|
Family ID: |
32590087 |
Appl. No.: |
11/501600 |
Filed: |
August 8, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10710229 |
Jun 28, 2004 |
7087994 |
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11501600 |
Aug 8, 2006 |
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09944465 |
Aug 30, 2001 |
6756251 |
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10710229 |
Jun 28, 2004 |
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Current U.S.
Class: |
257/678 ;
257/778; 257/787; 257/E21.503; 257/E23.004 |
Current CPC
Class: |
H01L 2224/92125
20130101; H01L 2924/15151 20130101; H01L 24/28 20130101; H01L
2924/00014 20130101; H01L 2924/01082 20130101; H01L 2924/01027
20130101; H01L 21/563 20130101; H01L 2924/01013 20130101; H01L
2924/09701 20130101; H01L 2224/83102 20130101; H01L 23/13 20130101;
H01L 2224/16225 20130101; H01L 2924/01049 20130101; H01L 2924/00014
20130101; H01L 2224/73203 20130101; H01L 2924/14 20130101; H01L
2224/73204 20130101; H01L 2924/01087 20130101; H01L 2924/0105
20130101; H01L 2924/01033 20130101; H01L 2224/05573 20130101; H01L
2924/01079 20130101; H01L 2924/01047 20130101; H01L 2224/05599
20130101 |
Class at
Publication: |
257/678 ;
257/787; 257/778 |
International
Class: |
H01L 23/28 20060101
H01L023/28 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 2001 |
SG |
200105099-6 |
Claims
1-13. (canceled)
14. A semiconductor device module, comprising: a support having a
mounting surface, a component surface, a plurality of component
terminal arrays at the component surface in which individual
component terminal arrays are configured to be associated with an
individual semiconductor die, and a plurality of elongated slots
through the support from the mounting surface to the component
surface, wherein individual slots are associated with individual
component terminal arrays; a plurality of semiconductor dies,
wherein the individual dies have a front side spaced apart from the
component surface by an underfill gap, a backside, and a die
terminal array at the front side, and wherein the individual die
terminal arrays are electrically connected to corresponding
individual component terminal arrays; and an underfill material at
least substantially filling the underfill gaps between the dies and
the component surface of the support.
15. The module of claim 14 wherein the semiconductor dies are the
same type of dies.
16. The module of claim 14 wherein the semiconductor dies include
first and second dies, and wherein the first dies are different
than the second dies.
17. The module of claim 14 wherein the underfill material at least
partially fills the elongated slots.
18. The module of claim 14 wherein the terminals of the die
terminal arrays are juxtaposed to corresponding terminals of
corresponding component terminal arrays, and wherein the module
further comprises solder balls electrically connecting the die
terminal arrays to corresponding component terminal arrays.
19. The module of claim 18 wherein the underfill material encases
the solder balls.
20. The module of claim 14 wherein the die terminal arrays and the
individual corresponding component terminal arrays have common
configurations, and wherein the module further comprises electrical
connectors in the underfill gaps extending between the die terminal
arrays and corresponding component terminal arrays.
21. The module of claim 20 wherein the underfill material encases
the electrical connectors.
22. The module of claim 14, further comprising electrical
connectors between the die terminals and corresponding component
terminals, and wherein the underfill material encapsulates the
electrical connectors while at least substantially filling the
underfill gaps.
23. A semiconductor device, comprising: a semiconductor die having
a front side, a backside, an integrated circuit, and a first
terminal array at the front side; a first support having a
component surface, a mounting surface, a second terminal array at
the component surface electrically coupled to the first terminal
array of the die, a third terminal array at the mounting surface,
and a first aperture through the first support from the component
surface to the mounting surface, the first aperture having a first
dimension and a second dimension different than the first
dimension, and the front side of the die being spaced part from the
component surface by a first underfill gap; a second support having
a terminal surface, a fourth terminal array at the terminal surface
electrically coupled to the third terminal array of the first
support, and a second aperture, wherein the mounting surface of the
first support is spaced apart from the terminal surface of the
second support by a second underfill gap; and an underfill material
at least substantially filling the first underfill gap, the first
aperture and the second underfill gap.
24. The semiconductor device of claim 23, further comprising first
electrical connectors electrically connecting the first terminal
array to the second terminal array and second electrical connectors
electrically connecting the third terminal array to the fourth
terminal array.
25. The semiconductor device of claim 24 wherein the underfill
material encapsulates the first and second electrical
connectors.
26. The semiconductor device of claim 24 wherein the underfill
material includes a first underfill material at least substantially
filling the first underfill gap and a second underfill material at
least substantially filling the second underfill gap.
27. The semiconductor device of claim 24 wherein the first and
second electrical connectors comprise solder balls.
28. The semiconductor device of claim 23 wherein the second support
comprises a printed circuit board, and wherein the semiconductor
device further comprises a plurality of semiconductor dies carried
by the printed circuit board.
29. A microelectronic device, comprising: a microelectronic die
having a front side, a backside, and a first terminal array at the
front side; a first support having a component surface, a mounting
surface, a second terminal array at the component surface
electrically connected to the first terminal array, and an
elongated aperture through the first support from the component
surface to the mounting surface, wherein the front side of the die
faces the component surface of the first support across an
underfill gap; and an underfill material at least substantially
filling the underfill gap.
30. The microelectronic device of claim 29 wherein the aperture is
configured to have one of an I-shape, a T-shape, a star shape, a
U-shape or an L-shape.
31. The microelectronic device of claim 29 wherein the underfill
gap is peripherally open.
32. The microelectronic device of claim 29, further comprising: a
second support having a first side, a second side, and an opening
through the second support from the first side to the second side,
wherein the first support is spaced apart from the second support
by a second gap; and a plurality of electrical connectors
electrically coupling the first terminal array to the second
terminal array.
33. The microelectronic device of claim 32 wherein the underfill
material at least substantially fills the underfill gap between the
die and the first support and the second gap between the first
support and the second support, and wherein the underfill material
at least substantially encases the electrical connectors.
34. The microelectronic device of claim 33 wherein the underfill
material includes a first underfill material between the die and
the first support and a second underfill material between the first
support and the second support.
35. The microelectronic device of claim 33 wherein the underfill
material includes a first underfill material between the die and
the first support and a second underfill material between the first
support and the second support, and wherein the first underfill
material has the same composition as the second underfill material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 09/944,465, entitled "METHOD OF MANUFACTURING
MICROELECTRONIC DEVICES, INCLUDING METHODS OF UNDERFILLING
MICROELECTRONIC COMPONENTS THROUGH AN UNDERFILL APERTURE," filed
Aug. 30, 2001, now U.S. Pat. No. 6,756,251, issued Jun. 29, 2004,
which claims foreign priority benefits of Singapore Application No.
200105099-6, filed Aug. 21, 2001, both of which are herein
incorporated by reference in their entireties.
TECHNICAL FIELD
[0002] This invention relates to microelectronic devices having
microelectronic components mounted on substrates and methods of
manufacturing such devices. The invention has particular utility in
connection with flip-chip packaging.
BACKGROUND
[0003] Microelectronic devices, such as memory devices and
microprocessors, typically include one or more microelectronic
components attached to a substrate. The microelectronic components
commonly include at least one die including functional features
such as memory cells, processor circuits, and interconnecting
circuitry. The dies of the microelectronic components may be
encased in a plastic, ceramic or metal protective covering. Each
die commonly includes an array of very small bond pads electrically
coupled to the functional features. These terminals can be used to
operatively connect the microelectronic component to the
substrate.
[0004] One type of microelectronic component which is gaining
increased acceptance is the "flip-chip" semiconductor device. These
components are referred to as "flip-chips" because they are
typically manufactured in wafer form having bond pads which are
initially facing upwardly. After manufacture is completed and the
semiconductor die is singulated from the wafer, it is inverted or
"flipped" such that the surface bearing the bond pads faces
downwardly for attachment to a substrate. The bond pads are usually
coupled to terminals, such as conductive "bumps," which are used as
electrical and mechanical connectors connecting the die to the
substrate. A variety of materials may be used to form the bumps on
the flip-chip, such as various types of solder and conductive
polymers. In applications using solder bumps, the solder bumps are
reflowed to form a solder joint between the flip-chip component and
the substrate. This leaves a small gap between the flip-chip and
the substrate. To enhance the joint integrity between the
microelectronic component and the substrate, an underfill material
is introduced into the gap between the components. This underfill
material helps equalize stress placed on the components and
protects the components from contaminants, such as moisture and
chemicals.
[0005] The underfill material typically is dispensed into the
underfill gap by injecting the underfill material along one or two
sides of the flip-chip. As shown schematically in FIG. 1, a bead of
an underfill material U may be dispensed along one side of the die
D. The underfill material will then be drawn into the gap between
the die D and the substrate S by capillary action. The direction of
this movement is indicated by the arrows in FIG. 1. While such a
"single stroke" process yields good results, the processing time
necessary to permit the underfill material U to flow across the
entire width of the die can reduce throughput of the manufacturing
process.
[0006] FIG. 2 illustrates an alternative approach wherein the
underfill material U is applied in an L-shaped bead which extends
along two adjacent sides of the die D. By reducing the average
distance which the underfill material has to flow to fill the
underfill gap, processing times can be reduced. However, this
L-stroke approach can lead to more voids in the underfill material,
adversely affecting the integrity of the bond between the die D and
the substrate S.
[0007] Typically, the underfill material U dispensed along the
edge(s) of the die D in this process has a relatively high
viscosity at dispensing temperatures. This permits a well-defined
bead of material to be applied adjacent a single die D,
facilitating a more dense arrangement of dies on the surface of the
substrate. To get the underfill material U to flow into the
underflow gap, the substrate is typically heated sufficiently to
reduce the viscosity of the underfill material. This significantly
increases manufacturing time and complexity.
[0008] Others have proposed pumping an underfill material into the
underfill gap through an opening in the substrate. For example,
U.S. Pat. No. 6,057,178 (Galuschki et al, the teachings of which
are incorporated herein by reference) adds the underfill material
via an orifice in the substrate. A viscous underfill material is
added to the orifice (e.g., by dispensing it under pressure). The
assembly must then be heated to allow the underfill material to
flow into the underfill gap.
[0009] U.S. Pat. No. 5,697,148 (Lance Jr. et al., the teachings of
which are incorporated herein by reference) also suggests
dispensing an underfill material into the underfill gap through the
substrate. The underfill material is injected under hydraulic
pressure through an injection port using a needle. Injecting
underfill material using a dispenser such as suggested in this
patent and in the Galuschki et al. patent requires precise
placement of the dispensing tip in the relatively small opening in
the substrate. Fairly complex vision systems must be employed to
ensure that the dispensing tip is properly aligned with the
opening. Using a small dispenser also makes it more difficult to
fill multiple underfill gaps between different die-substrate pairs
at one time.
SUMMARY OF THE INVENTION
[0010] The present invention provides certain improvements in
microelectronic devices and various aspects of their manufacture.
In accordance with one embodiment, the invention provides a
microelectronic device assembly which includes a microelectronic
component and a first support. The microelectronic component has a
facing surface, an exterior surface, and a first terminal array
carried on the facing surface. The first support has a component
surface, a mounting surface, a second terminal array, and an
aperture which extends through the support from the component
surface to the mounting surface. The second terminal array is
carried on the component surface and is electrically coupled to the
first terminal array of the microelectronic component. The aperture
has a first dimension and a second dimension less than the first
dimension. The component surface of the support is juxtaposed with
the facing surface of the microelectronic component to define a
first underfill gap between the component surface and the facing
surface. A first underfill material at least substantially fills
the first underfill gap.
[0011] In an alternative embodiment, the microelectronic device
assembly further includes a second support such as a circuit board.
In this embodiment, the first support includes a third terminal
array on its mounting surface. A second support has a fourth
terminal array carried on a terminal surface. The third terminal
array of the first support is electrically coupled to the fourth
terminal array of the second support. The mounting surface of the
first support is juxtaposed with the terminal surface of the second
support a define a second underfill gap therebetween. A second
underfill material, which may be the same as the first underfill
material, substantially fills the second underfill gap.
[0012] Another embodiment of the invention provides a method for
underfilling a microelectronic component which is electrically
coupled to a support to define an underfill gap, with an underfill
aperture extending through the support and in fluid communication
with the underfill gap. In accordance with this method, a stencil
is placed adjacent the underfill aperture, the stencil having a
stencil opening in registry with the underfill aperture. The
stencil opening defines, at least in part, a fill volume at least
as great as the volume of the underfill gap. The stencil opening is
filled with a flowable underfill material which is permitted to
flow through the support via the underfill aperture and
substantially fill the first underfill gap. The stencil may be
removed, leaving a completed, underfilled microelectronic device
assembly.
[0013] Another embodiment of the invention provides a method of
manufacturing a microelectronic device assembly including a support
and a plurality of microelectronic components. Each of the
microelectronic components may have a facing surface carrying a
terminal array and the support may have a mounting surface, a
component surface carrying a plurality of terminal arrays, and a
plurality of underfill apertures. For each microelectronic
component, a connecting material is deposited on the terminal array
of the microelectronic component and/or an associated one of the
terminal arrays of the support. The facing surface of each
microelectronic component is juxtaposed with the component surface
of the support such that the connecting material electrically
couples the terminal array of the microelectronic component with
the associated terminal array of the support. The facing surface of
each microelectronic component is spaced from the component surface
of the support to define a separate underfill gap between each
microelectronic component and the support. At least one of the
underfill apertures in the support is in fluid communication with
each of the underfill gaps. A stencil is placed adjacent to the
mounting surface of the support, with the stencil having a separate
stencil aperture in registry with each of the underfill apertures
in the support. Each stencil aperture defines, at least in part, a
fill volume at least as great as the volume of the underfill gap in
fluid communication with the underfill aperture with which the
stencil aperture is registered. All of the stencil apertures are
filled with a flowable underfill material, preferably in a single
pass. The underfill material is permitted to flow through the
support via the apertures and laterally outwardly therefrom to
substantially fill each of the underfill gaps. The stencil may be
removed, leaving the final microelectronic device assembly.
[0014] In accordance with still another embodiment, the invention
provides a method of underfilling a microelectronic component which
is electrically coupled to a support such that the microelectronic
component and the support define an underfill gap therebetween.
According to this method, an underfill aperture in the support is
filled with an underfill material. The underfill aperture has a
first dimension and second dimension less than the first dimension.
The underfill material is allowed to flow outwardly from the
underfill aperture to substantially fill the underfill gap. In one
particular adaptation of this embodiment, the microelectronic
component has a pair of spaced-apart lateral edges and a pair of
spaced-apart transverse edges. The underfill aperture is spaced
farther from each of the lateral edges than from either of the
transverse edges. The underfill material flows outwardly from the
underfill aperture a greater distance, and covers a greater surface
area, in a lateral direction than in a transverse direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic illustration of a prior art underfill
process.
[0016] FIG. 2 is a schematic illustration of another prior art
underfill process.
[0017] FIG. 3 is a top elevation view of a microelectronic
component in accordance with an embodiment of the invention.
[0018] FIG. 4 is a top elevation view of a support which may be
connected to the die of FIG. 3 in accordance with an embodiment of
the invention.
[0019] FIG. 5 is top elevation view of a support in accordance with
another embodiment of the invention.
[0020] FIG. 6 is a top elevation view of a support in accordance
with yet another embodiment of the invention.
[0021] FIG. 7 is a top elevation view of a support in accordance
with still another embodiment of the invention.
[0022] FIG. 8 is a top elevation view of a support in accordance
with still another embodiment of the invention.
[0023] FIG. 9 is a top elevation view of a support in accordance
with still another embodiment of the invention.
[0024] FIGS. 10-12 are side elevation views schematically
illustrating a method of assembling a microelectronic device in
accordance with an embodiment of the invention.
[0025] FIG. 13 is a top elevation view schematically illustrating
placement of stencil to fill a plurality of underfill gaps in a
single step in accordance with another alternative embodiment of
the invention.
[0026] FIG. 14 is a top elevation view of a circuit board which may
be coupled to the support of FIG. 4 in accordance with another
embodiment of the invention.
[0027] FIGS. 15-17 are side elevation views schematically
illustrating a method for assembling a microelectronic device in
accordance with an alternative embodiment of the invention.
DETAILED DESCRIPTION
[0028] Various embodiments of the present invention provide
microelectronic devices or methods of manufacturing microelectronic
devices. The following description provides specific details of
certain embodiments of the invention illustrated in the drawings to
provide a thorough understanding of those embodiments. It should be
recognized, however, that the present invention can be reflected in
additional embodiments and the invention may be practiced without
some of the details in the following description.
[0029] FIGS. 3, 4, and 10-12 schematically depict the manufacture
of a microelectronic device 10 in accordance with one embodiment of
the invention. The microelectronic device 10 generally includes a
microelectronic component 20 and a support 40. The microelectronic
component 20 may be SIMM, DRAM, flash-memory, processors or any of
a variety of other types of microelectronic devices. Typically, the
microelectronic component 20 will be a semiconductor device of the
type commonly used in flip-chip manufacture. While the
microelectronic component 20 is illustrated in the drawings as
being a single element, it should be understood that the
microelectronic component 20 can comprise any number of
subcomponents. For example, the microelectronic component 20 may
comprise one or more dies attached to a common substrate, such as
in a stacked-die assembly.
[0030] FIG. 3 is a top view of the microelectronic component 20.
The microelectronic component includes a pair of spaced-apart
lateral edges 22a and 22b and a pair of spaced-apart transverse
edges 24a and 24b. The microelectronic component 20 also includes
an exterior surface 28 (FIGS. 10-12) and a facing surface 26. The
facing surface 26 includes a terminal array 30 comprising a
plurality of terminals 32 arranged on the facing surface 26 in a
predefined pattern. The terminals 32 are electrically connected to
functional components of the microelectronic component 20.
[0031] FIG. 4 shows an embodiment of a support 40 which is adapted
for use with the microelectronic component 20 shown in FIG. 3. The
support 40 may be flexible or rigid and have any desired
configuration. The support 40 may be formed of material commonly
used to manufacture microelectronic substrates, such as ceramic,
silicone, glass, or combinations thereof. The support 40 can
alternatively be formed of an organic material or other materials
suitable for PCBs. In one embodiment of the invention, the support
40 comprises a printed circuit board such as an FR-4 PCB. In
another embodiment, the support 40 may comprise a flexible
interposer such as a conventional polyimide tape (e.g., UPILEX,
commercially available from Ube Industries, Inc. of Tokyo, Japan;
KAPTON or MICROLUX, both commercially available from E.I. du Pont
de Nemours and Co. of Delaware, USA; or ESPANEX, commercially
available from Nippon Steel Chemical Co., Ltd. of Tokyo, Japan) and
this microelectronic device 10 may be attached to a circuit board,
as mentioned below in connection with FIGS. 15-17.
[0032] The support 40 shown in FIG. 4 includes a pair of
spaced-apart lateral edges 42a and 42b and a pair of spaced-apart
transverse edges 44a and 44b which together define the
circumference of the substrate. In the illustrated embodiment, the
support 40 is a parallelogram, with the lateral edges 42a and 42b
being parallel to one another and perpendicular to both of the
transverse edges 44a and 44b.
[0033] The support 40 has a component surface 46 and a mounting
surface 48 (FIGS. 10-12). The component surface 46 includes a
plurality of terminals 52 defining a terminal array 50. The
terminals 52 on the component surface 46 are arranged in a
predefined pattern which may generally correspond to the pattern of
the terminals 32 of the terminal array 30 on the microelectronic
component 20. The terminals 52 of the terminal array 50 may be
thought of as defining a footprint of the support 40. If so
desired, the terminals 52 may be electrically connected to
functional components contained within or attached to the support
40. In the illustrated embodiment, each of the terminals 52 is
connected to a single mounting terminal 56 carried on the mounting
surface 48. These mounting terminals 56 may be arranged in a
predefined pattern to define a mounting terminal array 54 on the
mounting surface. This can be particularly useful where the support
40 is intended to be connected to a second support, as discussed
below.
[0034] The substrate 40 also includes an underfill aperture 60
which passes through the substrate from the component surface 46 to
the mounting surface 48. The underfill aperture 60 has a first
dimension 62 and second dimension 64. The second dimension 64 is
smaller than the first dimension 62, yielding an asymmetrical shape
to the underfill aperture 60. In FIG. 4, the underfill aperture 60
is typified as an elongate slot. The first dimension 62 of the
aperture 60 may coincide with a major axis of the slot. This major
axis may extend along a midline which is parallel to one or both of
the lateral edges 42a and 42b.
[0035] The larger first dimension 62 of the underfill aperture 64
can be adjusted for differently sized microelectronic components 20
and supports 40. It is anticipated that in most applications the
first dimension will range from 3 mm to 25 mm. The smaller second
dimension 64 of the underfill aperture 60 may vary depending on the
size and shape of the support 40 and terminal array 50 on the
component surface and the nature of the underfill material. In one
embodiment of the invention, the second dimension 64 ranges from
0.03 mm to 0.5 mm. To enhance flow of underfill material 74 through
the underfill aperture 60, the second dimension is desirably at
least 50% greater than the largest particle size of any filler
present in the underfill material. The aspect ratio of the
underfill aperture 60 (i.e., the first dimension divided by the
shorter second dimension) is greater than one. In one embodiment of
the invention, the aspect ratio is greater than five.
[0036] In the embodiment of FIG. 4, the underfill aperture 60 is
spaced farther from each of the lateral edges 42a and 42b than from
either of the transverse edges 44a and 44b. The aperture 60 is
shown as being generally centered on the support 40. In particular,
the transverse distance from the periphery of the aperture 60 to a
first lateral edge 42a is the same as the transverse distance from
the other side of the aperture 60 to the other lateral edge 42b.
Similarly, the lateral distance from the periphery of the aperture
to a first transverse edge 44a is the same as the lateral distance
from the periphery of the aperture 60 to the other transverse edge
44b. It should be understood, though, that the aperture 60 need not
be centered, i.e., the aperture 60 may be positioned closer to one
of the lateral edges 42a and 42b than the other and/or closer to
one of the transverse edges 44a and 44b than the other.
[0037] FIG. 4 also shows (in phantom) a projection of the location
of the microelectronic component 20 with respect to the support 40
in one adaptation of the invention. When the support is so
positioned, the underfill aperture 60 is spaced farther from at
least one of the component's lateral edges 22a and 22b than it is
from one or both of the component's transverse edges 24a and 24b.
In the illustrated embodiment, the transverse distance 66a from the
periphery of the aperture 60 to the first lateral edge 22a of the
component 20 is the same as the transverse distance 66b from the
other side of the aperture 60 to the other lateral edge 22b. The
lateral distances 65a and 65b from the periphery of the aperture 60
to the component's transverse edges 24a and 24b, respectively, are
also equal to one another. However, the transverse distances 66a
and 66b are each greater than the lateral distances 65a and
65b.
[0038] FIGS. 5-9 illustrate alternative underfill apertures in
accordance with an embodiment of the invention. The support 40a of
FIG. 5 has a generally I-shaped slot 60a. The support 40b of FIG. 6
includes a generally T-shaped slot 60b. FIG. 7 illustrates a
support 40c which has a generally star-shaped underfill aperture
60c. This star-shaped aperture may be thought of as a plurality of
elongate slots which intersect one another generally at the center
of the support 40c to define the star-shaped aperture 60c. The
support 40d of FIG. 8 has a generally U-shaped slot 60d and the
support 40e of FIG. 9 has a generally L-shaped slot 60e. Both the
U-shaped slot 60d and the L-shaped slot 60e are illustrated as
being positioned generally within the boundaries of the terminal
array 50 of the support 40. If so desired, one or more of the legs
of these slots 60d and 60e may be positioned outside the area bound
by the terminal array 50, e.g., between the terminal array 50 and
one of the lateral edges 42. It should be understood that the
embodiments of FIGS. 4-9 are merely illustrative and a wide variety
of other underfill aperture shapes could also be employed.
[0039] As noted above, the present invention includes methods for
manufacturing microelectronic devices. In the following discussion,
reference will be made to the microelectronic component 20 and the
support 40 shown in FIGS. 3 and 4. It should be understood, though,
that many of the features shown in these drawings are not required
for manufacturing a microelectronic device according to the methods
outlined below.
[0040] Initially, the terminal array 30 of the microelectronic
component 20 is electrically coupled to the terminal array 50 on
the component surface 46 of the support 40. This electrical
coupling may be carried out in any known fashion. For example,
these components may be electrically coupled using standard flip
chip manufacturing techniques such as those taught in connection
with FIG. 3 of U.S. Pat. No. 5,697,148, (Lance, Jr. et al., the
entire teachings of which are incorporated herein by
reference).
[0041] Techniques for electrically coupling microelectronic
components to supports are well known in the art and need not be
discussed in great detail here. Briefly, though, a connecting
material is deposited on at least one of the two terminal arrays 30
and 50 which are to be connected to one another. For example,
solder "bumps" may be deposited on one or more terminals 32 of the
microelectronic component's terminal array 30. The connecting
material need not be solder, though. Instead, it may be any of a
variety of other materials known in the art, such as gold, indium,
tin, lead, silver, or alloys thereof that reflow to make electrical
interconnects. The connecting material may also be formed of
conductive polymeric or epoxy materials, which may be plated with
metals.
[0042] The facing surface 26 of the microelectronic component 20
may be juxtaposed with the component surface 46 of the support 40,
with the terminal arrays 30 and 50 generally aligned with one
another. The connecting material electrically couples one or more
terminals of the terminal array 30 to a corresponding terminal or
terminals of the terminal array 50 on the component surface 46, as
illustrated in FIG. 10. The connecting material may then be
reflowed, if necessary, to electrically couple the terminals 32 and
52. The resultant electrical connector 72 may also serve to
mechanically connect the microelectronic component 20 to the
support 40.
[0043] FIG. 10 illustrates such a partially assembled
microelectronic device 10. As can be seen in this drawing, the
electrical connectors 72 serve to space the facing surface 26 of
the microelectronic component 20 from the support's component
surface 46. This defines a peripherally open underfill gap 70
therebetween. The electrical connectors 72 are encompassed within
the underfill gap 70. The underfill gap 70 is in fluid
communication with the underfill aperture 60 in the support 40.
Positioning the underfill aperture 60 within the footprint of the
component surface's terminal array 50 assures registry of the
aperture 60 with the underfill gap 70.
[0044] In conventional manufacture, the flip chip die is positioned
above the substrate during the underfill process. In accordance
with one embodiment of the present invention, though, the partially
assembled microelectronic device is oriented to position the
support 40 above the microelectronic component 20.
[0045] The underfill gap 70 is filled by delivering an underfill
material 74 (shown schematically in FIG. 10) through the underfill
aperture 60 in the support 40. The underfill material 74 may be
selected to enhance the mechanical bond between the microelectronic
component 20 and the support 40, to help distribute stress on the
microelectronic component 20 and the electrical connectors 72, and
to increase structural integrity of the microelectronic device 10.
The underfill material may also help protect the microelectronic
component 20 and/or the electrical connectors 72 from degradation
by contaminants, such as moisture.
[0046] The underfill material 74 is typically a polymeric material,
such as an epoxy or acrylic resin, and may contain various types of
inert fillers. These fillers may comprise, for example, silica
particles. The underfill material is typically selected to have a
coefficient of thermal expansion which approximates that of the
microelectronic device 20 and/or the support 40 to help minimize
the stress placed on the microelectronic device 10. As discussed in
more detail below, the viscosity of the underfill material 74 is
selected to ensure that the underfill material will flow to fill
the underfill gap 70 under the selected processing conditions. In
particular, the underfill material should flow easily to fill the
volume of the underfill gap 70 while minimizing voids, bubbles, and
non-uniform distribution of the underfill material within the
underfill gap 70.
[0047] The underfill material 74 is desirably delivered to the
underfill gap 70 utilizing at least a majority of the underfill
aperture 60. Looking at the support 40 of FIG. 4, for example, it
is desirable that the underfill material be delivered along
substantially the entire first dimension 62 of the elongated slot
60. This may be accomplished in any of a variety of ways. If a
dispensing nozzle is utilized, for example, the nozzle may be moved
along the length of the aperture 60. Alternatively, the nozzle may
have an elongated dispensing tip which extends along at least a
portion of the first dimension 62 while having a width which is
smaller than the second dimension 64.
[0048] FIG. 11 shows one embodiment in which the underfill material
74 is delivered to the underfill gap 70 utilizing a stencil 80. The
stencil 80 includes a contact surface 82, an exterior surface 84,
and a stencil aperture or opening 86. The stencil aperture 86
passes through the entire thickness of the stencil 80, extending
from the contact surface 82 to the exterior surface 84. As
suggested in FIG. 13 (discussed in more detail below), the shape of
the stencil aperture 86 may, but need not, generally correspond to
the shape of the underfill aperture 60 in the substrate 40. For
example, if the underfill aperture 60 is an elongated slot, the
stencil aperture 86 may also be an elongated slot. If the underfill
aperture 60a is generally I-shaped, the stencil aperture 86a may be
I-shaped, too. If the underfill aperture 60b is generally T-shaped,
the stencil aperture 86b may also be T-shaped. If the underfill
aperture 60c is generally star-shaped, the stencil opening may also
be generally star-shaped. As suggested in FIG. 13, though, the
stencil aperture 86c may take a different shape, such as an
ellipse. If the underfill aperture 60d is generally U-shaped, the
stencil aperture may be U-shaped, and if the underfill aperture 60e
is generally L-shaped, the stencil aperture may be L-shaped.
[0049] In one embodiment, the stencil aperture 86 is at least as
large as the underfill aperture 60 and may be larger than the
underfill aperture 60. In particular, the stencil aperture 86 may
have a periphery which extends outwardly beyond the periphery of
the underfill aperture 60 when these two apertures are in registry
with one another. For example, the width 88 of the stencil aperture
86 may be greater than the width or second dimension 64 of the
underfill aperture 60. The length of the stencil aperture 86 may
also be longer than the length or first dimension 62 of the
underfill aperture 60.
[0050] In an alternative embodiment (not specifically illustrated),
the stencil aperture 86 is no larger than, and may be smaller than,
the underfill aperture 60. For example, the width 88 of the stencil
aperture 86 may be smaller than the width or second dimension 64 of
the underfill aperture 60 and the stencil aperture 86 may also be
shorter than the first dimension 62 of the underfill aperture 60.
In such an embodiment, the entire mounting surface 40 of the
support adjacent the underfill aperture 60 may be covered by the
stencil, reducing the volume of residue which may be left on the
surface of the support 40 when the underfill process is
complete.
[0051] The stencil 80 may be made of any desired material. As
explained below, the stencil opening 86 can be used to control the
volume of underfill material being provided to the underfill
aperture 60. As a consequence, a stencil 80 in accordance with one
embodiment of the invention may be flexible, but is not readily
compressed or stressed under the conditions of use outlined below.
Suitable stencil materials may include metals, photoimageable
polyamides, dry film photo masks, liquid photoimageable photomasks,
silicon, and ceramics. If so desired, the stencil 80 may be formed
of a material which is not wettable by the underfill material
74.
[0052] In use, the stencil 80 is positioned above the support 40.
In the illustrated embodiment, the contact surface 82 of the
stencil 80 is in direct physical contact with the mounting surface
48 of the support 40. This can be achieved by providing a separate
stencil 80 and positioning it directly on top of the support 40.
The stencil should be positioned to ensure that the stencil
aperture 86 is in registry with the underfill aperture 60. If so
desired, the mounting surface 48 of the support 40 and the contact
surface 82 of the stencil 80 may be provided with holes or Vernier
patterns (not shown) to serve as alignment guides for aligning the
stencil aperture 86 with the underfill aperture 60.
[0053] While the drawings illustrate a physically separate stencil
80, which may be reusable, it is also contemplated that the stencil
80 may be formed directly on the mounting surface 48 of the support
40, such as by using a coating of a liquid photoimageable
photomask. The stencil 80 may be held in place with respect to the
support 40 by tensioning the stencil 80 using a frame (not shown)
that holds the edges of the stencil against the support 40.
[0054] Once the stencil 80 is properly positioned with respect to
the support 40, the underfill materials 74 may be delivered to the
underfill aperture 60 via the stencil aperture 86. This may be
accomplished, for example, by "squeegeeing." In accordance with
this embodiment, a quantity of the underfill material 74 is applied
to the exterior surface 84 of the stencil 80. A squeegee blade 90
may then be dragged across the exterior surface 84, passing over
the stencil aperture 86. This will deliver a predictable volume of
the underfill material 74 to the stencil aperture 86.
[0055] The volume of underfill material 74 delivered through the
stencil aperture will depend, in part, on the thickness of the
stencil 80 and the surface area of the stencil aperture 86. The
stencil aperture 86, however, is in registry with the underfill
aperture 60. As a consequence, at least a portion of the underfill
material 74 may pass into the underfill aperture 60 during the
process of squeegeeing. The amount of underfill materials 74 which
passes into the underfill aperture 60 as the blade 90 passes over
the stencil aperture 86 will depend, in part, on the viscosity of
the underfill material 74. For this reason, the stencil aperture 86
may only partly define the fill volume of underfill material being
delivered in the squeegeeing process. The fill volume so defined
should be at least as great as the volume of the underfill gap 70
to ensure that the underfill gap 70 is substantially filled with
underfill material 74.
[0056] The underfill material 74 is permitted to flow through the
stencil aperture 86 and the underfill aperture 60 into the
underfill gap 70. The fill characteristics of the underfill
material 74 may be selected to permit the fill material to
substantially fill the underfill gap 70, readily flowing around the
electrical connectors 72 to encapsulate and protect the connectors
72, as shown in FIG. 12. If so desired, the viscosity of the
underfill material may be selected so it may fill the underfill gap
without aid of hydraulic pressure, relying instead on gravity
and/or capillary action, for example. In one embodiment, the
viscosity of the underfill material at the temperature under which
the squeegeeing takes place limits the flow of underfill material
into the underfill gap 70. This facilitates delivery of a more
precise volume of underfill material 74 into the central aperture
86 as the squeegee blade 90 passes over that opening. The viscosity
of the underfill material may then be reduced, e.g., by heating,
permitting the underfill material to flow through the underfill
aperture 60 and substantially fill the underfill gap without
requiring hydraulic pressure.
[0057] In another embodiment of the invention, the viscosity of the
underfill material is relatively low even at room temperature. In
particular, the underfill material can flow through the underfill
aperture 60 and substantially fill the underfill gap 70 at room
temperature without the aid of hydraulic pressure. While the
control of the volume of underfill material 74 delivered to the
aperture 86 may be a little less precise, a predictable volume can
be delivered by consistently controlling the speed and contact
pressure of the squeegee blade 90 during the squeegeeing
process.
[0058] As noted above in connection with FIG. 4, in one embodiment
of the invention, the underfill aperture 60 is spaced farther from
at least one of the microelectronic component's lateral edges 22a
and 22b than from at least one of the microelectronic component's
transverse edges 24a and 24b. In the embodiment of FIG. 4, the
transverse distances 66a and 66b from the underfill aperture 60 to
lateral edges 22a and 22b, respectively, are both greater than
either of the lateral distances 65a and 65b between the underfill
aperture 60 and the transverse edges 24a and 24b, respectively. As
a consequence, as the underfill material flows outwardly away from
the underfill aperture 60 to fill the underfill gap 70, it will
travel a greater distance laterally than it will travel
transversely to reach the outer edge of the microelectronic
component 20. The surface area of the microelectronic component 20
being covered by the underfill material will also be proportional
to the distance traveled, dictating that the underfill material
will cover a greater surface area laterally than it does
transversely as it flows outwardly away from the underfill aperture
60. The position of the underfill aperture 60 with respect to the
support 40 can appreciably reduce processing time and cost in
manufacturing microelectronic devices 10 in accordance with the
invention. Applying the bead of underfill material U along a single
edge of the die D, as illustrated in FIG. 1 and discussed above,
requires that the underfill material U flow across the entire width
of the die D. Applying the underfill material U along to adjacent
edges of the die D, as shown in FIG. 2, can reduce the average
distance which the underfill material U must travel to completely
fill the underfill gap. However, as the two fronts of the underfill
material converge, they may trap air, creating voids in the
underfill material. Additionally, at least some of the underfill
material must travel the entire width of the die D to reach the
farthest corner of the die.
[0059] Delivering the underfill material through the underfill
aperture 60 reduces the distance which the underfill material has
to travel to fill the underfill gap 70. For a given underfill
material, this will decrease the processing time necessary to fill
the underfill gap 70. Notably, surface tension will also tend to
keep the underfill material 74 from flowing beyond the outer edge
of the support 40. As a consequence, delivering the underfill
material 74 to the underfill gap 70 via the underfill aperture 60
allows multiple microelectronic components 20 to be added to a
single support without risk that capillary action will draw
underfill material U intended for one die D under an adjacent
component on the associated substrate S, which is a risk in the
process shown in FIGS. 1 and 2.
[0060] Others have proposed delivering underfill material to a
small, centrally located orifice through a substrate. For example,
U.S. Pat. No. 5,697,148 proposes pumping an underfill material
through a small hole drilled through a substrate. As can be seen in
FIG. 5 of this patent, this still requires that the underfill
material flow a substantial distance to completely fill the
underfill gap. Using an elongate underfill aperture 60 in
accordance with an embodiment of the present invention, however,
can materially reduce the distance which the underflow material
must travel to fill the underfill gap 70. In addition, the
relatively restrictive opening through the substrate suggested in
this and other patents limits the rate at which the underfill
material can be delivered to the underfill gap. Hence, either it
will take significantly longer to deliver the underfill material to
the underfill gap or the underfill material must be delivered at an
appreciably higher pressure, which can create its own difficulties.
Such a restricted opening in the substrate can also make it
difficult to deliver enough underfill material to fill the
underfill gap using a stencil process such as that outlined
above.
[0061] In comparison, the underfill aperture 60 in accordance with
one embodiment of the present invention provides a materially
greater surface area through which the underfill material can be
delivered without unduly sacrificing useful substrate real estate
which can be used to position functional elements or interconnects
in the substrate beneath the microelectronic component 20. The
underfill aperture 60 provides a wider passage way through which
underfill material can pass, reducing the pressure needed to get
the underfill material into the underfill gap in a reasonable
period of time. This also facilitates delivery of the underfill
material using the stencil 80 as discussed above.
[0062] Once the underfill material 74 has been delivered to the
underfill aperture 60, the stencil 80 may be removed. In one
embodiment, the stencil remains in place until the underfill
material has flowed to fill the underfill gap. Thereafter, the
stencil 80 may be removed, such as by lifting it off the mounting
surface 48 of the support 40. Alternatively, the stencil may be
removed by chemical etching or use of a solvent which would remove
the stencil 80 from the support 40. Particularly, if a higher
viscosity underfill material 74 is used and subsequently heated to
fill the underfill gap 70, the stencil can be removed before the
underfill material fills the underfill gap 70.
[0063] FIGS. 4-12 illustrate embodiments of the invention which
utilize a single underfill aperture to fill a single underfill gap
beneath a single microelectronic device. Using a stencil in
accordance with an embodiment to the present invention, however,
can allow the underfilling of multiple underfill gaps in a single
step.
[0064] In one such embodiment of the invention, a single substrate
40 is provided with multiple microelectronic components 20, as
shown in FIG. 13. The process of attaching each microelectronic
component 20 the substrate may be generally as outlined above. In
particular, the support 40 may be provided with multiple terminal
arrays, with each terminal array being associated with one of the
microelectronic components 20 to be added to the support 40. Then,
for each microelectronic component 20, a connecting material can be
deposited on one or both of the microelectronic component's
terminal array and the associated terminal array of the support.
The facing surface of each microelectronic component may then be
juxtaposed with the component surface of the support such that the
connecting material electrically couples the terminal array of the
components with the associated terminal arrays of the support.
[0065] As schematically shown in FIG. 13, the stencil may be
applied to the mounting surface 48 of the support with a separate
stencil aperture 86, 86a, 86b or 86c in registry with one of the
underfill apertures 60, 60a, 60b or 60c in the support 40. A
single, relatively large quantity of underfill material 74 may be
applied to the exterior surface 84 of the stencil 80. A squeegee
blade (not shown in FIG. 13) may then be moved across the exterior
surface 84 of the stencil 80, thereby filling all of the stencil
apertures with underfill material in a single pass.
[0066] This can materially reduce processing time to manufacture
such multi-component microelectronic devices as compared to prior
art methods. For example, in the process suggested in U.S. Pat. No.
5,697,148, the needle would have to be moved from one aperture to
the next, requiring relatively complex visualization equipment to
ensure proper alignment of the needle. A fixed period of time is
necessary to hydraulically deliver an appropriate quantity of
underfill material to each underfill gap. If one were to attempt to
adapt this technique to a mass manufacturing process, one may
utilize multiple needles. However, this would require a dedicated
needle array for each microelectronic device configuration. As the
configuration of the microelectronic component change from one
microelectronic device to another, the entire array of needles
would have to be replaced or adjusted.
[0067] FIG. 13 illustrates a single microelectronic device 10
having a wide variety of differently sized microelectronic
components 20 and a wide variety of shapes and sizes of underfill
apertures 60, 60a, 60b, and 60c. This is done primarily to
illustrate how various stencil aperture configurations can be
positioned in relation to different underfill apertures. It should
be understood that in many circumstances all of the underfill
apertures and stencil apertures will be of substantially the same
size and orientation.
[0068] This method allows a single substrate 40 with multiple
microelectronic components 20 and multiple underfill gaps to be
filled in a single pass. In a further embodiment of this method,
the support 40 is subsequently divided into a plurality of separate
supports, each of which carries at least one of the microelectronic
components. The support may be divided either before or after
removing the stencil 80. This facilitates the mass manufacture of
smaller microelectronic devices by filling in the underfill gaps of
multiple microelectronic devices in one simple step.
[0069] In another alternative embodiment of the invention, a
plurality of partially assembled microelectronic devices are
positioned adjacent to one another. The partially assembled
microelectronic devices may comprise one or more microelectronic
components 20 attached to a single substrate 40, such as
illustrated in FIG. 10. These microelectronic device assemblies
need not be positioned immediately adjacent to or abutting one
another; they need only be positioned close enough to enable them
to be covered using a single stencil. To facilitate proper
alignment of the stencil with the plurality of supports 40, the
supports 40 are desirably aligned such that their mounting surfaces
40 are generally co-planar.
[0070] The stencil 80 may have a plurality of stencil apertures 86
and the stencil would be positioned such that at least one of the
stencil apertures 86 is in registry with at least one underfill
aperture 60 of each of the supports 40. All of the stencil
apertures 86 may be filled with flowable underfill material in a
single pass, as discussed above in connection with FIG. 13. The
underfill material may be permitted to flow through each of the
supports via their respective underfill apertures to fill each of
the underfill gaps. Removing the stencil 80 will yield a plurality
of co-formed microelectronic device assemblies 10.
[0071] FIG. 14 schematically illustrates a stylized circuit board
110 which may be used in connection with a further embodiment of
the invention. This circuit board 110 has a pair of spaced-apart
lateral edges 112a and 112b and a pair of spaced-apart transverse
edges 114a and 114b. The circuit board 110 includes a terminal
surface 116 and an outer surface 118 (FIG. 15). The terminal
surface 116 bears a plurality of terminals 122 which define a
terminal array 120. This terminal array 120 is configured to be
electrically coupled to the terminal array 54 on the mounting
surface 48 of the support 40 (shown in FIG. 4). The circuit board
110 is shown as including a plurality of additional components 125
and an interface 126 which can be used to connect the circuit board
to another device. If so desired, the circuit board 110 may be a
rigid PCB, though any of the materials noted above in connection
with the support 40 could be used instead.
[0072] The circuit board 110 also includes a second underfill
aperture 130 which extends through the thickness of the circuit
board 110 from its terminal surface 116 to its outer surface 118.
The second underfill aperture has a first dimension 132 and a
second dimension 134 which is less than the first dimension 132. As
with the underfill aperture 60 of FIG. 4, the second underfill
aperture 130 in FIG. 14 is typified as an elongated slot. It should
be understood, though, that this second underfill aperture 130 may
take on a variety of different shapes, e.g., shapes analogous to
the underfill apertures shown in FIGS. 5-9.
[0073] FIGS. 15-17 schematically illustrate a method of one
embodiment to the invention for assembling a microelectronic device
10 such as that discussed above with a circuit board 110 or other
second support. This yields a larger microelectronic device 100 in
which the microelectronic device 10 discussed above may be
considered a subassembly. The process illustrated in FIGS. 15-17 is
directly analogous to the process outlined above in connection with
FIGS. 10-12. In particular, the terminal array 120 of the circuit
board 110 will be electrically coupled to the terminal array 54 on
the support's mounting surface 48 via electrical connectors 142.
This will define a second underfill gap 140 between the circuit
board 110 and the support 140. In FIGS. 15-17, the second underfill
aperture 130 is shown as being about the same size and positioned
vertically directly above the first underfill aperture 60. It
should be understood, however, that this is not necessary and the
two underfill apertures 60, 130 can be different sizes and
positioned in different locations or orientations with respect to
one another.
[0074] The second underfill gap 140 may be filled with a second
underfill material 144 in any desired fashion. For example, it may
be filled using a stencil 80 and squeegee blade 90 generally
outlined above in connection with FIGS. 10-12. Desirably, the
second underfill material not only fills the gap between the second
support's terminal surface 116 and the other support's mounting
surface 148, but also fills any remaining void in the underfill
aperture 60 in the support 40. This can be facilitated by
positioning the second underfill aperture 130 directly above the
first underfill aperture 60.
[0075] The second underfill material 144 may be different from the
underfill material 74. This may be advantageous if different design
objectives are required of the second underfill material 144. In
one embodiment of the invention, however, both of the underfill
materials 74 and 144 have the same composition.
[0076] The process outlined in FIGS. 15-17 start with a
microelectronic device 10 wherein the underfill gap 70 is already
filled with underfill material 74 before the microelectronic device
10 is attached to the second support 110. Thereafter, the second
underfill gap 140 is filled with the second underfill material 144
is a separate step. In an alternative embodiment, the first
underfill gap 70 and the second underfill gap 140 are filled with a
common underfill material in a single step. In accordance with this
embodiment, the underfill aperture 60 in the first support 40 is in
fluid communication with the second underfill gap 140. As shown in
FIGS. 15-17, the second underfill aperture 130 may be positioned
directly above the first underfill aperture 60. The first and
second underfill gaps 70 and 140 may then be filled with a common
underfill material 74 in a single step, e.g., using a stencil 80
and squeegee blade 90 analogous to that discussed above in the
context of FIGS. 10-12.
[0077] From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the spirit and scope of the invention.
Accordingly, the invention is not limited except as by the appended
claims.
* * * * *