US5803340A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Composite solder paste for flip chip bumping
Assignee: FlipChip International LLC
•
Filing: 1995-09-29
•
Granted: 1998-09-08
•
Expires: 2015-09-29
Abstract
Abstract Composite solder paste compositions adapted to be deposited using a dry film photoresist mask to form solder joints for flip chip integrated circuit devices. The composite solder paste compositions are characterized by the ability to flow at a first temperature during bumping reflow while the photoresist mask is present, yet upon subsequently reheating to a higher temperature yield solder joints capable of withstanding temperatures of 200° C. and higher. As such, the present invention retains the advantages associated with using a dry film photoresist as a mask during deposition of the solder, yet results in the formation of solder joints that exhibit enhanced reliability in severe thermal environments.
Inventors
- 👤 Shing Yeh
- 👤 Bradley Howard Carter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 15:21
CPC Classifications
H; H10; H10W; H10W72/00; H10W72/20; B; B23; B23K; B23K35/00; B23K35/02; B23K35/0222; B23K35/0244; B23K35/025; B23K35/22; B23K35/24; B23K35/26; B23K35/268; H05; H05K; H05K3/00; H05K3/30; H05K3/32; H05K3/34; H05K3/3465; H05K3/3485; H05K2201/00; H05K2201/02; H05K2201/0203; H05K2201/0263; H05K2201/0272; H05K2203/00; H05K2203/04; H05K2203/043; H05K2203/05; H05K2203/0562; H05K2203/0568; H05K2203/07; H05K2203/0756; H05K2203/0769; H05K3/346; H10W72/251
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
116 words
A solder paste composition comprising multiple solder paste constituents, a first solder paste constituent of the multiple solder paste constituents having lower liquidus and solidus temperatures than a second solder paste constituent of the multiple solder paste constituents, wherein the first solder paste constituent establishes a bumping reflow temperature at which the solder paste composition flows without liquefying all of the multiple solder paste constituents, and wherein a chip mount reflow temperature is established that is higher than the bumping reflow temperature and at which all of the multiple solder paste constituents liquefy in a manner that yields a solder having a homogenous alloy composition, the first and second solder paste constituents comprising indium-lead alloy powders.
Claim 2
Dependent Claim
116 words
A solder paste composition comprising multiple solder paste constituents, a first solder paste constituent of the multiple solder paste constituents having lower liquidus and solidus temperatures than a second solder paste constituent of the multiple solder paste constituents, wherein the first solder paste constituent establishes a bumping reflow temperature at which the solder paste composition flows without liquefying all of the multiple solder paste constituents, and wherein a chip mount reflow temperature is established that is higher than the bumping reflow temperature and at which all of the multiple solder paste constituents liquefy in a manner that yields a solder having a homogenous alloy composition, the first and second solder paste constituents comprising indium-lead alloy powders.
Claim 3
Dependent Claim
50 words
A solder paste composition as recited in claim 1 wherein the lead content of the second solder paste constituent is higher than the lead content of the first solder paste constituent such that the second solder paste constituent has higher liquidus and solidus temperatures than the first solder paste constituent.
Claim 4
Dependent Claim
26 words
A solder paste composition as recited in claim 2 wherein the lead content of the first solder paste constituent is at most about sixty weight percent.
Claim 5
Dependent Claim
26 words
A solder paste composition as recited in claim 2 wherein the lead content of the second solder paste constituent is at least about ninety weight percent.
Claim 6
Dependent Claim
82 words
A solder paste composition as recited in claim 1 wherein the first solder paste constituent comprises about 40 to about 50 weight percent indium and about 50 to about 60 weight percent lead, the second solder paste constituent comprises up to about 2.5 weight percent silver, about 2.5 to about 5 weight percent indium and about 92.5 to about 97.5 weight percent lead, and the first and second solder paste compositions are combined at a ratio of about 40:60 to about 50:50.
Claim 7
Dependent Claim
32 words
A solder paste composition as recited in claim 1 wherein the bumping reflow temperature is less than about 290° C. and the chip mounting reflow temperature is greater than about 300° C.
Claim 8
Dependent Claim
141 words
A spherical solder bump comprising: a first solder constituent comprising a first metal alloy; and a second solder constituent comprising a second metal alloy dispersed in the first solder constituent, the second solder constituent having higher liquidus and solidus temperatures than the first solder constituent, the second metal alloy being an indium-lead alloy containing up to about 2.5 weight percent silver and about 2.5 to about 5 weight percent indium; wherein the first solder constituent establishes a bumping reflow temperature for the solder bump at which the solder bump is formed without liquefying the second solder constituent, and the second solder constituent establishes a chip mount reflow temperature that is sufficient to cause both the first and second solder constituents to liquefy and form a solder having a liquidus temperature that is between that of the first and second solder constituents.
Claim 9
Dependent Claim
141 words
A spherical solder bump comprising: a first solder constituent comprising a first metal alloy; and a second solder constituent comprising a second metal alloy dispersed in the first solder constituent, the second solder constituent having higher liquidus and solidus temperatures than the first solder constituent, the second metal alloy being an indium-lead alloy containing up to about 2.5 weight percent silver and about 2.5 to about 5 weight percent indium; wherein the first solder constituent establishes a bumping reflow temperature for the solder bump at which the solder bump is formed without liquefying the second solder constituent, and the second solder constituent establishes a chip mount reflow temperature that is sufficient to cause both the first and second solder constituents to liquefy and form a solder having a liquidus temperature that is between that of the first and second solder constituents.
Claim 10
Dependent Claim
25 words
A solder bump as recited in claim 7 wherein the first solder constituent has a lead content of about fifty to about sixty weight percent.
Claim 11
Dependent Claim
25 words
A solder bump as recited in claim 7 wherein the second solder constituent has a lead content of about 92.5 to about 97.5 weight percent.
Claim 12
Dependent Claim
26 words
A solder bump as recited in claim 7 wherein the first and second solder constituents are present at a ratio of about 40:60 to about 50:50.
Claim 13
Dependent Claim
31 words
A solder bump as recited in claim 7 wherein the first metal alloy of the first solder constituent is an indium-lead alloy containing about forty to about fifty weight percent indium.
Claim 14
Independent Claim
197 words
A method for forming solder bumps for a flip chip circuit device, the method comprising the steps of: separately forming first and second solder paste constituents such that the second solder paste constituent has higher liquidus and solidus temperatures than the first solder paste constituent, the first and second solder paste constituents comprising indium-lead alloy powders; combining the first and second solder paste constituents to form a solder paste composition; depositing the solder paste composition on a substrate through a photoresist mask; heating the solder paste composition to a bumping reflow temperature at which the second solder paste constituent does not liquefy and at which the first solder paste constituent liquefies and causes the solder paste composition to flow and form a solder bump; cooling the solder paste composition so as to solidify the solder bump; registering the solder bump with a mounting surface; and heating the solder bump to a mount reflow temperature that is higher than the bumping reflow temperature, the mount reflow temperature being sufficient to liquefy both the first and second solder paste constituents so as to yield a solder joint having a composition based on the first and second solder paste constituents.
Claim 15
Independent Claim
197 words
A method for forming solder bumps for a flip chip circuit device, the method comprising the steps of: separately forming first and second solder paste constituents such that the second solder paste constituent has higher liquidus and solidus temperatures than the first solder paste constituent, the first and second solder paste constituents comprising indium-lead alloy powders; combining the first and second solder paste constituents to form a solder paste composition; depositing the solder paste composition on a substrate through a photoresist mask; heating the solder paste composition to a bumping reflow temperature at which the second solder paste constituent does not liquefy and at which the first solder paste constituent liquefies and causes the solder paste composition to flow and form a solder bump; cooling the solder paste composition so as to solidify the solder bump; registering the solder bump with a mounting surface; and heating the solder bump to a mount reflow temperature that is higher than the bumping reflow temperature, the mount reflow temperature being sufficient to liquefy both the first and second solder paste constituents so as to yield a solder joint having a composition based on the first and second solder paste constituents.
Claim 16
Dependent Claim
26 words
A method as recited in claim 12 wherein the first solder paste constituent is characterized by a lead content of at most about sixty weight percent.
Claim 17
Dependent Claim
26 words
A method as recited in claim 12 wherein the second solder paste constituent is characterized by a lead content of at least about ninety weight percent.
Claim 18
Dependent Claim
26 words
A method as recited in claim 12 wherein the first and second solder paste constituents are combined at a ratio of about 40:60 to about 50:50.
Claim 19
Dependent Claim
16 words
A method as recited in claim 12 wherein the second solder paste constituent further comprises silver.
Claim 20
Dependent Claim
70 words
A method as recited in claim 12 wherein: the first solder paste constituent comprises an alloy powder containing about forty to about fifty weight percent indium and about fifty to about sixty weight percent lead; and the second solder paste constituent comprises an alloy powder containing up to about 2.5 weight percent silver, about 2.5 to about 5 weight percent indium, and about 92.5 to about 97.5 weight percent lead.
References Cited (Backward Citations)
US2623273A
Cited
US4705205A
Cited
EP0164906A1
Cited
US5024372A
Cited
US5154341A
Cited
US5317191A
Cited
US5229070A
Cited
US5328521A
Cited
US5558271A
Cited
US5382300A
Cited
US5415944A
Cited
US5540379A
Cited
US5429293A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-09-07 | 2002-03-09 | 2002-09-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-09-07 | 2006-03-09 | 2006-09-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-09-07 | 2010-03-09 | 2010-09-08 | $7700.00 | Window Closed / Lapsed |