PCB Circuit Board Pretreatment Process Problems:
1. The problems that occur in the PCB circuit board manufacturing process are all kinds of strange, and the process engineer is often responsible for the forensic-autopsy (bad cause analysis and countermeasures). Therefore, the main purpose of this discussion question is to discuss one by one in the equipment area to include people, machines, materials, and conditions may lead to problems.
2. It will use the process of pre-treatment equipment, such as: inner layer pre-treatment line, electroplating a copper pre-treatment line, D/F, solder mask (solder mask)etc.
3. Take the PCB circuit board solder mask pretreatment line as an example (different manufacturers vary): brushing*2 groups->water washing->pickling->water washing->cold air knife->drying section ->Sun plate closing plate->discharging closing plate.
4. Generally, the brush wheel is #600, #800 gold steel brush, which will affect the roughness of the board surface and thus affect the adhesion of the ink and the copper surface. After the brush wheel has been used for a long time, if the product is not left or right when evenly placed, it is easy to produce the phenomenon of dog bones, which will cause uneven roughening of the board surface and even line deformation and different color difference between the copper surface and INK after printing, so it needs to be brushed. Before brushing, it needs to be done brushmark test (for D/F, a water break test is required), the width of brush marks is about 0.8~1.2mm, which varies depending on the product. After updating the brush, the level of the brush wheel needs to be adjusted. Make corrections, and need to add lubricating oil regularly. If the water is not boiled during brushing, or the spray pressure is too small to form a fan-shaped angle with each other, copper powder will easily occur, and a slight copper powder will cause a micro-short circuit during the finished product test (dense line area) or unqualified high voltage test.
Another problem that is easy to occur in pre-treatment is the problem of board surface oxidation, which will lead to board surface bubbles or cavitation after H/A.
1. The position of the solid water retaining roller in the pretreatment is wrong, so that the acid is brought into the washing section too much. If the number of washing tanks in the latter section is insufficient or the amount of water injected is insufficient, it will lead to acid residues on the board surface.
2. The water quality of the washing section is poor, or when there are impurities, there will be foreign objects attached to the copper surface.
3. If the water-absorbing roller is dry or saturated with water, it will not be able to effectively take away the water on the product to be made, which will make the residual water on the board surface and the residual water in the holes too much, and the subsequent air knife cannot fully function. The vacuoles caused at this time are mostly in the shape of tears at the edge of the via hole.
4. When the temperature of the board is still residual when the material is discharged, the board is stacked and closed, which will oxidize the copper surface in the board.
Generally speaking, a pH detector can be used to monitor the pH value of the water, and infrared rays are used to measure the residual temperature of the board surface. Wet conditions need to be specified. It is best to have two sets of suction wheels for alternate cleaning. The angle of the air knife needs to be confirmed before daily operation, and pay attention to whether the air duct in the drying section is detached or damaged.
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