US4582240A
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US
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Method for low temperature, low pressure metallic diffusion bonding of piezoelectric components
Assignee: Northrop Grumman Corp
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Filing: 1984-02-08
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Granted: 1986-04-15
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Expires: 2004-02-08
Abstract
Abstract A method for intermetallic diffusion bonding of piezoelectric components, wherein ceramic pieces with fired-on silver electrodes are stacked with a thin shim of solid indium alloy therebetween. The indium alloy preferably comprises 25% indium, 37.5% lead and 37.5% tin. The stack is placed under 150 psi compression and heated at a temperature of about 350 DEG for 30-48 hours in an inert gas. Almost immediately upon being heated, a liquid-solid diffusion takes place in which a small amount of the silver diffuses from the electrodes into the now liquid indium alloy. The alloy in the interface becomes saturated with silver producing a new quaternary alloy which has a higher melting point than the previous indium alloy shim. Thus, there is a gradual solidification of the alloy as the concentration of silver increases. After solidification of the new alloy during the remainder of the heating time, there is a gradual diffusion of the indium into the silver and vice versa. The bi-directional solid-solid diffusion of the indium and silver gives the bond a strength higher than known in the prior art.
Inventors
- 👤 Andrew A. Lux
- 👤 Gerald D. Schindler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 18:59
CPC Classifications
B; B23; B23K; B23K35/00; B23K35/22; B23K35/24; B23K35/26; B23K20/00; B23K20/22; B23K20/233; H; H10; H10N; H10N30/00; H10N30/01; H10N30/05; H10N30/057; H10N30/07; H10N30/072; H10N30/073
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
200 words
A method of diffusion bonding first and second mating components, comprising the steps of: (a) applying a noble metal to each of the first and the second components to form mating surfaces; (b) positioning a first layer of an alloy consisting essentially of indium, tin and lead between the noble metal mating surfaces of the first and second components to form a stack, while the surrounding temperature is a first temperature less than the liquidus point of the alloy thereby liquifying a small portion of the indium, tin and lead which dissolves a small amount of the noble metal after which the mixture of indium, tin, lead and noble metal alloy solidifies in intimate contact with the undissolved noble metal to provide a diffusion pathway between the solidified indium, tin, lead and noble metal alloy and the remaining noble metal layers; and (c) applying pressure to the stack so formed and while maintaining the pressure, increasing the temperature to a second temperature for a period of time sufficient to allow a diffusion bond to form such that the diffusion bond tensile strength is at least as great as the tensile strength of either of the first and the second components.
Claim 2
Independent Claim
200 words
A method of diffusion bonding first and second mating components, comprising the steps of: (a) applying a noble metal to each of the first and the second components to form mating surfaces; (b) positioning a first layer of an alloy consisting essentially of indium, tin and lead between the noble metal mating surfaces of the first and second components to form a stack, while the surrounding temperature is a first temperature less than the liquidus point of the alloy thereby liquifying a small portion of the indium, tin and lead which dissolves a small amount of the noble metal after which the mixture of indium, tin, lead and noble metal alloy solidifies in intimate contact with the undissolved noble metal to provide a diffusion pathway between the solidified indium, tin, lead and noble metal alloy and the remaining noble metal layers; and (c) applying pressure to the stack so formed and while maintaining the pressure, increasing the temperature to a second temperature for a period of time sufficient to allow a diffusion bond to form such that the diffusion bond tensile strength is at least as great as the tensile strength of either of the first and the second components.
Claim 3
Dependent Claim
21 words
The method as recited in claim 1, wherein the indium in the alloy is in the range of 12-80 composition %.
Claim 4
Dependent Claim
21 words
The method as recited in claim 2, wherein the lead in the alloy is in the range of 15-50 composition %.
Claim 5
Dependent Claim
21 words
The method as recited in claim 3, wherein the tin in the alloy is in the range of 37-70 composition %.
Claim 6
Dependent Claim
18 words
The method as recited in claim 1, wherein the alloy comprises 25% indium, 37.5% lead and 37.5% tin.
Claim 7
Dependent Claim
15 words
The method as recited in claim 5, wherein the second temperature is approximately 350° F.
Claim 8
Dependent Claim
14 words
The method as recited in claim 6, wherein the pressure is approximately 150 psi.
Claim 9
Dependent Claim
19 words
The method as recited in claim 7, wherein the period of time is in the range of 6-72 hours.
Claim 10
Dependent Claim
16 words
The method as recited in claim 7, wherein the period of time is approximately 30-48 hours.
Claim 11
Dependent Claim
16 words
The method as recited in claim 9, wherein the first and second components are ceramic material.
Claim 12
Independent Claim
171 words
A method of diffusion bonding first and second mating components, comprising the steps of: (a) applying a silver electrode to each of the first and second components to form mating surfaces; (b) positioning a first and a second layer of an alloy consisting essentially of indium, lead and tin between the silver electrode mating surfaces of the first and second components to form a stack and positioning a silver electrode lead with a solder tab between the first and second layers of alloy, while the surrounding temperature is a first temperature less than the liquidus point of the alloy; and (c) applying pressure to the stack so formed and while maintaining the pressure, increasing the temperature to a second temperature for a period of time sufficient to allow (i) the alloy to partially melt, (ii) a portion of the silver from the electrodes to diffuse into the alloy, (iii) the alloy to solidify, (iv) the indium gradually to diffuse into the silver, (v) the silver gradually to diffuse into the indium.
Claim 13
Independent Claim
171 words
A method of diffusion bonding first and second mating components, comprising the steps of: (a) applying a silver electrode to each of the first and second components to form mating surfaces; (b) positioning a first and a second layer of an alloy consisting essentially of indium, lead and tin between the silver electrode mating surfaces of the first and second components to form a stack and positioning a silver electrode lead with a solder tab between the first and second layers of alloy, while the surrounding temperature is a first temperature less than the liquidus point of the alloy; and (c) applying pressure to the stack so formed and while maintaining the pressure, increasing the temperature to a second temperature for a period of time sufficient to allow (i) the alloy to partially melt, (ii) a portion of the silver from the electrodes to diffuse into the alloy, (iii) the alloy to solidify, (iv) the indium gradually to diffuse into the silver, (v) the silver gradually to diffuse into the indium.
Claim 14
Dependent Claim
21 words
The method as recited in claim 11, wherein the indium in the alloy is in the range of 12-80 composition %.
Claim 15
Dependent Claim
21 words
The method as recited in claim 12, wherein the lead in the alloy is in the range of 15-50 composition %.
Claim 16
Dependent Claim
21 words
The method as recited in claim 13, wherein the tin in the alloy is in the range of 37-70 composition %.
Claim 17
Dependent Claim
18 words
The method as recited in claim 11, wherein the alloy comprises 25% indium, 37.5% lead and 37.5% tin.
Claim 18
Dependent Claim
15 words
The method as recited in claim 15, wherein the second temperature is approximately 350° F.
Claim 19
Dependent Claim
14 words
The method as recited in claim 16, wherein the pressure is approximately 150 psi.
Claim 20
Dependent Claim
19 words
The method as recited in claim 17, wherein the period of time is in the range of 6-72 hours.
Claim 21
Dependent Claim
16 words
The method as recited in claim 17, wherein the period of time is approximately 30-48 hours.
Claim 22
Dependent Claim
16 words
The method as recited in claim 19, wherein the first and second components are ceramic material.
Claim 23
Independent Claim
187 words
A method of diffusion bonding first and second ceramics, comprising the steps of: (a) applying a silver electrode to each of a first and a second ceramics to form mating surfaces; (b) positioning a first and a second layer of alloy, each layer consisting essentially of 25% indium, 37.5% tin and 37.5% lead, between the silver electrode mating surfaces of the first and the second ceramics, and positioning a silver electrode lead with a solder tab between the first and the second layers of alloy to form a stack, while the surrounding temperature is a first temperature less than the liquidus point of the alloy; and (c) applying a pressure of approximately 150 psi to the stack so formed, and while maintaining this pressure, increasing the temperature to a second temperature of approximately 350° F. for a period of 30-48 hours to allow (i) the alloy to partially melt, (ii) a portion of the silver from the electrodes to diffuse into the alloy, (iii) the alloy to solidify, (iv) the indium gradually to diffuse into the silver, and (v) the silver gradually to diffuse into the indium.
Claim 24
Independent Claim
187 words
A method of diffusion bonding first and second ceramics, comprising the steps of: (a) applying a silver electrode to each of a first and a second ceramics to form mating surfaces; (b) positioning a first and a second layer of alloy, each layer consisting essentially of 25% indium, 37.5% tin and 37.5% lead, between the silver electrode mating surfaces of the first and the second ceramics, and positioning a silver electrode lead with a solder tab between the first and the second layers of alloy to form a stack, while the surrounding temperature is a first temperature less than the liquidus point of the alloy; and (c) applying a pressure of approximately 150 psi to the stack so formed, and while maintaining this pressure, increasing the temperature to a second temperature of approximately 350° F. for a period of 30-48 hours to allow (i) the alloy to partially melt, (ii) a portion of the silver from the electrodes to diffuse into the alloy, (iii) the alloy to solidify, (iv) the indium gradually to diffuse into the silver, and (v) the silver gradually to diffuse into the indium.
Claim 25
Dependent Claim
21 words
The method as recited in claim 21, wherein the resulting tensile strength of the alloy after 48 hours is 5260 psi.
Claim 26
Independent Claim
173 words
A method of diffusion bonding a pair of ceramic resonators coded with a noble metal, comprising the steps of: fabricating an alloy shim of indium, tin and lead, said alloy shim having a preselected melting point; contacting one of said ceramic resonators at its noble metal face with a first side of said alloy shim; contacting the other of said ceramic resonators at its noble metal face with a second side of said alloy shim; heating said alloy shim to a temperature less than said preselected melting point but sufficiently high enough to soften said alloy shim; causing a small amount of said noble metal to be dissolved in said softened alloy whereby the melting point of said softened alloy is raised and said alloy resolidifies; and applying pressure to said ceramic resonators while maintaining them at an elevated temperature, said elevated temperature being substantially below said melting point so that said tin, indium and lead alloy diffuses into said noble metal producing a strong highly elastic mechanical bond between said ceramic resonators.
Claim 27
Independent Claim
173 words
A method of diffusion bonding a pair of ceramic resonators coded with a noble metal, comprising the steps of: fabricating an alloy shim of indium, tin and lead, said alloy shim having a preselected melting point; contacting one of said ceramic resonators at its noble metal face with a first side of said alloy shim; contacting the other of said ceramic resonators at its noble metal face with a second side of said alloy shim; heating said alloy shim to a temperature less than said preselected melting point but sufficiently high enough to soften said alloy shim; causing a small amount of said noble metal to be dissolved in said softened alloy whereby the melting point of said softened alloy is raised and said alloy resolidifies; and applying pressure to said ceramic resonators while maintaining them at an elevated temperature, said elevated temperature being substantially below said melting point so that said tin, indium and lead alloy diffuses into said noble metal producing a strong highly elastic mechanical bond between said ceramic resonators.
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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) | 1989-04-14 | 1989-10-14 | 1990-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-04-14 | 1993-10-14 | 1994-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-04-14 | 1997-10-14 | 1998-04-15 | $7700.00 | Window Closed / Lapsed |