US5170930A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Liquid metal paste for thermal and electrical connections
Assignee: Rateze Remote Mgmt LLC
•
Filing: 1991-11-14
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Granted: 1992-12-15
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Expires: 2011-11-14
Abstract
Abstract A thermally and electrically conductive paste for making a detachable and compliant connection between two surfaces. The paste comprises an equilibrium mixture of an electrically conductive liquid metal and particulate solid constituents, wherein at the temperature of the paste during connection the proportions of liquid metal and particulate solid constituents remain between the ultimate liquidus and the ultimate solidus of the phase diagram of the mixture and the paste remains non-solidified. in cryogenic and low temperature environments the paste forms a hardened bond with a TCE matched to a contacted surface.
Inventors
- 👤 Thomas P. Dolbear
- 👤 Colin A. MacKay
- 👤 Richard D. Nelson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 23:49
CPC Classifications
H; H05; H05K; H05K3/00; H05K3/30; H05K3/32; H05K3/34; H05K3/346; H01; H01B; H01B1/00; H01B1/02; H01B1/14; H01B1/16; H01R; H01R13/00; H01R13/02; H01R13/03; H01R4/00; H01R4/58; H10; H10W; H10W20/00; H10W20/40; H10W72/00; H05K3/3465; H05K3/3485; H10W72/01; H10W72/015; H10W72/01515; H10W72/071; H10W72/072; H10W72/07251; H10W72/073; H10W72/07331; H10W72/07336; H10W72/075; H10W72/20; H10W72/30; H10W72/321; H10W72/325; H10W72/351; H10W72/352; H10W72/851; H10W72/874; H10W72/884; H10W74/00; H10W74/10; H10W74/15; H10W90/00; H10W90/701; H10W90/721; H10W90/724; H10W90/731; H10W90/734
Claims Analysis
Total Claims: 59
Claim 1
Independent Claim
77 words
A method of making an electrically conductive detachable connection between two surfaces, comprising: releasably connecting the two surfaces together with a non-solidified paste comprised of an equilibrium mixture of an electrically conductive liquid metal and particulate solid constituents, wherein at the temperature of the paste during connection the proportions of liquid metal and particulate solid constituents remain between the ultimate liquidus and the ultimate solidus of the phase diagram of the mixture and the paste remains non-solidified.
Claim 2
Independent Claim
77 words
A method of making an electrically conductive detachable connection between two surfaces, comprising: releasably connecting the two surfaces together with a non-solidified paste comprised of an equilibrium mixture of an electrically conductive liquid metal and particulate solid constituents, wherein at the temperature of the paste during connection the proportions of liquid metal and particulate solid constituents remain between the ultimate liquidus and the ultimate solidus of the phase diagram of the mixture and the paste remains non-solidified.
Claim 3
Dependent Claim
19 words
The method of claim 1 wherein the liquid metal is selected from the group consisting of gallium and mercury.
Claim 4
Dependent Claim
13 words
The method of claim 1 wherein the liquid metal is a gallium alloy.
Claim 5
Dependent Claim
23 words
The method of claim 3 wherein the gallium alloy further comprises a material selected from the group consisting of bismuth, cadmium, and zinc.
Claim 6
Dependent Claim
29 words
The method of claim 1, further comprising alloying a material to the liquid metal in order to enhance the wetting of the particulate solid constituents by the liquid metal.
Claim 7
Dependent Claim
19 words
The method of claim 5 wherein the material is selected from the group consisting of nickel, silver, and antimony.
Claim 8
Dependent Claim
25 words
The method of claim 1, further comprising alloying a material to the liquid metal in order to lower the melting point of the liquid metal.
Claim 9
Dependent Claim
15 words
The method of claim 1 wherein the particulate solid constituents are a metal alloy powder.
Claim 10
Dependent Claim
52 words
The method of claim 1 wherein the particulate solid constituents are selected from the group consisting of alumina, aluminum, aluminum nitride, antimony, boron nitride, cobalt, chromium, cotton fibers, diamond, germanium, glass beads, gold, graphite, iron, lead, magnesium, manganese, molybdenum, platinum, silicon, silicon carbide, silver, tantalum, thallium, tin, titanium, tungsten, vanadium, and zinc.
Claim 11
Dependent Claim
23 words
The method of claim 1 wherein the particulate solid constituents are wet with the liquid metal but do not form reaction compounds therewith.
Claim 12
Dependent Claim
21 words
The method of claim 1 wherein the particulate solid constituents are wet with the liquid metal but do not dissolve therein.
Claim 13
Dependent Claim
45 words
The method of claim 1 wherein the particulate solid constituents are elongate and have a longitudinal axis oriented parallel to the plane of at least one of the surfaces in contact with the paste in order to enhance the thermal spreading capability of the paste.
Claim 14
Dependent Claim
22 words
The method of claim 1 wherein the particulate solid constituents are coated with a material that will wet with the liquid metal.
Claim 15
Dependent Claim
19 words
The method of claim 13 wherein the material is selected from the group consisting of nickel, silver, and antimony.
Claim 16
Dependent Claim
30 words
The method of claim 1 wherein the particulate solid constituents are encapsulated by a gas entrapped around each particle during the mixing with the liquid metal to create the paste.
Claim 17
Dependent Claim
19 words
The method of claim 1 wherein the particulate solid constituents are at least partially soluble in the liquid metal.
Claim 18
Dependent Claim
31 words
The method of claim 1 wherein the liquid metal and the particulate solid constituents do not produce a reaction compound and the particulate solid constituents are soluble in the liquid metal.
Claim 19
Dependent Claim
24 words
The method of claim 1 wherein the liquid metal and particulate solid constituents react to form a compound layer on the particulate solid constituents.
Claim 20
Dependent Claim
18 words
The method of claim 1 wherein the liquid metal is gallium and the particulate solid constituents are aluminum.
Claim 21
Dependent Claim
18 words
The method of claim 19 wherein the aluminum comprises 30% to 60% loading by volume of the paste.
Claim 22
Dependent Claim
18 words
The method of claim 1 wherein the liquid metal is gallium and the particulate solid constituents are tungsten.
Claim 23
Dependent Claim
18 words
The method of claim 21 wherein the tungsten comprises 30% to 60% loading by volume of the paste.
Claim 24
Dependent Claim
19 words
The method of claim 1 wherein the mixture has a viscosity in the range of 20,000 to 200,000 centipoise.
Claim 25
Dependent Claim
16 words
The method of claim 1 wherein the thickness of the paste connection is approximately 1-80 mils.
Claim 26
Dependent Claim
17 words
The method of claim 1 wherein the particulate solid constituents enhance the electrical conductivity of the paste.
Claim 27
Dependent Claim
17 words
The method of claim 1 wherein the particulate solid constituents enhance the thermal conductivity of the paste.
Claim 28
Dependent Claim
19 words
The method of claim 1 wherein the particulate solid constituents enhance the electrical and thermal conductivity of the paste.
Claim 29
Dependent Claim
21 words
The method of claim 1, further comprising adding additional solids to the paste to enhance the thermal conductivity of the paste.
Claim 30
Dependent Claim
19 words
The method of claim 28 wherein the thermal resistance of the paste is less than 0.1 K-cm 2 /W.
Claim 31
Dependent Claim
21 words
The method of claim 1, further comprising adding additional solids to the paste to enhance the electrical conductivity of the paste.
Claim 32
Dependent Claim
34 words
The method of claim 1, further comprising, after said releasably connecting step cooling the paste below the temperature of the ultimate solidus, thereby hardening the paste and providing a solid bond between the surfaces.
Claim 33
Dependent Claim
23 words
The method of claim 31, further comprising alloying the liquid metal before hardening the paste to decrease the temperature of the ultimate soldius.
Claim 34
Dependent Claim
17 words
The method of claim 31 wherein the hardened paste is cooled to a temperature below 30° C.
Claim 35
Dependent Claim
17 words
The method of claim 33 wherein the hardened paste is cooled to a temperature below 5° C.
Claim 36
Dependent Claim
17 words
The method of claim 34 wherein the hardened paste also provides an adhesive bond between the surfaces.
Claim 37
Dependent Claim
30 words
The method of claim 31, further comprising heating the hardened paste above the temperature of the ultimate solidus, thereby providing a compliant detachable bond of non-solidified paste between the surfaces.
Claim 38
Dependent Claim
37 words
The method of claim 31, further comprising adding additional solids to the paste before hardening the paste to more closely match the thermal coefficient of expansion of the hardened paste with at least one of the surfaces.
Claim 39
Dependent Claim
38 words
The method of claim 31, further comprising adding additional solids to the paste before hardening the paste to lower the elastic modulii of the hardened paste and thereby reduce the stress on at least one of the surfaces.
Claim 40
Dependent Claim
28 words
The method of claim 1 wherein at least one surface is a protective coating on a third surface to prevent the third surface from exposure to the paste.
Claim 41
Dependent Claim
11 words
The method of claim 39 wherein the liquid metal is gallium.
Claim 42
Dependent Claim
24 words
The method of claim 39 wherein the protective coating is selected from the group consisting of alumina, aluminum nitride, nickel, tungsten, tantalum and molybdenum.
Claim 43
Dependent Claim
37 words
The method of claim 39 wherein the protective coating is a metal that can yield a refractory oxide, and further comprising oxidizing the metal to form a continuous refractory oxide layer on said at least one surface.
Claim 44
Dependent Claim
24 words
The method of claim 42 wherein the metal is selected from the group consisting of nickel, chromium, titanium, tantalum, yttrium, scandium, zirconium, and niobium.
Claim 45
Dependent Claim
11 words
The method of claim 39 wherein said third surface is copper.
Claim 46
Dependent Claim
11 words
The method of claim 39 wherein said third surface is aluminum.
Claim 47
Dependent Claim
12 words
The method of claim 45 wherein the protective coating is anodized aluminum.
Claim 48
Dependent Claim
23 words
The method of claim 39 wherein the protective coating is electrically resistive and prevents the paste from electrically connecting to the third surface.
Claim 49
Dependent Claim
36 words
The method of claim 39 wherein the surface releasably connected to the protective coating by the paste is a second protective coating on a fourth surface to prevent the fourth surface from exposure to the paste.
Claim 50
Dependent Claim
18 words
The method of claim 39 wherein the protective coating is the same material as the particulate solid constituents.
Claim 51
Dependent Claim
27 words
The method of claim 39 wherein the paste contains gallium, said third one surface contains copper or aluminum, and the protective coating maintains a reliable interface therebetween.
Claim 52
Dependent Claim
20 words
The method of claim 1 wherein one surface is an integrated circuit chip and the other surface is a substrate.
Claim 53
Dependent Claim
26 words
The method of claim 1 wherein one surface is the outer end of a tape automated bonding lead and the other surface is a bonding pad.
Claim 54
Dependent Claim
21 words
The method of claim 1 wherein one surface is an integrated circuit chip and the other surface is a heat sink.
Claim 55
Dependent Claim
65 words
The method of claim 1, wherein one surface comprises a support frame with openings, a plurality integrated circuit chips closely positioned within the openings, and a removable sealant in the space in the openings between the chips and the support frame so as to form a sealed surface which prevents the paste deposited thereon from migrating therebeneath, and the other surface is a heat sink.
Claim 56
Dependent Claim
16 words
The method of claim 54 wherein the sealed surface and the paste form a hermetic seal.
Claim 57
Dependent Claim
35 words
The method of claim 54, further comprising depositing a first paste on the sealed surface, a foil on the first paste, a second paste on the foil, and the heat sink on the second paste.
Claim 58
Dependent Claim
17 words
The method of claim 56 wherein the second paste is easier to detach than the first paste.
Claim 59
Dependent Claim
45 words
The method of claim 56 wherein the second paste has a lower ultimate solidus than the first paste, and further comprising, after said releasably connecting step and said depositing step, cooling the pastes so that the first paste solidifies but the second paste remains non-solidified.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-12-15 | 1996-06-15 | 1996-12-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-12-15 | 2000-06-15 | 2000-12-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-12-15 | 2004-06-15 | 2004-12-15 | $7700.00 | Window Closed / Lapsed |