How to deal with the foaming problem on the board surface of high-frequency PCB circuit board？
Blistering on the surface of high-frequency PCB circuit boards is actually a problem of poor bonding force on the surface of the board, and by extension, it is also a problem with the surface quality of the surface of high-frequency PCB circuit boards, which includes two aspects:
1. The cleanliness of the high-frequency PCB circuit board surface.
2. The problem of surface micro-roughness (or surface energy).
The board surface blistering problem on all high-frequency PCB circuit boards can be summarized as the above reasons: the bonding force between the coatings is poor or too low, and it is difficult to resist the coating stress generated during the production process and assembly process in the subsequent production process.Mechanical stress and thermal stress, etc., will eventually cause different degrees of separation between the coatings.
Some factors that may cause poor quality of the high-frequency PCB circuit board surface in the production and processing process are summarized as follows:
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.
This may not be able to effectively remove the protective layer that is specially treated to prevent the oxidation of the copper foil on the surface of the high-frequency PCB circuit board during the production and processing of the substrate. Difficult, so it is important to pay attention to control during production and processing, so as not to cause blistering on the surface of high-frequency PCB circuit boards caused by poor bonding between the substrate copper foil and chemical copper on the surface of high-frequency PCB circuit boards; this problem occurs in thin When the inner layer is blackened, there will also be problems such as poor blackening and browning, uneven color, and partial blackening and browning.
2. Poor surface treatment caused by oil or other liquid contamination and dust pollution on the surface of high-frequency PCB circuit boards during machining (drilling, lamination, edge milling, etc.).
3. Immersion copper brush plate is bad:
The pressure of the grinding plate before sinking copper is too high, which will cause the deformation of the orifice to brush out the rounded corners of the copper foil at the orifice or even leak the base material at the orifice, which will cause blistering at the orifice during the process of copper sinking, electroplating, tin spraying and welding; even if brushing The plate does not cause leakage of the base material, but an overweight brush plate will increase the roughness of the copper at the orifice. Therefore, during the process of micro-etching and roughening, the copper foil at this place is prone to excessive roughening, and there will also be a certain quality. Hidden dangers; 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 liquid, and there are many chemical solvents such as various acids, bases, non-polar organics, etc., and the surface of the board cannot be washed clean, especially the adjustment of degreasing agent for copper sinking, which will not only cause cross contamination, but also Poor local treatment or poor treatment effect on the surface of the board, uneven defects, causing some problems in the bonding force; therefore, attention should be paid to strengthening the control of water washing, mainly including the flow of washing water, water quality, washing time, and water dripping from the board Control of time and other aspects; especially in winter when the temperature is low, the effect of washing will be greatly reduced, and more attention should be paid to the control of washing.
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