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PCB Plating

PCB Plating Process

PCB plating includes the following: 

Preparation of Substrates: The production of gold-plated board substrate should be a smooth surface and reliable quality of insulating materials, such as fiberglass cloth, epoxy resin and so on.

Production of Circuit Graphics: The surface of the substrate to produce circuit graphics, you can use etching, photolithography and other methods to produce accurate circuit graphics.

Pre-treatment: Pre-treatment such as cleaning and roughening of the substrate to improve the adhesion and appearance quality of the gold plating layer.

Plating: The pre-treated substrate is put into the plating solution and plated by electrochemical or chemical methods.

Cleaning and Drying: Residual chemicals and dirt are cleaned using a cleaning agent and then dried.

TestingTest the circuit board after plating, including appearance testing, electrical performance testing, etc., to ensure that the product quality meets the requirements.

It should be noted that the PCB gold-plating process requires strict control of the composition of the plating solution and process parameters to ensure that the adhesion of the gold-plated layer and the appearance of quality. At the same time, the plating process also needs to be continuously improved and innovated to meet the changing market demand and technology development trends.

PCB Plating

Characteristics of The PCB Plating Process

The PCB plating process includes the following features:

Improve Conductivity and Corrosion Resistance: Gold plating can significantly improve the conductivity and corrosion resistance of the PCB board, so that it has good soldering performance and reliability.

Better Oxidation Resistance: Gold plating can effectively prevent the PCB board oxidation, so that it remains stable.

Good Soldering Performance: The smooth surface of the gold plating layer can reduce soldering defects and customer complaints.

Harsh Storage Conditions: In order to maintain the performance and quality of the gold-plated boards, the storage conditions need to be strictly controlled to avoid humidity and pollution.

Environmentally Friendly Process: The waste liquid and slag in the gold plating process need to be properly disposed of to avoid pollution to the environment.

Higher Cost: Compared with other surface treatment processes, the cost of gold plating process is higher.

PCB  gold plating has many advantages, but the cost is high. When choosing whether to use the gold-plating process, need to be based on product performance requirements, production volume, cost and other factors for comprehensive consideration.

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PCB Plating Process Considerations

In the PCB plating process, the following points need to be noted:

Pre-treatment: Before plating the PCB board needs to be thoroughly cleaned to remove surface dirt, grease and oxides, etc., to ensure the adhesion and quality of the gold-plated layer.

Selection of Plating Solution: The appropriate plating solution should be selected according to the PCB board and design requirements to ensure the quality and stability of the plating layer.

Plating Thickness Control: The control of the thickness of the gold plating has an important impact on the performance of the circuit board. Too thick a metal layer may lead to soldering problems, while too thin a metal layer may affect the conductive properties. Therefore, in the PCB plating, you need to control the thickness of the metal layer.

Current and Voltage Control: In the plating process, the control of current and voltage is critical to the quality and uniformity of the plated layer. Stable current and voltage should be maintained to avoid uneven plating.

Temperature Control: Temperature control in the plating process also has an important effect on the quality and uniformity of the gold plating layer. Appropriate temperature should be maintained to promote the deposition and uniform distribution of metal ions.

Stirring: In the process of gold plating, it is necessary to constantly stir the plating solution to promote the uniform distribution of metal ions and prevent the production of precipitation.

Post-treatment: The PCB board needs to be thoroughly cleaned after gold plating to remove residual chemicals and impurities on the surface and to check for defects or undesirable phenomena.

Environmental Protection: The gold plating solution may produce harmful substances in the process of using, effective measures should be taken to reduce environmental pollution and harm to the health of employees.

Safety Measures: In the production process, appropriate safety protection equipment should be worn, such as acid- and alkali-resistant gloves, protective glasses, etc., in order to ensure the safety of employees.

Quality Inspection: Quality inspection should be carried out in the gold-plating process, such as the use of microscope inspection, image processing and other ways to scrutinize and measure the circuit board to ensure that the circuit board plating quality and reliability.

PCB  board plating process requires attention to a number of issues, the need for board manufacturers with advanced equipment and technical strength and strict quality management system to ensure that the production of circuit boards to meet customer requirements. At the same time, the design stage needs to take into account the performance and reliability requirements of the circuit, rational arrangement of component layout and wiring and other elements. 

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PCB Surface Treatment Contains

PCB surface  treatment has a variety of ways, the following list of several common treatment:

Hot air leveling (HASL): The PCB surface coated with molten tin-lead solder and heated compressed air leveling (blowing) process, so that it forms a layer of both resistance to copper oxidation and can provide good solderability of the coating layer. In higher density PCBs, the flatness of the hot air leveling will affect subsequent assembly.

Immersion Tin: Coating a layer of tin on the surface of the PCB to form a protective film to prevent copper oxidation. This is the simplest way of PCB surface treatment.

Silver Immersion: Covering a layer of silver on the copper surface through chemical methods, which plays a role in protecting the copper surface.

OSP (Organic Antioxidant): In the clean bare copper surface, the chemical method to grow a layer of organic skin film. This film has anti-oxidation, thermal shock resistance, moisture resistance and other characteristics, to protect the copper surface in the normal environment will not continue to rust (oxidation or sulfidation, etc.). At the same time, it must be easily removed by the flux in the subsequent high soldering temperatures in order to be soldered.

Chemical Precipitation of Nickel and Gold (ENIG): In the copper surface wrapped in a thick layer of good electrical properties of nickel and gold alloy and can be long-term protection of PCB.

PCB Mixed Surface Treatment Technology: Choose two or more than two surface treatment methods for surface treatment, common forms are: immersion nickel gold + antioxidant, electroplating nickel gold + immersion nickel gold, electroplating nickel gold + hot air leveling, immersion nickel gold + hot air leveling.

In addition, there are tin spraying, organic solderability protection film (OSP) and other treatment methods. The selection of these treatments depends mainly on the specific application needs and PCB design requirements).

Process description of different surface treatments:

Hot Air Leveling (Tin Spraying): Also known as hot air solder leveling, is a process of coating the PCB surface with molten tin (lead) solder and leveling it with heated compressed air to form a coating layer that is both resistant to copper oxidation and provides good solderability. During this process, solder and copper form copper-tin intermetallic compounds at the bonding point. PCBs undergo hot-air leveling by immersing them in molten solder and blowing the liquid solder flat with an air knife before the solder solidifies, which minimizes the bending of the solder on the copper surface and prevents the solder from bridging. Hot air leveling is divided into vertical and horizontal two kinds, generally believe that the horizontal type is better, mainly because of the horizontal hot air leveling plating layer is more uniform, can realize automatic production.

Organic Coating: It is a different process from other surface treatment processes, which acts as a barrier layer between copper and air. The simplicity and low cost of the organic coating process allows it to be widely used in the industry. However, organic coating does not provide good protection against oxidation of the copper surfaces because of the thinness of the coating. In the subsequent high soldering temperatures, this protective film must be easily and quickly removed by the flux, so that the exposed clean copper surface can be immediately bonded to the molten solder in a very short period of time to form a strong solder joint.

Immersion Tin: Since all current solders are tin-based, the tin layer is compatible with any type of solder.

OSP (Organic Solderability Protectant): A process that meets the requirements of the RoHS directive. the OSP layer is oxidation-proof, thermal shock resistant, and humidity-resistant, and is used to protect the copper surface from continuing to rust (oxidize or sulfide, etc.) in a normal environment. However, in the subsequent high soldering temperatures, this protective film must be easily and quickly removed by the flux, so that the exposed clean copper surface can be immediately combined with the molten solder in a very short period of time to become a solid solder joint.

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The Following are The Specific Steps for PCB Surface Treatment

Degreasing: Remove the grease and dirt attached to the PCB surface, which can be cleaned with organic solvents or cleaning agents.

Micro-etching: Use micro-etching agent to micro-etch PCB surface to increase the surface roughness and adhesion, which is conducive to the adhesion and combination of coatings.

Acid Washing: Use acidic cleaning agent to carry out acid washing treatment on the PCB surface to remove the oxidized layer and impurities, and improve the cleanliness and wettability of the surface.

Pure Water Cleaning: use pure water cleaning agent to clean the PCB surface, remove residual acidic substances and impurities to ensure the cleanliness of the surface.

Organic Coating: Use organic coating agent to coat the PCB surface, forming a protective film to improve the surface corrosion resistance and solderability.

Cleaning: Use the cleaning agent to clean the organic coating agent and other impurities remaining on the PCB surface after coating to ensure the cleanliness of the surface.

Drying: After cleaning the PCB surface for drying, you can use hot air drying or natural drying and other methods.

Inspection: The PCB after surface treatment is subjected to appearance inspection and performance test to ensure that the surface quality meets the requirements.

Packaging: The PCB with qualified inspection will be packaged to prevent contamination and damage.

The above are common PCB surface treatment steps, the specific steps may vary depending on the material, equipment and process. When choosing the surface treatment method, you need to consider the performance requirements of the product, cost, environmental protection and other factors.

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The Characteristics of PCB Surface Treatment Mainly Include

Improve Solderability: Through surface treatment, a protective film can be formed on the surface of the PCB board to prevent oxidation of the copper layer and improve solderability.

Protect The Circuit: Surface treatment can protect the circuit from environmental factors, such as moisture, dust, chemicals, etc., so as to ensure the stability and reliability of the circuit.

Aesthetics: Through the surface treatment, you can make the PCB board surface more smooth, beautiful, improve the appearance of the product quality.

Versatility: PCB surface treatment has a variety of methods to choose from, such as hot air leveling, organic coating, chemical nickel gold plating, etc., you can choose the appropriate treatment method according to different needs.

Environmental Protection: Some surface treatment methods use chemical reagents that need to be properly disposed of to avoid pollution of the environment. Therefore, when choosing a surface treatment method, it is necessary to consider its environmental friendliness.

Cost: Different surface treatment methods have different costs, which need to be considered according to the performance requirements of the product, production batch, cost and other factors.

Adaptability: PCB surface treatment can be adjusted and optimized according to different substrates, circuit graphics and use of the environment to adapt to a variety of complex application scenarios.

Weatherability: Through surface treatment, the weatherability of PCB boards can be enhanced so that they can work stably for a long time under harsh environmental conditions.

Conductivity: Surface treatment can improve the conductivity of the PCB board, reduce resistance and signal loss, thus improving the efficiency and performance of the circuit.

Adhesion: Surface treatment can improve the adhesion between the soldering points and the PCB board, reducing the possibility of poor soldering and peeling.

Repairability: Some surface treatment methods can make the PCB board has better repairability, convenient for subsequent repair and replacement.

Standardization: PCB  surface treatment has a certain degree of standardization, there is a certain degree of universality and interchangeability between different manufacturers and products, to facilitate production and use.

It should be noted that the quality of PCB surface treatment has an important impact on the performance and reliability of the product, so it is necessary to strictly control the parameters and operating conditions of the treatment process. At the same time, with the continuous development of technology, surface treatment methods and materials are also constantly updated, the need to constantly learn and master new technologies and knowledge.

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PCB Surface Treatment Precautions

A. PCB unpacked should be used in a timely manner, and it is recommended that pre-drying treatment before use, especially the PI substrate board in the flexible circuit board, such as the need for patch welding, it must be required to pre-drying treatment.

B. For chemical impregnated tin or silver impregnated products are recommended to be used up within 12 hours after unpacking, otherwise it must be repacked.

C. If the effective storage period is exceeded, the user can be dried and processed after the trial: if necessary, certain properties to re-performance test, after passing the test can still be used.

D. Usually save more than 3 months in the machine before the placement to avoid the existence of moisture hidden danger, need to carry out 2 hours of 150 degrees baking.

E. PCB surface treatment should be properly stored, avoid direct sunlight, high temperature, humidity and other unfavorable environmental conditions.

F. PCB surface treatment should be used as soon as possible, to avoid long time storage lead to performance degradation or pollution.

G. PCB surface treatment should pay attention to safety, avoid contact with harmful substances or other safety accidents.

H. PCB surface treatment needs to pay attention to the use period, preservation conditions, baking requirements and the use of safety, in order to ensure that the quality and performance of the product meets the requirements.

Surface Treatment

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