US5162257A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Solder bump fabrication method
Assignee: Amkor Technology Singapore Holding Pte Ltd
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Filing: 1991-09-13
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Granted: 1992-11-10
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Expires: 2011-09-13
Abstract
Abstract The base of solder bumps is preserved by converting the under-bump metallurgy between the solder bump and contact pad into an intermetallic of the solder and the solderable component of the under-bump metallurgy prior to etching the under-bump metallurgy. The intermetallic is resistant to etchants which are used to etch the under-bump metallurgy between the contact pads. Accordingly, minimal undercutting of the solder bumps is produced, and the base size is preserved. The solder may be plated on the under-bump metallurgy over the contact pad through a patterned solder dam layer having a solder accumulation region thereon. The solder dam is preferably a thin film layer which may be accurately aligned to the underlying contact pad to confine the wetting of the molten solder during reflow. Misalignment between the solder bump and contact pad is thereby reduced. The solder bumps so formed include an intermetallic layer which extends beyond the bump to form a lip around the base of the bump. This lip provides extra protection for the solder bump.
Inventors
- 👤 Edward K. Yung
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 11:53
CPC Classifications
H; H10; H10W; H10W72/00; H10W72/01; H10W72/012; H10W72/019; H05; H05K; H05K3/00; H05K3/30; H05K3/32; H05K3/34; H05K3/3452; H05K3/3465; H10W72/01251; H10W72/01255; H10W72/01257; H10W72/01261; H10W72/01951; H10W72/01953; H10W72/20; H10W72/231; H10W72/234; H10W72/241; H10W72/242; H10W72/251; H10W72/29; H10W72/90; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49117
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
173 words
A method of forming solder bumps on a plurality of contact pads on a substrate, comprising the steps of: forming an under-bump metallurgy on said contact pads and on said substrate between said contact pads; then forming solder dams on said under-bump metallurgy between said contact pads, said solder dams exposing said under-bump metallurgy over said contact pads; then forming solder accumulation regions on said solder dams, said solder accumulation regions exposing said under-bump metallurgy over said contact pads; then forming solder pads over said contact pads, on the under-bump metallurgy which is exposed by said solder dams and said solder accumulating regions; then; reflowing the solder pads to form solder bumps having an intermetallic layer of said under-bump metallurgy and said solder adjacent said contact pads; and then etching said solder dams and said under-bump metallurgy between said contact pads, with at least one etchant which etches said intermetallic layer more slowly than said solder dams and said under-bump metallurgy, to thereby reduce undercutting of said solder bumps adjacent said contact pads.
Claim 2
Independent Claim
173 words
A method of forming solder bumps on a plurality of contact pads on a substrate, comprising the steps of: forming an under-bump metallurgy on said contact pads and on said substrate between said contact pads; then forming solder dams on said under-bump metallurgy between said contact pads, said solder dams exposing said under-bump metallurgy over said contact pads; then forming solder accumulation regions on said solder dams, said solder accumulation regions exposing said under-bump metallurgy over said contact pads; then forming solder pads over said contact pads, on the under-bump metallurgy which is exposed by said solder dams and said solder accumulating regions; then; reflowing the solder pads to form solder bumps having an intermetallic layer of said under-bump metallurgy and said solder adjacent said contact pads; and then etching said solder dams and said under-bump metallurgy between said contact pads, with at least one etchant which etches said intermetallic layer more slowly than said solder dams and said under-bump metallurgy, to thereby reduce undercutting of said solder bumps adjacent said contact pads.
Claim 3
Dependent Claim
29 words
The method of claim 1 wherein said forming an under-bump metallurgy step is preceded by the step of forming a passivating layer on said substrate, between said contact pads.
Claim 4
Dependent Claim
48 words
The method of claim 1 wherein said forming an under-bump metallurgy step comprises the step of forming an under-bump metallurgy having a chromium layer adjacent said substrate and said contact pads, an intermediate chromium/copper phased layer on said chromium layer, and a copper layer on said chromium/copper layer.
Claim 5
Dependent Claim
43 words
The method of claim 1 wherein said forming solder dams step comprises the steps of: forming a thin film solder dam layer on said substrate, between and over said contact pads; and removing said thin film solder dam layer over said contact pads.
Claim 6
Dependent Claim
22 words
The method of claim 4 wherein said removing step comprises the step of lifting-off said solder dam layer over said contact pads.
Claim 7
Dependent Claim
36 words
The method of claim 1 wherein said solder depositing step comprises the step of plating solder over said contact pads, on the under-bump metallurgy which is exposed by said solder dams and said solder accumulation regions.
Claim 8
Dependent Claim
17 words
The method of claim 1 wherein said reflowing step comprises the step of melting said solder pads.
Claim 9
Dependent Claim
26 words
The method of claim 1 wherein said reflowing step further comprises the step of reflowing the solder pads to form a lip in said intermetallic layer.
Claim 10
Dependent Claim
42 words
The method of claim 1 wherein said solder comprises lead/tin solder, wherein said under-bump metallurgy includes copper, and wherein said reflowing step comprises the step of reflowing the solder pads to form solder bumps having an intermetallic layer of copper and tin.
Claim 11
Dependent Claim
37 words
The method of claim 1 wherein said forming solder accumulation regions step comprises the step of forming thick film solder accumulation regions on said solder dams, for containing said solder pads during said forming solder pads step.
Claim 12
Independent Claim
113 words
A method of forming solder bumps on a plurality of contact pads on a substrate, comprising the steps of: forming an under-bump metallurgy on said contact pads and on said substrate between said contact pads; then forming solder on the under-bump metallurgy over said contact pads, with the under-bump metallurgy between said contact pads being free of solder; then converting at least part of said under-bump metallurgy over said contact pads into an intermetallic layer of said under-bump metallurgy and said solder, by reflowing said solder; and then removing said under-bump metallurgy between said contact pads while preserving the intermetallic layer over said contact pads, to thereby reduce undercutting of the reflowed solder
Claim 13
Independent Claim
113 words
A method of forming solder bumps on a plurality of contact pads on a substrate, comprising the steps of: forming an under-bump metallurgy on said contact pads and on said substrate between said contact pads; then forming solder on the under-bump metallurgy over said contact pads, with the under-bump metallurgy between said contact pads being free of solder; then converting at least part of said under-bump metallurgy over said contact pads into an intermetallic layer of said under-bump metallurgy and said solder, by reflowing said solder; and then removing said under-bump metallurgy between said contact pads while preserving the intermetallic layer over said contact pads, to thereby reduce undercutting of the reflowed solder
Claim 14
Dependent Claim
29 words
The method of claim 11 wherein said forming an under-bump metallurgy step is preceded by the step of forming a passivating layer on said substrate, between said contact pads.
Claim 15
Dependent Claim
48 words
The method of claim 11 wherein said forming an under-bump metallurgy step comprises the step of forming an under-bump metallurgy having a chromium layer adjacent said substrate and said contact pads, an intermediate chromium/copper phased layer on said chromium layer, and a copper layer on said chromium/copper layer.
Claim 16
Dependent Claim
24 words
The method of claim 11 wherein said solder forming step comprises the step of plating solder on the under-bump metallurgy on said contact pads.
Claim 17
Dependent Claim
33 words
The method of claim 11 wherein said solder forming step comprises the step of forming solder on the under-bump metallurgy on said contact pads, while restricting formation of solder between said contact pads.
Claim 18
Dependent Claim
16 words
The method of claim 11 wherein said converting step comprises the step of melting said solder.
Claim 19
Dependent Claim
25 words
The method of claim 11 wherein said converting step further comprises the step of forming a lip in said intermetallic layer by reflowing said solder.
Claim 20
Dependent Claim
46 words
The method of claim 11 wherein said solder comprises lead/tin solder, wherein said under-bump metallurgy includes copper, and wherein said converting step comprises the step of converting at least part of said under-bump metallurgy over said contact pads into an intermetallic layer of copper and tin.
Claim 21
Dependent Claim
62 words
The method of claim 15 wherein said solder forming step comprises the steps of: forming solder accumulation regions on said under-bump metallurgy between said contact pads, said solder accumulation regions exposing said under-bump metallurgy over said contact pads; then forming solder on the under-bump metallurgy over said contact pads, with said solder accumulation region restricting formation of solder between said contact pads.
Claim 22
Dependent Claim
95 words
The method of claim 13 wherein said forming an under-bump metallurgy step further comprises the step of forming a second chromium layer on said copper layer; and wherein said solder forming step comprises the steps of: forming solder accumulation regions on said under-bump metallurgy between said contact pads, said solder accumulation regions exposing said under-bump metallurgy over said contact pads; then removing said second chromium layer over said contact pads; and then forming solder on said under-bump metallurgy over said contact pads, with said solder accumulative region restricting formation of solder between said contact pads.
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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) | 1995-11-10 | 1996-05-11 | 1996-11-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-11-10 | 2000-05-11 | 2000-11-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-11-10 | 2004-05-11 | 2004-11-10 | $7700.00 | Window Closed / Lapsed |