A method for electroless thick gold plating solution and electroless thick gold plating of LTCC copper-based materials

Abstract

The present invention relates to the technical field of electroless gold plating, and provides an electroless thick gold plating solution and a method for electroless thick gold plating on LTCC copper-based materials. The components of the electroless thick gold plating solution provided by the present invention include gold sulfite, alkali metal sulfite, sodium thiosulfate, benzotriazole, potassium polyvinyl sulfate, a pH adjuster, and water. The electroless thick gold plating solution provided by the present invention has the ability of autocatalytic reduction, does not need to form a gold layer by nickel displacement, and the pH value of the plating solution is alkaline, so it will not corrode the material during plating, greatly improving the wire bonding ability and welding performance of the coating. The electroless thick gold plating method provided by the present invention comprises the following steps: degreasing the LTCC copper-based material, and then successively performing glass etching, deoxidation, palladium activation, electroless nickel plating, pre-gold plating, and electroless thick gold plating. The present invention performs pre-gold plating before electroless thick gold plating, which can increase the adhesion between the gold layer and the nickel layer and improve the continuity and integrity of the deposition of the thick gold layer.

Description

Technical Field

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

[0002] LTCC (i.e., low temperature co-fired ceramics) is one of the key materials in electronic packaging and microelectromechanical systems. LTCC copper-based materials are LTCC materials with copper as the main conductive component, mainly composed of two parts: a copper electrode and a matching LTCC substrate.

[0003] LTCC copper-based materials have more excellent high-frequency characteristics than gold-based materials, and have no defects of silver migration of silver-based materials, and the price has great advantages. However, copper itself is easy to oxidize and has poor corrosion resistance, and it is necessary to electrolessly plate nickel and electroless thick gold on the copper surface, so that the LTCC copper-based materials have anti-corrosion ability and excellent welding performance.

[0004] When electroless thick gold plating is carried out by traditional methods, it reacts with the nickel layer through a displacement or semi-displacement semi-reduction method to increase the thickness of the gold layer. However, as the gold plating progresses, the gold layer completely blocks the nickel layer, and the gold-nickel displacement reaction can no longer be carried out, so the thickness of the obtained thick gold layer is small. In addition, the traditional electroless thick gold plating solution is acidic, which will corrode the LTCC material, attack and corrode the nickel layer while carrying out the gold-nickel displacement, and is extremely easy to produce nickel black discs, resulting in poor welding, and even the gold plating layer falling off, and the reliability is very poor. Summary of the Invention

[0005] In view of this, the present invention provides an electroless thick gold plating solution and a method for electroless thick gold plating of LTCC copper-based materials. The electroless thick gold plating solution provided by the present invention has an autocatalytic reduction ability, does not need to displace with nickel to form a thick gold layer, and the pH value of the electroless thick gold plating solution is alkaline, and it will not corrode the material during plating, greatly improving the wire bonding ability and welding performance of the plating layer, and having good reliability.

[0006] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] An electroless thick gold plating solution, comprising components with the following concentrations: 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 the solvent is water; wherein the concentration of gold sulfite is calculated as gold;

[0008] The pH value of the electroless thick gold plating solution ≥ 8.

[0009] Preferably, the alkali metal sulfite is potassium sulfite and / or sodium sulfite; the pH adjuster is sodium hydroxide.

[0010] Preferably, the pH value of the electroless thick gold plating solution is 8 - 8.4.

[0011] The present invention also provides a method for electroless thick gold plating on an LTCC copper-based material, comprising the following steps:

[0012] After degreasing the LTCC copper-based material, successively perform glass etching, deoxidation, palladium activation, electroless nickel plating, pre-gold plating, and electroless thick gold plating;

[0013] The plating solution used for the pre-gold plating comprises components with the following concentrations: potassium citrate 20 - 25 g / L, dipotassium hydrogen phosphate 20 - 25 g / L, potassium gold cyanide 2 - 3 g / L, and the solvent is water;

[0014] The plating solution used for the electroless thick gold plating is the electroless thick gold plating solution described in the above solution.

[0015] Preferably, the temperature of the pre-gold plating is 80 - 90 °C, the time is 5 - 8 min, and the pH value is 8 - 8.5; a thin gold layer is obtained by the pre-gold plating, and the thickness of the thin gold layer is 0.05 - 0.1 μm.

[0016] Preferably, the temperature of the electroless thick gold plating is 50 - 60 °C; a thick gold layer is obtained by the electroless thick gold plating, and the thickness of the thick gold layer is ≥0.1 μm.

[0017] Preferably, the temperature of the degreasing is 50 - 60 °C, the time is 5 - 8 min; the pH value of the degreasing solution used for the degreasing is 13 - 14.

[0018] Preferably, the etching solution used for the glass etching comprises components with the following concentrations: sodium hydroxide 30 - 40 g / L, sodium fluoride 3 - 5 g / L, and the solvent is water; the pH value of the etching solution is 13 - 14; the time of the glass etching is 1 - 2 min.

[0019] Preferably, the deoxidation solution used for the deoxidation comprises components with the following concentrations: sodium cyanide 5 - 10 g / L, sodium m-nitrobenzenesulfonate 5 - 10 g / L, and the solvent is water; the pH value of the deoxidation solution is 10 - 12; the time of the deoxidation is 1 - 2 min.

[0020] Preferably, the activation solution used for the palladium activation comprises components with the following 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 time of the palladium activation is 2 - 3 min;

[0021] The temperature of electroless nickel plating is 80 - 90 °C, and the time is 15 - 20 min; the thickness of the nickel layer obtained by electroless nickel plating is 3 - 5 μm.

[0022] The present invention provides an electroless thick gold plating solution, which comprises components with the following concentrations: 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 the solvent; wherein the concentration of gold sulfite is calculated based on gold; the pH value of the electroless thick gold plating solution ≥ 8. The present invention uses gold sulfite to provide gold ions, and sodium thiosulfate as a reducing agent. During electroless plating, the reducing agent can reduce gold ions to gold, thus realizing autocatalytic reduction. There is no need to displace nickel to form a thick gold layer, and the thickness of the thick gold layer can be increased only by extending the deposition time; moreover, the present invention uses benzotriazole as a corrosion inhibitor, potassium polyvinyl sulfate as a brightening agent, and alkali metal sulfite as a complexing agent, which can improve the chemical activity and stability of the plating solution under alkaline conditions, enabling the gold ions to deposit orderly, and obtaining a thick gold layer with good uniformity, good color, and high density; furthermore, the electroless thick gold plating solution provided by the present invention has an alkaline pH value, does not corrode the nickel layer and LTCC materials, greatly improves the wire bonding ability and welding performance of the coating, and the obtained coating has good reliability.

[0023] The present invention also provides a method for electroless thick gold plating on LTCC copper-based materials, which comprises the following steps: degreasing the LTCC copper-based materials, and then successively performing glass etching, deoxidation, palladium activation, electroless nickel plating, pre-gold plating, and electroless thick gold plating; the plating solution used for pre-gold plating comprises components with the following concentrations: 20 - 25 g / L of potassium citrate, 20 - 25 g / L of dipotassium hydrogen phosphate, 2 - 3 g / L of potassium gold cyanide, and water as the solvent; the plating solution used for electroless thick gold plating is the electroless thick gold plating solution described in the above scheme. The present invention first performs pre-gold plating before electroless thick gold plating to form a thin gold layer, which can increase the adhesion between the gold layer and the nickel layer. During electroless thick gold plating, the reduction and deposition of gold ions occur on the surface of the thin gold layer, thereby improving the continuity and integrity of the deposition of the thick gold layer. The results of the examples show that the thick gold layer prepared by the present invention can reach 2 μm without corroding the nickel layer, and at the same time, the wire bonding strength can reach 10 N.

[0024] Furthermore, in the traditional electroless thick gold plating process for LTCC copper-based materials, the treatment solutions used for deoxidation, palladium activation, electroless thick gold plating, etc. are all acidic, and the LTCC materials are easily corroded in an acidic environment, thus affecting the performance of the materials themselves. However, the plating solutions used for pre-gold plating and electroless thick gold plating in the present invention are both alkaline, and at the same time, the treatment solutions used for steps such as glass etching, deoxidation, palladium activation, and electroless nickel plating are also alkaline or near-neutral, greatly reducing the erosion of LTCC materials, thereby ensuring the electrical properties of the materials. Detailed implementation mode

[0025] The present invention provides an electroless thick gold plating solution, which comprises components with the following concentrations: 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 the solvent is water; wherein the concentration of gold sulfite is calculated based on gold;

[0026] The pH value of the electroless thick gold plating solution is ≥8.

[0027] In the present invention, the electroless thick gold plating solution comprises 2-4 g / L of gold sulfite (calculated based on gold), specifically it can be 2 g / L, 2.5 g / L, 3 g / L or 4 g / L.

[0028] In the present invention, the electroless thick gold plating solution comprises 50-60 g / L of alkali metal sulfite, specifically it can be 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 to make the gold ions stably exist in the plating solution and improve the stability of the plating solution.

[0029] In the present invention, the electroless thick gold plating solution comprises 20-30 g / L of sodium thiosulfate, specifically it can be 20 g / L, 22 g / L, 25 g / L, 26 g / L or 30 g / L; the sodium thiosulfate is a reducing agent, which can reduce gold ions.

[0030] In the present invention, the electroless thick gold plating solution comprises 1-2 g / L of benzotriazole, specifically it can be 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 avoid substrate corrosion.

[0031] In the present invention, the electroless thick gold plating solution comprises 0.1-0.2 g / L of potassium polyvinyl sulfate, specifically it can be 0.1 g / L, 0.15 g / L, 0.18 g / L or 0.2 g / L; the potassium polyvinyl sulfate is a brightening agent, which can improve the density of the thick gold layer.

[0032] In the present invention, the electroless thick gold plating solution comprises a pH adjuster at 0.2 - 0.3 g / L, specifically it can be 0.2 g / L, 0.25 g / L or 0.3 g / L; the pH adjuster is preferably sodium hydroxide; the pH value of the electroless thick gold plating solution is ≥8, preferably 8 - 8.4. By controlling the pH value of the electroless thick gold plating solution within the above range in the present invention, corrosion of the LTCC material can be avoided and the electrical properties of the material can be ensured.

[0033] In the present invention, the solvent of the electroless thick gold plating solution is water.

[0034] The present invention also provides a method for electroless thick gold plating on an LTCC copper-based material, comprising the following steps:

[0035] After degreasing the LTCC copper-based material, glass etching, deoxidation, palladium activation, electroless nickel plating, pre-gold plating and electroless thick gold plating are carried out in sequence.

[0036] In the present invention, the temperature of the degreasing is preferably 50 - 60°C, specifically it can be 50°C, 55°C or 60°C, the time of the degreasing is preferably 5 - 8 min, specifically it can be 5 min, 6 min, 7 min or 8 min; the pH value of the degreasing solution used for degreasing is preferably 13 - 14; in a specific embodiment of the present invention, the degreasing solution used for degreasing is preferably prepared from a degreasing powder and water, the degreasing powder is preferably the commercially available Huapu C2014 degreasing powder, and the concentration of the degreasing powder in the degreasing solution is preferably 50 - 60 g / L; the water mentioned in the present invention is all pure water and will not be elaborated further hereinafter; by degreasing under the above conditions in the present invention, the grease on the surface of the substrate can be removed and the adhesion of the coating can be improved.

[0037] In the present invention, the etching solution used for glass etching preferably comprises components with the following concentrations: sodium hydroxide 30 - 40 g / L, specifically it can be 30 g / L, 35 g / L or 40 g / L, sodium fluoride 3 - 5 g / L, specifically it can be 3 g / L, 4 g / L or 5 g / L, and the solvent of the etching solution is water; the pH value of the etching solution is preferably 13 - 14; the time of the 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. By carrying out glass etching under the above conditions in the present invention, the glass phase on the copper surface can be cleaned up, and it can be avoided that excessive glass phase will affect the effects of electroless nickel plating and gold plating.

[0038] In the present invention, the deoxidizing solution used for deoxidation preferably comprises components with the following concentrations: sodium cyanide 5 - 10 g / L, specifically it can be 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, sodium metanitrobenzenesulfonate 5 - 10 g / L, specifically it can be 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, and the solvent is water; the pH value of the deoxidizing solution is preferably 10 - 12, specifically it can be 10, 10.5, 11 or 12; the time for deoxidation is preferably 1 - 2 min. The present invention has no special requirement for the temperature of the deoxidation, and it can be carried out at room temperature. The present invention uses sodium cyanide and sodium metanitrobenzenesulfonate as the main components of the deoxidizing solution, 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 substrate material.

[0039] In the present invention, the activation solution used for palladium activation preferably comprises components with the following concentrations: palladium chloride 0.1 - 0.15 g / L, specifically it can be 0.1 g / L, 0.12 g / L, 0.13 g / L or 0.15 g / L, sodium chloride 30 - 40 g / L, specifically it can be 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 for palladium activation is preferably 2 - 3 min; the present invention has no special requirement for the temperature of the palladium activation, and it can be carried out at room temperature. The present invention carries out palladium activation under the above conditions, which can enable palladium to adsorb and be evenly distributed on the surface of the LTCC copper-based material, provide uniform catalytic sites for the reduction of metal ions, and enable nickel ions to be evenly deposited on the surface of the copper layer.

[0040] In the present invention, the temperature for electroless nickel plating is preferably 80 - 90 °C, specifically it can be 80 °C, 85 °C or 90 °C, the time for electroless nickel plating is preferably 15 - 20 min; the thickness of the nickel layer obtained by electroless nickel plating is preferably 3 - 5 μm; the pH value of the plating solution used for electroless nickel plating is preferably 6.5; in the specific embodiments of the present invention, the plating solution used for electroless nickel plating is preferably the commercially available Ensen JS-926 plating solution.

[0041] In the present invention, the plating solution used for the pre-gold plating preferably comprises components with the following concentrations: potassium citrate 20 - 25 g / L, specifically it can be 20 g / L, 22 g / L, 23 g / L or 25 g / L; dipotassium hydrogen phosphate 20 - 25 g / L, specifically it can be 20 g / L, 22 g / L, 23 g / L or 25 g / L; potassium gold cyanide 2 - 3 g / L, specifically it can be 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 it can be 80 °C, 85 °C or 90 °C. The time of the pre-gold plating is preferably 5 - 8 min, specifically it can be 6 min, 7 min or 8 min. 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. By forming a thin gold layer through pre-gold plating in the present invention, the adhesion between the gold layer and the nickel layer can be increased.

[0042] In the present invention, the plating solution used for the electroless thick gold plating is the electroless thick gold plating solution described in the above solution. The temperature of the electroless thick gold plating is preferably 50 - 60 °C, specifically it can be 50 °C, 55 °C or 60 °C. The electroless thick gold plating obtains a thick gold layer, and the thickness of the thick gold layer ≥ 0.1 μm, preferably 0.1 - 2 μm, more preferably 0.1 - 1.3 μm, and further preferably 0.5 - 1.3 μm. The time of the electroless 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 the specific embodiments of the present invention, the plating time of the electroless thick gold plating is preferably 15 - 130 min. When the plating time is 15 min, a thick gold layer with a thickness of 0.25 μm is obtained. When the plating time is 30 - 40 min, a thick gold layer with a thickness of 0.5 - 0.6 μm is obtained. When the plating time is 60 min, a thick gold layer with a thickness of 1 μm is obtained. When the plating time is 130 min, a thick gold layer with a thickness of 2 μm can be obtained.

[0043] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0044] Example 1

[0045] The LTCC copper substrate is degreased. The degreasing solution used is prepared from Huapu C2014 degreasing powder and water, where the concentration of the degreasing powder is 50 g / L, the pH value is 13, the degreasing temperature is 50 °C, and the time is 5 min.

[0046] The degreased LTCC copper substrate is placed in an etching solution for glass etching. The composition of the etching solution is: 30 g / L of sodium hydroxide, 3 g / L of sodium fluoride, with water as the solvent, a pH value of 13, an etching temperature of room temperature, and an etching time of 1 min.

[0047] The LTCC copper substrate after glass etching is placed in a deoxidizing solution for deoxidization. The composition of the deoxidizing solution is: 5 g / L of sodium cyanide, 5 g / L of sodium m-nitrobenzenesulfonate, with water as the solvent, a pH value of 10, a deoxidizing temperature of room temperature, and a deoxidizing time of 1 min.

[0048] The LTCC copper substrate after deoxidization is placed in an activating solution for palladium activation. The composition of the activating solution is: 0.1 g / L of palladium chloride, 30 g / L of sodium chloride, with water as the solvent, a pH value of 7, a palladium activation temperature of room temperature, and a palladium activation time of 2 min.

[0049] The LTCC copper substrate after palladium activation is placed in a plating solution for electroless nickel plating. The plating solution is Ensen JS-926, with a pH value of 6.5, a plating temperature of 80 °C, a plating time of 15 min, and the thickness of the obtained nickel layer is 3 μm.

[0050] The LTCC copper substrate after nickel plating is placed in a plating solution for pre-gold plating. The composition of the plating solution is: 20 g / L of potassium citrate, 20 g / L of dipotassium hydrogen phosphate, 2 g / L of potassium gold cyanide, with water as the solvent, a pH value of 8, a pre-gold plating temperature of 80 °C, and a pre-gold plating time of 5 min; the thickness of the obtained thin gold layer is 0.05 μm.

[0051] The LTCC copper substrate after pre-gold plating is placed in an electroless thick gold plating solution for electroless thick gold plating. The composition of the electroless thick gold plating solution is: gold sulfite, calculated as gold 3 g / L, 60 g / L of anhydrous potassium sulfite, 20 g / L of sodium thiosulfate, 1 g / L of benzotriazole, 0.1 g / L of potassium polyvinylsulfate, 0.2 g / L of sodium hydroxide, with water as the solvent, the pH value of the electroless thick gold plating solution is 8, the plating temperature is 50 °C, the plating time is 30 min, the thickness of the obtained thick gold layer is 0.5 μm, with bright color and dense coating.

[0052] The LTCC copper substrate plated with a thick gold layer is subjected to a soldering ability test, which is carried out using a handheld tensile machine. The results show that as the tensile force increases, the copper layer and the LTCC material separate, while the thick gold layer and the copper layer do not separate, indicating that the bonding strength between the thick gold layer and the copper layer of the present invention is higher.

[0053] The gold wire bonding strength of the LTCC copper substrate plated with a thick gold layer is tested, and the results show that the gold wire bonding strength is 10 N.

[0054] Example 2

[0055] Other conditions are the same as those in Example 1. Only the plating time of electroless thick gold is controlled to be 15 min, and a thick gold layer with a thickness of 0.25 μm is obtained. The LTCC copper substrate plated with the thick gold layer is subjected to gold wire bonding strength test and soldering ability test. The results show that the gold wire bonding strength is 4 N; in the soldering ability test, the copper layer and the LTCC material are separated, while the thick gold layer and the copper layer are not separated.

[0056] Example 3

[0057] Other conditions are the same as those in Example 1. Only the plating time of electroless thick gold is controlled to be 60 min, and a thick gold layer with a thickness of 1 μm is obtained. The LTCC copper substrate plated with the thick gold layer is subjected to gold wire bonding strength test and soldering ability test. The results show that the gold wire bonding strength is 12 N; in the soldering ability test, the copper layer and the LTCC material are separated, while the thick gold layer and the copper layer are not separated.

[0058] Example 4

[0059] Other conditions are the same as those in Example 1. Only the plating time of electroless thick gold is controlled to be 130 min, and a thick gold layer with a thickness of 2 μm is obtained. The LTCC copper substrate plated with the thick gold layer is subjected to soldering ability test. The results show that the copper layer and the LTCC material are separated, while the thick gold layer and the copper layer are not separated.

[0060] Example 5

[0061] The LTCC copper substrate is degreased. The degreasing solution used is prepared from Huapu C2014 degreasing powder and water. The concentration of the degreasing powder is 60 g / L, the pH value is 14, the degreasing temperature is 60 °C, and the time is 8 min.

[0062] The degreased LTCC copper substrate is placed in an etching solution for glass etching. The composition of the etching solution is: sodium hydroxide 40 g / L, sodium fluoride 5 g / L, the solvent is water, the pH value is 14, the etching temperature is room temperature, and the time is 2 min.

[0063] The LTCC copper substrate after glass etching is placed in a deoxidizing solution for deoxidation. The composition of the deoxidizing solution is: sodium cyanide 6 g / L, sodium m-nitrobenzenesulfonate 8 g / L, the solvent is water, the pH value is 11, the deoxidation temperature is room temperature, and the time is 2 min.

[0064] The deoxidized LTCC copper substrate is placed in an activating solution for palladium activation. The composition of the activating solution is: palladium chloride 0.15 g / L, sodium chloride 35 g / L, the solvent is water, the pH value is 7.5, the palladium activation temperature is room temperature, and the time is 3 min.

[0065] The palladium-activated LTCC copper substrate is placed in a plating solution for electroless nickel plating. The plating solution is Ensen JS-926, with a pH value of 6.5, a plating temperature of 90 °C, a time of 20 min, and the thickness of the obtained nickel layer is 5 μm.

[0066] The nickel-plated LTCC copper substrate is placed in a plating solution for pre-gold plating. The components of the plating solution are: potassium citrate 25 g / L, dipotassium hydrogen phosphate 25 g / L, potassium gold cyanide 3 g / L, the solvent is water, the pH value is 8.5, the pre-gold plating temperature is 90 °C, and the time is 8 min; the thickness of the obtained thin gold layer is 0.1 μm.

[0067] The pre-gold-plated LTCC copper substrate is placed in an electroless thick gold plating solution for electroless thick gold plating. The components of the electroless thick gold plating solution are: gold sulfite, calculated as gold 4 g / L, anhydrous potassium sulfite 50 g / L, sodium thiosulfate 30 g / L, benzotriazole 2 g / L, potassium polyvinyl sulfate 0.2 g / L, sodium hydroxide 0.25 g / L, the solvent is water, the pH value of the electroless thick gold plating solution is 8.3, the plating temperature is 60 °C, and the time is 40 min. The thickness of the obtained thick gold layer is 0.6 μm, and the obtained thick gold layer has a bright color and a dense coating.

[0068] The LTCC copper substrate plated with a thick gold layer is tested for gold wire bonding strength and soldering ability. The results show that the gold wire bonding strength is 10 N; in the soldering ability test, the copper layer and the LTCC material are separated, while the thick gold layer and the copper layer are not separated.

[0069] Comparative Example 1

[0070] Other conditions are the same as those in Example 1, except that the concentration of potassium polyvinyl sulfate in the electroless thick gold plating solution is changed to 0.05 g / L. The results show that the color of the obtained thick gold layer is darker.

[0071] Comparative Example 2

[0072] Other conditions are the same as those in Example 1, except that the concentration of potassium polyvinyl sulfate in the electroless thick gold plating solution is changed to 0.3 g / L. The results show that there is a missing plating phenomenon when plating the thick gold layer.

[0073] Comparative Example 3

[0074] Other conditions are the same as those in Example 1, except that the concentration of sodium thiosulfate in the electroless thick gold plating solution is changed to 15 g / L. The results show that the gold plating rate is significantly reduced, and only 0.05 μm is plated at 10 min.

[0075] Comparative Example 4

[0076] Other conditions are the same as those in Example 1, except that the concentration of sodium thiosulfate in the electroless thick gold plating solution is changed to 35 g / L. The results show that the stability of the plating solution becomes poor, precipitation occurs, the appearance is turbid, and a gold layer will also precipitate on the surface of the LTCC substrate.

[0077] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. 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 composed of the following components: 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; The concentration of gold sulfite is measured in gold; The pH value of the chemical thick gold plating solution is ≥8; The etching solution used for glass etching includes the following components in 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; The deoxidation liquid used for deoxidation includes the following components in concentrations: 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; The activation solution used for palladium activation includes the following components in concentration: 0.1-0.15 g / L of palladium chloride, 30-40 g / L of sodium chloride, and the solvent is water; the pH value of the activation solution is 7-7.

5.

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

4.

4. The method according to claim 1, 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.

5. The method according to claim 1, 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.

6. The method according to claim 1, 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.

7. The method according to claim 1, characterized in that The glass etching time is 1 to 2 minutes.

8. The method according to claim 4, characterized in that The deoxidation time is 1 to 2 minutes.

9. The method according to claim 1, characterized in that: The palladium activation time is 2 to 3 minutes; 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.