03 JUN

Comprehensive Analysis of PCB Copper Stripping: Unraveling Causes from Manufacturing Processes to Material Considerations

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  • Nov 21,2023
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circuit boardPCB dumping copper is often referred to as the PCB copper wire off bad, this time the circuit board manufacturers are said to be the laminate problem, requiring its production plant to bear the bad loss. Today Qinji editorial collection of the old drivers of this PCB dumping copper common reasons are analyzed below:

First, the circuit board factory process reasons:

1, excessive copper foil etching, the market use of electrolytic copper foil is usually single-sided galvanized (commonly known as gray foil) and single-sided copper plating (commonly known as red foil), the common dumping of copper is usually more than 70um zinc-plated copper foil, red foil and gray foil below 18um basically have not appeared in bulk dumping of copper.

After the customer's line is designed and etched, if the specification of the copper foil is changed but the etching parameters are not changed, the copper foil stays in the etching solution for too long. Because zinc is originally active metal, when the copper line on the PCB circuit board for a longer period of time in the etching solution immersion, will certainly cause the line side of the etching is excessive,2 oz copper thickness in mm resulting in some of the fine line backing zinc layer is completely reacted off and detached from the substrate, that is, the copper line off.

There is also a situation that the PCB circuit board etching parameters are not a problem, but after etching, washing, and drying bad, resulting in the copper line is also in the PCB circuit board on the surface of the residual etching solution surrounded by a longer period of time is not dealt with, but also cause the copper side of the line etched excessively and dumping copper. This situation is usually manifested in the concentration of fine lines, or humid weather period, the entire PCB circuit board will appear similar bad, peeling off the copper line to see its contact surface with the grass-roots level (the so-called roughened surface) color has changed, and the normal color of the copper foil is not the same as that seen in the bottom layer of the original color of the copper, copper foil at the thick line peeling strength is also normal.

2, PCB circuit board process in the local collision, the copper line by external mechanical force and detached from the substrate. This bad performance for poor positioning or orientation, shedding copper will have obvious distortion, or to the same direction of the scratches / impact marks. Peel off the defective copper wire to see the copper foil gross surface, you can see the copper foil gross surface color is normal, there will be no side-etching bad, copper foil peeling strength is normal.

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

Second, the laminate PCB:

Usually, the laminate as long as the hot pressure high temperature section for more than 30min after the copper foil and semi-cured sheet on the basic combination of the full, so the pressure is usually not interfere with the laminate in the combination of copper foil and substrate. However, in the process of laminate stacking, stacking, if PP pollution, or copper foil hair surface damage, will also cause the combination of copper foil and substrate after lamination is insufficient, resulting in the positioning (only for large boards) or sporadic copper line off,plated through hole vs via but the measurement of the stripping strength of copper foil near the stripped line will not be abnormal.

Third, the laminate raw materials:

1, as mentioned above, ordinary electrolytic copper foil is basically a gross foil galvanized or copper-plated products, if the peak of the gross foil production on the abnormal, or galvanized / copper-plated, plating dendrites poor, resulting in the peeling strength of the copper foil itself is not enough, the poor foil pressed plate made of PCB in the electronics factory plug-ins, the copper wire by the impact of the external forces will occur off. This kind of dumping copper bad peel off the copper line to see the gross surface of the copper foil (i.e., with the substrate contact surface) will not be obvious after the side of the corrosion, but the whole surface of the peeling strength of copper foil will be very poor.

2, copper foil and resin adaptability is poor: now using some special properties of the laminate, such as HTg sheet material, because the resin system is different, the curing agent is generally PN resin, resin molecular chain structure is simple, curing degree of cross-linking is low, it is inevitable to use a special peak of the copper foil and its matching. When the production of laminates using copper foil and the resin system does not match, caused by the sheet covered with metal foil peeling strength is not enough, plug-in will also appear when the copper wire off bad.