TWI755229B - Silver-plated layer electrolytically-stripping agent without cyanide, and method for electrolytically stripping silver-plated layer - Google Patents

Abstract

The invention provides an environmentally friendly type, silver-plated layer electrolytically-stripping agent without cyanide that is suitable for electronic parts such as lead frames and connectors. The silver-plated layer electrolytically-stripping agent comprises a hydantoin compound as a complexing agent and alkanolamide capable of enhancing the ability of stripping an extra part of silver-plated layer on the side of the lead frame that is not required and not causing damage to the substrate, and a gloss rise of the surface of a required part of silver-plated layer can be inhibited after stripping a silver-plated layer that is not required. The invention also provides a method for electrolytically stripping a silver-plated layer.

Description

Cyanide-free electrolytic silver stripping agent and electrolytic silver stripping method

The present invention relates to an electrolytic silver stripping agent, in particular to a cyanide-free electrolytic silver stripping agent.

Various components in the electronics industry, such as central processing units, circuit boards, memory, flip chips, and even hidden antennas in mobile phone casings, have metal-plated parts that perform critical functions. However, the earth's mineral resources are not inexhaustible and inexhaustible. Therefore, under the consideration of sustainable development, how to recover its metal components from waste has gradually become one of the important work links in the industry.

For example, light emitting diode (LED) leadframes and integrated circuit (IC) leadframes are silver-plated in certain areas for specific effects. The light-emitting diode system includes a lead frame formed using a copper tape, and light-emitting elements such as an LED chip mounted on the lead frame. Such a copper tape is formed with, for example, at least one of a copper (Cu) plating layer or a nickel (Ni) plating layer as a base plating layer, and a silver (Ag) plating layer for reflecting light from the light-emitting element as a surface Plating. In addition, the IC lead frame is a base that provides the integrated circuit chip to place the wires and connects the IC chip to the printed circuit board. In the known IC lead frame, a layer of silver is plated on the bonding area in order to provide better electrical bonding between the gold wire connecting the IC chip and the lead. In the process of disposing of non-conforming product to recover and reuse the underlying copper material, it is necessary to strip silver from copper or other metal layers. In addition, under the trend of rising silver prices, silver has recycling value.

The conventional electrolytic stripping method of the silver plating layer disclosed herein includes the following methods. (1) MIL-STD-871C (Jun. 2015), revealing that the substrate is copper alloy, cyanide-based electrolytic silver stripping solution: sodium cyanide 82~98 g/l, sodium hydroxide 8~22 g/l, operation The temperature range is 20 to 71 °C, the workpiece is the anode, and the maximum voltage for electrolysis is 2 V. However, the cyanide used in this method is a toxic chemical substance, which is harmful to the human body and pollutes the environment. (2) Japanese Patent Laid-Open Gazette, No. 2-104699 (1990), the patent of Uemura Industry Co., Ltd. discloses a silver-plating electrolytic silver stripper: succinimide (succinimide) 10~100 g/l, alkali metal conductive salt Such as NaOH, KOH and LiOH 3~12 g/l, to prevent the substrate from being corroded and causing the brightness variation of the underlying metal, pH 6~9.5, other additives such as buffers, including boric acid, potassium borate and sodium borate ≤ 50 g/l , The substrate of silver-plated layer such as copper, copper alloy, steel, stainless steel, nickel-iron alloy, etc., stainless steel cathode, the operating temperature range is 20~50℃, the voltage is 3~15 V, and the current density is 0.1~5 A/dm ² , The exposed pre-silver layer is completely removed, the glossy silver layer maintains the original brightness without discoloration, and the exposed copper layer maintains the brightness and is not corroded. (3) Japanese Open Patent Gazette, Unexamined 2002-30500 (Heisei 14) NE Chemcat Co., Ltd. proposed: the operation pH of succinimide is 7.5~9, pH>10, because succinimide is easily decomposed by adding water, As a result, the concentration is difficult to maintain and the life limit is short. In addition, Japanese Patent Laid-Open No. 7-243100, Japan Electroplating Eng. Co., Ltd. proposed that succinimide stripped silver more than 18 g/l, the result was uneven silver surface, with yellow smell, the stripping for 2 hours can be adjusted concentration and pH.

In order to improve the above-mentioned disadvantages of succinimide, hydantoin compounds have been proposed. Japanese Open Patent Gazette, JP 7-243100 (1995), Japan Electroplating Eng. Co., Ltd. proposed electrolytic silver stripping agent: hydantoin compound as complexing agent, pH adjusting agent and conductive salt, such as KOH, NaOH, chlorinated Potassium, potassium phosphate, etc., pH 7~12, operating temperature range 20~60°C, current density 0.5~10 A/dm ² , stainless steel cathode, pre-silvered and completely stripped, silver layer is not discolored, copper substrate and copper exposed There is no corrosion or discoloration on the surface. Japanese Patent Publication, JP 11-50298 (1999), Japan Electroplating Eng. Co., Ltd. patent proposes electrolytic silver stripper: hydantoin compound as complexing agent, aldehyde group and/or sulfonic acid group compound as gloss adjuster, pH adjuster and conductive salts, such as KOH, NaOH, potassium chloride, potassium phosphate, etc., pH 7~12, operating temperature range 20~60℃, current density 0.5~10 A/dm ² , pre-silvering is completely stripped, and the test piece remains The gloss of silver is 0.5~0.7 (0.5~0.7 before peeling treatment) has not changed, and the surface of silver-plated layer is glossy and has no irregularity. Japanese Patent Gazette, Patent No. 4312201 (2009) Nippon Mining Materials Co., Ltd. proposed electrolytic silver stripping agent: hydantoin compound as complexing agent, and adding aminocarboxylic acid, pH 9~12, stainless steel cathode, operating temperature range 10~60℃ , the current density is 0.1~50 A/dm ² . Stripping off the unnecessary silver layer, the substrate surface has good appearance and side stripping ability, the silver surface gloss is 0.41 (the silver surface gloss before stripping is 0.40, the larger the number, the higher the gloss), but it does not reduce the residual silver. Gloss. In practice, if the gloss of the residual silver is too high, it will cause adverse effects on image recognition during wire bonding. Japanese Patent Publication No. 10-298800 (1998), Japan Electroplating Eng. Co., Ltd. proposed electrolytic silver stripping agent: hydantoin compound as complexing agent, and adding high molecular nitrogen compound (molecular weight 100~70000) as gloss modifier, As well as pH adjusters and conductive salts, such as KOH, NaOH, potassium chloride, potassium phosphate, etc., pH 7~12, operating temperature range 20~60°C, current density 0.5~10 A/dm ² , pre-silver completely stripped , and reduces the gloss of residual silver.

The cyanide used in the above-mentioned conventional technology is a toxic chemical substance, which is harmful to the human body and the water environment.

The silver stripping agent containing succinimide used in the above-mentioned conventional technology is easily decomposed by adding water when the pH of the treatment solution is greater than 10, resulting in difficulty in maintaining the concentration and short lifespan. Imide decomposes early and has a short life span, so it has been replaced by hydantoin compounds.

The electrolytic silver stripper containing a hydantoin compound used in the above-mentioned conventional technology is used to strip off the connector and lead frame, and remove the unnecessary silver plated layer, which cannot reduce the gloss of the residual silver. The adjusting agent can reduce the gloss of the necessary part of the silver surface, but the molecular weight of the high molecular nitrogen compound also affects the gloss.

One object of the present invention is to provide an electrolytic silver stripping agent, which does not contain cyanide and polymer nitrogen compounds, can quickly strip off unnecessary silver plating layers on electronic parts such as connectors and lead frames, and can reduce residual silver of gloss.

In order to achieve the above purpose, the present invention relates to an electrolytic silver stripper, comprising 1-300 g/l of hydantoin compound; 10-150 g/l of pH adjuster and conductive salt; and 0.05-10 g/l of alkanolamide g/l.

In one aspect, the hydantoin compound is 1-methylhydantoin, 1,3-dimethylhydantoin, or 5,5-dimethylhydantoin ( 5,5-dimethylhydantoin).

In one aspect, the pH adjuster and conductive salt are selected from the group consisting of potassium hydroxide, sodium hydroxide, potassium phosphate, sodium phosphate, ammonium phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, and diammonium hydrogen phosphate. material from any of the ethnic groups.

In one aspect, the alkanolamide is selected from the group consisting of diethanolamide oleate, diethanolamide linoleate, N,N-diethanoldodecanolamide, and diethanolamide cocoate. material from any of the ethnic groups.

The electrolytic silver stripping agent of the present invention does not use cyanide, which is a toxic chemical substance, and can quickly strip off unnecessary silver plating layers on connectors and lead frames without damaging the substrate.

The invention provides an electrolytic silver stripping method, comprising: providing an electrolytic cell, which includes a cathode, an anode and an electrolytic silver stripping agent; placing a silver-containing substrate in the electrolytic cell, and combining with the electrolytic cell Anode connection; voltage applied for electrolytic silver stripping.

In one aspect, the above-mentioned electrolytic silver stripper includes 1-300 g/l of hydantoin compound; 10-150 g/l of pH adjuster and conductive salt; and 0.05-10 g/l of alkanolamide. l.

The electrolytic silver-stripping method of the present invention is an electrochemical process. Electric energy is provided from the outside to dissociate the unnecessary metal layer on the anode and dissolve it into the electrolyte, so that the unnecessary silver-plated layer is stripped off without any damage. The way in which the substrate is eroded.

A specific example of the present invention relates to an electrolytic silver stripper, including 1-300 g/l of hydantoin compound; 10-150 g/l of pH adjuster and conductive salt; and 0.05-10 g/l of alkanolamide l.

In a specific example, the concentration of the hydantoin compound contained in the electrolytic silver stripping agent of the present invention is 1-300 g/l, preferably 50-150 g/l, and suitable hydantoin compounds include 1-methyl hydantoin (1-methyl hydantoin). -methylhydantoin), 1,3-dimethylhydantoin (1,3-dimethylhydantoin) and 5,5-dimethylhydantoin (5,5-dimethylhydantoin), etc., 5,5-dimethylhydantoin is the most suitable Because, as a silver complex agent, when the concentration is low, the silver stripping efficiency is low and the dissolved silver content is small, 5,5-dimethyl hydantoin is 75 g/l, and the best state can strip silver 30 g/l ; When the concentration is high, the cost of dosing is increased, and the efficiency cannot be increased.

In a specific example, the pH adjuster and conductive salt contained in the electrolytic silver stripping agent of the present invention are selected from potassium hydroxide, sodium hydroxide, potassium phosphate, sodium phosphate, ammonium phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate and One of the materials of any group composed of diammonium hydrogen phosphate, the concentration of the pH adjuster and the conductive salt is 10~150 g/l, preferably 20~80 g/l, and the optimum pH of the treatment solution is greater than 10, when the concentration When the concentration is low, the conductivity of the treatment solution is low, and the silver stripping efficiency is low; when the concentration is high, the cost of dosing is increased, and the efficiency cannot be increased.

In a specific example, the alkanolamide contained in the electrolytic silver stripper of the present invention is selected from the group consisting of diethanolamide oleate, diethanolamide linoleate, N,N-diethanoldodecamide and coconut oleic acid. One of the materials of any group composed of diethanolamide, the concentration of alkanolamide is 0.05~10 g/l, preferably 0.1~5 g/l, alkanolamide is used as gloss adjuster, when the concentration is low When the concentration is high, the coating gloss is not improved significantly; when the concentration is high, the cost of dosing is increased, and the efficiency cannot be increased.

The electrolytic silver stripping agent of the present invention does not use cyanide, which is a toxic chemical substance, and can quickly strip off unnecessary silver plating layers on connectors and lead frames without damaging the substrate.

In addition, the present invention provides an electrolytic silver stripping method, comprising: providing an electrolytic cell, the electrolytic cell includes a cathode, an anode and an electrolytic silver stripping agent; placing a silver-containing substrate in the electrolytic cell, and Connect with the anode; apply a certain voltage for electrolytic silver stripping, wherein the electrolytic silver stripping agent includes 1~300 g/l of hydantoin compound; 10~150 g/l of pH adjusting agent and conductive salt; and alkanolamide (alkanolamide) 0.05~10 g/l.

The concentration of the above hydantoin compounds is 1~300 g/l, preferably 50~150 g/l. Suitable hydantoin compounds include 1-methylhydantoin, 1,3-dimethylhydantoin (1,3-dimethylhydantoin) and 5,5-dimethylhydantoin (5,5-dimethylhydantoin).

The concentration of the above pH adjusting agent and conductive salt is 10~150 g/l, preferably 20~80 g/l. Suitable pH adjusting agent and conductive salt include potassium hydroxide, sodium hydroxide, potassium phosphate, sodium phosphate, phosphoric acid Ammonium, dipotassium hydrogen phosphate, disodium hydrogen phosphate and diammonium hydrogen phosphate, etc. or mixtures thereof.

The concentration of the above-mentioned alkanolamide is 0.05~10 g/l, preferably 0.1~5 g/l, and suitable alkanolamides include oleic acid diethanolamide, linoleic acid diethanolamide, N,N- Diethanol laurylamide and cocoate diethanolamide, etc. or mixtures thereof.

In a specific example, insoluble materials such as graphite, platinum titanium mesh, platinum niobium mesh, and AISI 316 stainless steel can be used for the cathode of the electrolytic silver stripping method of the present invention. The anode of the electrolytic silver stripping method of the present invention can be made of AISI 316 stainless steel.

In a specific example, the operating temperature range of the electrolytic silver stripping method of the present invention is 20 to 60° C., preferably 45 to 50° C. When the temperature is low, the conductivity of the treatment solution is poor and the stripping efficiency is low; when the temperature is high, the cost is low. Energy, fast volatilization of the treatment solution, and large variation in the composition of the solution.

In a specific example, the operating pH of the electrolytic silver stripping method of the present invention is 7-14, preferably pH 10-11.

In a specific example, the operating current density of the electrolytic silver stripping method of the present invention is 0.5~10 A/dm ² , and the voltage is 2~4 V, preferably 2.5~3.5 V; when the voltage is lower than 2 V, the silver stripping efficiency is low; When the voltage is higher than 4 V, the silver stripping efficiency is fast, but the stripping is uneven.

The electrolytic silver-stripping method of the present invention is an electrochemical process. Electric energy is provided from the outside to dissociate the unnecessary metal layer on the anode and dissolve it into the electrolyte, so that the unnecessary silver-plated layer is stripped off without any damage. The way in which the substrate is eroded.

The operation parameters and test results of the embodiments of the electrolytic silver stripping method of the present invention are described below. Gloss test: record the average of three test points; tester: NDK VSR 400 gloss coater; Fischerscope X-ray XDLM X-ray fluorescence thickness gauge.

Example 1: Using a copper lead frame The substrate with cyanide bath copper/silver plating of 3~4 μ″ is the object to be treated, and the surface area of the electrolytically stripped silver is 0.4 dm ² . The electrolytic stripper used in this example Silver agents include 5,5-dimethylhydantoin (5,5-dimethylhydantoin) 100 g/l, KOH 40 g/l, and diethanolamide cocoate 0.01 g/l, for electrolytic silver stripping pH 10.88, operating temperature 45~50℃, stainless steel anode, voltage 3.74 V, current 0.8 A, electrolysis time 4 seconds, the average gloss before peeling is 0.646, and the average gloss remaining after peeling is 0.67.

Example 2: Using a copper lead frame The substrate with cyanide bath copper/silver plating of 3~4 µ″ is the object to be treated, and the surface area of the electrolytically stripped silver is 0.4 dm ² . The electrolytic stripper used in this example The silver agent includes 5,5-dimethyl hydantoin 100 g/l, KOH 40 g/l, and diethanolamide cocoate 0.05 g/l. The difference from Example 1 is to change diethanolamide cocoate. The concentration of amine. The operating pH during electrolytic silver stripping is 10.69, the operating temperature is 45~50 °C, the anode is stainless steel, the voltage is 3.48 V, the current is 0.8 A, the electrolysis time is 4 seconds, the average gloss before stripping is 0.646, and the test piece after stripping The residual average gloss was 0.5875.

Example 3: Using a copper lead frame The substrate with cyanide bath copper/silver plating of 3~4 μ″ is the object to be treated, and the surface area of the electrolytically stripped silver is 0.4 dm ² . The electrolytic stripper used in this example The silver agent includes 100 g/l of 5,5-dimethyl hydantoin, 40 g/l of KOH, and 0.2 g/l of diethanolamide cocoate. The difference from Example 1 is to change diethanolamide cocoate. The concentration of amine. The operating pH during electrolytic silver stripping is 10.64, the operating temperature is 45~50 °C, the anode is stainless steel, the voltage is 3.38 V, the current is 0.8 A, the electrolysis time is 4 seconds, the average gloss before stripping is 0.646, and the test piece after stripping The residual average gloss is 0.575.

Example 4: Using a copper lead frame The substrate with cyanide bath copper/silver plating of 3~4 μ″ is the object to be treated, and the surface area of the electrolytically stripped silver is 0.4 dm ² . The electrolytic stripper used in this example The silver agent includes 5,5-dimethyl hydantoin 100 g/l, KOH 60 g/l, and diethanolamide cocoate 1 g/l. The difference from Example 1 is to change KOH and cocoic acid diethanolamine. The concentration of ethanolamide. The operating pH during electrolytic silver stripping is 10.64, the operating temperature is 45~50 °C, the anode is stainless steel, the voltage is 3.24 V, the current is 0.8 A, the electrolysis time is 4 seconds, the average gloss before stripping is 0.646, and after stripping The average gloss remaining on the test piece is 0.5125.

Comparative Example 1: Using a copper lead frame with a cyanide bath copper/silver plating of 3~4 μ″ on the substrate as the object to be treated, the surface area of the electrolytically stripped silver is 0.4 dm ² . The electrolytic stripper used in this comparative example The silver agent refers to the content of Japanese Patent Laid-Open No. 10-298800, including 5,5-dimethylhydantoin (5,5-dimethylhydantoin) 100 g/l, KOH 40 g/l, and polyethyleneimine (polyethyleneimine) 2 g/l (the stock solution is dissolved in water to make 40 g/l, the addition amount is 50 ml/l), the operating pH of the electrolytic silver stripping is 10.88, the operating temperature is 45~50 °C, the anode is made of stainless steel, the voltage is 3.76 V, The current is 0.8 A, the electrolysis time is 4 seconds, the pre-silver is completely stripped, the silver layer in the functional area has no double color, the average gloss before stripping is 0.548, and the average gloss remaining after stripping is 0.418 .

Comparative Example 2: Using a copper lead frame with a cyanide bath copper/silver plating of 3~4 μ″ on the substrate as the object to be treated, the surface area of the electrolytically stripped silver is 0.4 dm ² . The electrolytic stripper used in this comparative example The silver agent includes 5,5-dimethylhydantoin 100 g/l, KOH 40 g/l, polyethyleneimine 2 g/l (the stock solution is dissolved in water to make 40 g/l, the addition amount is 50 ml/l) , and quaternary lauryl tripolyoxyethylene ammonium hydroxide (which is a cationic surfactant) 0.01 g/l, the operating pH for electrolytic silver stripping is 10.82, and the operating temperature is 45~50 ℃, the anode is made of stainless steel, the voltage is 2.76 V, the current is 0.8 A, the electrolysis time is 4 seconds, the pre-silvering is completely stripped, the average gloss before stripping is 0.584, and the average gloss remaining after stripping is 0.584, and cationic surfactant is added. , to reduce the operating voltage.

Comparative Example 3: Using a copper lead frame with a cyanide bath copper/silver plating of 3~4 μ″ on the substrate as the object to be treated, the surface area of the electrolytically stripped silver is 0.4 dm ² . The electrolytic stripper used in this comparative example The silver agent includes 5,5-dimethylhydantoin 100 g/l, KOH 40 g/l, polyethyleneimine 2 g/l (the stock solution is dissolved in water to make 40 g/l, the addition amount is 50 ml/l) , and PE6400 (polyoxyethylene, polyoxypropylene block polymer, a non-ionic surfactant) 0.01 g/l, the operating pH during electrolytic silver stripping is 10.88, the operating temperature is 45~50 ℃, the anode is made of stainless steel, The voltage was 2.76 V, the current was 0.8 A, the electrolysis time was 4 seconds, the pre-silver was completely stripped, the average gloss before stripping was 0.78, and the average gloss remaining after stripping was 0.881.

The electrolytic silver stripping agent of the present invention can be used in production lines such as LED and IC lead frames, and can quickly strip off unnecessary silver plating layers on the lead frames without damaging the substrate.

The foregoing descriptions of the embodiments and specific examples should be considered as illustrative, rather than limiting, of the invention as defined by the scope of the claims. It will be readily appreciated that numerous variations and combinations of the above-recited features may be utilized without departing from the invention as described in the claims. Such variations are intended to be included within the scope of the following claims.

Claims (10)

An electrolytic silver stripping agent comprises 1-300 g/l of hydantoin compound; 10-150 g/l of pH adjusting agent and conductive salt; and 0.05-10 g/l of alkanolamide. The electrolytic silver stripper according to claim 1, wherein the hydantoin compound is one of 1-methyl hydantoin, 1,3-dimethyl hydantoin and 5,5-dimethyl hydantoin. The electrolytic silver stripper of claim 1, wherein the pH adjuster and the conductive salt are selected from potassium hydroxide, sodium hydroxide, potassium phosphate, sodium phosphate, ammonium phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate and hydrogen phosphate One of the materials of any group composed of diammonium. The electrolytic silver stripper according to claim 3, wherein the alkanolamide is selected from the group consisting of oleic acid diethanolamide, linoleic acid diethanolamide, N,N-diethanol lauramide and cocoic acid diethanol One of the materials of any group consisting of amides. An electrolytic silver stripping method, comprising: providing an electrolytic cell, which comprises a cathode, an anode and an electrolytic silver stripping agent; placing a silver-containing substrate in the electrolytic cell and connecting with the anode; Apply a certain voltage to carry out electrolytic silver stripping, wherein the electrolytic silver stripping agent includes 1~300 g/l of hydantoin compound; 10~150 g/l of pH adjusting agent and conductive salt; and 0.05~10 g/l of alkanolamide l. The electrolytic silver stripping method of claim 5, wherein the cathode is graphite, platinum titanium mesh, platinum niobium mesh or AISI 316 stainless steel. The electrolytic silver stripping method of claim 5, wherein the applied voltage is 2-4 V. The electrolytic silver stripping method of claim 5, wherein the operating current density is 0.5-10 A/dm ² . The electrolytic silver stripping method of claim 5, wherein the operating temperature range is 20°C to 60°C. The electrolytic silver stripping method of claim 5, wherein the operating pH is 7-14.