Common reasons for PCB copper rejection

As a raw material supplier of PCB, I was often complained by customers about bad copper wire shedding (also known as copper dumping). In this case, all PCB factories are said to be the problem of laminate, requiring their production factories to bear bad losses. According to my years of customer complaint handling experience, the common reasons for PCB factory copper dumping are as follows:

I. PCB factory manufacturing process factors:

1, copper foil etching is excessive, the electrolytic copper foil used in the market is generally single-sided galvanized (commonly known as ashing foil) and single-sided copper plating (commonly known as red foil), common copper dumping is generally more than 70um galvanized copper foil, red foil and 18um below ashing foil basically have no batch copper dumping. When the customer line design is better than the etching line, if the copper foil specifications are changed and the etching parameters are not changed, the copper foil stays in the etching solution for too long. Because zinc is an active metal, when the copper wire on PCB is immersed in etching solution for a long time, it will inevitably lead to excessive line erosion, resulting in some fine line backing zinc layer is completely reacted off and separated from the base material, that is, the copper wire falls off. Another situation is that there is no problem with the ETCHING parameters of PCB, but the etching is washed after etching and the drying is poor, resulting in the copper wire is also surrounded by the etching liquid remaining on the SURFACE of PCB. If it is not treated for a long time, the copper wire will be excessively corroded and the copper will be thrown. General performance of this kind of circumstance is concentrated in the fine lines, or the weather wet period, the entire PCB will appear similar adverse, remove the copper wire to see its and grassroots interface (so-called coarsening surface) color have change, unlike normal copper foil color, is to see the underlying original copper color, thick lines of copper foil peel strength also normal.

2. In the PROCESS of PCB, local collision occurs, and the copper wire is separated from the base material by external mechanical force. This undesirable performance is poorly positioned or directional, the loose copper wire will have obvious distortion, or in the same direction of the scratch/impact mark. Peeling the copper wire at the bad place to see the copper foil hair surface, you can see that the color of the copper foil hair surface is normal, there will be no bad side erosion, and the copper foil peel strength is normal.

3, PCB circuit design is not reasonable, with thick copper foil design too thin circuit, will also cause excessive circuit etching and copper dumping.

Two, laminate process reasons:

Under normal circumstances, as long as the laminate is pressed at a high temperature for more than 30min, the copper foil and the semi-cured sheet are basically combined completely, so the pressing generally does not affect the binding force of the copper foil and the substrate in the laminate. However, in the process of laminate stacking and stacking, if PP pollution or damage of copper foil hair surface will also lead to insufficient binding force between copper foil and base material after lamination, resulting in positioning (only for large plates) or sporadic copper wire falling off, but there will be no abnormal copper foil peeling strength near the measured off line.

Three, laminate raw materials:

1, the above mentioned general electrolytic copper foil MAO foil galvanized or copper plating the processed products, when MAO foil production peak is abnormal, or zinc/copper plating, coating the dendrite, the peel strength of the copper foil itself is not enough, caused by the bad foil after pressing sheet made PCB electronics factory plug-in, copper wire fall off by external shocks will occur. This kind of bad copper stripping copper wire to see the copper foil hair surface (that is, the contact surface with the base material) will not be obvious side erosion, but the whole surface of copper foil peeling strength will be very poor.

2, the adaptability of copper foil and resin is poor: some special performance laminate used now, such as HTg sheet, because the resin system is not the same, the curing agent is generally PN resin, resin molecular chain structure is simple, the crosslinking degree is low when curing, is bound to use special peak copper foil and match. When the production of laminate using copper foil and the resin system does not match, resulting in plate covering metal foil peeling strength is not enough, plug-in will also appear bad copper wire peeling.