ELECTROLESS CoW PLATING METHOD

Abstract

To provide a method for subjecting a hybrid vehicle inverter double-sided radiation module capable of responding to the lead free of a solder material, having wear resistance, corrosion resistance and heat resistance by forming a tough cobalt tungsten alloy film on the surface of a component and having high conductivity to electroless CoW plating.SOLUTION: An electroless CoW plating method comprises: a plating solution control step of manufacturing a plating solution controlled so as to form a plating film having a W content of 35-58 wt.% on a Co base; a plating solution supply step of supplying the plating solution to a plating tank including a heater part; and an immersion step of heating an object to be plated at a predetermined temperature while immersing the object to be plated in the plating tank and rocking the object to be plated at a rate of 0.1-5.0 m / min in the plating solution while pouring the plating solution so as to be a solution flow of 1.0-300 L / min to the heater part used for a heat source.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for electroless CoW plating of a power card, which is an electronic component, for example, an inverter double-sided heat dissipation module for a hybrid vehicle. [Background technology]

[0002] In the hybrid system of a hybrid vehicle, both the engine and the motor drive the vehicle, so the power generated by the motor is controlled by an inverter and stored in the battery, or the energy generated by the engine is recovered by regenerative braking and supplied to the motor, thereby improving fuel efficiency and driving performance.A power card, which is an inverter double-sided heat dissipation module (equipped with a new cooling structure that cools the power semiconductor elements from both sides), is used for hybrid vehicles.

[0003] The Power Card is an inverter double-sided heat dissipation module for hybrid vehicles that efficiently boosts battery power to AC to operate the motor, or efficiently reduces the motor's electricity to DC to charge it. In this way, the inverter double-sided heat dissipation module "Power Card" for hybrid vehicles controls the inverter by switching the power on and off at high speed within the power control unit, the heart of the hybrid, and contributes to improved fuel efficiency (energy saving).

[0004] With the adoption of power cards, it is essential to adopt lead-free solder in order to reduce damage to the circuit formed on the surface of the element.The applicants have been working hard to develop the present invention, believing that by adopting cobalt tungsten plating and developing a cobalt tungsten plating process, it is possible to make solder materials lead-free, and by forming a tough cobalt tungsten alloy film on the surface of the parts, it is possible to provide wear resistance, corrosion resistance, heat resistance, and high conductivity for use in inverters, which are electronic components.

[0005] Patent Document 1 states that "the present invention aims to provide a method for forming a plating film of an alloy containing tungsten which has low stress, is excellent in terms of change over time during use and process stability, and further has excellent surface condition and precision, and a mask for X-ray lithography and a mold forming die manufactured by this plating method (Patent Document 1: Abstract; Problem)," and discloses an electrolytic plating method including the steps of forming a plating base electrode on the surface of a material to be plated, and depositing any one of an alloy of tungsten and nickel, an alloy of tungsten and iron, and an alloy of tungsten and cobalt on this plating base electrode by electrolytic plating (Patent Document 1: Abstract; Solution)." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-088385 Summary of the Invention [Problem to be solved by the invention]

[0007] The tungsten alloy plating method according to Patent Document 1 (Patent Document 1: Name of the invention) includes the steps of forming a plating base electrode on the surface of the material to be plated, and depositing any one of the alloys of tungsten and nickel, the alloy of tungsten and iron, and the alloy of tungsten and cobalt on this plating base electrode by electrolytic plating.However, the tungsten alloy plating method according to Patent Document 1 (Patent Document 1: Name of the invention) is undesirable because it is based on electrolytic plating, and has problems such as high cost, fragility of coating film, problem of solution processing, need for equipment investment, and difficulty in uniformity of coating film.

[0008] The object of the present invention is to provide a method for forming electroless CoW plating on a power card, which is an inverter double-sided heat dissipation module for a hybrid vehicle, for example, and which is compatible with lead-free solder materials, and which has a high electrical conductivity for use in an inverter as an electronic component, by forming a tough cobalt-tungsten alloy film on the surface of the component, and which has abrasion resistance, corrosion resistance, and heat resistance (by electroless CoW plating). [Means for solving the problem]

[0009] In order to solve the above problem, the invention described in claim 1 is an electroless CoW plating method comprising a plating solution preparation process for producing a plating solution adjusted to form a plating layer based on Co (cobalt) and having a W (tungsten) content of 35% to 58% by weight, a plating solution supply process for supplying the plating solution to a plating tank equipped with a heater unit, and an immersion process for impregnating the object to be plated in the plating tank, wherein in the immersion process, heat treatment is performed so that the temperature of the plating solution is 20°C to 90°C, and the plating solution is flowed toward the heater unit, which is a heat source, at a liquid flow rate of 1.0 to 300 L / min, while the object to be plated is oscillated in the plating solution at a speed of 0.1 to 5.0 m / min. In this specification, oscillation primarily refers to shaking (the object to be plated) in the vertical direction, but is a concept that includes all directions other than the vertical direction; in short, it refers to the movement of (the object to be plated) floating in the plating tank, which is a three-dimensional space.

[0010] The invention described in claim 2 is characterized in that, in the invention described in claim 1, the material of the plating bath is resin or coated with resin, which is an electroless CoW plating method.

[0011] The invention described in claim 3 is characterized in that, in the invention described in claim 1 or claim 2, the material of the heater is resin or coated with resin, which is an electroless CoW plating method. Effect of the Invention

[0012] The electroless CoW plating method of the present invention can provide a method for forming electroless CoW plating, which can be adapted to lead-free soldering materials, and can also provide abrasion resistance, corrosion resistance, heat resistance, and high conductivity for use in inverters, which are electronic components, by forming a tough cobalt-tungsten alloy film on the surface of the components.Specifically, the electroless CoW plating method can be provided for hybrid vehicle inverter double-sided heat dissipation module. [Brief description of the drawings]

[0013] [Figure 1] 1A to 1C are diagrams for explaining the electroless CoW plating method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <Electroless CoW plating method> An embodiment of the electroless CoW plating method according to the present invention will be described in detail below with reference to Fig. 1. Fig. 1 is a diagram for explaining the electroless CoW plating method according to the present invention. As shown in Fig. 1, the electroless CoW plating method according to the present invention includes a surface treatment step, a plating solution preparation step, a plating solution supply step, an immersion step (forming a plating layer), and a finishing step. Each step will be described below.

[0015] Surface Treatment Process : Before plating, the surface of the power card (the part to be plated) is thoroughly washed and pre-treated to remove oil and dirt. This improves the adhesion between the plating layer and the power card surface, improving the quality of the plating. Specifically, the surface of the power card (the part to be plated) is washed with an alkali wash, acid wash, neutral wash, etc. to remove dirt and grease.

[0016] Plating solution adjustment process: This is the process of preparing the electroless CoW plating solution. The essential components of the electroless CoW plating solution are water-soluble cobalt salt and water-soluble tungsten salt. When the electroless CoW plating process is performed on the object to be plated using the electroless CoW plating solution, an electroless CoW plating layer can be formed on the surface of the object to be plated. In order to obtain the barrier effect of the electroless CoW plating layer, it is necessary to form the electroless CoW plating layer (satisfying the barrier effect) by appropriately controlling the composition, temperature, pH, processing time, etc. of the electroless CoW plating solution during processing.

[0017] The source of cobalt ions may be any water-soluble cobalt compound that releases cobalt ions, and is preferably a water-soluble cobalt salt. As the water-soluble cobalt salt, for example, inorganic water-soluble cobalt salts such as cobalt sulfate and cobalt chloride; organic water-soluble cobalt salts such as cobalt carbonate and cobalt acetate can be used. A preferred cobalt compound is an inorganic water-soluble cobalt salt, and more preferably cobalt sulfate. These can be used alone or in combination of two or more.

[0018] The concentration of the water-soluble cobalt salt in the electroless CoW plating solution (Co equivalent) can improve the plating deposition rate by increasing the concentration of the water-soluble cobalt salt, and the resulting electroless CoW plating layer exhibits a more excellent barrier effect. If the concentration of the water-soluble cobalt salt is too high, it may cause a decrease in the stability of the electroless CoW plating solution. The concentration of the water-soluble cobalt salt in the electroless CoW plating solution (when it is contained alone, it is the single concentration, and when two or more are used in combination, it is the total concentration: Co equivalent) is preferably 0.2 g / L or more, more preferably 1.0 g / L or more, and even more preferably 1.5 g / L or more, and is preferably 5 g / L or less, more preferably 3 g / L or less, and even more preferably 2.5 g / L or less. In short, the concentration of the water-soluble cobalt salt in the electroless CoW plating solution (when it is used alone, it is the concentration of the salt alone, and when it is used in combination with two or more salts, it is the total concentration: Co equivalent) is preferably 1.5 g / L to 2.5 g / L. The composition analysis of the plating solution in the present invention is performed using an ICP emission spectroscopic analyzer.

[0019] The source of tungsten ion may be any tungsten compound that releases tungsten ion, and is preferably a water-soluble tungsten salt.As the water-soluble tungsten salt, for example, tungsten chloride, tungstic acid, tungstate salt, etc. are adopted, and as the tungstate salt, sodium tungstate, potassium tungstate, ammonium tungstate, etc. are adopted.These can be used alone or in combination of two or more kinds.

[0020] The concentration of the tungsten salt in the electroless CoW plating solution (W equivalent) can improve the plating deposition rate and the resulting electroless CoW plating layer exhibits a better barrier function when the concentration of the tungsten salt is high. If the concentration of the tungsten salt is too high, it may cause the stability of the electroless CoW plating solution to decrease. The concentration of the water-soluble tungsten salt in the electroless CoW plating solution (when it is contained alone, it is the single concentration, and when two or more are used in combination, it is the total concentration: W equivalent) is preferably 1 g / L or more, more preferably 3.5 g / L or more, even more preferably 5.0 g / L or more, even more preferably 7.0 g / L or more, and is preferably 23 g / L or less, more preferably 20 g / L or less, even more preferably 15 g / L or less, and even more preferably 9.0 g / L or less. In short, the concentration of the water-soluble tungsten salt in the electroless CoW plating solution (when it is contained alone, it is the concentration of the single salt, and when two or more salts are used in combination, it is the total concentration: W conversion) is preferably 7.0 g / L to 9.0 g / L. In addition, if the concentration of the water-soluble tungsten salt is 9.0 g / L or less, it is particularly preferable because an amorphous electroless CoW plating layer can be obtained.

[0021] The reducing agent used in the present invention may have the effect of reducing and precipitating cobalt ions and tungsten ions. For example, hypophosphorous acid; hypophosphites such as sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite; hydrazine salts such as hydrazine carbonate, hydrazine sulfate, neutral hydrazine sulfate, and hydrazine hydrochloride; hydrazines such as hydrazine; and dialkylamine borane. Among these, dialkylamine borane is preferred because it can form an amorphous electroless CoW plating layer. The electroless plating layer using the electroless CoW plating solution contains B (boron) derived from dialkylamine borane.

[0022] As the dialkylamine borane, dimethylamine borane, diethylamine borane, trimethylamine borane, etc. are adopted, and preferably dimethylamine borane is adopted. One or more kinds of dialkylamine borane can be used.

[0023] The concentration of the reducing agent in the electroless CoW plating solution varies depending on the type of reducing agent, but it is desirable to adjust it to a concentration that provides sufficient reduction. Considering the plating deposition rate, it is desirable to increase the reducing agent concentration, but if the reducing agent concentration becomes too high, the stability of the plating solution may decrease. In particular, by increasing the concentration of dialkylamine borane, preferably dimethylamine borane, plating defects such as skip phenomenon can be further suppressed, and the electroless CoW plating layer is formed on the plated object densely, i.e., without undeposited parts, and a uniform electroless CoW plating layer without appearance unevenness such as galling can be formed. If the concentration of dialkylamine borane is too high, the stability of the plating solution may decrease. The concentration of dialkylamine borane in the plating solution (when it is contained alone, it is the concentration of the single, when it is used in combination with two or more, it is the total concentration), preferably the concentration of dimethylamine borane, is preferably 1.7 g / L or more, more preferably 3.0 g / L or more, further preferably 4.0 g / L or more, and is preferably 8.4 g / L or less, more preferably 8.0 g / L or less. In short, the concentration of dialkylamine borane in the plating solution (when it is contained alone, it is the concentration of the single, when it is used in combination with two or more, it is the total concentration), preferably the concentration of dimethylamine borane, is desirably 4.0 g / L to 8.0 g / L.

[0024] The electroless CoW plating solution preferably contains a complexing agent. The complexing agent is effective in preventing precipitation of cobalt and tungsten and controlling the precipitation reaction of cobalt and tungsten. In the present invention, the complexing agent is not particularly limited as long as it has the above-mentioned effects. Examples of the complexing agent include organic acids such as citric acid, malic acid, succinic acid, acetic acid, malonic acid, tartaric acid, lactic acid, and oxalic acid; amino acids such as glycine, alanine, aspartic acid, and glutamic acid; and amines such as ethylenediamine, triethanolamine, and EDTA. One or more complexing agents can be used.

[0025] If the concentration of the complexing agent in the electroless CoW plating solution is too low, precipitation of Co or W or decomposition of the plating solution may occur. If the concentration of the complexing agent is too high, there may be some areas where the electroless CoW plating layer is not formed. The concentration of the complexing agent may be appropriately adjusted so as to obtain the desired effect, and is preferably 0.001 mol / L or more, more preferably 0.005 mol / L or more, and even more preferably 0.01 mol / L or more, and is preferably 1 mol / L or less, more preferably 0.5 mol / L or less, and even more preferably 0.1 mol / L or less. In short, the concentration of the complexing agent in the electroless CoW plating solution is preferably 0.01 mol / L to 0.1 mol / L. In addition, the water-soluble cobalt salt solution or water-soluble tungsten salt solution available as a raw material for preparing the plating solution may already contain a complexing agent. If the electroless CoW plating solution contains a sufficient amount of complexing agent due to the raw materials, no addition is necessary, but if necessary, a complexing agent may be added to the electroless CoW plating solution after preparation.

[0026] The electroless CoW plating solution is prepared by dissolving the above components in a solvent, preferably water. The electroless CoW plating solution of the present invention may contain various known additives as necessary. Examples include stabilizers, pH adjusters, and surfactants. These additives may also be derived from the raw materials and may be contained in the electroless CoW plating solution. The content of any component such as additives is not particularly limited, but it is desirable that it is within a range that does not impair the bath stability of the electroless CoW plating solution of the present invention or the barrier properties and adhesion of the formed electroless CoW plating film.

[0027] Examples of the stabilizer include lead compounds such as lead nitrate and lead acetate, cadmium compounds such as cadmium nitrate and cadmium acetate, thallium compounds such as thallium nitrate and thallium nitrate, antimony compounds such as antimony chloride and potassium antimonyl tartrate, chromium compounds such as chromium oxide and chromium sulfate, etc. The stabilizers can be used alone or in combination of two or more kinds.

[0028] The stabilizer concentration in the electroless CoW plating solution is not particularly limited, and may be any concentration that can improve stability. The stabilizer concentration (when a single stabilizer is included, it is the single concentration, and when two or more stabilizers are used in combination, it is the total concentration) is preferably 0.01 mg / L or more, more preferably 0.1 mg / L or more, and preferably 100 mg / L or less, more preferably 10 mg / L or less. In short, the stabilizer concentration in the electroless CoW plating solution is desirably 0.1 mg / L to 10 mg / L.

[0029] Examples of pH adjusters that can be used include acids such as hydrochloric acid, sulfuric acid, and phosphoric acid; and alkalis such as sodium hydroxide, potassium hydroxide, and aqueous ammonia. If the pH of the electroless CoW plating solution is too low, the deposition rate of cobalt and tungsten decreases, the film-forming properties of the electroless CoW plating layer decrease, and defects such as pores may occur on the film surface. On the other hand, if the pH is too high, the deposition rate of cobalt and tungsten may become too fast, making it difficult to control the film thickness. The pH of the electroless CoW plating solution is preferably 7 or more, more preferably 8 or more, and even more preferably 9 or more, and is preferably 12 or less, more preferably 11 or less, and even more preferably 10 or less.

[0030] As the surfactant, various known surfactants such as nonionic, anionic, cationic, and amphoteric surfactants can be used alone or in combination of two or more. The concentration of the surfactant in the electroless Co-W plating solution is not particularly limited, and may be at a level that provides the effect of addition. The concentration of the surfactant (when it is contained alone, it is the concentration of the single surfactant, and when it is contained in combination of two or more surfactants, it is the total concentration) is preferably 0.01 mg / L or more, more preferably 0.1 mg / L or more, and preferably 100 mg / L or less, more preferably 10 mg / L or less.

[0031] Plating liquid supply processIn the plating solution adjustment process, the plating solution adjusted to form a plating layer with a Co (cobalt) base and a W (tungsten) content of 35% to 58% by weight is supplied to a plating tank equipped with a heater. The plating tank is made of resin or resin-coated material. For example, it may be stainless steel coated with resin. The plating tank is provided with a heater that serves as a heat source for heat-treating the plating solution (adjusting the solution temperature). The heater that serves as the heat source is made of resin or resin-coated material. For example, it may be stainless steel coated with resin.

[0032] Dipping process (forming the plating layer) : The power card to be plated is immersed in the plating solution. When metal ions (Co, W ions) accumulate on the surface of the power card to be plated, a plating layer (CoW plating layer) is formed. The thickness of the plating layer formed is adjusted by the immersion time and the temperature and concentration of the plating solution.

[0033] The temperature of the electroless CoW plating solution during processing is appropriately set while considering the processing time so that a desired film thickness can be formed. If the solution temperature is too low, the deposition rate may be slow. On the other hand, if the solution temperature is too high, the deposition rate may be excessive, or the amount of water evaporated from the plating solution may increase, causing the solution composition to fluctuate. The temperature of the electroless CoW plating solution is preferably 20°C or higher, more preferably 25°C or higher, even more preferably 50°C or higher, and even more preferably 60°C or higher, and is preferably 90°C or lower, more preferably 80°C or lower, and even more preferably 75°C or lower. In short, the temperature of the electroless CoW plating solution is desirably 60°C to 75°C.

[0034] In the immersion process, the plating solution is circulated (flowed) toward the heater portion, which is the heat source, at a flow rate of 1.0 to 300 L / min (preferably, 100 to 200 L / min), while the power card, which is the object to be plated, is continuously swung in the plating solution at a speed of 0.1 to 5.0 m / min (preferably, 2 to 3 m / min). In other words, the power card, which is the object to be plated, is continuously moved (drifted) in the plating tank, which is a three-dimensional space.

[0035] Finishing process After plating, the plating film is washed and, if necessary, post-treatment such as drying is performed. This improves the adhesion and corrosion resistance of the plating layer, improving the quality of the plating. After the immersion process is completed, post-treatment is performed to remove the plating solution and impurities adhering to the plating layer surface. Specifically, washing with water, drying, oil film treatment, etc. are performed.

[0036] <Effects of electroless CoW plating method> The electroless CoW plating method of the present invention can accommodate lead-free solder materials, and can provide a method for forming electroless CoW plating on hybrid automobile inverter double-sided heat dissipation modules (by electroless CoW plating) that can provide wear resistance, corrosion resistance, and heat resistance by forming a tough cobalt-tungsten alloy film on the surface of the components, and can also provide high conductivity for use in inverters, which are electronic components.

[0037] In the immersion process of the electroless CoW plating method, the plating liquid is continuously flowed toward the heater part, which is the heat source (so that the plating liquid hits it), at a flow rate of 1.0 to 300 L / min (preferably, a flow rate of 100 to 200 L / min) to keep the temperature of the plating liquid constant, and the object to be plated is oscillated in the plating liquid at a speed of 0.1 to 5.0 m / min (preferably, a speed of 2 to 3 m / min), which contributes to improving the quality of the plating layer.

[0038] The electroless CoW plating process has made it possible to use lead-free solder materials. Furthermore, the electroless CoW plating formation method for hybrid vehicle inverter double-sided heat dissipation modules (using electroless CoW plating) has made it possible to provide high conductivity, an important element for electronic components.

[0039] <Example of change in electroless CoW plating process> The electroless CoW plating method of the present invention is not limited to the aspects of the above-mentioned embodiments, and the configuration of the surface treatment process → plating solution adjustment process → plating solution supply process → immersion process (formation of plating layer) → finishing process can be appropriately changed as necessary within the scope of the present invention. [Industrial Applicability]

[0040] The electroless CoW plating method according to the present invention has the excellent effects as described above, and can be suitably used as an electroless CoW plating method for a power card, which is an inverter double-sided heat dissipation module for a hybrid vehicle, which is an electronic component. It goes without saying that the electroless CoW plating method according to the present invention is not limited to application to a power card, which is an inverter double-sided heat dissipation module for a hybrid vehicle, which is an electronic component.

Claims

1. a plating solution preparation step of preparing a plating solution adjusted to form a plating layer having a Co (cobalt) base and a W (tungsten) content of 35% by weight to 58% by weight; a plating solution supplying step of supplying the plating solution to a plating tank equipped with a heater unit; The method includes a dipping step of immersing the object to be plated in the plating bath, In the immersion process, heat treatment is performed so that the temperature of the plating liquid is 20°C to 90°C, and the plating liquid is flowed toward the heater section, which is a heat source, at a liquid flow rate of 1.0 to 300 L / min, while the object to be plated is oscillated in the plating liquid at a speed of 0.1 to 5.0 m / min.

2. 2. The electroless CoW plating method according to claim 1, wherein the plating bath is made of resin or is coated with resin.

3. 3. The electroless CoW plating method according to claim 1, wherein the heater is made of a resin or is coated with a resin.

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