What is caused by the pcb board surface blistering

PCB board surface blistering is a problem of poor bonding force on the PCB board surface , which is also the surface quality problem of the PCB board surface , which contains two aspects :

1. The problem of the cleanliness of the board surface;          

2. Surface micro-roughness problem.

All board blister problems on all circuit boards can be summarized as above .

Because the adhesion between plating layer is poor or too low, it is difficult to resist the stress, mechanical stress and thermal stress in the process of subsequent production and assembly. Finally, the phenomenon of different degrees of separation between the plating layer is caused.

PCB board surface blistering.png

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

1 . Problem of substrate process treatment :

In particular , for some thinner substrates ( typically below 0.8 mm ) , it is not advisable to brush the board with a scrubber because of poor rigidity of the substrate .This may not be able to effectively remove the substrate in the process of production and processing to prevent surface oxidation of copper foil special treatment of the protective layer, the layer is thin, the brush board is easy to remove, but it is difficult to use chemical treatment, so in the production and processing, pay important attention control, so as to avoid the surface between the substrate and the adhesion of electroless copper foil due to poor surface bubble problem; the problem of blackening of the thin inner layer, there will be a black brown, uneven color, dark brown local other issues.

2. in the process of machining (drilling, laminating, milling, etc.), the surface of the oil or other liquids is contaminated with dust and the surface treatment is bad.

3. Poor copper brush plate:

Excessive pressure of grinding plate before copper sinking,cause orifice deformation brush out of orifice copper foil fillet or even orifice leakage base material,in this way , the phenomenon of hole blistering can be caused in the process of copper plating and tin plating welding;Even if the brush does not cause leakage of the substrate, but excessive brush will increase the roughness of hole copper, and therefore in the micro-roughening process prone to excessive roughening phenomenon, there will be a certain quality hidden danger;Therefore, we should pay attention to strengthening the control of the brush plate process, wear test and water film test will brush plate process parameters adjusted to the best governance.

4. Washing problems:

Due to the large amount of chemical water treatment to be carried out by the copper deposition and electroplating treatment ,Various kinds of acid, alkali, organic and other organic solvents are much many.The surface water washing is not clean, especially the deoiling agent of copper sink, which will not only cause cross pollution, but also lead to poor local treatment of the plate or poor treatment effect and uneven defect, resulting in some problems of adhesion.Therefore, attention should be paid to the control of water washing, including the control of water flow rate, water quality, washing time, and dripping time of plates, etc. In particular, the winter temperature is low, the washing effect will be greatly reduced, more attention should be paid to the strong control of water washing.

5. Micro - etching in pretreatment of sink copper  and pretreatment of pattern plating.

Excessive micro-erosion will cause the leakage of the substrate from the hole, resulting in blistering around the hole.Microetch deficiency can also cause adhesion caused by insufficient blistering phenomenon.Therefore, it is necessary to strengthen the control of microerosion, and the microetching depth of the usual pretreatment is 1.5---2 microns.The plating pretreatment of the pattern is 0.3 - -1 micron. The best conditions by means of chemical analysis and simple test weighing control microetch thickness or corrosion rate.In general, the surface of the board is brightly colored, even pink, without reflection.If the color is not uniform, or reflecting that meaning producing pretreatment have quality problems.

6 . Poor copper deposition :

Some rework board of  during reworking due to poor deplating,failure of rework method or improper control of micro - etching time during rework or other causes will cause blistering on the board surface.The rework of the copper board on the line if find the poor copper,can be washed directly from the line after washing after pickling without corrosion direct rework.It ' s better not to re - remove oil , micro - corrosion.For the board with thick  thickness board , the micro - etching bath should be de - plated and time - controlled , and then it is possible to measure the de - plating time with one or two boards , so as to ensure the effect of de - plating.After the application of brushing machine, a group of soft grinding brushes are used and then copper is deposited according to the normal production process, but the corrosion time should be reduced by half or necessary adjustment.

7. Oxidation of the board during production:

If the copper board is oxidized in the air , it is not only possible to cause no copper in the hole , rough surface of the board , but also may cause blistering of the board surface .

Heavy copper long storage time in acid solution, surface will occur and oxidation, the oxide film is difficult to remove; therefore, in the production process of heavy copper to timely thicken, not for a long time, generally at the latest within 12 hours after plating to thicken.

8.The activity of precipitated copper liquid is too strong:

9.In the process of graphics transfer, insufficient washing after development, too long time placement after development or too much dust in the workshop will result in poor surface cleanliness and poor fiber treatment effect, which may cause potential quality problems.

10.Organic pollution in electroplating bath, especially oil pollution, is more likely to appear in automatic line.

11.Before copper plating, the pickling bath should be replaced in time, too much pollution in the bath or too high copper content, which will not only cause the cleanliness of the plate, but also lead to the surface roughness and other defects.