1. Multi-layer circuit board Jafani bites copper
This problem must be traced back to the copper electroplating process. It is found that if the examples of deep hole barrel plating and buried hole barrel plating with high thickness-diameter ratio can be shown that the copper thickness is more evenly distributed, this kind of Jafani’s copper biting situation will be reduced. Moreover, in the process of multilayer circuit board, the stripping of metal material resist (such as pure tin layer) and the etching process of copper, etc., once there are too many etching processes and there are side etching conditions, there will also be gaps and electroplating process solution and micro etching solution.
In fact, the big problem of Jafani comes from the green paint project, in which the side erosion caused by the green paint condition and the embossed pattern of the skin film are the most likely to cause gaps. If the condition of green paint can be left with positive residual foot instead of negative side erosion, and the green paint is completely hardened and bottomed, the lack of copper biting by Jafani can be eliminated. For the actual operation of electroplating copper, try to make the electroplating copper in the deep hole more symmetrical in obvious mixing. At this time, it is necessary to mix with the help of ultrasonic wave and Eductor to improve the mass transfer of bath liquid and the thickness of copper. For the self-process of dipping silver plating on PCB, it is necessary to strictly control the micro-etching copper biting rate at the front end, and the smooth copper surface can also reduce the existence of gaps after green paint. In the end, the silver bath itself can’t show too strong copper biting reaction, the PH value should be neutralized, and the plating speed should not be too fast. It’s best to cut the thickness as thin as possible, and only in the optimized silver crystal can the anti-fading effect be done well.
2. Improvement of color fading of multilayer circuit boards
The improvement method is to increase the relative density of the coating and reduce its Porosity. Sulfur-free paper should be used as much as possible for packaging goods and sealed in many aspects to block off co2 and sulfur in the air, thus reducing the source of its fading. Moreover, the average temperature of the natural environment for storage management should not exceed 30℃, and the humidity of the environment should be less than 40%RH. It is best to adopt the current policy of “excellent first addition” to prevent problems caused by long-term storage.
3. Improvement of ionization environmental pollution on PCB surface of multilayer circuit board.
If the ion concentration of silver immersion bath solution can be reduced without hindering the coating quality, the ionization caused by adhesion on the surface will of course be enough to reduce the dosage. During cleaning after immersion plating, it should be dipped in pure water for more than one minute before drying, so as to reduce the ionization of adhesion. Moreover, the cleanliness of the finished board should also be tested regularly, so as to minimize the residual ionization on the surface of PCB and meet the industry standard. All the experiments done should be recorded so as to be prepared.
4. Improvement of copper exposure on silver surface of multilayer circuit boards.
All kinds of steps before silver plating need careful supervision, such as the inspection of “WaterBreak” after micro-etching the copper surface and the observation of very bright copper spots, all of which indicate that there will be some dirt on the copper surface. Micro-etched clean copper surface, its standing condition must be maintained for 40 seconds without water breaking. On-line machinery and equipment should also be maintained on time to maintain the symmetry of its water solubility, so as to obtain a more symmetrical silver coating. In practice, it is necessary to continuously carry out experiments of DOE test scheme on immersion barrel plating time, liquid temperature, mixing, and diameter size, etc., so as to obtain the best quality silver coating. For the immersion silver plating process of thick steel plates with deep holes and HDI micro-embedded orifice plates, the external force of ultrasonic wave and high current can also be used to help improve the spread of silver coating. The additional super-strong mixing of this bath liquid can indeed improve the working ability of wetting and exchanging yao water in deep holes and buried holes, which is of great help to all wet processes.
5. Improvement of micro-holes in spot welding of multilayer circuit boards.
Interfacial micro-hole is still a defect that is difficult to improve in immersion silver plating at present, because its real cause is still unknown, but at least some related reasons can be made clear. Therefore, the generation of welding micro-holes in the middle and lower reaches of the river can naturally be reduced by avoiding the generation of its related elements.
Among the relevant factors, the thickness of the silver layer is more important, so it is necessary to reduce the thickness of the silver layer as much as possible. Secondly, the micro-etching solved before can’t make the copper surface too unsmooth, and the symmetry of silver thickness is also one of the most important things. As for the organic compounds in the silver layer, it will be known in the opposite direction from the purity analysis of a little more sampling silver layer, in which the silver content cannot be less than 90% of the molecular ratio.