Palladium plating solution for palladium-plated copper-based bonding wire and preparation method of palladium plating solution

Abstract

The invention provides a palladium plating solution for a palladium-plated copper-based bonding wire and a preparation method of the palladium plating solution, the palladium plating solution comprises tetraammine palladium sulfate, isopropanolamine, sodium hypophosphite, boric acid, bismuth nitrate and polyethylene glycol, tetraammine palladium sulfate is adopted as a main salt of the palladium plating solution, sodium hypophosphite is selected as a reducing agent, boric acid and isopropanolamine are used as pH buffering agent regulators, and bismuth nitrate and polyethylene glycol are added into the palladium plating solution. Meanwhile, isopropanolamine serves as a complexing agent to stabilize palladium ions and improve the dispersing capacity and covering capacity of the plating solution, bismuth nitrate is used for improving the stability of the plating solution, and polyethylene glycol is used for enhancing the binding force between a palladium plating layer and the copper-based bonding wire; the novel palladium plating solution formula provided by the invention is good in practicability, and the palladium-plated copper-based bonding wire prepared by utilizing the palladium plating solution formula has good mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of bonding wires, in particular to a palladium plating solution for palladium-plated copper-based bonding wires and a preparation method thereof. Background Art

[0002] Copper-Based Bonding Wire is a material used for electronic packaging and connection, mainly used for interconnection between chips and substrates. It is usually made of high-purity copper or copper alloy and is a fine diameter high tensile strength metal wire. Common ones include alloy bonding wire, copper bonding wire, aluminum bonding wire, gold bonding wire, etc. The characteristics that bonding wire must have are corrosion resistance, conductivity, good connectivity, and fast bonding speed.

[0003] Palladium plating of copper-based bonding wire can improve its reliability and form a palladium coating with good oxidation resistance on the surface of the copper wire, thereby improving the bonding quality of the copper wire. The palladium source used in the existing copper-based palladium plating process is mainly palladium chloride, and the commonly used chelating agents include ethylenediamine, ammonia water, aminocarboxylic acid, aminosulfonic acid, etc. The reducing agents used are mainly sodium hypophosphite, formic acid, hydrazine hydrate, etc.

[0004] Palladium chloride is the main salt of palladium plating solution. It is stored and transported in liquid state and is not used in production operations. - The presence of palladium easily causes electrochemical corrosion of electrical components; therefore, the inventors have developed a new palladium plating solution to solve the above problems and meet application requirements. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a palladium plating solution for palladium-plated copper-based bonding wire and a method for preparing the same. The technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a palladium plating solution for palladium-plated copper-based bonding wires, the components of which include tetraamminepalladium sulfate, isopropanolamine, sodium hypophosphite, boric acid, bismuth nitrate, and polyethylene glycol.

[0007] Preferably, the concentration of palladium ions in the palladium plating solution is 1-8 g / L, and:

[0008]

[0009] Bismuth nitrate 3-6 mg / L,

[0010] Polyethylene glycol 0.5-2g / L.

[0011] In a second aspect, the present invention provides a method for preparing the palladium plating solution of the palladium-plated copper-based bonding wire, comprising the following steps:

[0012] S1. adding a palladium salt and isopropanolamine to an aqueous ammonia solution to form a complex, and adding sulfuric acid to react with the complex to form tetraamminepalladium sulfate;

[0013] S2. Add bismuth nitrate, polyethylene glycol and sodium hypophosphite to the tetraamminepalladium sulfate solution, and use boric acid to adjust the pH of the palladium plating solution to 7-9.

[0014] Preferably, the temperature of the palladium plating solution is controlled at 35-45°C.

[0015] The beneficial effects of the present invention are as follows: the present invention adopts tetraamminepalladium sulfate as the main salt of the palladium plating solution, and selects sodium hypophosphite as a reducing agent, boric acid and isopropanolamine as a pH buffer and a regulator, and isopropanolamine is used as a complexing agent to stabilize palladium ions, improve the dispersibility and covering ability of the plating solution, bismuth nitrate is used to improve the stability of the plating solution, and polyethylene glycol enhances the bonding force between the palladium plating layer and the copper-based bonding wire; the new palladium plating solution formula provided by the present invention has good practicality, and the palladium-plated copper-based bonding wire prepared by using the same has good mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0017] Figure 1 This is the morphology of the 20±1 μm palladium-plated copper-based bonding wire prepared in Example 1. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with embodiments and drawings.

[0019] Example 1

[0020] 1) Raw material preparation and pretreatment: ultrasonically clean the metal with anhydrous ethanol and dry it;

[0021] 2) Base material casting: Mix the dried metal copper, manganese, tungsten, boron and zirconium, and perform vacuum melting in a high-purity argon atmosphere with a vacuum degree of 10 -3 ~10 -2 MPa, the melting temperature is 1050-1250°C, and the melting time is 50-80 min; then directional continuous casting is performed to obtain a copper-based master alloy wire with a diameter of 30-60 μm;

[0022] 3) Surface activation treatment: using an organic solvent to clean and deoxidize the surface of the copper-based master alloy wire, and then immersing the copper-based master alloy wire in an acidic solution for activation;

[0023] 4) Surface palladium plating: A layer of metal palladium is plated on the surface of the copper-based master alloy wire after surface activation treatment. The electroplating solution is an alkaline palladium electroplating solution with a pH of 7-8 and an electroplating current density of 3A / dm 2 , the temperature of the palladium plating solution is 35-40°C; tetraammine palladium sulfate is added to the palladium plating solution to make the concentration of palladium ions 5g / L, sodium hypophosphite 20g / L, boric acid 15-30g / L, isopropanolamine 30-60mL / L, bismuth nitrate 5mg / L, polyethylene glycol 1g / L; the electroplating time is about 10-30 minutes, and a metal palladium layer with a surface thickness of about 0.2μm is formed;

[0024] 5) The electroplated wire is annealed, drawn, and annealed to obtain a 20±1 μm palladium-plated copper-based bonding wire.

[0025] Example 2

[0026] 1) Raw material preparation and pretreatment: ultrasonically clean the metal with anhydrous ethanol and dry it;

[0027] 2) Base material casting: Mix the dried metal copper, manganese, tungsten, boron and zirconium, and perform vacuum melting in a high-purity argon atmosphere with a vacuum degree of 10 -3 ~10 -2 MPa, the melting temperature is 1050-1250°C, and the melting time is 50-80 min; then directional continuous casting is performed to obtain a copper-based master alloy wire with a diameter of 30-60 μm;

[0028] 3) Surface activation treatment: using an organic solvent to clean and deoxidize the surface of the copper-based master alloy wire, and then immersing the copper-based master alloy wire in an acidic solution for activation;

[0029] 4) Surface palladium plating: A layer of metal palladium is plated on the surface of the copper-based master alloy wire after surface activation treatment. The electroplating solution is an alkaline palladium electroplating solution. The pH of the alkaline palladium electroplating solution is 7.5-8.5, and the current density of the electroplating is 3A / dm 2 The temperature of the palladium plating solution is 45-50°C; tetraammine palladium sulfate is added to make the concentration of palladium ions 3g / L, sodium hypophosphite 20g / L, boric acid 15-30g / L, isopropanolamine 30-60mL / L, bismuth nitrate 5mg / L, polyethylene glycol 1g / L; the electroplating time is about 10-30 minutes, and a metal palladium layer with a surface thickness of about 0.2μm is formed.

[0030] Example 3

[0031] 1) Raw material preparation and pretreatment: ultrasonically clean the metal with anhydrous ethanol and dry it;

[0032] 2) Base material casting: Mix the dried metal copper, manganese, tungsten, boron and zirconium, and perform vacuum melting in a high-purity argon atmosphere with a vacuum degree of 10 -3 ~10 -2 MPa, the melting temperature is 1050-1250°C, and the melting time is 50-80 min; then directional continuous casting is performed to obtain a copper-based master alloy wire with a diameter of 30-60 μm;

[0033] 3) Surface activation treatment: using an organic solvent to clean and deoxidize the surface of the copper-based master alloy wire, and then immersing the copper-based master alloy wire in an acidic solution for activation;

[0034] 4) Surface palladium plating: A layer of metal palladium is plated on the surface of the copper-based master alloy wire after surface activation treatment. The electroplating solution is an alkaline palladium electroplating solution. The pH of the alkaline palladium electroplating solution is 7.5-8.5, and the current density of the electroplating is 3A / dm 2 The temperature of the palladium plating solution is 40-45°C; tetraammine palladium sulfate is added to make the concentration of palladium ions 4g / L, sodium hypophosphite 20g / L, boric acid 15-30g / L, isopropanolamine 30-60mL / L, bismuth nitrate 5mg / L, polyethylene glycol 1g / L; the electroplating time is about 10-30 minutes, and a metal palladium layer with a surface thickness of about 0.2μm is formed.

[0035] The performance test of the 20±1 μm palladium-plated copper-based bonding wire in Example 1-3 was carried out, and the test results were as follows:

[0036]

[0037] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A palladium plating solution for palladium-plated copper-based bonding wire, characterized in that: Including tetraamminepalladium sulfate, isopropanolamine, sodium hypophosphite, boric acid, bismuth nitrate, and polyethylene glycol.

2. The palladium plating solution for palladium-plated copper-based bonding wire according to claim 1, characterized in that: The concentration of palladium ions is 1-8g / L, and:

3. A method for preparing a palladium plating solution for a palladium-plated copper-based bonding wire according to claim 1 or 2, characterized in that: The following steps are involved: S1. adding a palladium salt and isopropanolamine to an aqueous ammonia solution to form a complex, and adding sulfuric acid to react with the complex to form tetraamminepalladium sulfate; S2. Add bismuth nitrate, polyethylene glycol and sodium hypophosphite to the tetraamminepalladium sulfate solution, and use boric acid to adjust the pH of the palladium plating solution to 7-9.

4. The method for preparing a palladium plating solution for palladium-plated copper-based bonding wire according to claim 3, characterized in that: The temperature of the palladium plating solution is controlled at 35-45°C.

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