Cause analysis of wrinkle and bubble of welding ink on circuit board

Circuit boardbubbling is actually the problem of poor binding force on 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. The bubbling problem on all circuit boards can be summarized as the above reason. The adhesion 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, resulting in different degrees of separation between the coatings.

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

1 substrate processing problems: especially for some thinner substrate (generally 0.8mm below), because the substrate rigidity is poor, it is not suitable to use the brush plate. This may not be able to effectively remove the substrate in the process of production and processing to prevent the oxidation of copper foil and special treatment of the protective layer, although the layer is thin, brush plate is easier to remove, but the use of chemical treatment is more difficult, so in the production and processing of important attention to control, so as not to cause the substrate copper and chemical copper poor bonding force caused by the bubbling problem; This problem in the thin inner layer of blackening, there will also be bad blackening brown, uneven color, local black brown is not superior problems.

2.PCB board surface in machining (drilling, laminating, milling, etc.) process caused by oil pollution or other liquid dust pollution surface treatment phenomenon.

3. Copper sinking brush plate is bad: copper sinking before grinding plate pressure is too large, resulting in orifice deformation brush out orifice copper foil fillet and even orifice leakage substrate, so that in the process of copper plating, tin spraying and welding will cause orifice foaming phenomenon; Even if the brush plate does not cause leakage of the substrate, but the heavy brush plate will increase the roughness of the copper orifice, so in the process of micro-etching coarsening, the copper foil is easy to produce excessive coarsening phenomenon, there will be a certain quality hazard; Therefore, attention should be paid to strengthen the control of the brush process, the brush process parameters can be adjusted to the best through the wear mark test and water film test;

4. Washing problems: for copper plating treatment to go through a large number of chemical potion treatment, all kinds of acid, alkali, inorganic and other drugs solvent more, the board washing is not clean, especially copper adjustment oil removal agent, not only will cause cross pollution, but also cause the board local treatment of poor or poor treatment effect, uneven defects, resulting in some binding force problems; Therefore, attention should be paid to strengthen the control of washing, including the control of water flow, water quality, washing time, and plate dripping time, etc.; Especially in winter, the temperature is low, the washing effect will be greatly reduced, more attention should be paid to the strong control of washing;

5. Micro corrosion in copper plating and graphic plating pretreatment: excessive micro corrosion will cause the orifice leakage substrate, resulting in bubbling around the orifice; Insufficient micro erosion will also cause insufficient binding force, causing foaming phenomenon; Therefore, the control of microerosion should be strengthened. Generally, the corrosion depth of copper deposition before treatment is 1.5- 2 microns, and that of graphic electroplating before treatment is 0.3- 1 micron. If possible, it is best to control the corrosion thickness or corrosion rate by chemical analysis and simple test weighing method. Under normal circumstances, the PCB surface of the micro corrosion after bright color, uniform pink color, no reflection; If the color is not uniform, or reflective indicating that there is a quality hazard before processing; Pay attention to strengthen inspection; In addition, the copper content of the micro-etching tank, the temperature of the tank, the load, the content of the micro-etching agent, etc., should be paid attention to;

6. Copper rework poor: some copper or graphics after the rework board in the rework process because of poor fading plating, rework method is not correct or rework in the process of micro erosion time control or other reasons will cause bubbling board; If the copper plate rework on the line is found to be bad, it can be washed directly from the line after oil removal after pickling without corrosion directly rework; 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 and pay attention to time control. One or two printed circuit board can be used to roughly measure the plating time to ensure the plating effect; After the plating is finished, apply a group of soft grinding brushes to brush lightly and then sink copper according to the normal production process, but the corrosion time should be halved or adjusted as necessary