EP0603296B1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Solder bump fabrication method and solder bumps formed thereby
Assignee: MCNC Research and Development Institute
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Filing: 1992-09-11
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Granted: 1997-08-13
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Expires: 2012-09-11
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
EP
Data Source
google_patents
Last Synchronized
2026-11-01 23:37
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: 17
Claim 1
Independent Claim
332 words
A method of forming solder bumps ( 24 ) on a plurality of contact pads ( 12 ) on a substrate ( 10 ), comprising the steps of: forming an under-bump metallurgy ( 16 ) on said contact pads ( 12 ) and on said substrate ( 10 ) between said contact pads ( 12 ); then forming thick film solder retaining walls ( 28 ) on said substrate ( 10 ) between said contact pads ( 12 ), said solder retaining walls ( 28 ) exposing said under-bump metallurgy ( 16 ) over said contact pads ( 12 ) then forming solder pads ( 20 ) over said contact pads ( 12 ), on the under-bump metallurgy ( 16 ) which is exposed by said solder retaining walls ( 28 ); then reflowing the solder pads ( 20 ) to form solder bumps ( 24 ) having an intermetallic layer ( 22 ) of said under-bump metallurgy ( 16 ) extending adjacent to said contact pads ( 12 ); and then etching said under-bump metallurgy ( 16 ) between said contact pads ( 12 ); the method being characterized by: adding the step of forming thin film solder dams ( 18 ) on said under-bump metallurgy ( 16 ) between said contact pads ( 12 ) prior to the step of forming solder retaining walls, said solder dams ( 18 ) exposing said under-bump metallurgy ( 16 ) over said contact pads ( 12 ) and said retaining walls ( 28 ) being formed on said solder dams ( 18 ); and replacing said etching step with the step of etching said solder dams ( 18 ) and said under-bump metallurgy ( 16 ) between said contact pads, with at least one etchant which etches said intermetallic layer ( 22 ) more slowly than said solder dams ( 18 ) and said under-bump metallurgy ( 16 ), to said solder bumps ( 24 ) adjacent said contact pads ( 12 ).
Claim 2
Dependent Claim
32 words
The method of claim 1 wherein said forming an under-bump metallurgy step is preceded by the step of forming a passivating layer ( 14 ) on said substrate, between said contact pads.
Claim 3
Dependent Claim
57 words
The method of claim 1 wherein said forming an under-bump metallurgy step comprises the step of forming an under-bump metallurgy ( 16 ) having a chromium layer adjacent said substrate ( 10 ) and said contact pads ( 12 ), an intermediate chromium/copper phased layer on said chromium layer, and a copper layer on said chromium/copper layer.
Claim 4
Dependent Claim
60 words
The method of claim 1 wherein said forming thin film solder dams step comprises the steps of: forming a thin film solder dam layer ( 18 ) on said substrate ( 10 ), between and over said contact pads ( 12 ); and removing said thin film solder dam layer ( 18 ) over said contact pads ( 12 ).
Claim 5
Dependent Claim
28 words
The method of claim 4 wherein said removing step comprises the step of lifting-off said solder dam layer ( 18 ) over said contact pads ( 12 ).
Claim 6
Dependent Claim
51 words
The method of claim 1 wherein said solder depositing step comprises the step of plating solder ( 20 ) over said contact pads ( 12 ), on the under-bump metallurgy ( 16 ) which is exposed by said solder dams ( 18 ) and said solder retaining walls ( 28 ).
Claim 7
Dependent Claim
20 words
The method of claim 1 wherein said reflowing step comprises the step of melting said solder pads ( 20 ).
Claim 8
Dependent Claim
35 words
The method of claim 1 wherein said reflowing step further comprises the step of reflowing the solder pads ( 20 ) to form a lip ( 26 ) in said intermetallic layer ( 22 ).
Claim 9
Dependent Claim
60 words
The method of claim 1 wherein said solder ( 20 ), ( 24 ) comprises lead/tin solder, wherein said under-bump metallurgy ( 16 ) includes copper, and wherein said reflowing step comprises the step of reflowing the solder pads ( 20 ) to form solder bumps ( 24 ) having an intermetallic layer ( 22 ) of copper and tin.
Claim 10
Dependent Claim
34 words
The method of claim 1 wherein said forming solder pads step comprises the step of plating solder ( 20 ) on the under-bump metallurgy ( 16 ) on said contact pads ( 12 ).
Claim 11
Dependent Claim
46 words
The method of claim 1 wherein said forming solder pads step comprises the step of forming solder ( 20 ) on the under-bump metallurgy ( 16 ) on said contact pads ( 12 ), while restricting formation of solder between said contact pads ( 12 ).
Claim 12
Dependent Claim
29 words
The method of claim 1 wherein said reflowing step further comprises the step of forming a lip ( 26 ) in said intermetallic layer ( 22 ) during reflow.
Claim 13
Dependent Claim
96 words
The method of claim 11 wherein said forming solder pads step comprises the steps of: forming solder retaining walls ( 28 ) on said under-bump metallurgy ( 16 ) between said contact pads ( 12 ), said solder retaining walls ( 28 ) exposing said under-bump metallurgy ( 16 ) over said contact pads ( 12 ); then forming solder ( 20 ) on the under-bump metallurgy over said contact pads ( 12 ), with said solder retaining walls ( 28 ) restricting formation of solder ( 20 ) between said contact pads ( 12 ).
Claim 14
Dependent Claim
135 words
The method of claim 3 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 forming solder pads step comprises the steps of: forming solder retaining walls ( 28 ) on said under-bump metallurgy ( 16 ) between said contact pads ( 12 ), said solder retaining walls ( 28 ) exposing said under-bump metallurgy ( 16 ) over said contact pads ( 12 ); then removing said second chromium layer over said contact pads ( 12 ); and then forming solder ( 20 ) on said under-bump metallurgy ( 16 ) over said contact pads ( 12 ), with said solder retaining walls ( 28 ) restricting formation of solder ( 20 ) between said contact pads ( 12 ).
Claim 15
Dependent Claim
96 words
An interconnection system for a microelectronic substrate ( 10 ) comprising: a plurality of contact pads ( 12 ) on said substrate ( 10 ); a spheroidal solder bump ( 24 ) on each of said contact pads ( 12 ) having a base on said contact pad ( 12 ); and a circular lip ( 26 ) on said spheroidal solder bump ( 24 ) at the base thereof, extending outwardly from said solder bump ( 24 ) over the associated contact pad ( 12 ), to thereby protect the contact pad ( 12 ).
Claim 16
Dependent Claim
34 words
The interconnection system of claim 15 wherein said spheroidal solder bump ( 24 ) is a spheroidal lead-tin solder bump and wherein said circular lip ( 26 ) is a copper/tin intermetallic circular lip.
Claim 17
Dependent Claim
25 words
The interconnection system of claim 15 wherein said circular lip ( 26 ) extends outwardly a few microns from said solder bump ( 24 ).
References Cited (Backward Citations)
No citation records indexed.
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