US4912545A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bonding of aligned conductive bumps on adjacent surfaces
Assignee: Nytell Software LLC
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Filing: 1987-09-16
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Granted: 1990-03-27
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Expires: 2007-09-16
Abstract
Abstract A bump bonding process and product are disclosed in which both pressure and heating are used in situations where the temperature should not exceed a predetermined amount, e.g., bonding of a photoconductor array to a module containing electronic processing devices. The bonding process involves eutectic alloying of indium and bismuth, allowing welding of the bumps at a temperature substantially below the two metals' melting points. In one version of the invention, bumps on adjacent substrates are directly aligned. In another version, each bump on one substrate is wedged between a pair of bumps on the other substrate.
Inventors
- 👤 Tiong C. Go
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:54
CPC Classifications
H; H10; H10W; H10W72/00; H10W72/20; H10W72/071; H10W72/072; H10W72/07221; H10W72/07227; H10W72/07231; H10W72/07236; H10W72/07251; H10W72/07254; H10W72/241; H10W72/244; H10W72/247; H10W72/248; H10W72/251; H10W72/252
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
143 words
For use in bonding electrically-conductive bumps on one planar surface to electrically-conductive bumps on another planar surface, where the surfaces are in proximity to elements which necessitate a predetermined temperature limit substantially lower than usual soldering temperatures, a method comprising: forming a plurality of bonding bumps on each planar surface, each pump including two alloying metals having a eutectic temperature which is (a) substantially below the melting point of either alloying metal, and (b) below the predetermined temperature limit; adjusting the surface levels to bring them into parallelism; aligning the respective bonding bumps on the two surfaces; exerting a pressure forcing the aligned bumps together; simultaneously heating the bumps to at least the eutectic temperature of the alloying metals, in order to facilitate conductive engagement of the aligned bumps; and limiting the maximum heating temperature to a level below the predetermined temperature limit.
Claim 2
Dependent Claim
143 words
For use in bonding electrically-conductive bumps on one planar surface to electrically-conductive bumps on another planar surface, where the surfaces are in proximity to elements which necessitate a predetermined temperature limit substantially lower than usual soldering temperatures, a method comprising: forming a plurality of bonding bumps on each planar surface, each pump including two alloying metals having a eutectic temperature which is (a) substantially below the melting point of either alloying metal, and (b) below the predetermined temperature limit; adjusting the surface levels to bring them into parallelism; aligning the respective bonding bumps on the two surfaces; exerting a pressure forcing the aligned bumps together; simultaneously heating the bumps to at least the eutectic temperature of the alloying metals, in order to facilitate conductive engagement of the aligned bumps; and limiting the maximum heating temperature to a level below the predetermined temperature limit.
Claim 3
Dependent Claim
34 words
The method of claim 1 in which: each bump comprises a pair of alloying metals whose eutectic temperature is below 80° C.; and the heating temperature is controlled to avoid exceeding approximately 80° C.
Claim 4
Dependent Claim
30 words
The method of claim 2 in which each bump comprises: a relatively high buildup of indium material; and a thin layer of a different metal on top of the indium.
Claim 5
Dependent Claim
17 words
The method of claim 3 in which the thin layer on top of the indium is bismuth.
Claim 6
Dependent Claim
53 words
The method of claim 1 in which the heating of the bumps is accomplished by: maintaining the bumps during bonding in a substantially enclosed area; and flowing an inert gas through the enclosed area, the gas having a controlled temperature, and being sufficiently heavy to prevent access of oxygen to the enclosed area.
Claim 7
Dependent Claim
56 words
The method of claim 2 in which the heating of the bumps is accomplished by: maintaining the bumps during bonding in a substantially enclosed area; and flowing an inert gas into the enclosed area, such gas being maintained at a temperature slightly higher than the eutectic alloying temperature of the pair of metals in the bumps.
Claim 8
Dependent Claim
46 words
The method of claim 4 in which the heating of the bumps is accomplished by: maintaining the bumps during bonding in a substantially enclosed area; and flowing an inert gas over the bumps, such gas being maintained at a temperature between 72° C. and 80° C.
Claim 9
Dependent Claim
91 words
An electrically-conducting bump bonded structure adjacent to elements which necessitate a predetermined temperature limit, said structure comprising: two planar surfaces, each having a plurality of metal bonding bumps facing the other surface and aligned with the bumps thereon; the bonding bumps each comprising a combination of eutectic alloying metals, which cause bonding of the aligned bumps by the alloying of such metals at their eutetic temperature; the eutectic temperature of the alloying metals being (a) substantially below the melting point of either allowing metal, and (b) below the predetermined temperature limit.
Claim 10
Dependent Claim
91 words
An electrically-conducting bump bonded structure adjacent to elements which necessitate a predetermined temperature limit, said structure comprising: two planar surfaces, each having a plurality of metal bonding bumps facing the other surface and aligned with the bumps thereon; the bonding bumps each comprising a combination of eutectic alloying metals, which cause bonding of the aligned bumps by the alloying of such metals at their eutetic temperature; the eutectic temperature of the alloying metals being (a) substantially below the melting point of either allowing metal, and (b) below the predetermined temperature limit.
Claim 11
Dependent Claim
58 words
The structure of claim 8 in which each bump comprises: a relatively large buildup of indium on the planar surface; and a thin layer of bismuth on top of the indium which alloys with the indium to produce an alloy bond having a depth determined by the eutectic ratio of the two metals and by their relative amounts.
Claim 12
Dependent Claim
47 words
The bump bonding method of claim 1 in which: a pair of bumps on one surface are aligned with a single bump on the other surface; and each single bump is wedged between its aligned pair of bumps during the pressure and heating which cause conductive engagement.
Claim 13
Dependent Claim
47 words
The bump bonding method of claim 2 in which: a pair of bumps on one surface are aligned with a single bump on the other surface; and each single bump is wedged between its aligned pair of bumps during the pressure and heating which cause conductive engagement.
Claim 14
Dependent Claim
47 words
The bump bonding method of claim 4 in which: a pair of bumps on one surface are aligned with a single bump on the other surface; and each single bump is wedged between its aligned pair of bumps during the pressure and heating which cause conductive engagement.
Claim 15
Dependent Claim
37 words
The electrically-conducting structure of claim 8 in which: the bonding bumps on one surface are provided in pairs; and each bonding bump on the other surface is wedged between a pair of bumps in the bonded structure.
Claim 16
Dependent Claim
37 words
The electrically-conducting structure of claim 9 in which: the bonding bumps on one surface are provided in pairs; and each bonding bump on the other surface is wedged between a pair of bumps in the bonded structure.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-03-26 | 1993-09-25 | 1994-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-03-26 | 1997-09-25 | 1998-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-03-26 | 2001-09-25 | 2002-03-27 | $7700.00 | Window Closed / Lapsed |