When the copper wire of PCB board falls off (also known as copper dumping), PCB brands will claim that it is the laminate problem and require their production factories to bear the bad losses.
1. PCB factory manufacturing process factors:
1. Excessive etching of copper foil.
Electrolytic copper foil used on the market is generally single-side galvanized (commonly known as ashing foil) and single-side plated copper (commonly known as red foil), the common copper is generally more than 70um galvanized copper foil, reddening foil and 18um below the basic have not been a batch of copper. When the circuit design is better than the etching line, if the copper foil specifications change and the etching parameters do not change, it will make the copper foil stay in the etching solution for too long.
Because zinc is an active metal, when the copper wire on PCB board 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 drying is poor, resulting in copper wire is also in PCB surface residual etching liquid surrounded, a long time without treatment, will also produce copper wire side corrosion excessive and throw copper.
This situation is generally concentrated in the fine line, or 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 PCB production process, and the copper wire is separated from the base material by external mechanical force.
This poor performance positioning problems, falling copper wire will have obvious distortion, or in the same direction of scratches or impact marks. 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 unreasonable.
Wires designed too thin with thick copper foil can also result in excessive etching 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 stacking and stacking of laminates, if PP pollution or copper foil wool surface damage, it will also lead to insufficient bonding force between copper foil and substrate after lamination, resulting in positioning deviation (only for large plates) or sporadic copper wire loss, but there will be no abnormality in the stripping strength of copper foil near the stripping line.
Three, laminate raw material reasons:
1, it is mentioned above that 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 circuit board, plug-in in the electronics factory, copper wire will fall off by external impact. This kind of bad stripping copper wire copper foil surface (i.e. contact surface with the substrate) will not have obvious side erosion, but the whole surface of copper foil peeling strength will be very poor.
2. Poor adaptability of copper foil and resin: some laminates with special properties are used now, 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, low crosslinking degree when curing, is bound to use special peak copper foil and match. When the copper foil used in the production of laminate does not match the resin system, resulting in insufficient peeling strength of sheet metal foil, plug-in will also appear bad copper wire shedding.