What are the reasons for the blistering of PCB board?
From the poor bonding of the board surface and the board surface quality problems, the reason can be divided into:
1, the cleanliness of the board;
2, the surface micro-roughness (or surface energy) problem.
The poor quality of the board surface during production and processing can be divided into:
1) substrate processing problems: In particular for some thin substrates (usually 0.8mm or less), because the substrate rigidity is poor, brushing machine brush should not be used. In this way, it may be impossible to effectively remove the protective layer specially treated to prevent oxidation of the surface copper foil in the production process of the substrate. Although the layer is relatively thin, the brush plate can be easily removed, but it is difficult to adopt chemical treatment, so the production is difficult. Important attention is paid to processing to avoid foaming on the board due to poor bonding between the copper foil on the board substrate and the chemical copper; this problem also occurs when the thin inner layer is blackened. Poor, uneven color, local black brown can not be the problem.
2) . The phenomenon that the surface of the board surface is not treated properly due to oil contamination or other liquid contamination caused by machining (drilling, laminating, milling, etc.).
3), sinking copper brush plate bad: copper pre-grinding plate pressure is too large, resulting in hole deformation brushed hole copper foil hole or even hole leakage substrate, so that in the copper plating electroplating spray welding process will cause Hole blistering phenomenon; even if the brush plate does not cause leakage of the substrate, but the excessive brush plate will increase the copper roughness of the hole, so the copper foil at this point in the process of micro-etching roughening can easily cause excessive over-coarsening phenomenon. There will be certain quality risks; therefore, it is necessary to pay attention to the control of the brush plate process. The brush plate process parameters can be adjusted to the best through the wear scar test and the water film test.
4). Washing problem: Because the heavy copper electroplating treatment requires a large amount of chemical treatment, all kinds of acid-base non-polar organic medicines have many solvents, and the board surface is not washed clean, especially the adjustment of the degreasing agent by sink copper will not only cause cross-contamination. , At the same time, it will also cause local poor treatment of the board or poor processing results, non-uniform defects, resulting in some problems with the binding force; therefore, we must pay attention to strengthening the control of water washing, mainly including the flow of washing water, water quality, washing time , And the control of the plate dripping time and other aspects; particularly low winter temperatures, water washing effect will be greatly reduced, but also pay attention to the strong control of washing;