What are the reasons for the PCB board to drop copper

Local collision occurs in the PCB circuit board process, and the copper wire is separated from the base by external mechanical force. This phenomenon is a poor positioning, and the copper wire will have obvious distortion, or scratches and impact marks in a uniform direction. Pull out the copper wire of the bad place to see the copper foil surface, it can be seen that the copper foil surface is normal, there will be no side erosion, and the copper foil peeling strength is normal.

PCB circuit board design is unreasonable. Designing a thin line with thick copper foil will also cause excessive etching of the line and copper.

Copper foil is excessively etched. Electrolytic copper foil used on the market is generally unilateral galvanized (commonly known as ash foil) and single-sided copper plating (commonly known as red foil). Common bismuth copper is generally galvanized copper foil of 70 um or more. There are basically no batches of beryllium copper in the red foil and the ash foil below 18um. When the customer circuit is designed to pass through the etched line, if the copper foil specification is changed and the etching parameters are not changed, the residence time of the copper foil in the etching solution is too long. Since zinc is originally a lively metal, when the copper wire on the PCB is immersed in the etching solution for a long time, it will lead to excessive side etching of the line, causing some fine line backing zinc layer to be completely reacted and detached from the substrate. That is, the copper wire falls off.

There is also a case where there is no problem with the PCB etching parameters, but the water is washed after etching, and the drying is poor, so that the copper wire is also surrounded by the etching liquid remaining on the surface of the PCB board. If it is left untreated for a long time, the copper line is excessively etched. And bismuth copper. This situation is generally manifested on the thin line, or in the wet weather, there will be similar defects on the whole PCB. The color of the contact surface with the base layer (the so-called roughened surface) has been changed after peeling off the copper wire. Unlike the normal copper foil color, the original copper color is seen, and the peel strength of the copper foil at the thick line is also normal.