Analysis of the three main reasons for PCB rejection of copper
2016/7/19 15:03:13

...PCB's copper wire is off (also often said the rejection of copper), PCB plant is said to be the problem of laminate, requires its production plant to bear the bad losses. According to the customer complaint handling experience in many years, PCB factory dumped there are several common causes of copper:
One, PCB plant process factors:
1, copper foil etching excessive, electrolytic copper foil used in the market generally sided galvanized (commonly known as ashing foil) and single copper (commonly known as red foil), common throwing copper general 70UM above galvanized copper foil, red foil and 18um following ashing foil basically has not appeared batch rejection of copper. Customers line design is better than etched line, if the specifications of copper foil after the change and the etching parameters unchanged, resulting in copper foil in the etching liquid residence time is too long. Because zinc is originally lively metal. When the PCB copper wire for a long time in the etching solution soaking, will inevitably lead to line side etching excessive, resulting in some fine line backing zinc layer is fully reflect off and substrate detachment, the copper loss. There is a situation in which PCB etching parameters no problem, but after etching and washing with water and drying adverse, resulting in copper wire is also surrounded by PCB surface residual etching solution, for a long time without treatment, will produce copper side erosion over to dump copper. This is focused on the performance of thin lines on the road, or wet weather period, the whole PCB will appear similar adverse, peel the copper to see the and primary contact surface (i.e. the so-called coarse surface color has changed, and normal copper color, see is underlying the original copper color, thick lines copper foil peel strength is also normal.
2, the PCB process of local collision, copper wire under external mechanical and material detachment. This bad performance for bad positioning or fixed direction, off the copper wire will be significantly distorted, or to the same direction of scratches / impact marks. Bad copper peel look rough copper foil surface, you can see the copper foil facial hair color is normal, there will be no lateral erosion bad, copper foil peel strength.
3, PCB line design is not reasonable, with a thick copper foil design fine lines, can also cause excessive etching and rejection of copper.
Two, the cause of the laminate process:
Under normal circumstances, laminates as long as hot pressing period of more than 30 min, and copper foil prepreg basically with complete, so pressing generally does not affect to laminate copper foil and substrate binding force. But in the laminate stack, stacking process, if the PP pollution, or copper hair surface damage, resulting in laminated after copper foil and substrate binding force is insufficient, cause positioning (only needle to plate) or sporadic copper loss, but measured off-line near copper foil peel strength wouldn't be abnormal.
Three, laminate raw material reasons:
1, the above mentioned ordinary electrolytic copper foil is hair foil galvanized or copper treated products, if hair foil production peak is abnormal, or zinc / copper plating, coating dendrite adverse, resulting in copper foil peel strength is not enough, the adverse foil pressed sheet made of PCB in electronics factory plug wire by external shocks will happen to fall off. Such rejection adverse ripping copper copper copper foil facial hair (i.e. with the substrate contact surface) does not significantly lateral erosion, but the entire surface of the copper foil peel strength will is very poor.
2, the adaptability of the copper foil and the resin is undesirable: now the use of some special properties of the laminates, such as sheet HTG, resin system is not the same, the use of curing agent is generally PN resins, resin molecular chain has the advantages of simple structure, curing with low crosslinking degree is bound to use special peak value of copper foil and matching. When the production of laminates using copper foil and the resin system does not match, caused by plate coating metal foil peel strength is not enough, plug-in will appear copper off bad.