1. Excessive etching of copper foil. The electrolytic copper foil used in the market is generally single -sided galvanized (commonly known as gray foil) and single -sided copper plating (commonly known as red foil). Common copper shampoo is generally galvanized copper above 70um or more Foil, red foil and gray foil below 18um basically have not seen batch -shaped copper. When the customer line design is better than the etching line, if the copper foil specifications change and the etch parameters have not changed, causing the copper foil to stay in the etching solution for too long. Because zinc was originally a lively metal, when the copper line on the PCB was soaked in the etching solution for a long time, it would cause excessive line erosion of the line, resulting in some thin lines against the zinc layer. That is, the copper thread falls off. Another situation is that there is no problem with the PCB etching parameters, but after etching, water washing, and poor drying, resulting in the copper wires are also surrounded by the etching solution left by the PCB noodles. If it is not processed for a long time, the copper line side erosion will also cause excessive etching and excessive corrosion of the copper line. Drop copies. In this case, it is generally manifested on the detailed line, or in the period of humid weather, similar badness will appear on the entire PCB. Dipping the copper thread to see that the color of the contact surface with the grassroots (that is, the so -called coarse surface) has changed. Unlike the color of normal copper foil, the bottom of the original copper is seen, and the peeling strength of the copper foil at the thick line is normal.

　　2. Local collisions in the PCB process, and the copper line is separated from the substrate from the external mechanical force. This adverse manifestation is adverse positioning or fixed directionality, and the copper thread will be distorted obviously, or scratches/impact marks in the same direction. The copper threads are peeled to see the copper foil surface. You can see that the color of the copper foil surface is normal, and there will be no poor side erosion.

　　3. The design of the PCB line is unreasonable, and the detailed lines with thick copper foil will also cause the line erosion to etch too much and throw the copper