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Cause Of Foaming Of PCB During PCBA Assembling
Jun 16, 2017

  Cause of foaming of PCB during PCBA assembling

  During the PCBA assembly process, the cause of the plate surface blistering is the problem of poor board adhesion, that is, the surface quality of the plate, which contains two aspects: the problem of cleanliness of the plate surface, surface micro-roughness (or surface energy) problems. Basically all board surface blister problem can be summed up in these two reasons.

  The adhesion between the coating is poor or too low, because it is difficult to resist the coating stress, mechanical stress and thermal stress during the process of production and PCBA assembling, so that the separation between the layers can be caused by different degrees. The following is a summary of some of the factors that may result in poor surface quality during PCB production and PCBA assembly.

  1, the process of substrate processing problems: Especially for some of the thinner substrates (general 0. Below 8mm), because the substrate rigidity is poor, it is not suitable to use brush board machine. This may not effectively remove the substrate production and processing in order to prevent the plate surface oxidation and special treatment of the protective layer, although the layer is thinner, brush board is easy to remove, but the use of chemical treatment has a greater difficulty, so in the production and processing of important attention to control, in order to avoid the surface of the substrate copper foil and chemical bonding between the poor caused by the problem of plate foaming; This problem in the thin inner layer of the black, there will be black brown, color uneven, local black brown is not the best problem.

  2, plate surface in machining (drilling, laminating, milling, etc.): In this process caused by oil or other liquids contaminated with dust pollution surface treatment of undesirable phenomena.

  3, Immersion copper brush plate bad: Before sinking copper grinding plate pressure too large, resulting in hole deformation brush out of the hole mouth copper foil fillet or even pore leakage of the base material, so in the immersion copper electroplating tin spray welding process will cause the hole foaming phenomenon; even if the brush plate does not cause leakage of the substrate, however, the heavy brush board will increase the roughness of copper hole, so in the process of micro-etching in the copper foil can easily produce coarse excessive phenomenon, there will be a certain quality hidden trouble; Therefore, we should pay attention to strengthen the control of brush plate process, The process parameters of the brush board can be adjusted to the optimum through the grinding test and the water film Test.

  4, washing problem: Due to the immersion of copper electroplating treatment to undergo a large number of chemical treatment, so all kinds of acid and alkali nonpolar organic solvents More, the plate surface washed unclean, especially the adjustment of the copper oil remover, not only will cause cross-contamination, at the same time will also cause the plate surface treatment of poor or poor treatment, uneven defects, resulting in some PCBA assembly of the binding force of the problem; Therefore, we should pay attention to strengthen the control of washing, mainly including cleaning water flow, water quality, washing time, and plate parts drop Water time and other aspects of control; especially in winter, the temperature is low, the effect of washing will be greatly reduced, more attention will be given to the control of the washing.