The cause of the blistering problem on the board

The blistering of the board surface is actually a problem of poor bonding of the board surface. The extension is also the surface quality problem of the board surface. This includes two aspects:

  The problem of board cleanliness; 2. The problem of surface micro-roughness (or surface energy).

  The problem of blistering on all boards can be summarized as the above reasons.

  The bonding force between the coatings is poor or too low, and it is difficult to resist the plating stress, mechanical stress and thermal stress generated during the production process and the assembly process, and finally cause different degrees of separation between the plating layers.

The cause of the blistering problem on the board

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

  Problems with substrate processing:

  Especially for some thinner substrates (generally 0.8mm or less), since the substrate is poor in rigidity, it is not suitable to use a brushing machine to brush the board.

  This may not effectively remove the protective layer that is specially treated to prevent oxidation of the copper foil on the board during the production process of the substrate. Although the layer is thin, the brush plate is easier to remove, but there is a great difficulty in chemical treatment, so in production Important attention control of processing, so as to avoid the problem of blistering of the board caused by poor bonding between the copper foil of the board surface and the chemical copper; this problem also occurs when the thin inner layer is blackened, there will also be blackening browning. Bad, uneven color, partial black browning and other problems.

  2. The surface of the board is contaminated by oil or other liquids caused by machining (drilling, laminating, milling, etc.).

  3. Bad copper brushing board:

  The pressure of the pre-sinking plate is too large, causing the deformation of the orifice to brush out the copper foil round corners of the orifice or even the hole leakage of the substrate, so that the blistering phenomenon of the orifice will occur during the process of copper-plated electroplating and tinning welding; The plate does not cause leakage of the substrate, but the excessively heavy brush plate will increase the roughness of the copper of the aperture. Therefore, during the process of micro-etching and coarsening, the copper foil is likely to be excessively roughened, and there will be a certain quality. Hidden dangers; therefore, it is necessary to pay attention to the control of the brushing process, and the process parameters of the brushing plate can be adjusted to the best through the wear scar test and the water film test;

  4. Washing problem:

  Because the copper plating treatment has to undergo a large amount of chemical syrup treatment, all kinds of acid-base and non-polar organic solvents and other solvents are more, the board surface is not washed, especially the copper-adjusting degreaser will not only cause cross-contamination, but also cause Poor local treatment of the board surface or poor treatment effect, uneven defects, causing some problems in bonding; therefore, attention should be paid to strengthening the control of water washing, mainly including cleaning water flow, water quality, washing time, and dripping of plates. Time and other aspects of control; especially in winter, the temperature is lower, the washing effect will be greatly reduced, and more attention should be paid to the control of water washing;

  5. Micro-etching in pre-thinking copper and pre-pattern plating:

  Excessive micro-etching will cause the hole to leak into the substrate, causing foaming around the hole; insufficient micro-etching will also cause insufficient bonding force and cause foaming; therefore, it is necessary to strengthen the control of micro-etching; The etch depth is 1.5--2 microns, and the micro-etching before pattern plating is 0.3--1 micron. It is best to control the micro-etching thickness or the etch rate by chemical analysis and simple test weighing method; After eroding, the surface of the board is bright, uniform pink, and non-reflective; if the color is uneven, or there is reflection, there is a quality hazard in the pre-treatment of the process; pay attention to strengthen inspection; in addition, the copper content of the micro-etching tank, bath temperature, load , micro-etching agent content, etc. are all items to be noted;

  6. Poor copper rework:

  Some of the copper or the reworked reworked plates are re-worked due to poor fading, rework methods, improper control of micro-etching time during rework, or other reasons, which may cause blistering of the board; rework of the immersed copper board is found online. Poor copper can be directly removed from the line after degreasing by water washing. It is best not to re-de-oil, micro-etching; for plates that have been thickened by plates, should be etched by micro-etching grooves. Pay attention to the time control, you can use a plate or two to measure the fading time to ensure the fading effect; after the fading is finished, apply a brush to the soft brush and then press the copper according to the normal production process, but the etched The eclipse time should be halved or adjusted as necessary;

  7. The surface of the board is oxidized during production:

  If the copper plate is oxidized in the air, it may not only cause copper in the hole, the surface of the plate is rough, but also may cause foaming on the surface; the copper plate is stored in the acid for too long, and the surface of the plate is also oxidized. Such an oxide film is difficult to remove; therefore, the copper plate should be thickened in time during the production process, and the storage time is not too long, and the copper plating is generally required to be thickened within 12 hours at the latest;

  8. The activity of the copper bath is too strong:

  The content of the three components in the newly opened cylinder or bath solution is too high, especially the copper content is too high, which will cause the bath liquid to be too active, the chemical copper deposit is rough, and the hydrogen and cuprous oxide are mixed in the chemical copper layer. Excessive defects caused by excessive physical properties of the plating layer and poor bonding; the following methods can be appropriately adopted: reducing the copper content, (replenishing pure water into the bath), including three major components, appropriately increasing the complexing agent and the stabilizer The content, the temperature of the bath is appropriately lowered, etc.;

  9. Insufficient water washing after development in the process of graphic transfer, excessively long time after development or excessive dust in the workshop, etc., will result in poor cleanness of the board surface, and the fiber treatment effect is slightly poor, which may cause potential quality problems;

  10. Organic pollution, especially oil stains, in the plating tank is more likely to occur for automatic lines;

  11. Before the copper plating, the acid pickling tank should be replaced in time, the contamination in the bath is too much, or the copper content is too high, which will not only cause the problem of cleanliness of the board surface, but also cause defects such as rough surface;

  12. In addition, in some factories in winter, when the bath liquid is not heated, it is necessary to pay special attention to the charging of the plate in the production process, especially the plating tank with air agitation, such as copper nickel; Before the nickel plating, add a warm water washing tank (water temperature is about 30-40 degrees) to ensure the compactness of the initial deposition of the nickel layer is good;

  In the actual production process, there are many reasons for causing foaming on the board surface. The author can only do a brief analysis. For different manufacturers, the technical level of the equipment may cause blistering caused by different reasons. The specific situation should be analyzed in detail, and it is not possible to generalize. The above reasons are analyzed in terms of priority and importance, and are basically analyzed in accordance with the production process. In this series, it is only to provide you with a solution to the problem and a broader vision, and hope for the production and problems of everyone. In terms of solution, it can play a role in attracting jade!