US5122200A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of cleaning printed circuit boards using formic acid
Assignee: Motorola Solutions Inc
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Filing: 1990-09-17
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Granted: 1992-06-16
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Expires: 2010-09-17
Abstract
Abstract Solder pastes having vehicles including formic acid-soluble organic acids as fluxing agents are described. Fluxing agents may be compounds of the formula: ##STR1## where R is an electron withdrawing group. In one embodiment, R is selected from the group consisting of fluorine, chlorine, bromine, iodine, sulfur, hydroxyl, nitrile, and benzyl. Other suitable formic-acid fluxing agents include, but are not limited to, adipic acid, acrylic acid, polyacrylic acid, methacrylic acid and polymethacrylic acid. The compounds clean oxides from the printed circuit boards (PCBs) under assembly and then volatilize leaving a residue to be cleaned away. The cleaning step involves rinsing with formic acid. No undesired residue remains indicating that the organic acids of the invention are effective in cleaning boards. Such acid fluxing agents can be used mixed with typical solder components, such as lead/tin solder pastes, or applied topically to solders, such as solder balls; both techniques permit the assembly of PCBs more easily with high quality bonds, and with little or no residue. Malic acid is a preferred organic acid fluxing agent. The formic acid cleaning step may be followed by a water rinse.
Inventors
- 👤 James L. Davis
- 👤 Robert W. Pennisi
- 👤 Fadia Nounou
- 👤 Robert J. Mulligan
- 👤 Bobby D. Landreth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 18:08
CPC Classifications
B; B23; B23K; B23K35/00; B23K35/22; B23K35/36; B23K35/3612; B23K35/3618; C; C23; C23G; C23G1/00; C23G1/02; C23G1/10; C23G1/103; H; H05; H05K; H05K3/00; H05K3/22; H05K3/26; H05K2203/00; H05K2203/07; H05K2203/0779; H05K2203/0786; H05K2203/0789; H05K2203/12; H05K2203/122; H05K3/30; H05K3/32; H05K3/34; H05K3/3465; H05K3/3485
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
125 words
A method of mounting electronic components on a printed circuit board providing a residue cleanable with formic acid comprising the steps of: formulating a solder paste by mixing together: a solder paste vehicle comprising: a solvent; and a fluxing agent selected from the group consisting of organic acids soluble in formic acid; and a solder powder comprising a metal selected from the group consisting of lead, tin, antimony, silver and mixtures thereof; applying the solder paste to a metallic surface to be soldered; placing at least one electronic component on the metallic surface to be soldered; causing the solder paste to flow and form a solder bond producing a residue on the metallic surface; and removing the residue by washing the surface with formic acid.
Claim 2
Independent Claim
125 words
A method of mounting electronic components on a printed circuit board providing a residue cleanable with formic acid comprising the steps of: formulating a solder paste by mixing together: a solder paste vehicle comprising: a solvent; and a fluxing agent selected from the group consisting of organic acids soluble in formic acid; and a solder powder comprising a metal selected from the group consisting of lead, tin, antimony, silver and mixtures thereof; applying the solder paste to a metallic surface to be soldered; placing at least one electronic component on the metallic surface to be soldered; causing the solder paste to flow and form a solder bond producing a residue on the metallic surface; and removing the residue by washing the surface with formic acid.
Claim 3
Dependent Claim
40 words
The method of claim 1 where the fluxing agent is selected from the group consisting of an organic acid having the formula: ##STR3## where R is an electron withdrawing group, and adipic acid, acrylic acid, polyacrylic acid and mixtures thereof.
Claim 4
Dependent Claim
23 words
The method of claim 2 where R is selected from the group consisting of fluorine, chlorine, bromine, iodine, sulfur, hydroxyl, nitrile, and benzyl.
Claim 5
Dependent Claim
27 words
The method of claim 1 where the proportion of the organic acid in the vehicle ranges from about 0.1 to about 60 wt. % of the vehicle.
Claim 6
Dependent Claim
11 words
The method of claim 1 where the solvent is an alcohol.
Claim 7
Dependent Claim
14 words
The method of claim 1 where the organic acid fluxing agent is malic acid.
Claim 8
Dependent Claim
42 words
The method of claim 1 where the solder paste comprises the following formulation: about 6 to about 8 wt. % solvent; about 2 to about 5 wt. % organic acid fluxing agent; and about 85 to about 92 wt. % solder powder.
Claim 9
Dependent Claim
17 words
The method of claim 7 where there is also present up to about 3 wt. % paraformaldehyde.
Claim 10
Independent Claim
166 words
A method of mounting electronic components on a printed circuit board providing a residue cleanable with formic acid comprising the steps of: formulating a solder paste by mixing together: a solder paste vehicle comprising: a solvent; and a fluxing agent selected from the group consisting of an organic acid having the formula: ##STR4## where R is an electron withdrawing group, and adipic acid, acrylic acid, polyacrylic acid and mixtures thereof, and where the proportion of the organic acid in the vehicle ranges from about 0.1 to about 60 wt. % of the vehicle; and a solder powder comprising a metal selected from the group consisting of lead, tin, antimony, silver and mixtures thereof; applying the solder paste to a metallic surface to be soldered; placing at least one electronic component on the metallic surface to be soldered; causing the solder paste to flow and form a solder bond producing a residue on the metallic surface; and removing the residue by washing the surface with formic acid.
Claim 11
Independent Claim
166 words
A method of mounting electronic components on a printed circuit board providing a residue cleanable with formic acid comprising the steps of: formulating a solder paste by mixing together: a solder paste vehicle comprising: a solvent; and a fluxing agent selected from the group consisting of an organic acid having the formula: ##STR4## where R is an electron withdrawing group, and adipic acid, acrylic acid, polyacrylic acid and mixtures thereof, and where the proportion of the organic acid in the vehicle ranges from about 0.1 to about 60 wt. % of the vehicle; and a solder powder comprising a metal selected from the group consisting of lead, tin, antimony, silver and mixtures thereof; applying the solder paste to a metallic surface to be soldered; placing at least one electronic component on the metallic surface to be soldered; causing the solder paste to flow and form a solder bond producing a residue on the metallic surface; and removing the residue by washing the surface with formic acid.
Claim 12
Dependent Claim
23 words
The method of claim 9 where R is selected from the group consisting of fluorine, chlorine, bromine, iodine, sulfur, hydroxyl, nitrile, and benzyl.
Claim 13
Dependent Claim
11 words
The method of claim 9 where the solvent is an alcohol.
Claim 14
Dependent Claim
14 words
The method of claim 9 where the organic acid fluxing agent is malic acid.
Claim 15
Dependent Claim
42 words
The method of claim 9 where the solder paste comprises the following formulation: about 6 to about 8 wt. % solvent; about 2 to about 5 wt. % organic acid fluxing agent; and about 85 to about 92 wt. % solder powder.
Claim 16
Dependent Claim
17 words
The method of claim 13 where there is also present up to about 3 wt. % paraformaldehyde.
Claim 17
Independent Claim
210 words
A method of mounting electronic components on a printed circuit board providing a residue cleanable with formic acid comprising the steps of: formulating a solder paste by mixing together: a solder paste vehicle comprising: a solvent; and a fluxing agent selected from the group consisting of an organic acid having the formula: ##STR5## where R is an electron withdrawing group, and adipic acid, acrylic acid, polyacrylic acid and mixtures thereof, and where the proportion of the organic acid in the vehicle ranges from about 0.1 to about 60 wt. % of the vehicle; and a solder powder comprising a metal selected from the group consisting of lead, tin, antimony, silver and mixtures thereof; where the solder paste comprises the following formulation: about 6 to about 8 wt. % solvent; about 2 to about 5 wt. % organic acid fluxing agent; about 85 to about 92 wt. % solder powder; about 0 to about 3 wt. % paraformadehyde; applying the solder paste to a metallic surface to be soldered; placing at least one electronic component on the metallic surface to be soldered; causing the solder paste to flow and form a solder bond producing a residue on the metallic surface; and removing the residue by washing the surface with formic acid.
Claim 18
Independent Claim
210 words
A method of mounting electronic components on a printed circuit board providing a residue cleanable with formic acid comprising the steps of: formulating a solder paste by mixing together: a solder paste vehicle comprising: a solvent; and a fluxing agent selected from the group consisting of an organic acid having the formula: ##STR5## where R is an electron withdrawing group, and adipic acid, acrylic acid, polyacrylic acid and mixtures thereof, and where the proportion of the organic acid in the vehicle ranges from about 0.1 to about 60 wt. % of the vehicle; and a solder powder comprising a metal selected from the group consisting of lead, tin, antimony, silver and mixtures thereof; where the solder paste comprises the following formulation: about 6 to about 8 wt. % solvent; about 2 to about 5 wt. % organic acid fluxing agent; about 85 to about 92 wt. % solder powder; about 0 to about 3 wt. % paraformadehyde; applying the solder paste to a metallic surface to be soldered; placing at least one electronic component on the metallic surface to be soldered; causing the solder paste to flow and form a solder bond producing a residue on the metallic surface; and removing the residue by washing the surface with formic acid.
Claim 19
Dependent Claim
23 words
The method of claim 15 where R is selected from the group consisting of fluorine, chlorine, bromine, iodine, sulfur, hydroxyl, nitrile, and benzyl.
Claim 20
Dependent Claim
11 words
The method of claim 15 where the solvent is an alcohol.
Claim 21
Dependent Claim
14 words
The method of claim 15 where the organic acid fluxing agent is malic acid.
Claim 22
Independent Claim
111 words
A method of mounting electronic components on a printed circuit board providing a residue cleanable with formic acid comprising the steps of: formulating a solder comprising a solder powder comprising a metal selected from the group consisting of lead, tin, antimony, silver and mixtures thereof soldering at least one electronic component on a metallic surface by means of solder bonds; causing the solder paste to flow and form a solder bond; topically applying a fluxing agent selected from the group consisting of organic acids soluble in formic acid to the solder bond which produces a residue on the metallic surface; and removing the residue by washing the surface with formic acid.
Claim 23
Independent Claim
111 words
A method of mounting electronic components on a printed circuit board providing a residue cleanable with formic acid comprising the steps of: formulating a solder comprising a solder powder comprising a metal selected from the group consisting of lead, tin, antimony, silver and mixtures thereof soldering at least one electronic component on a metallic surface by means of solder bonds; causing the solder paste to flow and form a solder bond; topically applying a fluxing agent selected from the group consisting of organic acids soluble in formic acid to the solder bond which produces a residue on the metallic surface; and removing the residue by washing the surface with formic acid.
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) | 1995-06-16 | 1995-12-16 | 1996-06-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-06-16 | 1999-12-16 | 2000-06-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-06-16 | 2003-12-16 | 2004-06-16 | $7700.00 | Window Closed / Lapsed |