Cause of PCB falling solder plate

PCB circuit board in the production process, often encounter some process defects, such as PCB circuit board copper wire off bad (is also often said to throw copper), affect product quality. The common reasons for PCB circuit board throwing copper are as follows:

PCB circuit board 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), 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.

2. Local collision occurs in PCB process, 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, PCB circuit design is not reasonable, with thick copper foil design of too thin line, will also cause excessive line etching and copper.

Laminate process reason

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.

Laminate raw material reason

1, ordinary electrolytic copper foil is galvanized or copper-plated products, if the peak value of the wool foil production is abnormal, or galvanized/copper plating, coating dendritic 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 peeling strength will be poor.

2. Poor adaptability of copper foil and resin: some laminates with special properties are used now, such as HTg sheet, because of different resin systems, the curing agent used is generally PN resin, resin molecular chain structure is simple, low crosslinking degree when curing, 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.

In addition, it may be that improper welding in the client leads to the loss of the welding pad (especially single and double panels, multilayer boards have a large area of floor, fast heat dissipation, welding temperature is high, it is not so easy to fall off) :

Repeatedly welding a spot will weld the pad off;

High temperature of soldering iron is easy to weld off the pad;

Too much pressure exerted by the soldering iron head on the pad and too long welding time will weld the pad off.