PCB Tech - Three main reasons for PCB copper flake shedding

The copper wire falling off of PCB (also known as copper dumping) is not good. PCB manufacturers say that the laminate is the problem and require their production factories to bear the bad losses. According to customer complaint handling experience, common reasons for PCB factory copper dumping are as follows:

Do you know the three main reasons for LED screen PCB copper flake falling off

One, 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 ash foil) and single-sided copper plating (commonly known as red foil), the common copper dumping is generally more than 70um galvanized copper foil, red foil and ash foil below 18um 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 a lively metal, when the copper wire on THE LED advertising screen PCB is soaked in etching solution for a long time, it will 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. There is a local collision in the PCB process of LED advertising screen, 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. The PCB circuit design of LED advertising screen is unreasonable, and the thin circuit designed with thick copper foil will also cause excessive etching of the circuit 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. LED advertising screen has mentioned above ordinary 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, 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. LED advertising screen copper foil and resin adaptability: now use some special performance laminate, such as HTg board, 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 match. When the production of laminate using copper foil and the resin system does not match, resulting in plate covering metal foil feeling strength is not enough, plug-in will also appear bad copper wire peeling.