Aluminum-based silicon carbide surface composite coating process

Abstract

The invention discloses an aluminum-based silicon carbide surface composite coating process, and aims to solve the problems that in the prior art, a single chemical nickel coating only has the characteristics of the chemical nickel coating, the phosphorus content cannot be uniformly distributed in the coating, and large uncertainty is caused to a subsequent welding process. According to the technical scheme, the aluminum-based silicon carbide surface composite coating technology is characterized in that the technological process comprises the following steps of chemical oil removal, acid pickling, zinc deposition 1, zinc stripping, zinc deposition 2, nickel alkaline treatment, chemical nickel treatment, nickel aminosulfonate treatment, nickel protection and drying. According to the aluminum-based silicon carbide surface composite coating technology, on the premise that the thickness uniformity of the product coating is not affected, the welding dip plating part on the surface of the aluminum-based silicon carbide product can be increased, and the thickness of the single-layer chemical nickel is increased to 95% or above of the composite coating from 90%.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and more specifically, to a composite coating process for aluminum-based silicon carbide surfaces. Background Technology

[0002] Currently, the market uses a single-layer electroless nickel plating method for surface treatment of aluminum-based silicon carbide products. However, electroless nickel plating: existing technology is a single electroless nickel plating layer, which only possesses the characteristics of electroless nickel plating. The phosphorus content cannot be evenly distributed in the plating layer, causing significant uncertainty for subsequent welding processes.

[0003] Meanwhile, the potential of nickel-phosphorus alloys is lower than that of pure nickel, and the phosphorus distribution in the coating is uneven (local high-phosphorus areas), which easily leads to "micro-galvanic corrosion" (high-phosphorus areas are the anode and low-phosphorus areas are the cathode). After welding, if there are gaps in the weld joint (such as gaps caused by poor welding), the corrosion rate will be significantly accelerated, especially in humid and high-temperature environments, where "weld joint corrosion" is likely to occur, affecting the reliability of electrical connections. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a composite coating process for aluminum-based silicon carbide surfaces, which can increase the welding immersion portion of the aluminum-based silicon carbide product surface without affecting the uniformity of the coating thickness, increasing it from 90% of single-layer electroless nickel to over 95% of the composite coating.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: the process flow includes the following steps: chemical degreasing → pickling → zinc immersion 1 → zinc stripping → zinc immersion 2 → alkaline nickel → chemical nickel → nickel aminosulfonate → nickel protection → drying;

[0006] The chemical degreasing process includes the following steps: placing the raw material into the degreasing tank of the equipment, which is equipped with heating pipes, water pipes, and valves to facilitate heating of the raw material and water storage. It is also equipped with an exhaust system and a temperature display to facilitate temperature control of the raw material during the hot immersion degreasing process. The concentration is 50-150 ml / L, the temperature is 50-65℃, and the time is 8-12 min. The pressure of the raw material is ≤1.8 kg when the valve is opened, and the liquid level needs to be level with the overflow port.

[0007] The pickling process includes the following steps: the degreased raw material is poured into the tank of the pickling equipment, and the pickling concentration is 180-300ml / L, the time is 40-100sec, the temperature is 20-40℃, and the liquid level needs to be level with the overflow port.

[0008] The zinc precipitation process includes the following steps: the pickled raw material is poured into the zinc precipitation equipment and placed in the tank of the equipment. At the same time, a temperature display, exhaust device, cooling pipe, heating pipe, water pipe and valve are installed. The zinc precipitation temperature is 15-25℃, the concentration is 10-30%, the time is 20-60 seconds, and the liquid level needs to be level with the overflow port.

[0009] The zinc stripping process includes the following steps: the raw material after the first zinc precipitation is poured into the zinc stripping equipment tank, the zinc concentration is 180-300 ml / L, the time is 30-100 seconds, the temperature is 20-40℃, and the liquid level needs to be level with the overflow port.

[0010] The second zinc precipitation process includes the following steps: If the raw material requires a second zinc precipitation effect, the zinc precipitation equipment is washed with water and the overflow flow rate is >100L / h. Then, it is subjected to a second zinc precipitation and placed into the tank of the zinc precipitation equipment. The temperature is 15-25℃, the concentration is 10-30%, and the time is 20-60 seconds. At the same time, the liquid level needs to be level with the overflow port.

[0011] The alkaline nickel plating process includes the following steps: After zinc precipitation, the raw material needs to undergo alkaline nickel plating in a tank opened in the equipment, with a nickel ion concentration of 4.9-6 g / L, a hypophosphite concentration of 25-40 g / L, a time of 5-10 minutes, a temperature of 20-40℃, a pH value of 9.6-11.5, and a filtration pressure of ≤1.8 kg.

[0012] The chemical nickel process includes the following steps: After alkali nickel treatment, the raw material needs to be treated with chemical nickel. The chemical nickel is placed into a tank containing the raw material. The raw material is processed using heating elements and a filter. Simultaneously, the nickel ion concentration is 2.3-3.6 g / L, the sodium hypophosphite concentration is 15-25 g / L, the processing time is 20-40 minutes, the temperature is 80-90℃, the pH value is 4.8-5.4, and the filtration pressure is ≤1.8 kg.

[0013] The process of adding nickel sulfamate includes the following steps: It requires the use of a tank solenoid valve, rectifier, filter, cooling pipe, electrode rod, anode plate, etc. Nickel sulfamate is added to ensure that the nickel ion concentration in the processed raw material is 80-100 g / L, the nickel chloride concentration is 5-25 g / L, the boric acid concentration is 35-55 g / L, the current is 1-3 A / dm², the temperature is 40-65℃, the pH value is 3.5-5.5, the time is 10-30 min, the filtration pressure is ≤1.8 kg, and the anode can be visually seen at the nickel corner. Simultaneously, the liquid level needs to be level with the overflow port.

[0014] The nickel protection process includes the following steps: the raw material is located in the tank of the equipment, the temperature during the processing is 20-40℃, the concentration is 10-30ml / L, the time is 10-80sec, and the filtration pressure is ≤1.8Kg;

[0015] The drying process includes the following steps: the raw materials are dried using a drying process, with the time controlled at 20-30 minutes and the temperature controlled at 100-150℃.

[0016] The present invention is further configured such that: after the chemical degreasing step, an ultrasonic device can be used to perform ultrasonic degreasing on the raw material to achieve the effect of secondary degreasing of the raw material, and the concentration of degreasing is controlled at 40-70g / L, the temperature is controlled at 50-65℃, the current is ≥2A, and the time is 0.5-5min. After degreasing, when the filter is used for filtration, the pressure is ≤1.8Kg, and the liquid level needs to be level with the overflow port.

[0017] The present invention is further configured such that the steps also include water washing and pure water washing operations: after each processing step is completed, water washing or pure water washing operations are performed in sequence, and water washing cleans the raw materials through a water washing tank, while pure water washing uses a water washing tank and a hanger to clean the raw materials, and the flow rate of water washing is overflow rinsing >100L / h.

[0018] The present invention is further configured such that the water washing also includes ultrasonic water washing: ultrasonic water washing uses a water washing tank and ultrasonic equipment, the flow rate is controlled at overflow rinsing >100L / h, the current is ≥2A, and the time is automatically controlled by PLC.

[0019] In summary, the present invention has the following beneficial effects:

[0020] 1. This invention combines the advantages of both electroless nickel plating and nickel sulfamate plating, and its solderability is greatly improved compared to the single-layer electroless nickel plating of the prior art.

[0021] 2. This invention is a composite coating, which adds a layer of nickel sulfamate coating to the chemical nickel coating, which can combine the uniformity of the coating and the weldability, and greatly improve the yield of the welding process.

[0022] 3. The present invention solves the problem of increasing the welding immersion portion on the surface of aluminum-based silicon carbide products from 90% of single-layer chemical nickel plating to more than 95% of composite plating without affecting the uniformity of the product coating thickness. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to specific embodiments. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0024] The present invention will now be described in detail with reference to the embodiments.

[0025] The process flow includes the following steps: chemical degreasing → pickling → zinc immersion 1 → zinc stripping → zinc immersion 2 → alkaline nickel → electroless nickel → nickel aminosulfonate → nickel protection → drying;

[0026] This technology encompasses composite coatings of electroless nickel and nickel sulfamate, combining the advantages of both coating types.

[0027] Among them, the advantages of electroless nickel plating include extremely high coating uniformity.

[0028] The deposition process is only related to the catalytic activity of the workpiece surface and is not affected by the current distribution. No matter how complex the workpiece shape is (such as deep holes, blind holes, grooves, and small parts), a coating with a consistent thickness can be obtained. For example, for precision parts with a hole diameter ≤0.5mm and a depth-to-diameter ratio >10:1, the coating thickness deviation can be controlled within ±5%, which far exceeds the uniformity performance of electroplating (such as nickel sulfamate electroplating) on ​​complex structures.

[0029] Advantages of nickel sulfamate plating: Pure nickel has a high melting point (1455℃), but electroplated nickel layers are typically thin (5-20μm) and free of low-melting-point impurities such as phosphorus. During soldering, solder (such as tin-lead solder, lead-free solder Sn-Cu, Sn-Ag-Cu) can spread rapidly on its surface—pure nickel has high surface activity and readily forms stable intermetallic compounds (IMCs, such as Ni3Sn4) with tin (Sn) in the solder, exhibiting excellent wettability and a wider soldering temperature window (suitable for conventional electronic soldering temperatures of 180-250℃). The IMC (Ni3Sn4) layer formed by pure nickel and solder is thin and uniform, with high bonding strength and good solder joint toughness (not prone to brittle fracture). Even after high-temperature aging (such as 150℃ / 1000h), the IMC layer grows slowly, and the solder joint strength decays little, making it suitable for applications with high reliability requirements (such as automotive electronics and aerospace).

[0030] The process flow includes the following steps: chemical degreasing → pickling → zinc immersion 1 → zinc stripping → zinc immersion 2 → alkaline nickel → electroless nickel → nickel aminosulfonate → nickel protection → drying;

[0031] Chemical degreasing includes the following process: raw materials are placed in the degreasing tank of the equipment, which is equipped with heating pipes, water pipes, and valves to facilitate heating of the raw materials and water storage. It is also equipped with an exhaust device and a temperature display to facilitate temperature control of the raw materials during the hot immersion degreasing process. The concentration is 50-150 ml / L, the temperature is 50-65℃, and the time is 8-12 min. The pressure of the raw materials filtered by opening the valve is ≤1.8Kg, and the liquid level needs to be level with the overflow port.

[0032] Pickling includes the following process: the degreased raw materials are poured into the tank of the pickling equipment, and the pickling concentration is 180-300ml / L, the time is 40-100sec, the temperature is 20-40℃, and the liquid level needs to be level with the overflow port.

[0033] Zinc precipitation process 1 includes the following steps: the pickled raw material is poured into the zinc precipitation equipment and placed in the tank of the equipment. At the same time, a temperature display, exhaust device, cooling pipe, heating pipe, water pipe and valve are installed. The zinc precipitation temperature is 15-25℃, the concentration is 10-30%, the time is 20-60 seconds, and the liquid level needs to be level with the overflow port.

[0034] The zinc stripping process includes the following steps: the raw material after the first zinc precipitation is poured into the zinc stripping equipment tank, the zinc concentration is 180-300ml / L, the time is 30-100sec, the temperature is 20-40℃, and the liquid level needs to be level with the overflow port.

[0035] The second zinc precipitation process includes the following steps: If the raw material requires a second zinc precipitation effect, the zinc precipitation equipment is washed with water and the overflow flow rate is >100L / h. Then, it is subjected to a second zinc precipitation and placed into the tank of the zinc precipitation equipment. The temperature is 15-25℃, the concentration is 10-30%, and the time is 20-60 seconds. At the same time, the liquid level needs to be level with the overflow port.

[0036] Alkali nickel leaching includes the following process: After zinc precipitation, the raw material needs to undergo alkali nickel leaching in a tank opened in the equipment, with a nickel ion concentration of 4.9-6 g / L, hypophosphite concentration of 25-40 g / L, a time of 5-10 min, a temperature of 20-40℃, a pH value of 9.6-11.5, and a filtration pressure of ≤1.8 kg.

[0037] Chemical nickel processing includes the following steps: After alkali nickel processing, the raw material needs to be added with chemical nickel. The chemical nickel is placed into a tank containing the raw material. The raw material is processed using heating elements and a filter. Simultaneously, the nickel ion concentration is 2.3-3.6 g / L, the sodium hypophosphite concentration is 15-25 g / L, the processing time is 20-40 minutes, the temperature is 80-90℃, the pH value is 4.8-5.4, and the filtration pressure is ≤1.8 kg.

[0038] The process of nickel sulfamate production includes the following steps: It requires the use of tank solenoid valves, rectifiers, filters, cooling pipes, electrode rods, and anode plates. Adding nickel sulfamate ensures that the processed raw material has a nickel ion concentration of 80-100 g / L, a nickel chloride concentration of 5-25 g / L, a boric acid concentration of 35-55 g / L, a current of 1-3 A / dm², a temperature of 40-65℃, a pH value of 3.5-5.5, a time of 10-30 minutes, and a filtration pressure ≤1.8 kg. The anode can be visually seen at the nickel corner, and the liquid level must be level with the overflow port.

[0039] Nickel protection includes the following process: the raw material is located in the tank of the equipment, the temperature during the processing is 20-40℃, the concentration is 10-30ml / L, the time is 10-80sec, and the filtration pressure is ≤1.8Kg;

[0040] The drying process includes the following steps: the raw materials are dried using a drying process, with the time controlled at 20-30 minutes and the temperature controlled at 100-150℃.

[0041] After the chemical degreasing step, ultrasonic equipment can be used to perform ultrasonic degreasing on the raw materials to achieve a secondary degreasing effect. The concentration of degreasing should be controlled at 40-70g / L, the temperature at 50-65℃, the current at ≥2A, and the time at 0.5-5min. After degreasing, when using a filter, the pressure should be ≤1.8Kg, and the liquid level should be level with the overflow port.

[0042] The process also includes water washing and pure water washing: after each processing step, the raw materials are washed with water or pure water in sequence. Water washing uses a water washing tank to clean the raw materials, while pure water washing uses a water washing tank and hangers to clean the raw materials. At the same time, the flow rate of water washing is overflow rinsing >100L / h.

[0043] Simultaneously, water washing also includes ultrasonic water washing: ultrasonic water washing uses a water washing tank and ultrasonic equipment, with the flow rate controlled at overflow rinsing >100L / h, current ≥2A, and time automatically controlled by PLC.

[0044] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A process for surface composite plating of aluminum-based silicon carbide, characterized in that: The process comprises the following steps: chemical degreasing, pickling, zinc precipitation I, zinc precipitation II, alkaline nickel, chemical nickel, nickel sulfamate, nickel protection, and drying. The chemical degreasing comprises the following process: the raw material is placed in the degreasing tank of the equipment, and the equipment is provided with heating pipes, water pipes, valves and the like, facilitating the heating and water storage operation of the raw material, and is provided with an exhaust device and a temperature display, facilitating the control of the temperature of the raw material in the hot dip degreasing process, and the concentration is 50-150 ml / L, the temperature is 50-65℃, the time is 8-12 min, the pressure of the filtered raw material is ≤1.8 Kg through the valve, and the liquid level needs to be flush with the overflow port. The pickling comprises the following process: the degreased raw material is poured into the tank body of the pickling equipment, The concentration of pickling is 180-300 ml / L, the time is 40-100 sec, the temperature is 20-40℃, and the liquid level needs to be flush with the overflow port. The zinc precipitation I comprises the following process: the pickled raw material is poured into the zinc precipitation equipment, The concentration of zinc precipitation II is 180-300 ml / L, the time is 30-100 sec, the temperature is 20-40℃, and the liquid level needs to be flush with the overflow port. The zinc precipitation II comprises the following process: the raw material needs to be secondly zinc precipitated, so that the zinc precipitation equipment is washed by water and the overflow drift is >100 L / h, then the raw material is secondly zinc precipitated and then put into the tank body of the zinc precipitation equipment, the temperature is 15-25℃, the concentration is 10-30%, the time is 20-60 sec, and the liquid level needs to be flush with the overflow port. The alkaline nickel comprises the following process: the raw material after the end of zinc precipitation needs to be alkaline nickel in the tank body of the equipment, the nickel ion concentration is 4.9-6 g / L, the hypophosphite is 25-40 g / L, the time is 5-10 min, the temperature is 20-40℃, the pH value is 9.6-11.5, and the filtration pressure is ≤1.8 Kg; The chemical nickel comprises the following process: the raw material after alkaline nickel needs to be added with chemical nickel, so that the chemical nickel is put into the tank body of the equipment containing the raw material, and the raw material is processed through the setting of heating pipes and filters, meanwhile, the nickel ion concentration is 2.3-3.6 g / L, the sodium hypophosphite is 15-25 g / L, the time is 20-40 min, the temperature is 80-90℃, the pH value is 4.8-5.4, and the filtration pressure is ≤1.8 Kg; ​ The nickel sulfamate includes the following flow: the electromagnetic valve, rectifier, filter, cooling pipe, pole, anode plate and so on need to be used to the tank body, the nickel sulfamate is added, the nickel ion concentration of the processed raw material is 80-100g / L, the nickel chloride concentration is 5-25g / L, the boric acid concentration is 35-55g / L, the current is 1-3A / dm2, the temperature is 40-65℃, the pH value is 3.5-5.5, the time is 10-30min, the pressure during filtering is ≤1.8Kg, and the anode can be observed in the nickel angle, and the liquid level needs to be flush with the overflow port; The nickel protection includes the following flow: the raw material is located in the tank body of the equipment, the temperature during processing is 20-40℃, the concentration is 10-30ml / L, the time is 10-80sec, and the filtering pressure is ≤1.8Kg; The drying includes the following flow: the raw material is dried by drying, the time is controlled to be 20-30min, and the temperature is controlled to be 100-150℃.

2. The aluminum-based silicon carbide surface composite plating process according to claim 1, characterized by: After the chemical oil removal step, the raw material can be subjected to ultrasonic oil removal by using ultrasonic equipment, so as to realize the effect of secondary oil removal of the raw material, the concentration of oil removal is controlled to be 40-70g / L, the temperature is controlled to be 50-65℃, the current is ≥2A, the time is 0.5-5min, the pressure is ≤1.8Kg during filtering after oil removal, and the liquid level needs to be flush with the overflow port.

3. The aluminum-based silicon carbide surface composite plating process according to claim 1, wherein: The step also includes water washing and pure water washing operations: after each processing step, water washing or pure water washing is sequentially performed, water washing is performed by using a water washing tank to clean the raw material, pure water washing is performed by using a water washing tank and a hanger to clean the raw material, and the overflow rinsing flow of water washing is >100L / h.

4. The aluminum-based silicon carbide surface composite plating process according to claim 3, characterized by: The water washing also includes ultrasonic water washing: the ultrasonic water washing uses a water washing tank and ultrasonic equipment, the flow is controlled to be >100L / h, the current is ≥2A, and the time is automatically controlled by PLC.