U.S. patent application number 11/745784 was filed with the patent office on 2007-11-08 for alloy compositions and techniques for reducing intermetallic compound thickness and oxidation of metals and alloys.
This patent application is currently assigned to Indium Corporation of America. Invention is credited to Hong-Sik Hwang, Ning-Cheng Lee.
Application Number | 20070256761 11/745784 |
Document ID | / |
Family ID | 38694420 |
Filed Date | 2007-11-08 |
United States Patent
Application |
20070256761 |
Kind Code |
A1 |
Hwang; Hong-Sik ; et
al. |
November 8, 2007 |
ALLOY COMPOSITIONS AND TECHNIQUES FOR REDUCING INTERMETALLIC
COMPOUND THICKNESS AND OXIDATION OF METALS AND ALLOYS
Abstract
Alloy compositions and techniques for reducing IMC thickness and
oxidation of metals and alloys are disclosed. In one particular
exemplary embodiment, the alloy compositions may be realized as a
composition of alloy or mixture consisting essentially of from
about 90% to about 99.999% by weight indium and from about 0.001%
to about 10% by weight germanium and unavoidable impurities. In
another particular exemplary embodiment, the alloy compositions may
be realized as a composition of alloy consisting essentially of
from about 90% to about 99.999% by weight gallium and from about
0.001% to about 10% by weight germanium and unavoidable
impurities.
Inventors: |
Hwang; Hong-Sik; (Clinton,
NY) ; Lee; Ning-Cheng; (New Hartford, NY) |
Correspondence
Address: |
HUNTON & WILLIAMS LLP;INTELLECTUAL PROPERTY DEPARTMENT
1900 K STREET, N.W., SUITE 1200
WASHINGTON
DC
20006-1109
US
|
Assignee: |
Indium Corporation of
America
Utica
NY
|
Family ID: |
38694420 |
Appl. No.: |
11/745784 |
Filed: |
May 8, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60746710 |
May 8, 2006 |
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Current U.S.
Class: |
148/400 ;
420/555 |
Current CPC
Class: |
H01L 2924/0134 20130101;
H01L 2224/29105 20130101; H01L 2224/29305 20130101; H01L 2224/83192
20130101; H01L 2224/29309 20130101; H01L 2924/0132 20130101; H01L
24/13 20130101; H01L 2224/29109 20130101; H01L 2224/2929 20130101;
H01L 2224/29305 20130101; H01L 2224/29309 20130101; H01L 2224/29309
20130101; H01L 2924/01082 20130101; H01L 2924/3651 20130101; B23K
35/24 20130101; H01L 2224/29301 20130101; H01L 2924/0132 20130101;
H01L 2924/0134 20130101; H01L 2224/13109 20130101; H01L 2924/01032
20130101; H01L 2924/0133 20130101; H01L 2224/05568 20130101; H01L
24/32 20130101; H01L 2224/29105 20130101; H01L 2224/32014 20130101;
H01L 2224/29109 20130101; H01L 2224/29105 20130101; H01L 2224/29305
20130101; H01L 2224/29313 20130101; H01L 2924/0132 20130101; H01L
2224/29309 20130101; H01L 2224/29309 20130101; H01L 2224/13109
20130101; H01L 2224/32012 20130101; H01L 2924/0103 20130101; H01L
2224/13105 20130101; H01L 2924/00014 20130101; H01L 2924/01025
20130101; H01L 2924/01033 20130101; H01L 2924/0133 20130101; H01L
23/3736 20130101; H01L 2224/13105 20130101; H01L 2224/29309
20130101; H01L 2224/29311 20130101; H01L 2924/01327 20130101; H01L
2224/29305 20130101; H01L 2224/29105 20130101; H01L 2924/01049
20130101; H01L 2924/014 20130101; H01L 2224/29109 20130101; H01L
2224/13109 20130101; H01L 2224/83191 20130101; H01L 2224/13105
20130101; H01L 2224/13105 20130101; H01L 2224/29109 20130101; H01L
2224/2929 20130101; H01L 2224/29309 20130101; C22C 28/00 20130101;
H01L 2224/13105 20130101; H01L 2224/29105 20130101; H01L 2924/0133
20130101; H01L 2224/29105 20130101; H01L 2224/29105 20130101; H01L
2224/29109 20130101; H01L 2224/29309 20130101; H01L 2224/29313
20130101; H01L 2224/81192 20130101; H01L 2924/00014 20130101; H01L
2924/0133 20130101; H01L 2224/29111 20130101; H01L 2224/29305
20130101; H01L 2224/29305 20130101; H01L 2224/29305 20130101; H01L
2224/29305 20130101; H01L 2924/0132 20130101; H01L 2224/13099
20130101; H01L 23/3733 20130101; H01L 2224/13109 20130101; H01L
2224/29101 20130101; H01L 2224/29105 20130101; H01L 2224/29109
20130101; H01L 2924/0133 20130101; H01L 2224/16221 20130101; H01L
2224/29113 20130101; H01L 23/4275 20130101; H01L 2224/13105
20130101; H01L 2224/29105 20130101; H01L 2224/29305 20130101; H01L
2224/29305 20130101; H01L 2224/29309 20130101; H01L 2224/29109
20130101; H01L 2224/29109 20130101; H01L 2224/16225 20130101; H01L
2224/29305 20130101; H01L 2224/29101 20130101; H01L 2224/29113
20130101; H01L 2924/0105 20130101; H01L 2224/05573 20130101; H01L
24/16 20130101; H01L 2224/29109 20130101; H01L 2224/29109 20130101;
H01L 2224/29301 20130101; H01L 2224/29305 20130101; H01L 2224/29105
20130101; H01L 2224/29301 20130101; H01L 2224/29305 20130101; H01L
2224/29309 20130101; H01L 2224/29309 20130101; H01L 2924/01047
20130101; H01L 2924/01047 20130101; H01L 2924/0103 20130101; H01L
2924/01049 20130101; H01L 2924/0105 20130101; H01L 2924/01032
20130101; H01L 2924/00014 20130101; H01L 2924/01049 20130101; H01L
2924/01082 20130101; H01L 2924/01083 20130101; H01L 2924/00014
20130101; H01L 2924/01025 20130101; H01L 2924/01032 20130101; H01L
2924/01049 20130101; H01L 2924/01022 20130101; H01L 2924/0108
20130101; H01L 2924/00 20130101; H01L 2924/0103 20130101; H01L
2924/01031 20130101; H01L 2924/01047 20130101; H01L 2924/01049
20130101; H01L 2924/0105 20130101; H01L 2924/0105 20130101; H01L
2924/0105 20130101; H01L 2924/01083 20130101; H01L 2924/01083
20130101; H01L 2924/01032 20130101; H01L 2924/0103 20130101; H01L
2924/00014 20130101; H01L 2924/01032 20130101; H01L 2924/01047
20130101; H01L 2924/01083 20130101; H01L 2924/0105 20130101; H01L
2924/0105 20130101; H01L 2924/01083 20130101; H01L 2924/01032
20130101; H01L 2924/01025 20130101; H01L 2924/01049 20130101; H01L
2924/01083 20130101; H01L 2924/01049 20130101; H01L 2924/01015
20130101; H01L 2924/01049 20130101; H01L 2924/01082 20130101; H01L
2924/01047 20130101; H01L 2924/01032 20130101; H01L 24/29 20130101;
H01L 2224/13109 20130101; H01L 2924/0132 20130101; H01L 2924/01322
20130101; H01L 2924/0133 20130101; H01L 2224/13109 20130101; H01L
2224/29105 20130101; H01L 2224/29109 20130101; H01L 2924/01006
20130101; H01L 2924/01079 20130101; H01L 23/42 20130101; H01L
2924/01049 20130101; H01L 2224/29105 20130101; H01L 2924/01032
20130101; H01L 2924/01082 20130101; H01L 2924/00014 20130101; H01L
2924/01025 20130101; H01L 2924/01049 20130101; H01L 2924/01047
20130101; H01L 2924/01031 20130101; H01L 2924/01047 20130101; H01L
2924/01049 20130101; H01L 2924/0105 20130101; H01L 2924/0105
20130101; H01L 2924/00014 20130101; H01L 2924/00014 20130101; H01L
2924/01049 20130101; H01L 2924/0105 20130101; H01L 2924/01082
20130101; H01L 2924/01031 20130101; H01L 2924/01049 20130101; H01L
2924/00014 20130101; H01L 2924/01049 20130101; H01L 2924/0105
20130101; H01L 2924/01022 20130101; H01L 2924/00014 20130101; H01L
2924/0103 20130101; H01L 2924/01049 20130101; H01L 2924/01049
20130101; H01L 2924/014 20130101; H01L 2924/00014 20130101; H01L
2924/00014 20130101; H01L 2924/00014 20130101; H01L 2924/01048
20130101; H01L 2924/00014 20130101; H01L 2924/00014 20130101; H01L
2924/00014 20130101; H01L 2924/01049 20130101; H01L 2924/0105
20130101; H01L 2924/01082 20130101; H01L 2924/01015 20130101; H01L
2924/01083 20130101; H01L 2924/01015 20130101; H01L 2924/0103
20130101; H01L 2924/01032 20130101; H01L 2924/00012 20130101; H01L
2924/0103 20130101; H01L 2924/01049 20130101; H01L 2924/01049
20130101; H01L 2924/0105 20130101; H01L 2924/01083 20130101; H01L
2224/05599 20130101; H01L 2924/01032 20130101; H01L 2924/0105
20130101; H01L 2924/01015 20130101; H01L 2924/00014 20130101; H01L
2924/01022 20130101; H01L 2924/01049 20130101; H01L 2924/01049
20130101; H01L 2924/01049 20130101; H01L 2924/0105 20130101; H01L
2924/0105 20130101; H01L 2924/01082 20130101; H01L 2924/0105
20130101; H01L 2924/01083 20130101; H01L 2924/01083 20130101; H01L
2924/0103 20130101; H01L 2924/01025 20130101; H01L 2924/00014
20130101; H01L 2924/01022 20130101; H01L 2924/01031 20130101; H01L
2924/01049 20130101; H01L 2924/01082 20130101; H01L 2924/01083
20130101; H01L 2924/01032 20130101; H01L 2924/01032 20130101; H01L
2924/0105 20130101; H01L 2924/01082 20130101; H01L 2924/01032
20130101; H01L 2924/01032 20130101; H01L 2924/0105 20130101; H01L
2924/0105 20130101; H01L 2924/01083 20130101 |
Class at
Publication: |
148/400 ;
420/555 |
International
Class: |
C22C 28/00 20060101
C22C028/00 |
Claims
1. A composition of alloy or mixture consisting essentially of from
about 90% to about 99.999% by weight indium and from about 0.001%
to about 10% by weight germanium and unavoidable impurities.
2. A composition of alloy or mixture consisting essentially of from
about 90% to about 99.999% by weight indium and from about 0.001%
to about 10% by weight of one or more of germanium, manganese,
phosphorus, and titanium.
3. A composition of alloy consisting essentially of from about 90%
to about 99.999% by weight gallium and from about 0.001% to about
10% by weight germanium and unavoidable impurities.
4. A composition of alloy consisting essentially of from about 90%
to about 99.999% by weight gallium and from about 0.001% to about
10% by weight of one or more of germanium, manganese, phosphorus,
and titanium.
5. A composition of alloy consisting essentially of gallium-indium
alloy, gallium-indium-tin alloy, gallium-indium-tin-zinc alloy,
cadmium, cadmium alloys, indium-lead alloy, indium-lead-silver
alloy, mercury, mercury alloys, bismuth-tin alloy,
indium-tin-bismuth alloy, and mixtures thereof containing from
about 0.001% to about 10% by weight of one or more of germanium,
manganese, phosphorus, and titanium and unavoidable impurities.
6. A method of incorporating from about 0.001% to about 10% by
weight of one or more dopants including one or more of germanium,
manganese, phosphorus, and titanium in a metal or metal alloy
comprising from about 90% to about 99.999% by weight gallium or
indium, the method comprising: mixing the one or more dopants into
the metal or metal alloy as a solution with heat.
7. The method of claim 6, further comprising: cooling the mixture
quickly to get finer dopant or intermetallic particles that diffuse
faster than larger particles.
8. A method of incorporating from about 0.001% to about 10% by
weight of one or more dopants including one or more of germanium,
manganese, phosphorus, and titanium in a metal or metal alloy
comprising from about 90% to about 99.999% by weight gallium or
indium, the method comprising: mixing the one or more dopants as
particulates into a molten metal or metal alloy; and cooling the
molten metal or metal alloy with the one or more dopant
particulates to form a metal or metal alloy composite.
9. A method of incorporating from about 0.001% to about 10% by
weight of one or more dopants including one or more of germanium,
manganese, phosphorus, and titanium in a metal or metal alloy
comprising from about 90% to about 99.999% by weight gallium or
indium, the method comprising: mixing the one or more dopants into
a solid form of the metal or metal alloy by mechanical force.
10. A method of incorporating from about 0.001% to about 10% by
weight of one or more dopants including one or more of germanium,
manganese, phosphorus, and titanium in a metal or metal alloy
comprising from about 90% to about 99.999% by weight gallium or
indium, the method comprising: mixing the one or more dopants as
particulates into a metal or metal alloy powder to form a metal or
metal alloy powder mixture.
11. A method of incorporating from about 0.001% to about 10% by
weight of one or more dopants including one or more of germanium,
manganese, phosphorus, and titanium in a metal or metal alloy
comprising from about 90% to about 99.999% by weight gallium or
indium, the method comprising: putting the one or more dopants as
particulates in an interconnecting substrate with the metal or
metal alloy.
12. The method of claim 11, wherein the interconnecting substrate
includes at least one of a pad on circuit board, a heat spreader, a
heat sink, and a back side of component.
13. A metallurgical interconnect material formed of the composition
in any of claims 1 to 5.
14. A thermal interface material formed of the composition in any
of claims 1 to 5.
15. The thermal interface material of claim 14, further comprising
one or more of a phase change material, a thermally conductive gel,
a thermally conductive tape, and a thermal grease.
16. A thermally conductive filler formed of the composition in any
of claims 1 to 5.
17. A thermally conductive medium formed of the composition in any
of claims 1 to 5.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority to U.S. Provisional
Patent Application No. 60/746,710, filed May 8, 2006, which is
hereby incorporated by reference herein in its entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates generally to electrical and
thermal conduction and, more particularly, alloy compositions and
techniques for reducing intermetallic compound (IMC) thickness and
oxidation of metals and alloys.
BACKGROUND OF THE DISCLOSURE
[0003] When working with electronic devices, solder joints should
give sufficient reliability during service. Solder joint
reliability largely relies on IMC growth that is caused by time and
heat generated during service. In general, thicker IMC causes
reliability problems due to brittleness of IMC, formation of
Kirkendall voiding, and/or depletion of metal layer(s) upon which
solder is applied, especially, when the metal layer(s) is thin such
as in under bump metallization (UBM).
[0004] On the other hand, the development of new thermal interface
materials (TIM's) is required to address increases in device
processing speeds and heat generation. Thermal solders are very
attractive because they have high thermal conductivities. Soldered
TIM's have similar problems as solder joints in that IMC growth
causing reliability problems may occur as devices run at elevated
temperatures.
[0005] Low melting point metals, including liquid metals, are also
useful as thermally conductive materials due to good conformity of
the low melting point metals with contacting surfaces, good
metallic phase continuity of the low melting point metals at
service temperatures, and the formation of good thermally
conductive pathways or chains of the low melting point metals at
service temperatures. The use of low melting point metals, however,
is limited in some specific applications due to rapid oxidation and
high reactivity.
[0006] New types of TIM's, such as polymer solder hybrids (PSH),
have been recently introduced wherein a polymer matrix acts as an
adhesive on a surface of a die or package and solder filler serves
as a thermal conductor. Several possible applications of low
melting point metals have been attempted as thermal conductive
fillers or as a part of conductive fillers in PSH's. However, low
melting point metals, including liquid metals, oxidize very quickly
and form loosely aggregated solids, which easily delaminate at
interfaces. As a result, using this type of TIM is very
challenging.
[0007] In view of the foregoing, it would be desirable to provide
techniques for reducing IMC thickness and oxidation of metals and
alloys which overcome the above-described inadequacies and
shortcomings.
SUMMARY OF THE DISCLOSURE
[0008] Alloy compositions and techniques for reducing IMC thickness
and oxidation of metals and alloys are disclosed. In one particular
exemplary embodiment, the alloy compositions may be realized as a
composition of alloy or mixture consisting essentially of from
about 90% to about 99.999% by weight indium and from about 0.001%
to about 10% by weight germanium and unavoidable impurities. In
another particular exemplary embodiment, the alloy compositions may
be realized as a composition of alloy or mixture consisting
essentially of from about 90% to about 99.999% by weight indium and
from about 0.001% to about 10% by weight of one or more of
germanium, manganese, phosphorus, and titanium. In yet another
particular exemplary embodiment, the alloy compositions may be
realized as a composition of alloy consisting essentially of from
about 90% to about 99.999% by weight gallium and from about 0.001%
to about 10% by weight germanium and unavoidable impurities. In
still another particular exemplary embodiment, the alloy
compositions may be realized as a composition of alloy consisting
essentially of from about 90% to about 99.999% by weight gallium
and from about 0.001% to about 10% by weight of one or more of
germanium, manganese, phosphorus, and titanium. In still yet
another particular exemplary embodiment, the alloy compositions may
be realized as a composition of alloy consisting essentially of
gallium-indium alloy, gallium-indium-tin alloy,
gallium-indium-tin-zinc alloy, cadmium, cadmium alloys, indium-lead
alloy, indium-lead-silver alloy, mercury, mercury alloys,
bismuth-tin alloy, indium-tin-bismuth alloy, and mixtures thereof
containing from about 0.001% to about 10% by weight of one or more
of germanium, manganese, phosphorus, and titanium and unavoidable
impurities.
[0009] The alloy compositions may take the form of a metallurgical
interconnect material, a thermal interface material, a thermally
conductive filler, or a thermally conductive medium. The thermal
interface material may comprise one or more of a phase change
material, a thermally conductive gel, a thermally conductive tape,
and a thermal grease.
[0010] In one particular exemplary embodiment, the techniques may
be realized as a method of incorporating from about 0.001% to about
10% by weight of one or more dopants including one or more of
germanium, manganese, phosphorus, and titanium in a metal or metal
alloy comprising from about 90% to about 99.999% by weight gallium
or indium, wherein the method comprises mixing the one or more
dopants into the metal or metal alloy as a solution with heat. The
mixture may be quickly cooled to get finer dopant or intermetallic
particles that diffuse faster than larger particles.
[0011] In another particular exemplary embodiment, the techniques
may be realized as a method of incorporating from about 0.001% to
about 10% by weight of one or more dopants including one or more of
germanium, manganese, phosphorus, and titanium in a metal or metal
alloy comprising from about 90% to about 99.999% by weight gallium
or indium, wherein the method comprises mixing the one or more
dopants as particulates into a molten metal or metal alloy, and
cooling the molten metal or metal alloy with the one or more dopant
particulates to form a metal or metal alloy composite.
[0012] In another particular exemplary embodiment, the techniques
may be realized as a method of incorporating from about 0.001% to
about 10% by weight of one or more dopants including one or more of
germanium, manganese, phosphorus, and titanium in a metal or metal
alloy comprising from about 90% to about 99.999% by weight gallium
or indium, wherein the method comprises mixing the one or more
dopants into a solid form of the metal or metal alloy by mechanical
force.
[0013] In another particular exemplary embodiment, the techniques
may be realized as a method of incorporating from about 0.001% to
about 10% by weight of one or more dopants including one or more of
germanium, manganese, phosphorus, and titanium in a metal or metal
alloy comprising from about 90% to about 99.999% by weight gallium
or indium, wherein the method comprises mixing the one or more
dopants as particulates into a metal or metal alloy powder to form
a metal or metal alloy powder mixture.
[0014] In another particular exemplary embodiment, the techniques
may be realized as a method of incorporating from about 0.001% to
about 10% by weight of one or more dopants including one or more of
germanium, manganese, phosphorus, and titanium in a metal or metal
alloy comprising from about 90% to about 99.999% by weight gallium
or indium, wherein the method comprises putting the one or more
dopants as particulates in an interconnecting substrate with the
metal or metal alloy, wherein the interconnecting substrate may
include at least one of a pad on circuit board, a heat spreader, a
heat sink, and a back side of component.
[0015] The present disclosure will now be described in more detail
with reference to exemplary embodiments thereof as shown in the
accompanying drawings. While the present disclosure is described
below with reference to exemplary embodiments, it should be
understood that the present disclosure is not limited thereto.
Those of ordinary skill in the art having access to the teachings
herein will recognize additional implementations, modifications,
and embodiments, as well as other fields of use, which are within
the scope of the present disclosure as described herein, and with
respect to which the present disclosure may be of significant
utility.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to facilitate a fuller understanding of the present
disclosure, reference is now made to the accompanying drawings, in
which like elements are referenced with like numerals. These
drawings should not be construed as limiting the present
disclosure, but are intended to be exemplary only.
[0017] FIG. 1 is a table of IMC thickness and Nickel (Ni) layer
consumption of aged pure Indium (In) and 2% Germanium (Ge)/Indium
(In) samples in accordance with an embodiment of the present
disclosure.
[0018] FIG. 2 shows a scanning electron microscopy (SEM) picture,
magnified .times.1000, of a pure Indium (In) sample on a Nickel
(Ni)/Gold (Au) substrate aged for 1000 hrs at 150.degree. C. in
accordance with an embodiment of the present disclosure.
[0019] FIG. 3 shows a scanning electron microscopy (SEM) picture,
magnified .times.1000, of a 2% Germanium (Ge)/Indium (In) sample on
a Nickel (Ni)/Gold (Au) substrate aged for 1000 hrs at 150.degree.
C. in accordance with an embodiment of the present disclosure.
[0020] FIG. 4 shows a scanning electron microscopy (SEM) picture,
magnified .times.3000, of a 2% Germanium (Ge)/Indium (In) sample on
a Nickel (Ni)/Gold (Au) substrate aged for 1000 hrs at 150.degree.
C. in accordance with an embodiment of the present disclosure.
[0021] FIG. 5 is a table of IMC compositions of aged pure Indium
(In) and 2% Germanium (Ge)/Indium (In) samples in accordance with
an embodiment of the present disclosure.
[0022] FIG. 6 shows a graph of oxide formed in a 85.degree. C./85%
relative humidity chamber for pure Gallium (Ga) and 0.05% and 0.1%
Germanium (Ge)-doped Gallium (Ga) in accordance with an embodiment
of the present disclosure.
[0023] FIG. 7 shows a graph of oxide formed in a 85.degree. C./85%
relative humidity chamber for 0.5%, 1%, 2%, and 5% Germanium
(Ge)-doped Gallium (Ga) in accordance with an embodiment of the
present disclosure.
[0024] FIG. 8 shows a graph of oxide formed in a 85.degree. C./85%
relative humidity chamber for 0.0001% and 0.0005% Germanium
(Ge)-doped Gallium (Ga) in accordance with an embodiment of the
present disclosure.
[0025] FIG. 9 shows a graph of oxide formed in a 85.degree. C./85%
relative humidity chamber for Gallium (Ga)/Indium (In) alloys with
and without 0.5% Germanium (Ge) in accordance with an embodiment of
the present disclosure.
[0026] FIG. 10 shows a graph of oxide formed in a 85.degree. C./85%
relative humidity chamber for Indium (In)/Bismuth (Bi) alloys with
and without 0.5% Germanium (Ge) in accordance with an embodiment of
the present disclosure.
[0027] FIG. 11 shows a graph of oxide formed in a 85.degree. C./85%
relative humidity chamber for Gallium (Ga) alloys containing 0.5%
Phosphorus (P), 0.5% Titanium (Ti), 0.5% Manganese (Mn), and no
dopants in accordance with an embodiment of the present
disclosure.
[0028] FIG. 12 is a table of relative peak intensity of Germanium
(Ge) to Gallium (Ga) with different laser power for 2% Germanium
(Ge)/Gallium (Ga) in accordance with an embodiment of the present
disclosure.
[0029] FIG. 13 shows a graph of ICP-MS spectrum of 2% Germanium
(Ge)/Gallium (Ga) for 15% laser power in accordance with an
embodiment of the present disclosure.
[0030] FIG. 14 shows a graph of ICP-MS spectrum of 2% Germanium
(Ge)/Gallium (Ga) for 25% laser power in accordance with an
embodiment of the present disclosure.
[0031] FIG. 15 shows a mounting configuration wherein a
metallurgical bond is formed between a pad of an electronic
component and a pad of a substrate through an interconnecting
material, such as solder, in accordance with an embodiment of the
present disclosure.
[0032] FIG. 16 shows an application of a TIM in an electronic
assembly in accordance with an embodiment of the present
disclosure.
[0033] FIG. 17 shows a simplified example of a first TIM in the
form of a phase change material, a thermally conductive gel, a
thermally conductive tape, or a thermal grease that comprises a
polymeric matrix filled with a thermally conductive filler between
an IHS and an electronic component in accordance with an embodiment
of the present disclosure.
[0034] FIG. 18 shows an example wherein a first TIM is a PSH where
a thermally conductive filler stays as a liquid at service
temperature and a polymeric matrix gives mechanical adhesion
between an IHS and an electronic component in accordance with an
embodiment of the present disclosure.
[0035] FIG. 19 shows an example wherein TIM material may be placed
directly between an IHS and an electronic component without a
polymeric matrix in accordance with an embodiment of the present
disclosure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0036] Alloy compositions and techniques for reducing IMC thickness
and oxidation of metals and alloys in accordance with embodiments
of the present disclosure are described. Such alloy compositions
and techniques were discovered through experimental testing. For
example, in order to solve problems of solder joint reliability, an
IMC growth test was used to reveal a technique for preventing IMC
growth of interconnect material such as solder and TIM in
accordance with an embodiment of the present disclosure. That is,
significant, unprecedented effects were observed when IMC growths
of 2% (wt) Germanium (Ge)/Indium (In) and pure Indium (In) on an
electrolytic Nickel (Ni)/Gold (Au) substrate after aging in a
150.degree. C. oven for 1000 hours. IMC thickness and Nickel (Ni)
layer consumption of samples were measured after aging the samples.
As shown in the table of FIG. 1, total IMC thickness of pure Indium
(In) was about 18.8-19.6 microns while the IMC thickness of 2%
Germanium (Ge)/Indium (In) was about 2.0-3.4 microns. The original
thickness of Nickel (Ni) layer of the substrate was 5.3 microns and
the Nickel (Ni) layer consumption of samples with pure Indium (In)
and 2% Germanium (Ge)/Indium (In) were determined as 45.3-49.1% and
3.8-7.5%, respectively. FIGS. 2 and 3 show scanning electron
microscopy (SEM) pictures of a pure Indium (In) sample and a 2%
Germanium (Ge)/Indium (In) sample, respectively, on an electrolytic
Nickel (Ni)/Gold (Au) substrate after aging in a 150.degree. C.
oven for 1000 hours. The decrease in IMC in the 2% Germanium
(Ge)/Indium (In) sample is readily apparent. When seen at higher
magnification, it is also apparent that the IMC consists of three
layers (see FIG. 4).
[0037] In order to understand the mechanism for thinner IMC in
germanium-doped indium, energy dispersive spectrometry (EDS) is
helpful and thus was performed. The table of FIG. 5 summarizes EDS
analysis results for the pure Indium (In) sample and the 2%
Germanium (Ge)/Indium (In) sample.
[0038] Summarizing, as shown in FIG. 2, only one layer of IMC is
found in the pure Indium (In) sample. However, as shown in FIGS. 3
and 4, three layers of IMC are found in the 2% Germanium
(Ge)/Indium (In) sample. As shown in the table of FIG. 5, the
composition of the IMC in the pure Indium (In) sample was
determined to be (Ni, Au).sub.28In.sub.72, Meanwhile, the
composition of the first IMC layer (i.e., closest to solder) of the
2% Germanium (Ge)/Indium (In) sample was determined to be 54%
Indium (In), 32% Nickel (Ni), 13% Germanium (Ge), and 1% Gold (Au).
It should be noted, however, that the actual composition of the
first IMC layer of the 2% Germanium (Ge)/Indium (In) sample may not
be precisely accurate because the first IMC layer of the 2%
Germanium (Ge)/Indium (In) sample was thinner than the measurement
resolution. Thus, materials in areas other than the first IMC layer
of the 2% Germanium (Ge)/Indium (In) sample may be included in the
composition of the first IMC layer of the 2% Germanium (Ge)/Indium
(In) sample. The second IMC layer of the 2% Germanium (Ge)/Indium
(In) sample, however, was thicker than the first IMC layer of the
2% Germanium (Ge)/Indium (In) sample and thus it was possible to
determine the exact composition of the second IMC layer of the 2%
Germanium (Ge)/Indium (In) sample as (Ni, In, Au).sub.50Ge.sub.50.
The composition of third IMC layer of the 2% Germanium (Ge)/Indium
(In) sample was same as the composition of the IMC in the pure
Indium (In) sample.
[0039] It is believed that Germanium (Ge) reacts with Nickel (Ni)
in the early stages of aging to form Germanium (Ge)-rich IMC layers
and that these Germanium (Ge)-rich IMC layers protect the Nickel
(Ni) layer from reaction with solder. It is also believed that when
a certain IMC layer forms a dense and stable layer that can block
inter-diffusion between solder and a substrate material, thinner
total IMC and less consumption of the substrate material such as
for UBM is observed. Thus, it is further believed that formation of
such a protective IMC layer results in better reliability. From the
discussion above, it may be concluded that the thin layer(s) of
Germanium (Ge)-rich IMC plays a role as diffusion barrier to slow
down solder diffusion to substrate.
[0040] In order to solve problems of oxidation of metals, including
low melting temperature metals, an oxidation test was used to
reveal a technique for preventing oxidation in accordance with an
embodiment of the present disclosure. Indeed, the above-described
significant, unprecedented effects of Germanium (Ge) were also
observed in low melting temperature metals such as gallium in the
oxidation test. That is, samples of low melting temperature metals
99.95% Gallium (Ga)/0.05% Germanium (Ge), 99.9% Gallium (Ga)/0.1%
Germanium (Ge), and pure Gallium (Ga) were placed in a 85.degree.
C./85% relative humidity chamber. Metal oxide formed on top of the
metals in a vial. The amount of oxide was determined by measuring
the height of the oxide part (volume) formed on top of the metals.
The amount of oxide for the pure Gallium (Ga) sample increased
rapidly and showed about 90% oxide in 10 days. In contrast, the
samples of Gallium (Ga) containing small amounts of Germanium (Ge)
showed much slower oxidation rates. Indeed, the 99.95% Gallium
(Ga)/0.05% Germanium (Ge) and 99.9% Gallium (Ga)/0.1% Germanium
(Ge) samples didn't show a significant amount of oxide until after
80 days in the 85.degree. C./85% relative humidity chamber (see
FIG. 6).
[0041] To see if higher concentrations of Germanium (Ge) may give
better oxidation properties, samples of Gallium (Ga) containing
0.5, 1, 2, and 5% (wt) Germanium (Ge) were tested. As shown in FIG.
7, there is no big improvement by using higher concentrations of
Germanium (Ge).
[0042] To check for a lower limit of the effective amount of
Germanium (Ge), 0.0001% Germanium (Ge)/Gallium (Ga) and 0.0005%
Germanium (Ge)/Gallium (Ga) were tested. As shown in FIG. 8, only a
slight effect was observed for these alloys.
[0043] Gallium (Ga)/Indium (In) is a eutectic alloy and thus may
also be a good thermal interface material. The anti-oxidation
effect of Germanium (Ge) on such an alloy would therefore be of
interest in view of the above findings. Therefore, the oxidation
rate of a 78.6% Gallium (Ga)/21.4% Indium (In) alloy was compared
with a 0.5% Germanium (Ge)/78.2% Gallium (Ga)/21.3% Indium (In)
alloy. As shown in FIG. 9, the Germanium (Ge)-containing Gallium
(Ga)/Indium (In) alloy showed a much more stable oxidation
property.
[0044] Bismuth (Bi)/Indium (In) is also a eutectic alloy and thus
may also be a good thermal interface material. The anti-oxidation
effect of Germanium (Ge) on such an alloy would therefore be of
interest in view of the above findings. Therefore, the oxidation
rate of a 66.7% Indium (In)/33.3% Bismuth (Bi) alloy was compared
with a 0.5% Germanium (Ge)/66.4% Indium (In)/33.1% Bismuth (Bi)
alloy. As shown in FIG. 10, only a slight anti-oxidation effect was
observed for the Germanium (Ge)-containing Indium (In)/Bismuth (Bi)
alloy.
[0045] For comparison purposes, the anti-oxidation effect of other
dopants on Gallium (Ga) would be of interest in view of the above
findings. Therefore, the oxidation rate of 0.5% Phosphorus
(P)/Gallium (Ga), 0.5% Titanium (Ti)/Gallium (Ga), and 0.5%
Manganese (Mn)/Gallium (Ga) were compared with pure Gallium (Ga).
As shown in FIG. 11, some anti-oxidation effect was observed for
the Phosphorus (P), Titanium (Ti), and Manganese (Mn)-doped Gallium
(Ga), but not as much as Germanium (Ge)-doped Gallium (Ga).
[0046] The mechanism for using Germanium (Ge) to protect Gallium
(Ga) from oxidation was investigated. It was assumed that a thin
Germanium (Ge)-containing protective layer was formed and that this
layer protected further reaction of Gallium (Ga) with oxygen. A
laser ablation ICP-MS method was used to verify this mechanism. The
laser ablation ICP-MS method is widely used for surface composition
analysis. During this method a high energy laser ablates a small
area of the surface of a sample. The ablated material is then
transferred into an ICP-MS analysis chamber. The higher the laser
intensity, the deeper the ablation.
[0047] When lower laser power (15%) was used so that the ablation
was shallow, the relative intensity of the Germanium (Ge) major
peak (68.8-68.9) was 31-32% to the Gallium (Ga) major peak
(68.8-68.9) for 2% Germanium (Ge)/Gallium (Ga). When the higher
laser power (25%) was used, the relative intensity of Germanium
(Ge) was 8-10%. The results give qualitative evidence that the
Germanium (Ge) atoms go to the surface to protect the alloy from
oxidation. The test has repeated at a different spot of the sample
and showed the same result. FIGS. 12-14 show the analysis
results.
[0048] Referring to FIG. 15, there is shown a mounting
configuration wherein a metallurgical bond is formed between a pad
2 of an electronic component 1 and a pad 4 of a substrate 5 through
an interconnecting material 3, such as solder, in accordance with
an embodiment of the present disclosure. IMC layers build up
between the solder interconnecting material 3 and the component pad
2 and/or the substrate pad 4. The compositions described herein may
reduce IMC growth between the solder interconnecting material 3 and
the component pad 2 and/or the substrate pad 4 to increase
reliability of the electronic component 1.
[0049] Referring to FIG. 16, there is shown an application of a TIM
in an electronic assembly in accordance with an embodiment of the
present disclosure. The electronic assembly comprises a substrate 5
connected to an electronic component 1 through interconnecting
material 10. An integrated heat spreader (IHS) 8 is attached to a
top side of the electronic component 1 using a first TIM 9 to
dissipate heat generated from the electronic component 1. The IHS 8
is also connected to a heat sink 6 by a second TIM 7 for further
dissipation of heat.
[0050] One of the most effective materials for the first TIM 9 and
the second TIM 7 is a thermal solder such as indium, indium alloys,
gallium-indium alloy, gallium-indium-tin alloy,
gallium-indium-tin-zinc alloy, indium-lead alloy,
indium-lead-silver alloy, bismuth-tin alloy, and indium-tin-bismuth
alloy. The compositions described herein may reduce IMC growth
between the electronic component 1 and the IHS 8 and/or between the
IHS 8 and the heat sink 6 to increase reliability.
[0051] Referring to FIG. 17, there is shown a simplified example of
the first TIM 9 in the form of a phase change material, a thermally
conductive gel, a thermally conductive tape, or a thermal grease
that comprises a polymeric matrix 12 filled with a thermally
conductive filler 11 between the IHS 8 and the electronic component
1 in accordance with an embodiment of the present disclosure. The
conductive filler 11 may include indium, indium alloys, gallium,
gallium-indium alloy, gallium-indium-tin alloy,
gallium-indium-tin-zinc alloy, cadmium, cadmium alloys, indium-lead
alloy, indium-lead-silver alloy, mercury, mercury alloys,
bismuth-tin alloy, and indium-tin-bismuth alloy. The compositions
described herein may improve oxidation properties and reduce
reactivity of the thermally conductive filler 11.
[0052] Referring to FIG. 18, there is shown an example wherein the
first TIM 9 is a PSH where a thermally conductive filler 13 stays
as a liquid at service temperature and the polymeric matrix 12
gives mechanical adhesion between the IHS 8 and the electronic
component 1 in accordance with an embodiment of the present
disclosure. The thermally conductive filler 13 may include indium,
gallium, gallium-indium alloy, gallium-indium-tin alloy,
gallium-indium-tin-zinc alloy, cadmium, cadmium alloys, indium-lead
alloy, indium-lead-silver alloy, mercury, mercury alloys,
bismuth-tin alloy, and indium-tin-bismuth alloy. The compositions
described herein may improve oxidation properties and reduce
reactivity of the thermally conductive filler 13.
[0053] Referring to FIG. 19, there is shown an example wherein TIM
material 15 may be placed directly between the IHS 8 and the
electronic component 1 without the polymeric matrix 12 in
accordance with an embodiment of the present disclosure. The TIM
material 15 may be liquid metal such as gallium or low melting
point metals or alloys. A confiner 14 may be used to prevent the
TIM material 15 in liquid form from leaking out from between the
IHS 8 and the electronic component 1. The compositions described
herein may improve oxidation properties and reduce reactivity of
the TIM material 15.
[0054] The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are intended to fall within the scope of the present
disclosure. Further, although the present disclosure has been
described herein in the context of a particular implementation in a
particular environment for a particular purpose, those of ordinary
skill in the art will recognize that its usefulness is not limited
thereto and that the present disclosure may be beneficially
implemented in any number of environments for any number of
purposes. Accordingly, the claims set forth below should be
construed in view of the full breadth and spirit of the present
disclosure as described herein.
* * * * *