The PCB pre-processing stage plays a crucial role in determining the efficiency and outcome of the overall manufacturing process. This article discusses the potential issues arising from human, machine, material, and environmental factors in the PCB pre-processing stage, with the aim of achieving optimal results through effective operation.
1. The pre-processing equipment used in this stage includes systems such as the inner layer pre-processing line, electroplating-copper pre-processing line, D/F line, solder mask (SM) process line, and others.
2. Taking the solder mask pre-treatment line for rigid PCB as an example (which may vary by manufacturer): it typically involves a sequence of steps including brush grinding (2 sets) → water washing → pickling → water washing → cold air knife → drying section → solar disc rewinding → discharge rewinding.
3. Generally, a #600 or #800 gold steel brush is used, which influences the surface roughness of the PCB and, in turn, affects the ink adhesion to the copper surface. However, if the brush wheel is used excessively, or if the product is not placed properly on both sides, it can result in “dog bone” defects, leading to uneven roughening of the surface and even circuit deformation.
After printing, the copper surface may exhibit a color difference compared to the ink. This requires the entire brushing operation. Prior to brushing, a brush mark test is necessary (for D/F, a water break test is required). The brush mark width typically ranges from 0.8 to 1.2mm, depending on the product, with some variation. After brushing, the brush wheel’s level must be adjusted, and lubricating oil should be applied regularly. If the water isn’t heated during brushing, or if the spray pressure is insufficient and the fan angle isn’t properly formed, copper powder may accumulate. Even small amounts of copper powder can lead to micro short circuits (closed line areas) or failed high-voltage tests in the finished product.
Another issue in the pretreatment process is the oxidation of the board surface, which can result in bubbles or cavitation after H/A processing.
1. The position of the solid water retention roller in the pretreatment section may be incorrect, causing excessive acid to be carried into the washing section. If the number of washing tanks in the following stages is inadequate or the water flow is insufficient, acid residues may remain on the board.
2. Poor water quality in the washing section, or the presence of impurities, can also cause foreign matter to adhere to the copper surface.
3. If the water absorption roller is either too dry or saturated with water, it will be ineffective at removing water from the product. This can lead to excessive residual water on the plate and in the holes, preventing the subsequent air knife from working properly. This often results in cavitation, particularly in the form of tears around the via holes.
4. If the board’s temperature is still high when it is discharged, stacking the boards will lead to oxidation of the copper surface.
To address these issues, a pH detector should be used to monitor the water’s pH value during production, while the surface temperature of the board can be measured using infrared sensors. A solar disk rewinding device can be installed between the discharge and stacked rewinding sections to cool the boards. Additionally, the wetting of the suction rollers should be carefully managed. It is advisable to have two sets of suction rollers for alternating cleaning. The air knife’s angle should be checked before daily operations, and attention should be given to ensuring that the air ducts in the drying section are secure and not damaged.
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1. The pre-processing equipment used in this stage includes systems such as the inner layer pre-processing line, electroplating-copper pre-processing line, D/F line, solder mask (SM) process line, and others.
2. Taking the solder mask pre-treatment line for rigid PCB as an example (which may vary by manufacturer): it typically involves a sequence of steps including brush grinding (2 sets) → water washing → pickling → water washing → cold air knife → drying section → solar disc rewinding → discharge rewinding.
3. Generally, a #600 or #800 gold steel brush is used, which influences the surface roughness of the PCB and, in turn, affects the ink adhesion to the copper surface. However, if the brush wheel is used excessively, or if the product is not placed properly on both sides, it can result in “dog bone” defects, leading to uneven roughening of the surface and even circuit deformation.
After printing, the copper surface may exhibit a color difference compared to the ink. This requires the entire brushing operation. Prior to brushing, a brush mark test is necessary (for D/F, a water break test is required). The brush mark width typically ranges from 0.8 to 1.2mm, depending on the product, with some variation. After brushing, the brush wheel’s level must be adjusted, and lubricating oil should be applied regularly. If the water isn’t heated during brushing, or if the spray pressure is insufficient and the fan angle isn’t properly formed, copper powder may accumulate. Even small amounts of copper powder can lead to micro short circuits (closed line areas) or failed high-voltage tests in the finished product.
Another issue in the pretreatment process is the oxidation of the board surface, which can result in bubbles or cavitation after H/A processing.
1. The position of the solid water retention roller in the pretreatment section may be incorrect, causing excessive acid to be carried into the washing section. If the number of washing tanks in the following stages is inadequate or the water flow is insufficient, acid residues may remain on the board.
2. Poor water quality in the washing section, or the presence of impurities, can also cause foreign matter to adhere to the copper surface.
3. If the water absorption roller is either too dry or saturated with water, it will be ineffective at removing water from the product. This can lead to excessive residual water on the plate and in the holes, preventing the subsequent air knife from working properly. This often results in cavitation, particularly in the form of tears around the via holes.
4. If the board’s temperature is still high when it is discharged, stacking the boards will lead to oxidation of the copper surface.
To address these issues, a pH detector should be used to monitor the water’s pH value during production, while the surface temperature of the board can be measured using infrared sensors. A solar disk rewinding device can be installed between the discharge and stacked rewinding sections to cool the boards. Additionally, the wetting of the suction rollers should be carefully managed. It is advisable to have two sets of suction rollers for alternating cleaning. The air knife’s angle should be checked before daily operations, and attention should be given to ensuring that the air ducts in the drying section are secure and not damaged.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
