Common causes of copper dumping on PCB circuit boards
For SMT processing enterprises, if we are a relatively deep manufacturers may have involved in the front-end and back-end, PCB, components, SMT makes the entire process, is equal to the whole processing in their own hands, so to control the quality of the products and the quality problem of the subsequent back are good, but for the production of professional on grounds of cost and profit, many enterprises are only involves one of the links.Then the quality factors beyond our control will require us to pay more cost to maintain our quality rate.So today we mainly want to talk about some process defects in PCB circuit board.
In the manufacturing process of PCB circuit board, some process defects are often encountered, such as bad copper wire shedding of PCB circuit board (also known as copper dumping), which affects product quality.There are several common reasons for PCB circuit board copper dumping:
I. PCB circuit board manufacturing process factors:
1. Excessive etching of copper foil. The electrolytic copper foil used in the market is generally single-sided zinc plating (commonly known as gray foil) and single-side copper plating (commonly known as red foil).
2. Partial collision occurred in the PCB circuit board process, and the copper wire was separated from the base material due to external mechanical force.This defect is characterized by poor positioning or directional alignment, and the copper wire may have obvious distortion or scratch/impact marks in the same direction.If you look at the surface of the copper foil, you can see that the color of the surface of the copper foil is normal.
3. Unreasonable PCB circuit design, too thin circuit design with thick copper foil will also lead to excessive line etching and copper dumping.
Ii. Laminate manufacturing process reason:
Under normal circumstances, as long as the high temperature section of the laminate exceeds 30min, the copper foil and the semi-solidified sheet will be completely combined, so the compaction will not affect the binding force of the copper foil and the base material in the laminate.However, in the process of laminar lamination and stacking, if PP pollution or damage to the copper foil wool surface, there will also be insufficient binding force between the copper foil and the base material after lamination, resulting in positioning (only for the large plate) or sporadic copper wire falling off.
Iii. Laminate raw materials
1. Common electrolytic copper foil is the product treated by galvanized or copper-plated wool foil. If the peak value of wool foil is abnormal, or when galvanized or copper-plated, the coating crystal branch is poor, resulting in insufficient peeling strength of copper foil itself.This kind of bad copper dumping can be seen by stripping the copper wire. The surface of the copper foil wool (that is, the contact surface with the base material) will not undergo obvious side erosion, but the stripping strength of the whole copper foil will be very poor.
2. Poor adaptability of copper foil and resin: some laminate with special properties, such as HTg sheet materials, are used because of the different resin system. The curing agent is generally PN resin, and the structure of the resin molecular chain is simple.When producing laminate, the copper foil is not matched with the resin system, which results in insufficient peel strength of the metal foil coated with the sheet material, and the copper wire will fall off badly when the plug is inserted.
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