The foaming of the circuit board is actually the problem of poor bonding force of the board, that is, the surface quality of the board, which contains two aspects.

1. The cleanliness of the board;

2. Surface micro-roughness (or surface energy) problem. All the bubbling problems on the board can be summarized as the above reasons. The binding force between the coatings is poor or too low,

and it is difficult to resist the coating stress, mechanical stress and thermal stress generated in the production and processing process and assembly process in the subsequent production and

processing process, and eventually cause different degrees of separation between the coatings.

Some factors that may cause poor surface quality in the production and processing process are summarized as follows:

1. Substrate processing problems: especially for some thinner substrates (generally below 0.8mm), because the substrate rigidity is poor, it is not appropriate to brush the board. This may not be able

to effectively remove the substrate production process to prevent the copper foil oxidation and special treatment of the protective layer, although the layer is thin, brush plate is easier to remove, but

the use of chemical treatment there are greater difficulties, so in the production and processing of important attention to control, so as not to cause the substrate copper foil and chemical copper poor

bonding force caused by the foaming problem; When this problem is blackened in the thin inner layer, there will also be poor blackening and Browning, uneven color, and poor local blackening and

Browning.

2. Poor surface treatment caused by oil or other liquids contaminated with dust during machining (drilling, laminating, milling, etc.).

3. Poor copper sinking brush plate: the grinding plate pressure is too large before copper sinking, resulting in hole deformation and brush out copper foil fillet and even hole leakage substrate, so that

in the process of copper plating and tin-spraying welding, it will cause hole foaming phenomenon; Even if the brush plate does not cause leakage of the substrate, the heavy brush plate will increase

the roughness of the copper at the orifice, so the copper foil there is easy to produce excessive coarsening phenomenon in the process of micro-etching and coarsening, and there will be certain

hidden dangers of quality; Therefore, we should pay attention to strengthen the control of the brush process, and the brush process parameters can be adjusted to the best through the wear mark test

and the water film test.

4. washing problems: for copper plating treatment to go through a large number of chemical solution treatment, all kinds of acid, alkali, inorganic and other pharmaceutical solvents, the board

washing is not clean, especially the copper adjustment degreasing agent, not only will cause cross pollution, but also cause the local treatment of the board poor or poor treatment effect, uneven

defects, resulting in some problems in binding force; Therefore, we should pay attention to strengthen the control of washing, mainly including the control of the flow rate of cleaning water, water

quality, washing time, and the drip time of the board; Especially in winter when the temperature is low, the washing effect will be greatly reduced, and more attention should be paid to the control of

washing;

5. Micro-corrosion in copper pre-treatment and graphic electroplating pre-treatment: excessive micro-corrosion will cause the orifice to leak the substrate, resulting in bubbles around the orifice;

Lack of microerosion will also cause insufficient binding force, resulting in foaming phenomenon; Therefore, it is necessary to strengthen the control of micro-erosion; Generally, the micro-corrosion

depth of copper deposition before treatment is 1.5– 2 microns, and the micro-corrosion depth of graphic electroplating before treatment is 0.3– 1 microns. If possible, it is best to control the micro-

corrosion thickness or corrosion rate by chemical analysis and simple test weighing method. Under normal circumstances, the surface of the board after micro-etching is bright in color, uniform pink

color, no reflection; If the color is not uniform, or there are reflections, indicating that there is a quality hazard in the pre-process treatment; Pay attention to strengthen inspection; In addition, the

copper content of the micro-etching tank, the temperature of the tank liquid, the loading capacity, the content of the micro-etching agent are all items that should be paid attention to;

6. Poor rework of sunk copper: some rework plates after sinking copper or graphics turn in the rework process because of poor plating, rework method or improper control of micro-corrosion time in

the rework process or other reasons will cause foaming of the board; The rework of the sunk copper plate can be directly removed from the line after water washing if the sunk copper is found to be

bad, and then acid-washed and reworked directly without corrosion; It is best not to re-remove oil, micro-corrosion; For the plate that has been electrically thickened, the plating should be removed

by micro-etching groove, pay attention to time control, you can roughly measure the plating time with one or two plates to ensure the plating effect; After the plating is finished, apply a set of soft

grinding brushes to brush lightly and then sink copper according to the normal production process, but the etching time should be halved or adjusted as necessary;