PCB Tech - Prevention methods of PCB immersion silver plating process

PCB introduced the following five common silver-plating defects through Yaoshui merchants and mechanical equipment manufacturers and their PCB circuit boards and other on-site relief scientific research, and found some prevention and improvement methods, which can show that the multi-layer PCB proofing factory solves Difficulties and work to improve the qualification rate are now introduced as follows:

1: Javani multilayer circuit board bites copper

This problem must be traced back to the copper electroplating process, and found that if the target is a high-diameter ratio deep-hole rolled and buried-hole rolled plate, it will be degraded if it can be displayed more comprehensively. This Javan copper bite. In the multilayer PCB process, the stripping of metal material inhibitors (such as pure tin layer) and copper in the etching process, once the etching process and side etching conditions are too much, it will also cause gaps and the existence of electroplating process liquids and micro-etching liquids.

In fact, the biggest problem comes from the green paint project, where side erosion and film relief patterns caused by the condition of the green paint are most likely to cause gaps. If the remaining feet instead of negative side corrosion can eliminate the copper bitten by the copper, this will make the green paint look positive and will be removed by the hard bottom after the green paint is completely grounded. In order to make the actual operation of copper electroplating as much as possible in the obvious mixing and deep hole copper electroplating, it can also use ultrasonic and powerful flowers (Educor) to help the mixing to improve the quality of the fluid and copper everywhere. For immersing the PCB board in the self-made silver plating process, the micro-etching copper rate at the front end must be strictly controlled, and the smooth copper surface can also reduce the presence of green paint. In the end, the silver tank itself should not have too strong occluding copper reflection, the PH value should be neutral, and the board speed should not be too fast. It is best to make the thickness as thin as possible, and it can be done on the best silver crystals. To do a good job of anti-color effect. Multilayer circuit board

2: Improved color loss of multilayer PCB

The way to improve the coating is to increase the relative density and reduce its porosity (porosity). As far as possible, the packaged goods should choose sulfur-free paper and multi-sided sealing to block carbon dioxide and sulfur in the air, thereby reducing the color difference of the light source. In addition, the average temperature of storage management in the natural environment is not suitable to exceed 30 degrees Celsius, and the environmental humidity must be less than 40% RH. It is best to adopt the priority plus current policy first to prevent long-term storage and cause difficulties.

3: Improve the ionization environment pollution on the surface of the PCB circuit board of the multilayer circuit board

If the ion concentration of the silver plating bath cannot be reduced under the condition of impairing the quality of the coating, the ionization of the surface is of course sufficient to reduce the drug. In the leaching cleaning, try to pass in pure water before drying and absorb it for one minute to reduce the adhesion and ionization. And for the assembled board, we must try our best to test its cleanliness, as far as possible to minimize the residual ionization on the surface of the PCB circuit board and meet industry standards. The experiments carried out should be saved for preparation.

4: Improvement of copper on the silver surface of multilayer circuit boards

Carefully adjust all the steps before silver plating, such as the "waterproof" test (WaterBreak refers to water-soluble) after micro-corrosion on the copper surface and the inspection of very bright copper spots, indicating that there will be some dirt on the copper surface. The slightly corroded copper surface is very clean and tidy, and its standing state must be maintained for 40 seconds without water cut. The production line equipment should also be maintained on time to maintain its water solubility uniformity in order to obtain a more balanced silver plating layer. In practice, in order to obtain the best quality silver-plated layer, and in order to obtain the best silver-plated layer, it is necessary to conduct continuous DOE test procedure experiments on leaching time, liquid temperature, mixing and diameter size. Thick steel plate and its HDI micro-buried plate silver plating process can also choose ultrasonic and strong external force to help improve the entire silver layer. Now, this extra super mixing of tank fluid can improve the wetting and exchange capacity of Yao Ming water in deep and buried holes, and it is very helpful for all wet processes.

5: Improvement of multi-layer PCB spot welding microvia

Interface microvias are still more difficult to improve at this stage of silver plating defects, because the real cause of it has not fallen from the stone, but at least some related reasons can be clarified. Therefore, when trying to avoid the appearance of its related elements, it is natural to reduce the generation of micro-holes in the middle and downstream welding.

Related elements are also more closely structured with the thickness of the silver layer in order to reduce the thickness of the silver layer as much as possible. Secondly, the microetching of the pre-solution can not make the copper surface too smooth, and the uniform thin silver is also one of the most important. The composition of organic compounds in the silver layer can be understood by analyzing the purity of the silver layer. This method requires a little more sampling, and the silver content must not be less than 90% of the molecular ratio.