U.S. patent application number 09/894706 was filed with the patent office on 2001-11-08 for micro-flex technology in semiconductor packages.
Invention is credited to Bertin, Claude Louis, Ference, Thomas George, Fifield, John Atkinson, Howell, Wayne John.
Application Number | 20010039074 09/894706 |
Document ID | / |
Family ID | 22305515 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010039074 |
Kind Code |
A1 |
Bertin, Claude Louis ; et
al. |
November 8, 2001 |
Micro-flex technology in semiconductor packages
Abstract
Thin-film microflex twisted-wire pair and other connectors are
disclosed. Semiconductor packages include microflex technology that
electrically connects at least one chip to another level of
packaging. Microflex connectors, such as thin-film twisted-wire
pair connectors according to the present invention provide superior
electrical performance, which includes reduced line inductance,
incorporation of integrated passive components, and attachment of
discrete passive and active components to the microflex. All of
these features enable operation of the chip at increased
frequencies.
Inventors: |
Bertin, Claude Louis; (South
Burlington, VT) ; Ference, Thomas George; (Essex
Junction, VT) ; Howell, Wayne John; (Williston,
VT) ; Fifield, John Atkinson; (Underhill,
VT) |
Correspondence
Address: |
ARLEN L. OLSEN
SCHMEISER, OLSEN & WATTS
3 LEAR JET LANE
SUITE 201
LATHAM
NY
12110
US
|
Family ID: |
22305515 |
Appl. No.: |
09/894706 |
Filed: |
June 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09894706 |
Jun 28, 2001 |
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09105382 |
Jun 26, 1998 |
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Current U.S.
Class: |
438/107 ;
257/E23.034; 257/E23.036; 257/E23.069; 257/E25.013 |
Current CPC
Class: |
H01L 23/49531 20130101;
H01L 2924/00013 20130101; H01L 25/0657 20130101; H01L 2924/10253
20130101; H01L 2924/14 20130101; H01L 2924/14 20130101; H01L
2224/451 20130101; H01L 2224/4824 20130101; H01L 2225/06551
20130101; H05K 1/0228 20130101; H01L 2224/29099 20130101; H01L
2924/00 20130101; H01L 2924/3011 20130101; H01L 2924/00 20130101;
H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L 2924/00014
20130101; H01L 2924/00012 20130101; H01L 2924/00 20130101; H01L
2225/06517 20130101; H01L 2924/19041 20130101; H01L 24/48 20130101;
H01L 2924/00013 20130101; H01L 23/49816 20130101; H01L 2924/07811
20130101; H01L 2225/06579 20130101; H01L 2924/07811 20130101; H01L
2224/48091 20130101; H01L 2924/30107 20130101; H01L 2924/181
20130101; H01L 2224/16 20130101; H01L 2224/451 20130101; H01L
2224/451 20130101; H01L 2224/73204 20130101; H01L 2924/19107
20130101; H01L 2924/10253 20130101; H01L 24/45 20130101; H01L
2924/181 20130101; H01L 2224/48091 20130101; H01L 2225/06527
20130101; H01L 23/49524 20130101; H01L 2924/01079 20130101 |
Class at
Publication: |
438/107 |
International
Class: |
H01L 021/48 |
Claims
What is claimed is:
1. An apparatus comprising: a thin-film microflex connector for
electrically connecting at least one chip to an other device.
2. The apparatus of claim 1, wherein said thin-film microflex
connector is a twisted-wire pair connector.
3. The apparatus of claim 2, wherein said twisted-wire pair
connector comprises: a first thin-film metal wire having a first
middle portion and a first end portion defined on a first thin-film
layer; a thin-film interconnection layer; and a second thin-film
metal wire having a second middle portion and a second end portion
defined on a second thin-film metal layer, wherein said first
middle portion of said first thin-film metal wire crosses over said
second middle portion of said second thin-film metal wire and said
first end portion is connected to said second end portion through
said thin-film interconnection layer.
4. The apparatus of claim 1, wherein said thin-film microflex
connector comprises a capacitor in parallel to a power source.
5. The apparatus of claim 1, wherein said thin-film microflex
connector comprises an integrated resistor.
6. The apparatus of claim 1, wherein said thin-film microflex
connector connects to discrete devices through a second connection
on a middle portion of said microflex connector.
7. The apparatus of claim 1, further comprising: a leadframe,
wherein said thin-film microflex connector is electrically
connected to an outer lead of said leadframe and to said at least
one chip.
8. The apparatus of claim 7, wherein said thin-film microflex
connector is electrically connected to a metal substrate.
9. The apparatus of claim 7, wherein a metal substrate is etched
away from said thin-film microflex connector.
10. The apparatus of claim 7, wherein said at least one chip
comprises: C4 connections for electrically connecting said at least
one chip to said thin-film microflex connector and said
leadframe.
11. The apparatus of claim 7, wherein said at least one chip
comprises: a first chip electrically and mechanically connected to
thin-film microflex connector; and a second chip electrically
connected to said first chip.
12. The apparatus of claim 1, wherein said at least one chip
comprises: a first chip electrically and mechanically connected to
thin-film microflex connector; and a second chip electrically
connected to said first chip.
13. The apparatus of claim 1, wherein said at least one chip
comprises: a first chip electrically and mechanically connected to
thin-film microflex connector; and a second chip electrically
connected to said first chip and electrically and mechanically
connected to said thin-film microflex connector.
14. The apparatus of claim 12, wherein said thin-film microflex
connector is mechanically connected to a top and a bottom portion
of said first chip.
15. The apparatus of claim 1, wherein said thin-film microflex
connector further comprises a microflex top portion and a microflex
bottom portion, wherein said microflex top portion is mechanically
connected to a chip top portion of said at least one chip and said
microflex bottom portion is mechanically connected to a chip bottom
portion of said at least one chip.
16. The apparatus of claim 15, wherein said thin-film microflex
connector further comprises: electrical connections at said bottom
portion of said thin-film microflex connector for electrically
connected said chip top portion to said other device.
17. A twisted-wire pair connector comprising: a first thin-film
metal wire having a first middle portion and a first end portion
defined on a first thin-film layer; a thin-film interconnection
layer; and a second thin-film metal wire having a second middle
portion and a second end portion defined on a second thin-film
metal layer, wherein said first middle portion of said first
thin-film metal wire crosses over said second middle portion of
said second thin-film metal wire and said first end portion is
connected to said second end portion through said thin-film
interconnection layer.
18. A method for fabricating a microflex/leadframe chip package
comprising the steps of: a) providing at least one chip; b)
fabricating a thin-film microflex connector; and c) connecting said
at least one chip to a second device with said microflex
connector.
19. The method of claim 18, wherein step b) further comprises the
steps of: b1) depositing a first thin-film dielectric layer on a
first material; b2) defining vias in said first thin-film
dielectric layer; b3) depositing a first thin-film metal layer in
said vias and over said first thin-film dielectric layer; b4)
defining a first set of metal lines of said microflex connector in
said first thin-film metal layer; b5) laying down a second
thin-film dielectric layer; b6) defining a second set of vias in
said second thin-film dielectric layer; b7) depositing a second
thin-film metal layer in said second set of vias and over said
second thin-film dielectric layer; b8) defining a second set of
metal lines of said microflex connector in said second thin-film
metal layer; and b9) defining said first material around said first
thin-film metal layer.
20. The method of claim 19, wherein step b9) comprises the step of:
etching said substrate.
21. The method of claim 19, wherein step b9) comprises the step of:
stamping said substrate.
22. The method of claim 19, wherein said first material comprises a
substrate which is separated from said first thin-film metal
layer.
23. A chip package comprising: at least one chip; a thin-film
microflex connector connected to said at least one chip for
electrically connecting said at least one chip to an outside
device; and. an encapsulation connected to said at least one chip
and said microflex connector for protecting said at least one chip
and said microflex connector;
24. The chip package of claim 23, wherein said thin-film microflex
connector is a twisted-wire pair connector.
25. The chip package of claim 23, further comprising: a leadframe,
wherein said microflex connector is electrically connected to an
outer lead of said leadframe and to said at least one chip.
26. The chip package of claim 23, wherein said at least one chip
comprises: a first chip electrically and mechanically connected to
thin-film microflex connector; and a second chip electrically
connected to said first chip.
27. The chip package of claim 23, wherein said at least one chip
comprises: a stack of chips electrically connected to said
thin-film microflex connector on at least two faces of said stack.
Description
RELATED APPLICATIONS
[0001] This application is related to two co-pending applications:
Dkt. No. BU9-97-063, U.S. Ser. No. ______ entitled "Highly
Integrated Chip-on-Chip Packaging", by Bertin et al; and Dkt. No.
BU9-98-011, U.S. Ser. No. ______ entitled "Chip-on-Chip
Interconnections of Varied Characteristics", by Ference et al. The
related applications are assigned to the assignee of record, are
filed concurrently herewith, and are herein incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The invention relates generally to semiconductor devices,
and more specifically, to packaging in semiconductor devices.
[0004] 2. Background Art
[0005] In a conventional semiconductor integrated-circuit package,
electrical connections to the bonding pads of a chip may be
provided through a thin metal leadframe, which is typically stamped
or chemically etched from strips of copper-containing materials.
The leadframe includes a number of thin, closely-spaced conductive
inner leads that radially extend away from the edges of the chip.
The inner leads diverge away from the chip and extend through the
exterior walls of the molded package where they form the external
I/O leads for the package.
[0006] Some examples of conventional semiconductor
integrated-circuit packages are found in the following U.S.
Patents: U.S. Pat. No. 3,978,516, "Lead Frame Assembly for a
Packaged Semiconductor Microcircuit" issued Aug. 1976 to Noe; U.S.
Pat. No. Re. 35,353, "Process for Manufacturing a Multi-Level Lead
Frame" issued Oct. 1996 to Tokita et al. ; and U.S. Pat. No.
5,365,409, "Integrated Circuit Package Design Having an
Intermediate Die-Attach Substrate Bonded to a Leadframe" issued
Nov. 1994 to Kwon et al. In the aforementioned patents, thin-film
and thick-film material is used to form unique inner leads to
increase speed and/or flexibility of conventional semiconductor
packages.
[0007] One problem, though, with conventional semiconductor
packages is that the current lead lengths are too inductive for the
increased speed of operations of DRAMs. As chip sizes are reduced,
the length of the lead frame segment to package edge increases,
further increasing inductance. This excessive lead inductance
results in degraded electrical performance of the package.
Furthermore, the chip I/O pitch is limited because of the leadframe
fabrication capabilities and package stresses are created when
large chips are mechanically coupled to the leadframe inside a
plastic encapsulated package.
SUMMARY OF THE INVENTION
[0008] It is thus an advantage of the present invention to provide
thin-film connectors, such as thin-film twisted-wire pairs that
eliminate the above-described and other limitations.
[0009] The advantages of the invention are realized by thin-film
microflex connectors, such as thin-film microflex twisted-wire pair
connectors, that electrically connect at least one chip to another
level of packaging. Thus, microflex connectors according to the
present invention provide superior electrical performance, which
includes reduced line inductance, incorporation of integrated
passive components, and attachment of discrete passive and active
components to the microflex. All of these features enable operation
of a chip at increased frequencies.
[0010] The foregoing and other advantages and features of the
invention will be apparent from the following more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The preferred exemplary embodiments of the present invention
will hereinafter be described in conjunction with the appended
drawings, where like designations denote like elements, and:
[0012] FIG. 1 is a plan view showing a thin-film wiring configured
into a twisted-wire pair in accordance with a preferred embodiment
of the present invention;
[0013] FIG. 2 is an exploded view of FIG. 1 including the thin-film
layers;
[0014] FIG. 3 is a top perspective view of one of the thin-film
wiring of FIG. 1;
[0015] FIGS. 4, 5 and 6 are cross-sectional views showing exemplary
embodiments of the twisted-wire pair of FIG. 1;
[0016] FIG. 7 is a flowchart illustrating a fabrication sequence of
the twisted-wire pair of FIG. 6;
[0017] FIG. 8 is an exemplary package utilizing the thin-film
microflex in accordance with a second embodiment of the present
invention;
[0018] FIGS. 9, 10, 11, 12, and 13 are cross-sectional views
showing exemplary embodiments of the thin-film microflex structures
of FIG. 8;
[0019] FIG. 14 is an exemplary package utilizing the twisted-wire
pair of FIG. 6;
[0020] FIGS. 15 and 16 are exemplary packages utilizing the
twisted-wire pair of FIG. 5;
[0021] FIG. 17 is a plan view of a semiconductor leadframe package
using the twisted-wire pair of FIG. 1 in accordance with an
embodiment of the present invention;
[0022] FIG. 18 is a cross-sectional view of a semiconductor package
including two chips utilizing the twisted-wire pair of FIG. 6;
[0023] FIGS. 19 and 20 are cross-sectional views of exemplary
semiconductor packages using the twisted-wire pair of FIG. 5 for
connections to other devices;
[0024] FIG. 21 is a plan view of FIG. 19;
[0025] FIG. 22 is a plan view of two chips connected with the
twisted-wire pair of FIG.
[0026] FIGS. 23, 24 and 25 are cross-sectional views of chip-scale
packaging utilizing the twisted-wire pair of FIG. 5;
[0027] FIG. 26 is a plan view of a vertical leadframe package using
the twisted-wire pair of FIG. 1 in accordance with an embodiment of
the present invention; and
[0028] FIGS. 27 and 28 are cross-sectional views of stacked chip
packaging utilizing the twisted-wire pair of FIG. 5.
DETAILED DESCRIPTION OF THE DRAWINGS
[0029] Referring to FIG. 1, a microflex thin-film twisted-wire pair
10 in accordance with a preferred embodiment of the present
invention is shown. The twisted-wire pair 10 comprises termination
pad 15, thin-film wire having a middle portion and end portions
made from a top layer of thin-film 14, a thin-film wire having a
middle portion and end portions made from a bottom layer of
thin-film 12 and vias, or studs 18, in an interconnection layer of
thin-film connecting the end portions of the top layer thin-film
wire 14 to the end portions of the bottom layer thin-film wire 12,
wherein the middle portions of the top and bottom layer cross each
other. FIG. 2 illustrates each of the layers--top 14,
interconnection 18 and bottom 12, with the respective thin-film
wiring. FIG. 3 then shows one completed wire fabricated from the
top layer 14, interconnection layer 18 and bottom layer 12 of
thin-film, extending from termination pad to termination pad.
Although the twisted-wire pair is the preferred embodiment of this
invention, it is to be understood that other wiring and/or elements
may also be made from the microflex thin-film, such as a single
wire, capacitors, resistors, etc., which will be discussed in
reference to FIGS. 9-13 below. The microflex connectors greatly
enhance electrical performance and compactability in semiconductor
packaging. As will be seen in subsequent examples, replacing long
inner leads with a microflex twisted-pair wire in semiconductor
leadframe packaging reduces the inner-lead inductance, thus
enhancing the electrical performance, and reduces package stresses
since the chip connects mechanically to a more compliant material.
This enables new product applications for larger, higher I/O and
more electrically-enhanced chips.
[0030] FIGS. 4-7 illustrate exemplary procedures in fabricating a
microflex twisted-wire pair for semiconductor packaging, wherein
FIG. 7 is a flowchart depicting the process of fabricating FIG.
6.
[0031] In FIG. 4, metal lines 22 and 26 are plated onto a kapton
carrier 28 and an interlayer connection is made using plated
thru-holes 24. The resulting flexible, thin-film wire 20A is
similar to the microflex thin-film wire 10 of FIG. 3, except that
thin-film wire 20A is generally larger than the microflex thin-film
wire 10 and will thus differ from microflex thin-film wire 10 in
electrical characteristics and wiring ground rules.
[0032] FIG. 5 illustrates a cross-section of a microflex
twisted-wire pair 20B just prior to release from silicon wafer
carrier 30. The twisted-wire pair 20B comprises dielectric layers
32, passivation layers 38, barrier layer 36, release layer 34, and
silicon wafer carrier 30. The resulting twisted-wire pair is a
free-standing microflex wire.
[0033] FIG. 6 illustrates an example of fabricating a microflex
twisted-wire pair 20C, or other microflex connectors (hereinafter
referred to as microflex), wherein the microflex may be in contact,
both mechanically and electrically, to a dielectric or other
substrate (e.g., an outer lead in a leadframe) via substrate
connection 42 and may also comprise a free-standing microflex 50.
The free-standing microflex 50 is formed by etching away 44
substrate 40. The free-standing microflex 50 may then be
mechanically coupled to the top surface of the chip through
adhesives, lamination etc. and electrically coupled to the chip
through connections such as wirebonding, solder ball (C4)
connections, conductive epoxy, Au bumps, anisotropic conductive
adhesive, transient liquid phase bonding, polymer-metal composite
paste, thermal compression bonding etc. A microflex/leadframe
structure, as discussed in reference to FIGS. 8-12 below may also
be fabricated by mechanically and electrically coupling the
microflex to the leadframe/microflex substrate. This coupling
allows the utilization of standard plastic encapsulated packing
tooling and processing.
[0034] FIG. 7 is a flowchart 100 illustrating a process by which a
microflex/leadframe structure, such as one in FIG. 6, may be
fabricated. The first step (step 102) includes coating a substrate
(metal) sheet with a first thin-film dielectric layer, such as a
photodefineable epoxy or polyimide. Then, the first thin-film
dielectric layer is exposed and developed (step 104) to form vias
for connection between the substrate and the microflex wiring
(including twisted-wire pair wiring) and cleared areas and
openings. If necessary, a cure is applied (step 106), and then a
first thin-film metal is deposited (step 108). The thin-film metal
is coated with photoresist (step 108) and the metal is exposed and
developed (step 110) to create metal lines. A second thin-film
dielectric layer, such as a passivation layer is then applied (step
112), vias are developed (step 114) and a cure is applied (step
116). A second thin-film metal layer is then deposited (step 118),
and is coated with photoresist (step 120). Metal lines are then
defined (step 122). If the substrate is to be punched/stamped (step
124 =yes), then the leadframe structure is defined by punching the
metal substrate (step 134). If the substrate is not to be
punched/stamped (step 124 =no) the microflex side of the
microflex/leadframe structure is protected (step 126) and
photoresist is deposited on the bottom side of the structure (step
128). The substrate (metal) features are then defined and etched
(step 130) and the microflex protection layer is removed (step
132). The steps enclosed by box 113 may be repeated depending upon
the layers of microflex desired.
[0035] An alternative to the fabrication process outlined above is
to fabricate the microflex separate from the metal substrate (such
as in FIG. 5). The free-standing microflex can then be mechanically
and electrically coupled either to a patterned or unpatterned
leadframe, or used in other applications, such as chip-scale
packaging, and stacked-chip packaging as discussed below.
[0036] FIG. 8 illustrates a semiconductor package 21 A wherein chip
60 is electrically connected to the outer lead 56 through microflex
45. Microflex 45 is fabricated with an opening which enables a
wirebond connection 53 to connect to the I/O pads of chip 60. Chip
60, lead frame 56, microflex 45, and wirebond 53 assembly is
encapsulated in plastic 54, forming semiconductor package 21A.
Adhesive film 62 is placed between chip 60 and microflex 45.
[0037] FIGS. 9-13 illustrate exemplary microflex 45 that may be
utilized in FIG. 8. As seen in FIG. 9, a microflex twisted-wire
pair 55 is used to electrically connect chip 60 to outer lead 56.
An electrical connection 52 connects microflex 55 to outer lead 56.
As aforementioned, microflex twisted-wire pair 55 replaces the long
inner leads in semiconductor leadframe packaging and thus reduces
the inner-lead inductance.
[0038] FIG. 10 illustrates a microflex connector 45 having an
integrated resistor 41. Integrated resistor 41 is formed through
the incorporation of a high resistance link 41 in the thin-film.
This resistance link is used for enhanced electrical performance
where circuit inductance is high. Thus, the input is dampened when
there is too much inductance, allowing for a high performance
system.
[0039] FIG. 11 illustrates a microflex connector 45 with an
integrated capacitor 41 in parallel with the power supply, and
located between power supply and ground. In this example, a three
level thin-film capacitor (e.g., metal-polyimide-metal) is
fabricated within microflex 45 providing excellent decoupling and
high frequency performance. A wirebond 48 is shown, which couples
the microflex to the chip 60 (FIG. 8). Capacitor 41 may also be
created with two levels of metal.
[0040] FIG. 12 shows a microflex connector 45 that allows for C4
connections with discrete devices, such as discrete device 46.
Discrete device 46 may be connected to any portion of microflex
connector 45, such as a middle portion. Thus, a discrete device may
be electrically connected to chip 60 (FIG. 8) through microflex
connector 45. The discrete device characteristics may include
passive circuitry (e.g., capacitor, resistor, or diode) and/or
active circuitry.
[0041] FIG. 13 shows a microflex connector 45 that allows for the
connection of a discrete device 47A through a fillet
interconnection 47B, typical of industry-standard surface mount
technology (SMT). Again, the discrete device may be electrically
connected to chip 60 (FIG. 8).
[0042] Although specific examples have been shown for FIGS. 9-13,
it is to be understood that other thin-film microflex connectors
may also be formed, such as a line and ground plane. Also, although
in the following examples a twisted-wire pair is specifically shown
for the microflex, it is to be understood that the microflex
discussed in the previous figures may also be used. Besides the
benefits discussed above with the various microflex connectors, the
microflex technology of the present invention allows for
transmission line impedances to match (Zooutput =Zoload).
Furthermore, the inductance is improved by a factor of ten times
from a standard leadframe, and the ground bounce improves
significantly (approximately 44%).
[0043] FIG. 14 illustrates a semiconductor package 21 B wherein
chip 60 is electrically connected to the outer lead 56 through
microflex 55, which is similar to microflex 20C of
[0044] FIG. 6. Microflex 55 is fabricated with an opening which
enables a solder ball (C4) connection 64 to connect to the I/O pads
of chip 60. An electrical connection 52 connects microflex 55 to
outer lead 56. A plastic encapsulation 54 encloses semiconductor
package 21B. As seen in FIG. 14 and subsequent figures, one of the
many advantage of the present invention is the ability of utilizing
C4 technology with leadframes and plastic encapsulation. This
combination is possible because of the microflex technology of the
present invention.
[0045] FIGS. 15 and 16 illustrate semiconductor packages 23A and
23B wherein microflex 55 is attached to (as a free-standing
microflex such as in FIG. 5) or fabricated on a carrier/support 58.
The outer leads 56 are electrically coupled to microflex 55 via
wirebonding 53 and also mechanically coupled to microflex 55 and
carrier/support 58. FIG. 15 shows a wirebond connection 57
electrically connecting chip 60 to microflex 55. FIG. 16
illustrates a solder ball connection 64 electrically connecting
chip 60 to microflex 55.
[0046] FIG. 17 illustrates a top-down view of a semiconductor
package similar to one depicted in FIG. 8. The microflex leadframe
structure depicted in FIG. 17 is fabricated using the process
outlined in FIG. 7, built on metal substrate 71. Cross-hatched
region 68 is the microflex region, which contains microflex, such
as twisted-wire pair, line/ground plane, microflex with a
capacitor, etc. The leadframe support (element 58 of FIG. 8) is
depicted by lines 72. Region 66 portrays the outer lead regions
(containing outer lead 56 of FIG. 8). As aforementioned, the
microflex electrically connects the package to leads 66. The
package may be wirebonded to leads through a wirebond pad array
70.
[0047] FIG. 18 illustrates combining chip-on-chip component
technology (e.g. chip-on-chip component technology as disclosed in
IBM patent disclosure BU9-97-063 referenced above) and microflex
technology. As seen in FIG. 18, a first chip 60 connects to a
second chip 80 through C4 connections 64. Although C4 connectors
are specifically shown, other appropriate connectors may also be
used to interconnect the chips, such as solder bumps, PMC paste,
conductive epoxy, anisotropic conductive adhesive, etc. In this
example, microflex 55 is electrically connected to chip 80 via
wirebonding 53 and mechanically bonded to chip 80 via adhesive 74.
Thus, microflex 55 provides electrical signals to/from outer lead
56 from/to both chip 80 and chip 60.
[0048] FIG. 19 illustrates semiconductor package 67 comprising chip
60, microflex 55 and encapsulation 54. FIG. 21 illustrates the
top-down view of semiconductor package 67 of FIG. 19. As seen in
FIGS. 19 and 21, microflex 55 comprises bare metal outer leads and
thus may also function as part of semiconductor package 67,
enabling interconnection between chip 60 and the next level of
assembly. In this example, the electrical and mechanical
performance advantages of microflex technology, such as a reduction
in lead inductance and reduction in package stresses, are realized
and enhanced. In addition, thermal management problems are
minimized through the enhanced electrical performance of the
package and through chip 60, which being exposed in this package
improves heat transfer.
[0049] As seen in FIGS. 20 and 22, two chips, chip 60 and chip 80,
are interconnected and attached to microflex 55, forming a
semiconductor package. Specifically, FIG. 20 illustrates the
attachment of chips 60 and 80 to two sides of microflex 55 through
C4 connectors. FIG. 22 is a top-down view of a generic
semiconductor package comprising chips 60 and 80 interconnected
with microflex 55, such as twisted-wire pair to reduce
inductance.
[0050] FIGS. 23-25 illustrate exemplary chip-scale packaging
utilizing microflex technology. As seen in FIGS. 23-25, chip 60
(chip 90 in FIG. 24) is electrically connected to microflex 55
through wirebond 53, and is mechanically connected to microflex 55
through adhesive 74. An encapsulant 54 is used on the exposed side
of chip 60. Microflex 55 wraps around chip 60 and provides a high
electrical performance connection between chip 60 and the next
level of packaging through electrical connectors 64 such as solder
ball arrays. Adhesive 74 may be selected to achieve enhanced solder
ball fatigue performance. For example, if a silicone-based adhesive
is used, then the differential thermal expansion between chip 60
and the substrate (not shown) to which the chip-scale package is
connected can be accommodated without the use of a solder ball
encapsulant. This feature enables removal and replacement of the
chip-scale packages, which is particularly important for
chip-on-chip component applications wherein component removal and
replacement is critical to achieving overall module yields. Solder
balls also allow for a continuous contact to the chip I/O
throughout an entire burn-in process. If the electrical connectors
64 happen to be wirebond connectors, the wirebond pads may easily
be converted to solder balls, and visa versa.
[0051] As seen in FIG. 24, chip 90 may shrink 91 without affecting
the electrical connectors 64. Thus, using microflex 55 in a
chip-scale package provides a low-cost module since the entire
package does not need to be redesigned to accommodate any
shrinkage.
[0052] In FIG. 25, chip 80 is connected to chip 60, which is
coupled to microflex 55. For this embodiment, a wirebond
encapsulant 69 and solder ball encapsulant 65 protects the exposed
sections of the chip assembly. One example of this embodiment is
chip 80 being an SRAM and chip 60 being a microprocessor. Merging
logic and memory chips can provide significantly enhanced
electrical performance compared with current technology.
[0053] A leadframe package 140 is shown in FIG. 26. A chip in
package 140 may be wirebonded to leads 148 through wirebonds 152.
Microflex 145 electrically connects the chip within package 140 to
leads 148. An opening 154 in microflex 145 allows for wirebonding
to the chip. Support structures 144 support microflex 145. In this
example, three different microflex connectors are used: thin-film
wiring 146, a twisted-wire pair 155 and microflex with a resistor
142.
[0054] FIGS. 27 and 28 illustrate a stacked chip structure 160 that
utilizes microflex 176 to allow for compaction and high performance
of the stacked chips 161. As seen in FIG. 27, stacked chips 161 are
separated by glue line 162, in which is inserted a transfer metal
164. The transfer metal 164 connects to a C4 solder ball 170
through C4 pad 168. A C4 pad 172 in microflex 176 allows for each
chip 161 to connect to a bond pad 180, or wire bond 178 through
thin-film wiring 174 in microflex and microflex 176. An adhesive
182 connects one face of chip 161 to microflex 176. FIG. 28
illustrates the microflex region comprising C4 pads 172, thin-film
wiring 174, twisted-wire pair 176 and bond pad 180, which wrap
around chips 161.
[0055] One of the key advantages of the microflex technology is
that superior electrical performance (compared with currently
available technologies) is possible. This superior electrical
performance includes reduced line inductance, incorporation of
integrated passive components, and attachment of discrete passive
and active components to the microflex. All of these features
enable operation of the chip at increased frequencies.
[0056] Thus, microflex technology according to the present
invention allow for enhanced electrical, mechanical and thermal
performance in semiconductor packages. Furthermore, microflex
technology allows for personalization of chips and packages by
providing various chip-to-microflex interconnection configurations,
as seen from the embodiments and examples of the present invention,
increasing the ability to offer customer-specific personalization
at a low-cost.
[0057] While the invention has been particularly shown and
described with reference to a preferred embodiment thereof, it will
be understood by those skilled in the art that the foregoing and
other changes in form and details may be made therein without
departing from the spirit and scope of the invention.
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