Do you know the three reasons why PCB copper flakes fall off?

PCB copperwire falling off (also often said copper dumping) is bad, PCB factories are said to be the problem of laminate, requiring its production factory to bear bad losses. According to customer complaint handling experience, PCB factory copper dumping common reasons are as follows:

Do you know the three reasons why LED panel PCB copper sheet falls off

First, PCB factory manufacturing process factors

1. Copper foil etching is excessive, electrolytic copper foil used on the market is generally single-side galvanized (commonly known as gray foil) and single-side plated copper (commonly known as red foil), the common copper is generally more than 70um galvanized copper foil, red foil and 18um below the basic ash foil has not been a batch of copper.

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 residence time of copper foil in the etching liquid is too long. Because zinc is active metal, when the copper wire on the LED advertising screen PCB is soaked in etching liquid for a long time, it will lead to excessive side erosion of the line, resulting in some fine line backing zinc layer is completely reacted off and separated from the substrate, that is, the copper wire falls off.

There is also a situation that PCB etching parameters have no problem, but after etching washing, and poor drying, resulting in copper wire is also in PCB surface residual etching liquid surrounded, a long time without treatment, will also produce excessive copper wire side erosion and copper. This situation is generally manifested as concentrated on the fine line, or in the wet weather period, the whole PCB will appear similar bad, strip the copper wire to see its contact surface with the base (namely, the so-called coarse surface) color has changed, and the normal copper foil color is not the same, see is the bottom of the original copper color, thick line copper foil peeling strength is normal.

2. Partial collision occurs in the PCB process of LED advertising screen, and the copper wire is separated from the substrate by external mechanical force. This defect manifests as poor positioning or orientation, falling copper wire will have obvious distortion, or in the same direction of the scratch/impact mark. Peel off the bad part of the copper wire to see the copper foil surface, you can see the normal color of the copper foil surface, there will be no bad side erosion, copper foil peeling strength is normal.

3. The PCB circuit design of LED advertising screen is not reasonable, and the thin circuit designed with thick copper foil will also cause excessive etching of the line and copper throwing.

Two, laminate process reasons

Under normal circumstances, as long as the hot pressing high temperature section of laminate more than 30 minutes, copper foil and semi-cured sheet is basically combined completely, so pressing generally will not affect the binding force of copper foil and substrate in laminate. However, in the process of laminate stacking and stacking, if PP pollution or copper foil surface damage, it will also lead to insufficient bonding force between copper foil and substrate after laminate, resulting in positioning (only for the large plate) or sporadic copper wire loss, but the stripping strength of copper foil near the stripping line will not be abnormal.

Three, laminate raw material reasons

1. LED advertising screen mentioned above ordinary electrolytic copper foil are wool foil galvanized or copper-plated products, if the peak value of wool foil production is abnormal, or galvanized/copper plating, coating crystal dendral is bad, resulting in copper foil itself peeling strength is not enough, the bad foil pressed board made of PCB plug-in in the electronics factory, copper wire will fall off by external impact. This kind of bad stripping copper wire copper foil surface (that is, contact surface with the substrate) after the obvious side erosion, but the whole surface of copper foil stripping strength will be very poor.

2. LED advertising screen copper foil and resin poor adaptability: now use some special performance laminate, such as HTg board, because the resin system is not the same, the use of curing agent is generally PN resin, resin molecular chain structure is simple, curing degree of crosslinking is low, 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 sheet metal foil peeling strength is not enough, plug-in will also appear bad copper wire shedding.