Chemical thick gold plating solution and method for chemical thick gold plating of LTCC copper-based material

Abstract

The invention relates to the technical field of chemical gold plating, and provides a chemical thick gold plating solution and a method for chemical thick gold plating of an LTCC copper-based material. The chemical thick gold plating solution provided by the invention comprises the following components: gold sulfite, alkali metal sulfite, sodium thiosulfate, benzotriazole, polyethylene potassium sulfate, a pH regulator and water. The chemical thick gold plating solution provided by the invention has self-catalytic reduction capacity, does not need to be replaced with nickel to form a gold layer, and the pH value of the plating solution is alkaline, so that a material cannot be corroded during plating, and the gold wire bonding capacity and the welding performance of a plating layer are greatly improved. The chemical thick gold plating method provided by the invention comprises the following steps of: removing oil from an LTCC copper-based material, and sequentially carrying out glass etching, deoxidation, palladium activation, chemical nickel plating, gold pre-plating and chemical thick gold plating. Gold pre-plating is carried out before thick gold chemical plating, the adhesive force between the gold layer and the nickel layer can be increased, and the deposition continuity and integrity of the thick gold layer are improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical gold plating, in particular to a chemical thick gold plating solution and a method for chemical thick gold plating of LTCC copper-based materials. Background Art

[0002] LTCC (Low Temperature Co-fired Ceramic) is one of the key materials in electronic packaging and micro-electromechanical systems. LTCC copper-based materials are LTCC materials with copper as the main conductive component, mainly consisting of copper electrodes and matching LTCC substrates.

[0003] LTCC copper-based materials have better high-frequency characteristics than gold-based materials, and do not have the silver migration defect of silver-based materials, and have a very advantageous price. However, copper itself is easy to oxidize and has poor corrosion resistance. It is necessary to plate chemical nickel and chemical thick gold on the copper surface to make LTCC copper-based materials have corrosion resistance and excellent welding performance.

[0004] When the traditional method of chemical thick gold plating is used, the thickness of the gold layer is increased by reacting with the nickel layer through replacement or semi-replacement and semi-reduction. However, as the gold plating proceeds, the gold layer completely blocks the nickel layer, and the gold-nickel replacement reaction can no longer be carried out, so the thickness of the resulting thick gold layer is relatively small. In addition, the traditional chemical thick gold plating solution is acidic and will corrode the LTCC material. While performing the gold-nickel replacement, it will attack and corrode the nickel layer, which is very likely to produce nickel black disks, resulting in poor welding and even the shedding of the gold plating layer, and the reliability is very poor. Summary of the invention

[0005] In view of this, the present invention provides a chemical thick gold plating solution and a method for chemical thick gold plating of LTCC copper-based materials. The chemical thick gold plating solution provided by the present invention has self-catalytic reduction ability, does not need to be replaced with nickel to form a thick gold layer, and the pH value of the chemical thick gold plating solution is alkaline, and the material will not be corroded during plating, which greatly improves the gold wire bonding ability and welding performance of the plating layer, and has good reliability.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A chemical thick gold plating solution comprises the following components in concentration: 2-4 g / L gold sulfite, 50-60 g / L alkali metal sulfite, 20-30 g / L sodium thiosulfate, 1-2 g / L benzotriazole, 0.1-0.2 g / L potassium polyvinyl sulfate, 0.2-0.3 g / L pH adjuster, and the solvent is water; wherein the concentration of gold sulfite is calculated in terms of gold; The pH value of the chemical thick gold plating solution is ≥8.

[0007] Preferably, the alkali metal sulfite is potassium sulfite and / or sodium sulfite; and the pH adjuster is sodium hydroxide.

[0008] Preferably, the pH value of the chemical thick gold plating solution is 8-8.4.

[0009] The present invention also provides a method for chemically plating thick gold on LTCC copper-based materials, comprising the following steps: After degreasing the LTCC copper-based material, glass etching, deoxidation, palladium activation, chemical nickel plating, pre-gold plating and chemical thick gold plating are performed in sequence; The plating solution used in the pre-gold plating includes the following components in concentration: 20-25 g / L potassium citrate, 20-25 g / L dipotassium hydrogen phosphate, 2-3 g / L potassium gold cyanide, and the solvent is water; The plating solution used for the chemical thick gold plating is the chemical thick gold plating solution described in the above scheme.

[0010] Preferably, the pre-gold plating temperature is 80-90° C., the time is 5-8 min, and the pH value is 8-8.5; the pre-gold plating obtains a thin gold layer, and the thickness of the thin gold layer is 0.05-0.1 μm.

[0011] Preferably, the temperature of the chemical thick gold plating is 50-60° C.; the chemical thick gold plating obtains a thick gold layer, and the thickness of the thick gold layer is ≥0.1 μm.

[0012] Preferably, the degreasing temperature is 50-60°C and the time is 5-8 minutes; the pH value of the degreasing liquid used for the degreasing is 13-14.

[0013] Preferably, the etching solution used for glass etching includes components with the following concentrations: 30-40 g / L sodium hydroxide, 3-5 g / L sodium fluoride, and the solvent is water; the pH value of the etching solution is 13-14; and the glass etching time is 1-2 min.

[0014] Preferably, the deoxidation liquid used for deoxidation comprises the following components in concentration: 5-10 g / L sodium cyanide, 5-10 g / L sodium m-nitrobenzene sulfonate, and the solvent is water; the pH value of the deoxidation liquid is 10-12; and the deoxidation time is 1-2 min.

[0015] Preferably, the activation solution used for palladium activation includes the following components in concentration: palladium chloride 0.1-0.15 g / L, sodium chloride 30-40 g / L, and the solvent is water; the pH value of the activation solution is 7-7.5; the palladium activation time is 2-3 min; The temperature of the chemical nickel plating is 80-90° C., and the time is 15-20 min. The thickness of the nickel layer obtained by the chemical nickel plating is 3-5 μm.

[0016] The invention provides a chemical thick gold plating solution, comprising the following components in concentration: 2-4 g / L of gold sulfite, 50-60 g / L of alkali metal sulfite, 20-30 g / L of sodium thiosulfate, 1-2 g / L of benzotriazole, 0.1-0.2 g / L of potassium polyvinyl sulfate, 0.2-0.3 g / L of pH adjuster, and water as solvent; wherein the concentration of the gold sulfite is calculated in terms of gold; and the pH value of the chemical thick gold plating solution is ≥8. The invention adopts gold sulfite to provide gold ions, and sodium thiosulfate as a reducing agent. When chemical plating is performed, the reducing agent can reduce the gold ions to gold, thereby realizing self-catalytic reduction, and does not need to replace with nickel to form a thick gold layer. The thickness of the thick gold layer can be increased only by extending the deposition time. In addition, the invention adopts benzotriazole as a corrosion inhibitor, potassium polyvinyl sulfate as a brightener, and alkali metal sulfite as a complexing agent, which can improve the chemical activity and stability of the plating solution under alkaline conditions, so that the gold ions can be deposited in an orderly manner, and a thick gold layer with good uniformity, good color and high density can be obtained. In addition, the pH value of the chemical thick gold plating solution provided by the invention is alkaline, and the nickel layer and the LTCC material will not be corroded, the gold wire bonding ability and welding performance of the plating layer are greatly improved, and the obtained plating layer has good reliability.

[0017] The present invention also provides a method for chemically plating thick gold on LTCC copper-based materials, comprising the following steps: after degreasing the LTCC copper-based materials, glass etching, deoxidation, palladium activation, chemical nickel plating, pre-gold plating and chemical thick gold plating are sequentially performed; the plating solution used for the pre-gold plating comprises the following concentrations of components: 20-25 g / L potassium citrate, 20-25 g / L dipotassium hydrogen phosphate, 2-3 g / L potassium gold cyanide, and the solvent is water; the plating solution used for the chemical thick gold plating is the chemical thick gold plating solution described in the above scheme. The present invention first performs pre-gold plating before chemical thick gold plating to form a thin gold layer, which can increase the adhesion between the gold layer and the nickel layer. During chemical thick gold plating, the reduction deposition of gold ions is carried out on the surface of the thin gold layer, thereby improving the continuity and integrity of the thick gold layer deposition. The results of the embodiment show that the thick gold layer prepared by the present invention can reach 2 μm without corroding the nickel layer, and the gold wire bonding strength can reach 10N.

[0018] Furthermore, in the conventional LTCC copper-based material chemical thick gold plating process, the treatment solutions used for deoxidation, palladium activation, chemical thick gold plating, etc. are all acidic, and the LTCC material is easily corroded in an acidic environment, thereby affecting the performance of the material itself. The plating solutions used for the pre-gold plating and chemical thick gold plating of the present invention are all alkaline, and the treatment solutions used for the glass etching, deoxidation, palladium activation, chemical nickel plating, etc. steps are also alkaline or nearly neutral, which greatly reduces the corrosion of the LTCC material, thereby ensuring the electrical properties of the material. DETAILED DESCRIPTION

[0019] The invention provides a chemical thick gold plating solution, comprising the following components in concentration: 2-4 g / L gold sulfite, 50-60 g / L alkali metal sulfite, 20-30 g / L sodium thiosulfate, 1-2 g / L benzotriazole, 0.1-0.2 g / L potassium polyvinyl sulfate, 0.2-0.3 g / L pH adjuster, and the solvent is water; wherein the concentration of the gold sulfite is calculated in terms of gold; The pH value of the chemical thick gold plating solution is ≥8.

[0020] In the present invention, the chemical thick gold plating solution includes 2-4 g / L of gold sulfite (in terms of gold), specifically 2 g / L, 2.5 g / L, 3 g / L or 4 g / L.

[0021] In the present invention, the chemical thick gold plating solution includes 50-60 g / L of alkali metal sulfite, specifically 50 g / L, 53 g / L, 55 g / L, 58 g / L or 60 g / L; the alkali metal sulfite is preferably potassium sulfite and / or sodium sulfite, specifically anhydrous potassium sulfite and / or anhydrous sodium sulfite; the alkali metal sulfite is a complexing agent, which can form a complex with gold ions, so that the gold ions are stably present in the plating solution, thereby improving the stability of the plating solution.

[0022] In the present invention, the chemical thick gold plating solution includes 20-30 g / L of sodium thiosulfate, specifically 20 g / L, 22 g / L, 25 g / L, 26 g / L or 30 g / L; the sodium thiosulfate is a reducing agent and can reduce gold ions.

[0023] In the present invention, the chemical thick gold plating solution includes 1-2 g / L of benzotriazole, specifically 1 g / L, 1.3 g / L, 1.5 g / L or 2 g / L; the benzotriazole is a corrosion inhibitor, which can form a protective film on the surface of the substrate to prevent corrosion of the substrate.

[0024] In the present invention, the chemical thick gold plating solution includes 0.1-0.2 g / L of potassium polyvinyl sulfate, specifically 0.1 g / L, 0.15 g / L, 0.18 g / L or 0.2 g / L; the potassium polyvinyl sulfate is a brightener, which can improve the density of the thick gold layer.

[0025] In the present invention, the chemical thick gold plating solution includes a pH adjuster of 0.2-0.3 g / L, specifically 0.2 g / L, 0.25 or 0.3 g / L; the pH adjuster is preferably sodium hydroxide; the pH value of the chemical thick gold plating solution is ≥8, preferably 8-8.4. The present invention controls the pH value of the chemical thick gold plating solution within the above range, which can avoid corrosion of the LTCC material and ensure the electrical properties of the material.

[0026] In the present invention, the solvent of the chemical thick gold plating solution is water.

[0027] The present invention also provides a method for chemically plating thick gold on LTCC copper-based materials, comprising the following steps: After degreasing the LTCC copper-based material, glass etching, deoxidation, palladium activation, chemical nickel plating, pre-gold plating and chemical thick gold plating are performed in sequence.

[0028] In the present invention, the degreasing temperature is preferably 50-60°C, specifically 50°C, 55°C or 60°C, the degreasing time is preferably 5-8min, specifically 5min, 6min, 7min or 8min; the pH value of the degreasing liquid used for degreasing is preferably 13-14; in a specific embodiment of the present invention, the degreasing liquid used for degreasing is preferably prepared from degreasing powder and water, the degreasing powder is preferably commercially available Huapu C2014 degreasing powder, and the concentration of the degreasing powder in the degreasing liquid is preferably 50-60g / L; the water described in the present invention is all pure water, which will not be repeated later; the present invention carries out degreasing under the above conditions, which can remove grease on the surface of the substrate and improve the adhesion of the coating.

[0029] In the present invention, the etching solution used for glass etching preferably includes the following concentrations of components: 30-40 g / L of sodium hydroxide, specifically 30 g / L, 35 g / L or 40 g / L, 3-5 g / L of sodium fluoride, specifically 3 g / L, 4 g / L or 5 g / L, the solvent of the etching solution is water; the pH value of the etching solution is preferably 13-14; the time of glass etching is preferably 1-2 min, and the present invention has no special requirements for the temperature of the glass etching, and it can be carried out at room temperature. The present invention performs glass etching under the above conditions, which can clean the glass phase on the copper surface and avoid excessive glass phase affecting the effect of chemical nickel plating and gold plating.

[0030] In the present invention, the deoxidation liquid used for deoxidation preferably includes the following concentrations of ingredients: sodium cyanide 5-10g / L, specifically 5g / L, 6g / L, 7g / L, 8g / L, 9g / L or 10g / L, sodium m-nitrobenzene sulfonate 5-10g / L, specifically 5g / L, 6g / L, 7g / L, 8g / L, 9g / L or 10g / L, and the solvent is water; the pH value of the deoxidation liquid is preferably 10-12, specifically 10, 10.5, 11 or 12; the deoxidation time is preferably 1-2min. The present invention has no special requirements for the deoxidation temperature, and it can be carried out at room temperature. The present invention uses sodium cyanide and sodium m-nitrobenzene sulfonate as the main components of the deoxidation liquid, which can effectively remove the oxide layer on the copper surface, improve the adhesion of the coating, and can achieve deoxidation under alkaline conditions to avoid corrosion of the base material.

[0031] In the present invention, the activation solution used for palladium activation preferably includes the following concentrations of components: palladium chloride 0.1-0.15 g / L, specifically 0.1 g / L, 0.12 g / L, 0.13 g / L or 0.15 g / L, sodium chloride 30-40 g / L, specifically 30 g / L, 35 g / L, 38 g / L or 40 g / L, and the solvent is water; the pH value of the activation solution is preferably 7-7.5; the time of palladium activation is preferably 2-3 min; the present invention has no special requirements for the temperature of palladium activation, and it can be carried out at room temperature. The present invention performs palladium activation under the above conditions, which can make palladium adsorbed and evenly distributed on the surface of LTCC copper-based materials, provide uniform catalytic sites for the reduction of metal ions, and enable nickel ions to be uniformly deposited on the surface of the copper layer.

[0032] In the present invention, the temperature of the chemical nickel plating is preferably 80-90°C, specifically 80°C, 85°C or 90°C, and the time of the chemical nickel plating is preferably 15-20min; the thickness of the nickel layer obtained by the chemical nickel plating is preferably 3-5μm; the pH value of the plating solution used for the chemical nickel plating is preferably 6.5; in a specific embodiment of the present invention, the plating solution used for the chemical nickel plating is preferably the commercially available Ensen JS-926 plating solution.

[0033] In the present invention, the plating solution used for the pre-gold plating preferably includes the following concentrations of components: 20-25 g / L of potassium citrate, specifically 20 g / L, 22 g / L, 23 g / L or 25 g / L, 20-25 g / L of dipotassium hydrogen phosphate, specifically 20 g / L, 22 g / L, 23 g / L or 25 g / L, 2-3 g / L of potassium gold cyanide, specifically 2 g / L, 2.2 g / L, 2.5 g / L or 3 g / L, and the solvent is water; the temperature of the pre-gold plating is preferably 80-90°C, specifically 80°C, 85°C or 90°C, the time of the pre-gold plating is preferably 5-8 min, specifically 6 min, 7 min or 8 min, and the pH value of the pre-gold plating is preferably 8-8.5; the pre-gold plating obtains a thin gold layer, and the thickness of the thin gold layer is preferably 0.05-0.1 μm. The present invention forms a thin gold layer by pre-plating gold, which can increase the adhesion between the gold layer and the nickel layer.

[0034] In the present invention, the plating solution used for the chemical thick gold plating is the chemical thick gold plating solution described in the above scheme; the temperature of the chemical thick gold plating is preferably 50-60°C, specifically 50°C, 55°C or 60°C; the chemical thick gold plating obtains a thick gold layer, the thickness of the thick gold layer is ≥0.1μm, preferably 0.1-2μm, more preferably 0.1-1.3μm, and further preferably 0.5-1.3μm; the time of the chemical thick gold plating is preferably controlled according to the thickness of the thick gold layer, the longer the time, the greater the thickness of the thick gold layer. In a specific embodiment of the present invention, the plating time of the chemical thick gold plating is preferably 15-130min, when the plating time is 15min, a 0.25μm thick gold layer is obtained, when the plating time is 30-40min, a 0.5-0.6μm thick gold layer is obtained, when the plating time is 60min, a 1μm thick gold layer is obtained, and when the plating time is 130min, a 2μm thick gold layer can be obtained.

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1 The LTCC copper substrate was degreased using a degreasing liquid prepared from Huapu C2014 degreasing powder and water, wherein the concentration of the degreasing powder was 50 g / L, the pH value was 13, the degreasing temperature was 50°C, and the time was 5 min.

[0037] The degreased LTCC copper substrate is placed in an etching solution for glass etching, wherein the components of the etching solution are: 30 g / L sodium hydroxide, 3 g / L sodium fluoride, the solvent is water, the pH value is 13, the etching temperature is room temperature, and the time is 1 min.

[0038] The LTCC copper substrate after glass etching is placed in a deoxidation solution for deoxidation, wherein the components of the deoxidation solution are: 5 g / L sodium cyanide, 5 g / L sodium m-nitrobenzene sulfonate, the solvent is water, the pH value is 10, the deoxidation temperature is room temperature, and the time is 1 minute.

[0039] The deoxidized LTCC copper substrate was placed in an activation solution for palladium activation, wherein the components of the activation solution were: 0.1 g / L palladium chloride, 30 g / L sodium chloride, the solvent was water, the pH value was 7, the palladium activation temperature was room temperature, and the time was 2 minutes.

[0040] The palladium activated LTCC copper substrate was placed in a plating solution for chemical nickel plating, wherein the plating solution was Enson JS-926, the pH value was 6.5, the plating temperature was 80°C, the time was 15 minutes, and the thickness of the obtained nickel layer was 3 μm.

[0041] The nickel-plated LTCC copper substrate is placed in a plating solution for pre-gold plating, wherein the composition of the plating solution is: 20 g / L potassium citrate, 20 g / L dipotassium hydrogen phosphate, 2 g / L potassium gold cyanide, the solvent is water, the pH value is 8, the pre-gold plating temperature is 80°C, and the time is 5 minutes; the thickness of the obtained thin gold layer is 0.05 μm.

[0042] The LTCC copper substrate after pre-gold plating is placed in a chemical thick gold plating solution for chemical thick gold plating, wherein the chemical thick gold plating solution comprises: gold sulfite, 3 g / L in terms of gold, 60 g / L anhydrous potassium sulfite, 20 g / L sodium thiosulfate, 1 g / L benzotriazole, 0.1 g / L potassium polyvinyl sulfate, 0.2 g / L sodium hydroxide, the solvent is water, the pH value of the chemical thick gold plating solution is 8, the plating temperature is 50°C, the time is 30 min, and the thickness of the obtained thick gold layer is 0.5 μm, the color is bright, and the plating layer is dense.

[0043] The welding ability test of the LTCC copper substrate plated with a thick gold layer was carried out using a handheld tensile tester. The results showed that as the tensile force increased, the copper layer and the LTCC material separated, while the thick gold layer and the copper layer did not separate, indicating that the bonding strength between the thick gold layer and the copper layer of the present invention is higher.

[0044] The gold wire bonding strength of the LTCC copper substrate plated with a thick gold layer was tested, and the results showed that the gold wire bonding strength was 10N.

[0045] Example 2 The other conditions were the same as those in Example 1, except that the plating time of the thick gold plating was controlled to 15 min, and a thick gold layer with a thickness of 0.25 μm was obtained. The LTCC copper substrate plated with the thick gold layer was subjected to a gold wire bonding strength test and a welding capability test, and the results showed that the gold wire bonding strength was 4N; in the welding capability test, the copper layer and the LTCC material were separated, while the thick gold layer and the copper layer were not separated.

[0046] Example 3 The other conditions were the same as those in Example 1, except that the plating time of the thick gold plating was controlled to 60 min, and a thick gold layer with a thickness of 1 μm was obtained. The LTCC copper substrate plated with the thick gold layer was subjected to a gold wire bonding strength test and a welding capability test, and the results showed that the gold wire bonding strength was 12N; in the welding capability test, the copper layer and the LTCC material were separated, while the thick gold layer and the copper layer were not separated.

[0047] Example 4 The other conditions were the same as those in Example 1, except that the plating time of the thick gold plating was controlled to 130 min, and a thick gold layer with a thickness of 2 μm was obtained. The soldering ability test was performed on the LTCC copper substrate plated with the thick gold layer, and the results showed that the copper layer and the LTCC material were separated, while the thick gold layer and the copper layer were not separated.

[0048] Example 5 The LTCC copper substrate was degreased using a degreasing liquid prepared from Huapu C2014 degreasing powder and water, wherein the concentration of the degreasing powder was 60 g / L, the pH value was 14, the degreasing temperature was 60°C, and the time was 8 min.

[0049] The degreased LTCC copper substrate is placed in an etching solution for glass etching, wherein the etching solution comprises 40 g / L sodium hydroxide, 5 g / L sodium fluoride, the solvent is water, the pH value is 14, the etching temperature is room temperature, and the etching time is 2 minutes.

[0050] The LTCC copper substrate after glass etching is placed in a deoxidation solution for deoxidation, wherein the deoxidation solution comprises: 6 g / L sodium cyanide, 8 g / L sodium m-nitrobenzene sulfonate, the solvent is water, the pH value is 11, the deoxidation temperature is room temperature, and the time is 2 minutes.

[0051] The deoxidized LTCC copper substrate was placed in an activation solution for palladium activation, wherein the components of the activation solution were: 0.15 g / L palladium chloride, 35 g / L sodium chloride, the solvent was water, the pH value was 7.5, the palladium activation temperature was room temperature, and the time was 3 minutes.

[0052] The palladium activated LTCC copper substrate was placed in a plating solution for chemical nickel plating, wherein the plating solution was Enson JS-926, the pH value was 6.5, the plating temperature was 90°C, the time was 20 minutes, and the thickness of the obtained nickel layer was 5 μm.

[0053] The nickel-plated LTCC copper substrate is placed in a plating solution for pre-gold plating, wherein the composition of the plating solution is: 25 g / L potassium citrate, 25 g / L dipotassium hydrogen phosphate, 3 g / L potassium gold cyanide, the solvent is water, the pH value is 8.5, the pre-gold plating temperature is 90°C, and the time is 8 minutes; the thickness of the obtained thin gold layer is 0.1 μm.

[0054] The LTCC copper substrate after pre-gold plating is placed in a chemical thick gold plating solution for chemical thick gold plating, wherein the chemical thick gold plating solution comprises: gold sulfite, 4 g / L in terms of gold, 50 g / L anhydrous potassium sulfite, 30 g / L sodium thiosulfate, 2 g / L benzotriazole, 0.2 g / L potassium polyvinyl sulfate, 0.25 g / L sodium hydroxide, the solvent is water, the pH value of the chemical thick gold plating solution is 8.3, the plating temperature is 60°C, the time is 40 min, the thickness of the obtained thick gold layer is 0.6 μm, the obtained thick gold layer is bright in color, and the plating layer is dense.

[0055] The LTCC copper substrate plated with a thick gold layer was subjected to gold wire bonding strength tests and welding capacity tests. The results showed that the gold wire bonding strength was 10N; in the welding capacity test, the copper layer and the LTCC material were separated, while the thick gold layer and the copper layer were not separated.

[0056] Comparative Example 1 Other conditions were the same as those in Example 1, except that the concentration of potassium polyvinyl sulfate in the chemical thick gold plating solution was changed to 0.05 g / L. The results showed that the color of the obtained thick gold layer was dark.

[0057] Comparative Example 2 Other conditions were the same as those in Example 1, except that the concentration of potassium polyvinyl sulfate in the chemical thick gold plating solution was changed to 0.3 g / L. The results showed that leakage plating occurred when plating a thick gold layer.

[0058] Comparative Example 3 Other conditions were the same as those in Example 1, except that the concentration of sodium thiosulfate in the chemical thick gold plating solution was changed to 15 g / L. The results showed that the gold plating rate was significantly reduced, with only 0.05 μm plated in 10 min.

[0059] Comparative Example 4 Other conditions were the same as those in Example 1, except that the concentration of sodium thiosulfate in the chemical thick gold plating solution was changed to 35 g / L. The results showed that the stability of the plating solution deteriorated, precipitation occurred, the appearance was turbid, and a gold layer was also precipitated on the surface of the LTCC substrate.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A chemical thick gold plating solution, characterized in that: The composition comprises the following concentrations: gold sulfite 2-4 g / L, alkali metal sulfite 50-60 g / L, sodium thiosulfate 20-30 g / L, benzotriazole 1-2 g / L, potassium polyvinyl sulfate 0.1-0.2 g / L, pH adjuster 0.2-0.3 g / L, and the solvent is water; The concentration of gold sulfite is measured in gold; The pH value of the chemical thick gold plating solution is ≥8.

2. The chemical thick gold plating solution according to claim 1, characterized in that: The alkali metal sulfite is potassium sulfite and / or sodium sulfite; the pH adjuster is sodium hydroxide.

3. The chemical thick gold plating solution according to claim 1, characterized in that: The pH value of the chemical thick gold plating solution is 8-8.

4.

4. A method for chemically plating thick gold on LTCC copper-based materials, characterized in that: The following steps are involved: After degreasing the LTCC copper-based material, glass etching, deoxidation, palladium activation, chemical nickel plating, pre-gold plating and chemical thick gold plating are performed in sequence; The plating solution used in the pre-gold plating includes the following components in concentration: 20-25 g / L potassium citrate, 20-25 g / L dipotassium hydrogen phosphate, 2-3 g / L potassium gold cyanide, and the solvent is water; The plating solution used for the chemical thick gold plating is the chemical thick gold plating solution according to any one of claims 1 to 3.

5. The method according to claim 4, characterized in that The pre-gold plating temperature is 80-90° C., the time is 5-8 min, and the pH value is 8-8.5; the pre-gold plating obtains a thin gold layer, and the thickness of the thin gold layer is 0.05-0.1 μm.

6. The method according to claim 4, characterized in that The temperature of the chemical thick gold plating is 50-60° C. The chemical thick gold plating obtains a thick gold layer, and the thickness of the thick gold layer is ≥0.1 μm.

7. The method according to claim 4, characterized in that The degreasing temperature is 50-60°C and the time is 5-8 minutes; the pH value of the degreasing liquid used for the degreasing is 13-14.

8. The method according to claim 4, characterized in that The etching solution used for glass etching includes the following components in concentration: 30-40 g / L sodium hydroxide, 3-5 g / L sodium fluoride, and the solvent is water; the pH value of the etching solution is 13-14; and the glass etching time is 1-2 min.

9. The method according to claim 4, characterized in that The deoxidation liquid used for deoxidation includes the following components in concentration: 5-10 g / L sodium cyanide, 5-10 g / L sodium m-nitrobenzene sulfonate, and the solvent is water; the pH value of the deoxidation liquid is 10-12; and the deoxidation time is 1-2 min.

10. The method according to claim 4, characterized in that The activation solution used for palladium activation includes the following components in concentrations: palladium chloride 0.1-0.15 g / L, sodium chloride 30-40 g / L, and the solvent is water; the pH value of the activation solution is 7-7.5; the palladium activation time is 2-3 min; The temperature of the chemical nickel plating is 80-90° C., and the time is 15-20 min. The thickness of the nickel layer obtained by the chemical nickel plating is 3-5 μm.