Board surface blistering is one of the more common quality defects in the circuit board production process. Because of the complexity of the circuit board production process and the complexity of process maintenance, it is difficult to prevent board surface blistering defects. Blistering on the surface of the circuit board actually means that the bonding force of the board surface is poor, that is, there is a surface quality problem on the board surface. So, what are the reasons for the foaming on the PCB circuit board?
1. The problem of substrate process treatment.
Especially for some thinner substrates (generally less than 0.8mm), because the rigidity of the substrate is poor, it is not suitable to use a brushing machine to brush the board, which may not be able to effectively remove the copper foil on the board surface during the production and processing process. Specially treated protective layer. Therefore, attention should be paid to control during production and processing, so as to avoid the board surface blistering problem caused by the poor bonding force between the substrate copper foil and chemical copper on the board surface.
2. Oil stains on the board surface caused by machining (drilling, lamination, edge milling, etc.), or other liquids contaminated with dust to contaminate the surface.
3. The sinking copper brush plate is bad.
Excessive pressure on the grinding plate before sinking copper causes deformation of the orifice, brushing out the rounded corners of the copper foil at the orifice or even leaking the base material at the orifice, which will cause blistering at the orifice during copper plating, tin spray welding, etc.; Therefore, attention should be paid to strengthening the control of the brushing process, and the parameters of the brushing process can be adjusted to the best through the wear mark test and the water film test.
4. Washing problem.
Because the electroplating treatment of copper sinking needs to be treated with a large amount of chemical medicine, the surface of the board is not cleaned, especially the adjustment of degreasing agent for copper sinking, which will not only cause cross contamination, but also cause poor local treatment or poor treatment effect on the board surface; therefore Attention should be paid to strengthening the control of water washing, mainly including the control of washing water flow, water quality, washing time, and plate dripping time.
5. Micro-etching in the pre-treatment of copper sinking and the pre-treatment of graphic electroplating.
Excessive micro-etching will cause the substrate to leak from the orifice, resulting in foaming around the orifice; insufficient micro-etching will also cause insufficient bonding force and cause foaming; therefore, it is necessary to strengthen the control of micro-etch; The etching depth is 1.5-2 microns, and the micro-etching is 0.3-1 microns in the pattern electroplating pretreatment. If possible, it is better to control the micro-etching thickness or the etching rate by chemical analysis and simple test weighing method.
6. The surface of the board is oxidized during the production process.
If the sinking copper plate is oxidized in the air, it may not only cause no copper in the hole, rough board surface, but also cause blistering on the board surface. Therefore, during the production process, the sinking copper plate should be thickened in time, and it should not be stored for too long.
7. Immersion copper rework is poor.
Some reworked boards after sinking copper or pattern conversion will cause blisters on the board surface due to poor deplating, incorrect rework method, improper control of micro-etching time during rework, or other reasons. Rework of sinking copper plate If the sinking copper is found to be defective on the line, it can be directly degreased from the line after washing with water, then pickled and reworked directly without corrosion; it is best not to degrease and micro-etch again.
