KR100312285B1 - Weak acidic electrolytic silver-plating peeling composition and method for peeling silver-plate using same - Google Patents

Abstract

The present invention relates to a weakly acidic electrolytic silver plating stripping composition for selectively stripping silver-plated portions of copper or copper plating alloy materials and iron-nickel alloy materials, and a stripping process using the same, wherein one or more organic acids, conductive salts, stabilizers and surfactants The weakly acidic electrolytic silver plating peeling composition of the present invention contains a much longer life than the conventional alkaline silver plating peeling agent, and when the silver plating is peeled off using the composition, it can be stably and continuously peeled off with little material erosion and a clean surface can be obtained. have.

Description

Slightly acidic electrolytic silver plating peeling composition and method for selectively peeling silver plating using same {WEAK ACIDIC ELECTROLYTIC SILVER-PLATING PEELING COMPOSITION AND METHOD FOR PEELING SILVER-PLATE USING SAME}

The present invention relates to a silver plated electrolytic peeling composition that selectively peels off silver plated portions on copper or copper plated alloy materials and iron-nickel alloy materials.

In general, a silver plating process is performed on a copper or copper plating alloy material and iron-nickel alloy material such as a lead lead frame, a printed circuit board and a connector, and then a solder plating process is performed in the following order.

Electrolytic degreasing step → washing step → acid treatment step → washing step → copper strike plating step → washing step → silver substitution prevention step → washing step → silver plating step → washing step → silver plating peeling step → washing step → molding step → solder -Lead alloy) plating step → washing step.

The silver plating peeling step of the above step is to selectively peel off only the silver plating plated on a part of the silver plated material, for example, a pad portion which is the center portion of the semiconductor lead frame.

Until now, many alkaline solutions are used as silver plating stripping agents for semiconductor lead frames. However, liquid alkalis require strong attention in pretreatment and post-treatment processes. Especially, they are very sensitive to temperature and shorten the life of the solution even if the liquid temperature is high. This makes the bath life of the solution very short. In addition, as the solution ages, the material erosion rate of the semiconductor lead frame increases, and the color of the solution turns dark blue.

In order to overcome the above problems, an electrolytic silver plating stripping solution (composition) of a weak acid type, which is not alkaline, has been developed, but a large effect has not been achieved yet.

The most recently developed weakly acidic electrolytic silver plating peeling composition is mostly manufactured based on lactic acid, and the viscosity of the solution is considerably high, resulting in high loss of solution and difficulty in washing with water. Sludge in metals is generated so that it floats in solution, floats on the leadframe, and adheres between the leadframes, causing various problems in the plating process. In addition, the above problems are further accumulated due to the characteristics of the plating process that does not frequently wash the negative electrode covered with the peeled silver plating sludge.

Accordingly, it is an object of the present invention to provide a weakly acidic electrolytic plating solution using an organic acid, which has almost no erosion of a material, a solution having a long life, stable and consistently excellent silver plating peeling, and a peeling process using the same.

In order to achieve the above object, the present invention provides a silver plating peeling composition containing at least one organic acid, a conductive salt, a stabilizer and a surfactant.

Hereinafter, the present invention will be described in more detail.

The silver plating peeling composition of the present invention can be applied to a semiconductor leadframe made of copper or copper alloy material and iron-nickel alloy material, and can be applied to both reel to reel equipment and cut-strip equipment.

The organic acid silver source that can be used in the silver plating peeling composition of the present invention mainly includes sulfonic acid-based, succinic acid-based, malic acid-based, lactic acid-based salts, or mixtures thereof, including methanesulfonic acid, lactic acid, ammonium succinate, Preference is given to DL-peracids or mixtures thereof. The organic acid salt is used at a concentration of 10 to 225 g / l, preferably 20 to 100 g / l.

Sources of the conductive salt that can be used in the silver plating peeling composition of the present invention include salts such as amine series, ammonium series, citric acid series, or mixtures thereof, and include dimethylamine, ammonium sulfate, ammonium phosphate, ammonium citrate, and citric acid. Preference is given to potassium, sodium citrate or mixtures thereof. The conductive salt is used at a concentration of 10 to 150 g / l, preferably 20 to 100 g / l.

Stabilizers that can be used in the silver plating peeling composition of the present invention mainly include urea-based, alcohol-based, imide-based, amine-based salts or mixtures thereof, and thiourea, diethyl thiourea, thioacetamide , Ethanolamine, triethylenetetraamine, isopropyl alcohol or mixtures thereof are preferred. The stabilizer is used at a concentration of 2 to 30 g / l, preferably 5 to 15 g / l.

Surfactants that can be used in the silver plating peeling composition of the present invention include sulfonic acid series, ethoxyl series, amino series or mixtures thereof, naphthalene-1-sulfonic acid (alpha) sodium, N, N-di Preference is given to ethyl-1,3-diaminopropane, beta-naphtholethoxylate or mixtures thereof. The surfactant is used at a concentration of 0.05 to 2 g / l, preferably 0.1 to 1 g / l.

The organic acid salt, conductive salt, stabilizer and surfactant are sequentially dissolved in distilled water to prepare the weakly acidic electrolytic silver plating peeling composition of the present invention.

The weakly acidic electrolytic silver plating peeling composition used in the present invention has a specific gravity of 5 to 8 Be (Baume), a pH of 5 to 7, a use temperature of 20 to 35 ° C, and a negative electrode current density of 0.3 to 1.5 A / dm ² .

Under the above conditions, the silver plated material is used as the positive electrode (+), and the stainless steel mesh or plate is used as the negative electrode (−) to hang on the conductive hanger, and the silver plating is applied through current.

The weakly acidic electrolytic silver plated peeling composition of the present invention has the following characteristics:

(1) It is possible to selectively peel off the silver plated portion on the copper or copper alloy material and the iron-nickel alloy material without giving any erosion to the material;

(2) contains no cyanide compounds or peroxides, the solution is very stable, has a high silver peeling capacity, and hardly generates peeled sludge;

(3) the viscosity of the solution is low, the solution loss is small, so the washing is easy;

(4) uniform liquidity and peeling rate are maintained, solution life is long and the consumption of conductive salts is uniform;

(5) The exfoliated material surface is uniform and slightly gloss.

The present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited only to the following examples.

Example 1

The following components were sequentially dissolved in distilled water to prepare a weakly acidic electrolytic silver plating peeling composition having a specific gravity of 7 Be and a pH of 6.5.

100 g / l methanesulfonic acid

Lactic acid 75 g / ℓ

DL-apple acid 50 g / ℓ

Dimethylamine 15 g / L

Thiourea 2 g / L

Naphthalene-1-sulfonic acid (alpha) sodium 0.08 g / L

Using the weakly acidic silver plating peeling composition prepared above, the material was peeled off under conditions of a temperature of 28 ° C. and a cathode current density of 1 A / dm ² , and the surface of the material showed a uniform and clean peeling effect.

Example 2

The following components were sequentially dissolved in distilled water to prepare a weakly acidic electrolytic silver plating peeling composition having a specific gravity of 7 Be and a pH of 6.5.

100 g / l methanesulfonic acid

Lactic Acid 55 g / ℓ

Succinic acid 50 g / ℓ

Potassium Citrate 20 g / ℓ

Triethylenetetraamine 5 g / L

N, N-diethyl-1,3-diaminopropane 0.5 g / l

Using the weakly acidic silver plating peeling composition prepared above, the material was peeled off under conditions of a temperature of 28 ° C. and a cathode current density of 1 A / dm ² , and the surface of the material showed a uniform and clean peeling effect.

Example 3

The following components were sequentially dissolved in distilled water to prepare a weakly acidic electrolytic silver plating peeling composition having a specific gravity of 7 Be and a pH of 6.5.

Methanesulfonic acid 120 g / l

Lactic Acid 55 g / ℓ

Ammonium Succinate 30 g / L

Ammonium Phosphate 25 g / L

Triethanolamine 5 g / L

Beta-naphthol ethoxylate 0.7 g / l

Using the weakly acidic silver plating peeling composition prepared above, the material was peeled off under conditions of a temperature of 28 ° C. and a cathode current density of 1 A / dm ² , and the surface of the material showed a uniform and clean peeling effect.

Example 4

The following components were sequentially dissolved in distilled water to prepare a weakly acidic electrolytic silver plating peeling composition having a specific gravity of 7 Be and a pH of 6.5.

Lactic Acid 180 g / ℓ

Succinic acid 25 g / ℓ

Ammonium Phosphate 40 g / L

15 g / l ethylenediamine

Thioacetimide 7 g / L

Naphthalene-1-sulfonic acid (alpha) sodium 0.1 g / L

Using the weakly acidic silver plating peeling composition prepared above, the material was peeled off under conditions of a temperature of 28 ° C. and a cathode current density of 1 A / dm ² , and the surface of the material showed a uniform and clean peeling effect.

Example 5

The following components were sequentially dissolved in distilled water to prepare a weakly acidic electrolytic silver plating peeling composition having a specific gravity of 7 Be and a pH of 6.5.

Methanesulfonic acid 180 g / l

Ammonium Citrate 25 g / L

Succinic Acid 15 g / ℓ

Triethylenetetramine 6 g / l

Polyethylene glycol oleyl ether 0.1 g / l

Using the weakly acidic silver plating peeling composition prepared above, the material was peeled off under conditions of a temperature of 28 ° C. and a cathode current density of 1 A / dm ² , and the surface of the material showed a uniform and clean peeling effect.

As in the present invention, the weakly acidic electrolytic silver plating stripping composition containing one or more organic acids, conductive salts, stabilizers and surfactants has a much longer life than conventional alkaline silver plating stripping agents, and when the silver plating is stripped using the composition, there is little material erosion. It can be peeled off stably and continuously, and a clean surface can be obtained.

Claims (8)

10 to 225 g / l of at least one organic acid, 10 to 150 g / l of conductive salt, 2 to 30 g / l of stabilizer and 0.05 to 2 g / l of surfactant, having a specific gravity of 5 to 8 Be and a range of pH 5 to 7, Weakly acid electrolytic silver plating peeling composition. The method of claim 1, Methanesulfonic acid, lactic acid, succinic acid, ammonium succinate, DL-apple acid or a mixture thereof is used as the organic acid. The method of claim 2, Wherein said organic acid is methanesulfonic acid, lactic acid or a mixture thereof. The method of claim 1, As the conductive salt, dimethylamine, ammonium sulfate, ammonium phosphate, potassium citrate, ammonium citrate, sodium citrate or a mixture thereof is used. The method of claim 1, Thiourea, diethyl thiourea, thioacetamide, ethanolamine, triethylenetetraamine, isopropyl alcohol or a mixture thereof is used as the stabilizer. The method of claim 1, Use of naphthalene-1-sulfonic acid (alpha) sodium, N, N-diethyl-1,3-diaminopropane, beta-naphthol ethoxylate, polyethylene glycol oleyl ether or a mixture thereof as the surfactant Characterized in that the composition. The composition of claim 1 is immersed in silver plated material as positive electrode (+) and stainless steel mesh or plate as negative electrode (-) and subjected to current at a temperature of 20 to 35 ° C. and a cathode current density of 0.3 to 1.5 A / dm ² to obtain silver plating. Selectively peeling the silver plating using the weakly acidic electrolytic silver plating peeling composition, which comprises causing the peeling. The method of claim 7, wherein Method using reel to reel or cut-strip equipment.