Pink Ring of circuit board
The surface of the sheet is oxidized to form a undercoat (copper oxide and cuprous oxide). In essence, this fluff will by acid or reducing liquid corrosion, so that the original black or red brown fluff showing red copper; on the board after pressing, drilling and other subsequent processes, copper ring appears obvious color contrast dissolution in holes around the villi, which is called the pink ring.
The causes of pink circles
1, because the thickness of blackening - shape of the villi and villous melanization can cause different degrees of pink circle, but it can not effectively prevent the occurrence of hair blackening pink ring.
2, pressure - because of poor bonding (pressure, heating rate, flow rate, etc.) caused by the lack of adhesion between resin and oxide layer, resulting in the invasion of acid into the gap path.
3, drilling --- in the drilling, due to stress and high temperature caused by resin or oxide layer of delamination or fracture, so that acid intrusion corrosion.
4, chemical copper - in the through hole, there is acid solution, and make the villi dissolved.
Ways to improve the pink ring
1, improve the thickness and shape of oxidized villi
2. Storage, use and stacking of substrates
3. Improvement of bonding process conditions
4. Improvement of drilling conditions
5, wet process improvement
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