US4960236A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Manufacture of printed circuit board assemblies
Assignee: Multicore Solders Ltd
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Filing: 1989-08-14
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Granted: 1990-10-02
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Expires: 2009-08-14
Abstract
Abstract To avoid the use of harmful CFCs in the cleaning of soldered printed circuit board assemblies, their manufacture is accomplished using a screen-printable solder paste composition which will in use yield minimal flux residues which will not require removal by a solvent cleaning step. The paste composition is formulated by incorporating the powdered soft solder alloy in a liquid medium containing up to 10% by weight of a non-corrosive organic flux material, a substantially water-immiscible organic solvent, and one or more thickening agents.
Inventors
- 👤 Philip S. Hedges
- 👤 Wallace Rubin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 06:34
CPC Classifications
B; B23; B23K; B23K35/00; B23K35/22; B23K35/24; B23K35/26; B23K35/262; B23K35/36; B23K35/3612; B23K35/3615; B23K35/3618
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
152 words
In the manufacture of printed circuit board assemblies by a process including the steps of applying a solder cream to a printed circuit board in required locations thereon, mounting on the board the desired electronic components, and thereafter to subjecting the resulting printed circuit board assembly to an elevated temperature sufficient to cause solder reflow, the improvement which comprises utilising as the solder cream a screen-printable paste composition comprising from 80 to 95% by weight of a finely divided soft solder alloy having a particle size of up to 100 μm substantially uniformly dispersed in a liquid medium containing not more than 10% by weight of a non-corrosive organic flux material selected from organic carboxylic acids, amines and amine hydrohalide salts, a substantially water-immiscible organic solvent and one or more thickening agents, and thereby obviating the necessity of subjecting the soldered pcb assembly to a cleaning step after the solder reflow step.
Claim 2
Dependent Claim
152 words
In the manufacture of printed circuit board assemblies by a process including the steps of applying a solder cream to a printed circuit board in required locations thereon, mounting on the board the desired electronic components, and thereafter to subjecting the resulting printed circuit board assembly to an elevated temperature sufficient to cause solder reflow, the improvement which comprises utilising as the solder cream a screen-printable paste composition comprising from 80 to 95% by weight of a finely divided soft solder alloy having a particle size of up to 100 μm substantially uniformly dispersed in a liquid medium containing not more than 10% by weight of a non-corrosive organic flux material selected from organic carboxylic acids, amines and amine hydrohalide salts, a substantially water-immiscible organic solvent and one or more thickening agents, and thereby obviating the necessity of subjecting the soldered pcb assembly to a cleaning step after the solder reflow step.
Claim 3
Dependent Claim
33 words
The improvement as claimed in claim 1, wherein the liquid medium contains from 0.2 to 10% by weight of the flux material, and from 0.1 to 10% by weight of the thickening agent(s).
Claim 4
Dependent Claim
44 words
The improvement as claimed in claim 2, wherein the paste composition further comprises (1) a volatile amine capable of reacting with any excess acid remaining from the soldering operation and/or (2) a chelating agent capable of reducing any discoloration created by metal reaction products.
Claim 5
Dependent Claim
23 words
The improvement as claimed in claim 3, wherein the paste composition contains morpholine as the volatile amine and benzotriazole as the chelating agent.
Claim 6
Dependent Claim
16 words
The improvement as claimed in claim 1, wherein the flux material comprises an aliphatic carboxylic acid.
Claim 7
Dependent Claim
18 words
The improvement as claimed in claim 5, wherein two or more aliphatic dicarboxylic acids comprise the flux material.
Claim 8
Dependent Claim
19 words
The improvement as claimed in claim 1, wherein two or more thickening agents are present in the paste composition.
Claim 9
Dependent Claim
20 words
The improvement as claimed in claim 7, wherein ethyl cellulose and hydrogenated castor oil are both present as thickening agents.
Claim 10
Dependent Claim
23 words
The improvement as claimed in claim 1, wherein the substantially water-immiscible organic solvent is a monohydric compound optionally blended with a polyhydric compound.
Claim 11
Dependent Claim
26 words
The improvement as claimed in claim 9, wherein the monohydric compound is terpineol and the optional polyhydric compound is dipropylene glycol or triethylene glycol monoethyl ether.
Claim 12
Dependent Claim
100 words
A solder cream formulated for use in the soldering of electronic components to printed circuit boards whereby substantially no flux residues are formed after the solder reflow step, the solder cream being a screen- printable paste composition comprising from 80 to 95% by weight of a finely divided soft solder alloy having a particle size of up to 100 μm substantially uniformly dispersed in a liquid medium containing not more than 10% by weight of a non-corrosive flux material selected from organic carboxylic acids, amines and amine hydrohalide salts, a substantially water-immiscible organic solvent and one or more thickening agents.
Claim 13
Dependent Claim
100 words
A solder cream formulated for use in the soldering of electronic components to printed circuit boards whereby substantially no flux residues are formed after the solder reflow step, the solder cream being a screen- printable paste composition comprising from 80 to 95% by weight of a finely divided soft solder alloy having a particle size of up to 100 μm substantially uniformly dispersed in a liquid medium containing not more than 10% by weight of a non-corrosive flux material selected from organic carboxylic acids, amines and amine hydrohalide salts, a substantially water-immiscible organic solvent and one or more thickening agents.
Claim 14
Dependent Claim
34 words
A paste composition as claimed in claim 11, wherein the liquid medium contains from 0.2 to 10% by weight of the flux material, and from 0.1 to 10% by weight of the thickening agent(s).
Claim 15
Dependent Claim
45 words
A paste composition as claimed in claim 12, wherein the paste composition further comprises (1) a volatile amine capable of reacting with any excess acid remaining from the soldering operation and/or (2) a chelating agent capable of reducing any discoloration created by metal reaction products.
Claim 16
Dependent Claim
24 words
A paste composition as claimed in claim 13, wherein the paste composition contains morpholine as the volatile amine and benzotriazole as the chelating agent.
Claim 17
Dependent Claim
17 words
A paste composition as claimed in claim 11, wherein the flux material comprises an aliphatic carboxylic acid.
Claim 18
Dependent Claim
19 words
A paste composition as claimed in claim 15, wherein two or more aliphatic dicarboxylic acids comprise the flux material.
Claim 19
Dependent Claim
20 words
A paste composition as claimed in claim 11, wherein two or more thickening agents are present in the paste composition.
Claim 20
Dependent Claim
21 words
A paste composition as claimed in claim 17, wherein ethyl cellulose and hydrogenated castor oil are both present as thickening agents.
Claim 21
Dependent Claim
24 words
A paste composition as claimed in claim 11, wherein the substantially water-immiscible organic solvent is a monohydric compound optionally blended with a polyhydric compound.
Claim 22
Dependent Claim
27 words
A paste composition as claimed in claim 19, wherein the monohydric compound is terpineol and the optional polyhydric compound is dipropylene glycol or triethylene glycol monoethyl ether.
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) | 1993-10-01 | 1994-04-02 | 1994-10-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-10-01 | 1998-04-02 | 1998-10-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-10-01 | 2002-04-02 | 2002-10-02 | $7700.00 | Window Closed / Lapsed |