What are the reasons for the bubbling problem on the board surface of the circuit board? Bubbling on the circuit board surface is actually a problem of poor bonding between the board surfaces, and by extension, it is a problem of the surface quality of the board surface, which includes two aspects:

1. The issue of board cleanliness; 2. The issue of surface micro roughness (or surface energy).

The bubbling problem on all circuit boards can be summarized as the above reasons.

The poor or too low adhesion between the coatings makes it difficult to resist the coating stress, mechanical stress, thermal stress, and so on generated during the subsequent production and assembly processes, ultimately resulting in varying degrees of separation between the coatings. A summary of some factors that may lead to poor surface quality during the production and processing process is as follows:

1. Issues with substrate processing:

Especially for some thinner substrates (generally below 0.8mm), due to poor substrate rigidity, it is not suitable to use a brush machine to brush the board.

This may not effectively remove the protective layer specially treated to prevent oxidation of the copper foil on the board surface during the substrate production and processing process. Although this layer is thin and easy to remove by brushing, there are significant difficulties in using chemical treatment. Therefore, it is important to pay attention to control during production and processing to avoid the problem of poor bonding between the copper foil on the board substrate and the chemical copper, which can cause blistering on the board surface; When blackening thin inner layers, there may also be issues such as poor blackening and browning, uneven color distribution, and partially uneven blackening and browning.

2. The phenomenon of poor surface treatment caused by oil stains or other liquid infections, dust pollution, etc. formed during the machining process (drilling, laminating, milling, etc.) of the board surface.

3. Poor copper brush plate:

Excessive pressure on the grinding plate before copper sinking can cause deformation of the hole opening, resulting in the brushing of copper foil fillets and even leakage of the substrate at the hole opening. This can lead to bubbling at the hole opening during processes such as copper electroplating, tin spraying, and welding; Even if the brush plate does not form a leakage substrate, an excessively heavy brush plate will increase the roughness of the copper hole, so the copper foil in this area is prone to excessive roughening during the micro etching roughening process, which also poses a certain quality hazard; Therefore, attention should be paid to strengthening the control of the brushing process, and the brushing process parameters can be adjusted to the best through abrasion experiments and water film experiments;

4. Water washing issue:

Due to the use of various chemical solutions and solvents such as acid, alkali, non-polar organic compounds, etc. in copper electroplating treatment, the surface of the plate cannot be washed thoroughly. Especially when adjusting the degreaser for copper electroplating, it not only causes contamination but also results in poor or uneven treatment of the surface, leading to problems with bonding strength; Therefore, it is necessary to pay attention to strengthening the control of water washing, which mainly includes controlling the flow rate, water quality, washing time, and dripping time of the cleaning water; Especially in winter when the temperature is low, the water washing effect will be greatly reduced, so it is even more important to pay attention to the control of strong water washing;

5. Micro corrosion during copper deposition pretreatment and graphic electroplating pretreatment:

Excessive micro etching can cause leakage of the substrate through the pores, resulting in bubbling around the pores; Lack of micro corrosion can also lead to a lack of bonding force, causing foaming phenomenon; Therefore, it is necessary to strengthen the control of micro corrosion; The micro etching depth for general copper deposition pretreatment is 1.5-2 microns, and for graphic electroplating pretreatment it is 0.3-1 microns. If possible, it is best to control the micro etching thickness or etching rate through chemical analysis and simple experimental weighing methods; In general, the surface of the board after slight erosion has a bright color, uniform pink, and no reflection; If the color is uneven or there is reflection, it indicates that there is a quality hazard in the pre-treatment process; Pay attention to strengthening inspections; In addition, the copper content of the micro etching groove, the temperature of the groove solution, the load capacity, and the content of the micro etching agent are all important factors to pay attention to;

6. Poor copper sinking rework:

Some reworked boards with copper deposition or graphic conversion may experience blistering on the surface due to poor plating, incorrect rework methods, improper control of micro corrosion timing, or other reasons during the rework process; If poor copper deposition is found online during the rework of copper plates, it can be directly removed from the line after washing with water, and then acid washed without corrosion and reworked directly; It is best not to remove the oil from the beginning, as it may cause slight corrosion; Regarding the boards that have already been thickened, it is necessary to remove the plating from the micro etching groove now. Pay attention to the timing control and use one or two boards to roughly calculate the plating removal time to ensure the plating effect; After the plating is completed, a set of soft grinding brushes should be lightly brushed using a brush plate machine, and then copper should be deposited according to the normal production process, but the time for micro corrosion should be halved or adjusted as necessary;

7. During the production process, the board undergoes oxidation:

If the copper plate undergoes oxidation in the air, it may not only result in copper free pores and rough surface, but also cause bubbling on the surface; If the copper plate is stored in the acid solution for too long, the surface of the plate will also undergo oxidation, and this oxide film is difficult to remove; Therefore, during the production process, the copper plate should be thickened in a timely manner and should not be stored for too long. Generally, the copper plating should be thickened and completed within 12 hours at the latest;

8. The activity of the copper plating solution is too strong:

The high content of the three major components, especially copper, in the newly opened cylinder or tank solution of the copper deposition solution can lead to strong activity in the tank solution, rough accumulation of chemical copper, excessive doping of hydrogen gas, cuprous oxide, etc. in the chemical copper layer, resulting in a decrease in the physical properties and quality of the coating and poor adhesion; The following measures can be taken appropriately: reducing the copper content, adding pure water to the tank solution containing three major components, appropriately increasing the content of chelating agents and stabilizers, and appropriately lowering the temperature of the tank solution;

During the process of graphic transfer, insufficient washing after development, prolonged storage time after development, or excessive dust in the workshop can all result in poor surface cleanliness. If the fiber processing effect is slightly poor, it may lead to potential quality problems;

10. Organic pollution, especially oil stains, is present in the electroplating tank, which is more likely to occur in the automatic line;

11. Before copper plating, it is important to replace the immersion tank in a timely manner. If there is too much contamination in the tank solution or if the copper content is too high, it will not only cause problems with the cleanliness of the board surface, but also lead to defects such as rough board surface;

12. In addition, in some factories during winter, when the tank solution is not heated during production, special attention should be paid to the charging process of the plates into the tank, especially for plating tanks with air mixing, such as copper and nickel; It is best to add warm water to the nickel plating tank before nickel plating in winter (with a water temperature of around 30-40 degrees) to ensure that the initial nickel layer accumulates densely and well;

Article sourced from Jiangmen single and double-sided circuit boardhttp://www.yonghongpcb.com