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PCB in which the plating process and precautions are explained in detail

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The plating process in PCBs (Printed Circuit Boards) is a critical step in the manufacturing of circuit boards, which involves depositing metal (usually copper) onto specific areas of the board to form conductive paths. The following is a detailed description of the plating process and precautions to be taken:

Plating Process

Drilling: 

The drilling operation is performed first to create channels for conductive paths on the circuit board.

Pre-treatment: 

After drilling, the holes need to be pre-treated, including deburring and cleaning the holes of foreign objects to ensure smooth walls.

Degumming: 

During the drilling process, a layer of epoxy oil may form on the hole wall. Specific chemicals are required to remove this slime to ensure the quality of subsequent plating.

Chemical Copper Deposition (PTH): 

A thin layer of chemical copper is chemically deposited on the hole wall as a substrate for copper plating. This process is called Plating Through Hole (PTH).

Electroplated Copper: 

A uniform, dense metallic layer is formed by depositing metallic copper on top of a chemical copper layer using electrolysis. The electroplated copper layer has good electrical and thermal conductivity and mechanical ductility.

Graphics Transfer: 

The circuit image is transferred to the board through a photographic imaging process to form an anti-plating dry film image.

Etching: 

The copper layer is etched off the non-wiring portion of the circuit, leaving only the designed circuit pattern.

Post-processing: 

After plating is completed, post-processing, such as nickel plating, gold plating, etc., may be required to enhance the circuit board's corrosion resistance, solderability, and service life.

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Precautions

Cleanliness: 

Ensure that the circuit boards are thoroughly cleaned before plating and free of oil, dust or other impurities that may affect the adhesion and quality of the plating layer.

Drilling Quality: 

The precision and quality of drilling directly affects the formation of the plating layer, and it should be ensured that the drill holes are free of burrs and cracks.

Chemical Control: 

In the process of removing gum slag and chemical copper precipitation, the concentration of chemicals and processing time need to be strictly controlled, so as not to cause damage to the circuit board or plating layer quality problems.

Plating Parameters: 

current density, temperature, pH value and plating time in the plating process need to be precisely controlled to ensure the uniformity and thickness of the plating layer.

Environmental Protection: 

The plating process generates hazardous waste that needs to be disposed of properly and in compliance with environmental protection regulations.

Safe Operation: 

The plating process involves hazardous chemicals and equipment. Operators should wear appropriate protective equipment and strictly follow operating procedures.

Quality Inspection: 

After plating is completed, strict quality inspection should be conducted, including the thickness of the plated layer, adhesion and electrical conductivity, etc., to ensure that the product meets the quality standards.

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Other details

Pre-impregnation and Activation: 

Before plating, it is usually necessary to pre-impregnate and activate the board to ensure uniform deposition of the copper layer. Pre-soaking removes impurities and excess moisture from the board surface, while activation gives the copper surface better catalytic activity through chemicals, which facilitates the subsequent process of chemical copper plating or copper electroplating.

Micro-etching: 

Prior to copper plating, micro-etching provides a roughened surface that facilitates the adhesion of the plated layer. Micro-etching usually uses mild acidic solutions such as sulphuric acid and sodium persulfate to lightly etch the copper surface.

Maintenance of Plating Solution: 

The stability of plating solution has a direct impact on the quality of plating. It is necessary to regularly test and adjust the metal ion concentration, pH value, temperature and other parameters in the plating solution, and add the necessary additives in time, such as brightening agent, levelling agent, etc., in order to maintain the best working condition of the plating solution.

Quality Control of Plating Layer: 

During the plating process, the thickness, uniformity and adhesion of the plating layer need to be monitored and tested. This can be achieved through measuring instruments, peel tests, cross-section analysis, etc.

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Precautions

Environmental Control: 

The plating shop should be well ventilated to prevent the accumulation of harmful gases. Meanwhile, temperature and humidity control is also very important for the stability of plating solution and plating quality.

Equipment Maintenance: 

Regularly maintain and calibrate plating equipment to ensure the normal operation of the equipment and the accuracy of the plating process.

Operator Training: 

Ensure that operators receive appropriate training on the plating process, safe use of chemicals and emergency response measures.

Records and Traceability: 

Record in detail all parameters and operational steps in the plating process to facilitate quality traceability and problem solving.

Waste Disposal: 

Waste liquids and wastes generated during the plating process should be collected and disposed of in a classified manner in accordance with environmental protection requirements to avoid pollution to the environment.

Through comprehensive consideration of the above details and precautions, the overall performance and product quality of the PCB plating process can be effectively enhanced, while ensuring the safety and environmental protection of the production process.

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