# US 4,397,753 A · Solder stripping solution

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- Number: US 4,397,753 A
- Document ID: US4397753A
- Status: Granted
- Kind: A
- Application number: 06/420,482
- Filed: 1982-09-20
- Granted: 1983-08-09
- Earliest claimed: 1982-09-20
- Assignees: Circuit Chemistry Corporation
- Inventors: James J. Czaja
- Web page: https://patentgrep.com/patent/US4397753A

## CPC

- C23F 1/44: Compositions for etching metallic material from a metallic material substrate of different composition
- C09K 13/08: containing a fluorine compound
- H05K 3/067: {Etchants}
- C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS

## Abstract

Solder stripping solution having an extended life for stripping and removing tin-lead alloy solder or tin deposits from entire circuits or tabs with an insignificant amount of attack on the base epoxy laminate or underlay copper or nickel substrate while leaving a residue-free substrate surface. This solution can be utilized at room temperature or preferably slightly above, and has a prolonged useful life of weeks to months. The composition of the solution includes a hydroxyphenol in an aqueous solution of a nitro-substituted aromatic compound, an inorganic acid, and thiourea.

## Claims

### Claim 1

Solution for the removal of tin or tin-lead alloy solder from a copper or nickel base, said solution comprising:
(a) 20-150 g/l of a m-nitro substituted aromatic compound;
(b) 0.5-10 g/l of a thiourea selected from a group of thiourea per se, an alkyl thiourea or an aromatic thiourea;
(c) 0.1-50 percent by volume of an inorganic acid selected from a group including fluoboric acid, fluosilicic acid, sulfamic acid, or nitric acid; and,
(d) 0.1-50.0 g/l of a hydroxyphenol providing extended life to the stripping solution.

### Claim 2 (depends on 1)

Solution of claim 1 where the inorganic acid is nitric acid.

### Claim 3 (depends on 1)

Solution of claim 1 which also contains an ammonium ion of the formulation NH.sub.4 X in the range of 0.1-300 g/l, X being an ion consisting of either nitrate, fluoborate, acetate, halogen, or hydroxide.

### Claim 4 (depends on 1)

Solution of claim 1 which also contains a fluoborate ion of the formulation RBF.sub.4 in the range of 0.1-750 g/l, R being a cation consisting of either a hydrogen, ammonium, sodium or potassium ion.

### Claim 5

Non-peroxide solder stripper solution comprising:
(a) nitro-substituted aromatic compound of 20-150 g/l;
(b) fluoborate compound of 0.1-750 g/l;
(c) hydroxyphenol of 0.1-50 g/l;
(d) ammonium compound of 0.1-300 g/l;
(e) inorganic acid of 0.1-400 g/l;
(f) thiourea of 0.1-30 g/l;
(g) boric acid of 2-60 g/l; and
(h) water to one liter.

### Claim 6 (depends on 5)

Solution of claim 5 wherein said nitro-substituted aromatic compound is selected from o, m, or p-nitrochlorobenzenes, o, m, or p-nitrobenzenes, sulfonic acids, and o, m, or p-nitrobenzonic acids.

### Claim 7 (depends on 6)

Solution of claim 6 comprising sodium meta-nitrobenzenesulfonate.

### Claim 8 (depends on 5)

Solution of claim 5 wherein said ammonium compound is selected from ammonium nitrate, ammonium halides, ammonium acetate, or ammonium hydroxide in combination with sodium fluoborate, potassium fluoborate, or fluoboric acid.

### Claim 9 (depends on 8)

Solution of claim 8 comprising ammonium fluoborate.

### Claim 10 (depends on 5)

Solution of claim 5 wherein said inorganic acid is selected from fluoboric, fluosilic, sulfamic, or nitric acid.

### Claim 11 (depends on 10)

Solution of claim 10 comprising nitric acid.

### Claim 12 (depends on 5)

Solution of claim 5 wherein said hydroxyphenol comprises 3-hydroxyphenol.

### Claim 13 (depends on 5)

Solution of claim 5 wherein said thiourea is selected from alkyl and aromatic thiourea.

### Claim 14

Non-peroxide solder stripping solution comprising:
(a) sodium m-nitrobenzenesulfonate of 80 g/l;
(b) fluoboric acid of 276 g/l;
(c) boric acid of 8 g/l;
(d) 3-hydroxyphenol of 8 g/l;
(e) ammonium nitrate of 36 g/l;
(f) nitric acid of 90 ml/l;
(g) thiourea of 14 g/l;
(h) to one liter of water.

### Claim 15 (depends on 14)

Solution of claim 14 for stripping solder or tin in an SMOBC process.

### Claim 16 (depends on 14)

Solution of claim 14 for stripping solder or tin from printed circuit boards in a nickel-gold process.