Why does PCB board bubble?

Board bubbling is one of the most common quality defects in PCB production. Because of the complexity of PCB production process and process maintenance, especially in chemical wet treatment, it is difficult to prevent board bubbling defects. PCB circuit board surface bubbling may be the problem of poor binding force on the board surface, and then extended is the surface quality problem of the board surface, which contains two aspects:

1. PCB surface cleanliness.

2. Surface micro-roughness.

The bubbling problem on all circuit boards can be summarized as the above reason. The binding force between the coatings is poor or too low, and it is difficult to resist the plating stress, mechanical stress and thermal stress generated in the production and processing of the subsequent circuit board processing and assembly process, resulting in different degrees of separation between the coatings. Then some factors that may cause poor quality of the board in the process of production and processing are summarized as follows:

1, for some thinner substrate (generally 0.8mm below), due to poor rigidity of the substrate, is not suitable for brush plate brush machine, which may not be able to effectively remove the protective layer of special treatment to prevent the oxidation of copper foil on the surface. Although this layer is thinner and easier to remove, it is more difficult to use chemical treatment. Therefore, in the production and processing of the main attention to control, so as not to cause the board surface foaming problem caused by the poor bonding force between the substrate copper foil and chemical copper, this problem in the thin inner layer of Browning, there will be poor Browning, uneven color, local Browning is not good.

2, PCB board in drilling, laminating, milling and so on. The phenomenon of oil or other liquid contamination, dust pollution and poor surface treatment caused by processing.

3, the grinding plate pressure is too large before copper sinking, resulting in orifice deformation, brush out orifice copper foil fillet, and even orifice leakage substrate, so in the process of copper plating, tin spraying welding, it will cause orifice 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 orifice, so in the process of micro-erosion coarsening, the copper foil is easy to produce excessive coarsening phenomenon, there will be a certain quality hazard, so we should pay attention to strengthen the control of the brush plate process, through the wear mark test and water film test to adjust the brush plate process parameters to the best.

4, because the copper plating treatment to go through a large number of chemical potion treatment, all kinds of acid and alkali drugs more solvent, the board washing is not clean, especially the copper plating adjustment degreasing agent will not only cause cross pollution, but also cause the local treatment of the board poor or poor treatment effect, uneven defects and cause some problems in the binding force, so we should pay attention to strengthen the control of washing, It mainly includes the control of water flow, water quality, washing time, and plate dripping time

System. Especially in winter when the temperature is low, the effect of washing will be greatly reduced, more attention should be paid to strengthen the control of washing.

5. Excessive micro-corrosion in copper plating pretreatment and graphic plating pretreatment will cause orifice leakage substrate, resulting in bubbling around orifice, insufficient micro-corrosion will also cause insufficient bonding force, resulting in bubbling phenomenon, so we should strengthen the control of micro-corrosion, general copper plating pretreatment micro-corrosion depth in 1.5~2UM, graphic plating pretreatment micro-corrosion in 0.3~1UM, If conditions are best through chemical analysis and simple test weighing method to control the micro corrosion thickness or micro corrosion rate, under normal circumstances, the surface of the micro corrosion bright color without reflection, if the color is not uniform or reflective indicating the existence of quality hazards before the process, pay attention to strengthen the inspection, in addition, the copper content of the micro corrosion tank, tank temperature, load, micro corrosion agent content are to pay attention to the items.

6, the activity of the copper settling liquid is too strong, the content of the three components in the newly opened cylinder or tank of the copper settling liquid is too high, especially the copper content is too high, which will lead to the excessive activity of the tank liquid, the chemical copper deposition is rough, hydrogen, cuprous oxide in the chemical copper layer caused by excessive inclusion of the coating physical quality decline and poor binding force defects, can be appropriate to take the following methods can reduce the copper content. Add pure water to the tank, increase the content of complexing agent and stabilizer appropriately, and reduce the temperature of the tank appropriately.

7, such as the oxidation of the copper plate in the air, it may not only cause no copper in the hole, the board surface is rough, it may also cause the board surface bubbling, the copper plate in the acid storage time is too long the board surface will also occur oxidation, and the oxide film is difficult to remove. Therefore, the copper plate should be thickened in time during the production process, and should not be stored for too long. Generally, the thickened copper plating should be completed within 12 hours at the latest.

8, some copper or graphic transfer of the rework board in the rework process because of poor fading plating, rework method is not correct or in the process of rework micro corrosion time control, or other reasons will cause bubbles on the surface, copper plate rework if found on the line is bad, can be washed directly from the line after removing oil after pickling without micro corrosion direct rework, it is best not to remove oil again micro corrosion, For the plate has been electrothickened plate should be immediately micro erosion groove plating, pay attention to time control, can be used to roughly measure the plating time with one or two plates, ensure the plating effect, plating after the application of brush machine after a group of soft brush light brush and then according to the normal production process of copper, but the corrosion time should be halved or necessary adjustment.

9, graphics transfer process after the development of insufficient washing, development after placing time is too long or workshop dust too much will cause poor cleanliness of the board, fiber treatment effect is slightly poor may cause potential quality problems.

10, too much pollution or too high copper content in the tank will not only cause the cleanliness of the circuit board, but also cause rough surface defects, organic pollution in the plating tank, especially oil pollution, for the automatic line is more likely to appear.

11, in the production of the tank without heating, more attention should be paid to the live into the tank of the plate, especially the plating tank with air stirring, such as copper nickel, for nickel cylinder in winter the best in the nickel plating before heating water (water temperature is about 30-40 degrees), to ensure that the initial dense nickel layer deposition.