There are several common reasons for PCB factory to dump copper:
I. PCB factory manufacturing process factors:
1. Excessive etching of copper foil, 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), common copper dumping is generally more than 70um of galvanized copper foil, red foil and less than 18um of ash foil has not appeared bulk copper dumping.
When the customer's line design is better than the etch line, if the copper foil specifications are changed but the etch parameters remain unchanged, the copper foil will stay in the etch solution for too long.
Because zinc is a kind of active metal, when the copper wire on PCB is soaked in etching solution for a long time, it will lead to excessive corrosion on the side of the line, causing the zinc layer on the back of some thin lines to be 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 PCB etching parameters. However, after etching, washing and drying are not good, resulting in the copper wire being surrounded by the etching solution left on the PCB surface. If the copper wire is left untreated for a long time, excessive corrosion on the side of the copper wire will occur and copper will be dumped.
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. Local collision occurs in PCB process, and the copper wire is separated from the substrate by external mechanical force.
This defect is characterized by poor positioning or directionality, obvious distortion of the dropped copper wire, or scratches/impact marks in the same direction.
Peel the copper wire at the wrong place to see the copper foil hair, you can see that the copper foil hair color is normal, there will be no side corrosion, the copper foil peeling strength is normal.
3. Unreasonable PCB circuit design. Too thin circuit design with thick copper foil will lead to excessive etching and copper rejection.
II. Reasons for laminate manufacturing process:
Under normal circumstances, as long as the hot pressing section of the laminate is more than 30min, the copper foil and the semi-curing sheet are basically completely combined, so the pressing will not affect the adhesion between the copper foil and the substrate in the laminate.
However, in the laminate stacking and stacking process, if PP pollution, or copper foil surface damage, will also lead to insufficient adhesion between copper foil and substrate after lamination, resulting in positioning (only for the large plate) or scattered copper wire fall off, but there will be no abnormal copper foil peeling strength near the delamination.
III. Reasons for raw material of laminate:
1. The above mentioned general 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, caused by the bad foil after pressing sheet made PCB electronics factory plug-in, copper wire fall off by external shocks will occur.
Such casting copper poor stripping copper wire to see copper foil surface (that is, contact with the substrate surface) will not obvious side corrosion, but the whole copper foil stripping strength will be very poor.
2. Poor adaptability of copper foil and resin: for some laminates with special properties, such as HTg plate, due to different resin systems, the curing agent used is usually PN resin. The molecular chain structure of the resin is simple and the crosslinking degree during curing is low.
When the production of laminates using copper foil does not match the resin system, resulting in plate covering metal foil peeling strength is not enough, the plug-in will also appear copper wire off bad.
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Post time: Sep-06-2019