Copper fall off is a common problem in PCB fabrication. Let’s see the below reasons to learn more about it.
1. The copper foil is over-etched. The electrolytic copper foils used in the market are generally single-sided galvanized (commonly known as ashing foil) and single-sided copper plating (commonly known as red foil). Commonly thrown copper is generally galvanized copper above 70um Foil, red foil and ash foil below 18um basically have no batch copper rejection.
When the customer circuit design is better than the etching line, if the copper foil specifications are changed but the etching parameters remain unchanged, the residence time of the copper foil in the etching solution is too long. Because zinc is originally an active metal, when the copper wire on the PCB is soaked in the etching solution for a long time, it will inevitably lead to excessive side corrosion of the circuit, causing some thin circuit backing zinc layer to be completely reacted and separated from the substrate. That is, the copper wire falls off.
Another situation is that there is no problem with the etching parameters of the PCB circuit board, but after the etching is washed with water and poor drying, the copper wire is also surrounded by the residual etching solution on the PCB circuit board. If it is not processed for a long time, copper wires will also be generated. Excessive undercutting and dumping of copper. This situation is generally manifested as concentrated on thin circuits, or during periods of wet weather, similar defects will appear on the entire PCB circuit board. Strip the copper wire to see that the color of the contact surface with the base layer (the so-called roughened surface) is already The change is different from the normal copper foil color. What you see is the original copper color of the bottom layer, and the peel strength of the copper foil at the thick line is also normal.
2. A local collision occurred in the PCB circuit board process, and the copper wire was separated from the base material by external mechanical force. This poor performance is poor positioning or orientation, the copper wire will be obviously twisted, or scratches/impact marks in the same direction. Peel off the defective copper wire and look at the rough surface of the copper foil, you can see that the color of the rough surface of the copper foil is normal, there will be no side erosion, and the peeling strength of the copper foil is normal.
3. The circuit design of the PCB circuit board is unreasonable. If the circuit is designed with thick copper foil to be too thin, it will also cause excessive etching of the circuit and copper rejection.
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