In the process of PCBA circuit board assembly, causing a large reason for the foaming of the circuit board surface is the problem of poor binding force, that is, the surface quality of the board, which contains two aspects: the cleanliness of the board; The problem of surface microscopic roughness (or surface energy). Basically all the problems of the board surface foam on the circuit board can be summarized into these two reasons. The poor or too low bonding force between the coatings is due to the difficulty in resisting the coating stress, mechanical stress and thermal stress generated in the subsequent production and processing process and the PCBA assembly process, which eventually leads to different degrees of separation between the coatings.
The following is a summary of some factors that may cause poor panel quality during PCB manufacturing and PCBA assembly.
So may be unable to effectively remove the substrate in order to prevent the surface oxidation of copper foil in the process of production and processing and special processing layer, while the layer is thinner, brush plate is easy to remove, but the chemical processing is difficult, so important to pay attention to control in the production processing, lest cause panel substrate copper foil and copper chemical bonding force between the surface bubbles caused by bad; This kind of problem in the thin inner layer of melanization, there will also be poor melanization and Browning, color imbalance, local black and brown is not equal.
Therefore, attention should be paid to strengthening the control of the brush process, and the brush process parameters can be adjusted to the best through the wear mark test and water film test.
Especially when the temperature is low in winter, the effect of washing will be greatly reduced, and more attention should be paid to the strong control of washing.
Under normal circumstances, the surface of the micro-etched bright color, uniform pink, no reflection; If the color is not uniform or reflective, it indicates that there are quality hazards in the process pretreatment; Pay attention to strengthen inspection;In addition, the copper content of the micro-corrosion tank, the temperature of the tank, the load, the content of micro-corrosion agent and so on should be paid attention.
It is best not to remove oil, micro-erosion; For the plates that have been electrically thickened, the micro-etched groove should be faded now. Pay attention to time control. You can use one or two plates to roughly measure the fading time to ensure the effect of the plating.
After the plating is finished, brush lightly with a group of soft grinding brushes followed by the brush machine and then sink the copper according to the normal production process, but the corrosion time should be halved or adjusted as necessary.
Some of the above can be said to be in the actual circuit board production and PCBA circuit board assembly process, the more common cause of the board foaming. Of course, there are many reasons for the foaming of the board, and for different manufacturers of equipment technology level may be caused by different reasons for the foaming phenomenon, so this needs to be analyzed on a case-by-case basis.
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