Selectively stripping tin or tin-lead alloys from copper substrates

Claim 2

In an acidic aqueous solution for selectively stripping tin or tin-lead alloy solder from a copper substrate comprising a nitro-substituted aromatic compound having at least one --NO 2 group attached to the aromatic ring and a water-solubilizing substituent also attached to the aromatic ring, an inorganic acid capable of reacting with tin and lead to form water-soluble salts thereof and incapable of reacting with tin and lead to form a water-insoluble compound film, a thiourea for preventing redeposition of stripped tin onto the copper substrate, and an organic acid of the formula RCOOH wherein R is 1-2C alkyl or a hydrogen atom, the improvement whereby a more rapid stripping of the tin or tin-lead alloy solder from the copper is provided, which comprises having present in the aqueous solution an effective amount of a haloacetic acid wherein the halo is chloro or bromo, the amount of said haloacetic acid being sufficient, in combination with said acid of the formula RCOOH wherein R has the meaning aforesaid, to synergistically accelerate the rate of stripping of the tin or tin-lead alloy solder from the copper substrate.

Claim 3

The solution of claim 1 wherein the haloacetic acid is present therein in amount within the range of 1 to 120 g/l.

Claim 4

The solution of claim 1 wherein the haloacetic acid is present therein in amount within the range of about 3.75 to 30.00 g/l.

Claim 5

The solution of claim 1 wherein the constituents are present therein in proportions within the following proportion ranges: ______________________________________ Nitro-substituted aromatic compound having one or more -NO.sub.2 groups attached to the aromatic ring nucleus and a water-solubil- izing group also attached to the aromatic ring 0.1-180 g/l Inorganic acid capable of reacting with tin and lead to form water-soluble salts thereof and incapable of reacting with tin and lead to form a water-insoluble compound film 3-500 g/l A thiourea 0.1-220 g/l Haloacetic acid wherein the halo is chloro or bromo 1-120 g/l Organic acid of formula RCOOH wherein R is 1-2C alkyl or hydrogen 1-120 g/l Water 10-990 g/l ______________________________________

Claim 6

The solution of claim 1 wherein the constituents are present therein in proportions within the following proportion ranges: ______________________________________ Nitro-substituted aromatic compound having one or more -NO.sub.2 groups attached to the -aromatic ring nucleus and a water-solubil- izing group also attached to the aromatic ring 15-75 g/l Inorganic acid capable of reacting with tin and lead to form water-soluble salts thereof and incapable of reacting with tin and lead to form a water-insoluble com- pound film 75-300 g/l A thiourea 3.75-60 g/l Haloacetic acid wherein the halo is chloro or bromo 3.75-30 g/l Organic acid of formula RCOOH wherein R is 1-2 g alkyl or hydrogen 7.5-22.5 g/l Water to 1 liter ______________________________________

Claim 7

The solution of claim 1 wherein the haloacetic acid is a chloroacetic acid.

Claim 8

The solution of claim 6 wherein the chloroacetic acid is trichloroacetic acid.

Claim 9

The solution of claim 4 wherein the haloacetic acid is a chloroacetic acid.

Claim 10

The solution of claim 8 wherein the chloroacetic acid is trichloroacetic acid.

Claim 11

The solution of 1 wherein the inorganic acid is a fluorine-containing inorganic acid, the thiourea is thiourea per se, and the organic acid of the formula RCOOH is formic acid.

Claim 12

The solution of 1 wherein the inorganic acid is a fluorine-containing inorganic acid, the thiourea is thiourea per se, and the organic acid of the formula RCOOH is formic acid.

Claim 13

The solution of claim 4 wherein the inorganic acid is a fluorine-containing inorganic acid, the thiourea is thiourea per se, and the organic acid of the formula RCOOH is formic acid.

Claim 14

The solution of claim 10 wherein the fluorine-containing inorganic acid is fluoboric acid.

Claim 15

The solution of claim 10 wherein the fluorine-containing inorganic acid is fluosilicic acid.

Claim 16

The solution of claim 11 wherein the fluorine-containing inorganic acid is fluoboric acid.

Claim 17

The solution of claim 11 wherein the fluorine-containing inorganic acid is fluosilicic acid.

Claim 18

In a method for stripping tin or a tin-lead alloy deposited on a copper substrate from the copper comprising contacting the tin or tin-lead alloy on the copper substrate with an acidic aqueous solution comprising a nitro-substituted aromatic compound having at least one --NO 2 group attached to the aromatic ring and a water-solubilizing substituent also attached to the aromatic ring, an inorganic acid capable of reacting with tine and lead to form water-soluble salts thereof and incapable of reacting with tin and lead to form a water-insoluble compound film, a thiourea for preventing re-deposition of dissolved tin onto the copper substrate, an organic acid of the formula RCOOH wherein R is 1-2C alkyl or a hydrogen atom, and continuing the contacting of the tin or tin-lead alloy on the copper substrate with the acidic aqueous solution until the tin or tin-lead alloy is dissolved from the copper substrate surface, the improvement whereby a more rapid stripping of the tin or tin-lead alloy solder from the copper is provided which comprises having present in the acidic aqueous stripping solution during the stripping an effective amount of a haloacetic acid wherein the halo is chloro or bromo, the amount of said haloacetic acid being sufficient, in combination with said acid of the formula RCOOH wherein R has the meaning aforesaid, to synergistically accelerate the rate of stripping of the tin or tin-lead alloy solder from the copper substrate.

Claim 19

In a method for stripping tin or a tin-lead alloy deposited on a copper substrate from the copper comprising contacting the tin or tin-lead alloy on the copper substrate with an acidic aqueous solution comprising a nitro-substituted aromatic compound having at least one --NO 2 group attached to the aromatic ring and a water-solubilizing substituent also attached to the aromatic ring, an inorganic acid capable of reacting with tine and lead to form water-soluble salts thereof and incapable of reacting with tin and lead to form a water-insoluble compound film, a thiourea for preventing re-deposition of dissolved tin onto the copper substrate, an organic acid of the formula RCOOH wherein R is 1-2C alkyl or a hydrogen atom, and continuing the contacting of the tin or tin-lead alloy on the copper substrate with the acidic aqueous solution until the tin or tin-lead alloy is dissolved from the copper substrate surface, the improvement whereby a more rapid stripping of the tin or tin-lead alloy solder from the copper is provided which comprises having present in the acidic aqueous stripping solution during the stripping an effective amount of a haloacetic acid wherein the halo is chloro or bromo, the amount of said haloacetic acid being sufficient, in combination with said acid of the formula RCOOH wherein R has the meaning aforesaid, to synergistically accelerate the rate of stripping of the tin or tin-lead alloy solder from the copper substrate.

Claim 20

The method of claim 16 wherein the haloacetic acid is present in the stripping solution in amount within the range of 1 to 120 g/l.

Claim 21

The method of claim 16 wherein the haloacetic acid is present in the stripping solution in amount within the range of about 3.75 to 30.00 g/l.

Claim 22

The method of claim 16 wherein the haloacetic acid is a chloroacetic acid.

Claim 23

The method of claim 19 wherein the chloroacetic acid is trichloroacetic acid.