Sheet foaming is one of the more common quality defects in the production process of circuit board. Because of the complexity of the production process of circuit board and the complexity of process maintenance, especially in chemical wet treatment, the prevention of sheet foaming defects is more difficult. Based on many years of actual production experience and service experience, the causes of sheet foaming are briefly analyzed. Hope to help the industry peers!
The bubbling of the circuit board is actually the problem of poor bonding force of the board, and by extension, the surface quality of the board, which contains two aspects: 1. The cleanliness of the board; 2. The problem of surface micro-roughness (or surface energy); 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, which may not be able to effectively remove the protective layer specially treated to prevent the oxidation of copper foil on the board during the production and processing of the substrate, although the layer is thinner and the brush board is easier to remove, but there are greater difficulties in using chemical treatment. Therefore, it is important to pay attention to control in the production and processing, so as not to cause the foaming problem caused by the poor bonding force between the substrate copper foil and the chemical copper; When the thin inner layer is blackened, there will also be poor blackening and Browning, uneven color, and poor local blackening and Browning.
2. the surface in machining (drilling, laminating, milling, etc.) process caused by oil or other liquids contaminated with dust pollution surface treatment phenomenon;
3. the copper brush plate is bad: the grinding plate pressure is too large before the copper sedimentation, resulting in the deformation of the orifice and the brush out of the orifice copper foil and even the orifice leakage of the substrate, so that the orifice foaming phenomenon will be caused in the process of copper plating and tin-spraying welding; 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: Because copper plating treatment to go through a large number of chemical potion treatment, all kinds of acid, alkali, organic and other drugs more solvent, the board washing is not clean, especially 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 binding force problems; 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 pre-treatment of copper deposition and pre-treatment of graphic electroplating; Excessive microerosion will cause substrate leakage at the orifice, resulting in bubbling 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 color of the plate after micro-etching is bright, uniform pink, 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. the activity of copper sedimentation liquid is too strong; The high content of three components in the newly opened cylinder or bath, especially the high content of copper, will lead to the excessive activity of the bath, the rough deposition of chemical copper, the excessive inclusion of hydrogen and cuprous oxide in the chemical copper layer, resulting in the deterioration of the physical quality of the coating and poor binding force. The following methods can be properly adopted: reduce the copper content,(add pure water to the tank liquid) including three components, appropriately increase the content of complexing agent and stabilizer, and appropriately reduce the temperature of the tank liquid;
7. the surface oxidizes in the production process; If the copper plate oxidizes in the air, it may not only cause no copper in the hole, the plate surface is rough, but also cause the plate surface to blister; If the copper plate is stored in the acid solution for a long time, the surface of the plate will oxidize, and this 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. Bad copper rework; Some of the rework plates after copper sinking or graphic transformation will cause foaming in the rework process because of poor fading plating, wrong rework method or improper control of micro-corrosion time in the rework process or other reasons; 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;
9. Insufficient washing after development in the graphics transfer process, too long placement time after development or too much dust in the workshop, etc., will cause poor cleanliness of the board, and the fiber treatment effect is slightly poor, which may cause potential quality problems;
10. copper plating pretreatment acid tank should pay attention to timely replacement, too much pollution in the tank, or the copper content is too high, will not only cause the cleanliness of the board, but also cause the board surface rough and other defects;
11. there is organic pollution in the plating tank, especially oil pollution, which is more likely to occur for the automatic line;
12. in addition, in the case of no heating in the production of some factories in the winter, special attention should be paid to the charged into the tank of the production process, especially the plating tank with air stirring, such as copper nickel; For the nickel cylinder in winter, it is best to add a warm washing tank before nickel plating (the water temperature is about 30-40 degrees) to ensure that the initial dense deposit of the nickel layer is good;
In the actual production process, there are many reasons for the bubbling of the surface, the author can only do a brief analysis, for different manufacturers of equipment technical level may appear different reasons caused by the bubbling phenomenon, the specific situation to be specific analysis, can not be generalized, hand-me-down; The above reason analysis is not divided into primary and secondary and importance, basically according to the production process to do a brief analysis, in this series, just to provide you with a direction to solve the problem and a broader vision, I hope to everyone's process production and problem solving, can play a role in attracting jade!
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