Discussion on the cause of foaming on PCB surface of copper plating

The surface bubble in the production process of PCB is one of the most common quality defects, because of the complexity and maintenance of production process of circuit board and complex process, especially in the wet chemical treatment, the prevention of surface blister is difficult.


The board surface of the circuit board is actually a foaming problem of bad surface binding force, and then extended surface quality problem is the board, which includes two aspects: 1. surface cleanliness problems; 2. surface roughness problem; all of the circuit board surface bubble problem can be reduced to the above reasons. Combined with bad force or low coating between, in the subsequent production process and assembly process to produce resistance in the process of production and processing of coating stress, mechanical stress and thermal stress, resulting in different degrees of separation coating.


Some factors that may cause poor quality in the process of production and processing are summarized as follows,


The 1. substrate processing problems; especially for some of the more thin substrate, the substrate because of poor rigidity, brush brush machine plate should not be, this may not 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 plate is easy to remove. But it is difficult to use chemical treatment, so in the production and processing of important attentional control, so as to avoid the substrate surface between the copper foil and copper chemical bonding force caused by poor surface bubble problem; this problem is black in thin layer, there will be a black brown, uneven color, dark brown is not local other issues


2. surface in the machining (drilling, laminating, milling, etc.) process of oil or other liquid contaminated with dust pollution, surface treatment is not good,


3. copper brush plate side: copper deposition before grinding plate pressure is too large, resulting in deformation of the orifice orifice orifice or brush copper fillet leakage substrate, this will result in the deposition of copper plating hole foaming phenomenon in the process of spraying tin welding; if the brush plate did not cause leakage of the substrate, but the heavy brush plate will increase the orifice of copper roughness in microetch coarsening process the copper foil is easy to produce excessive coarsening phenomenon, there will also be some quality problems; therefore should pay attention to strengthen the control process through the brush plate, wear test and test the water film parameters adjusted to the best political brush plate;


4. surface oxidation occurred in the production process; such as heavy copper in air oxidation, not only may cause the hole without copper, surface roughness, may also cause surface blistering; copper sink long time storage in acid solution, the surface will be oxidized, and the oxide film is difficult to remove in the production process; in the heavy copper to thicken, not for a long time, generally at the latest within 12 hours after plating to thicken;


5. copper copper or rework bad; some graphics after rework in rework process because the deplating method wrong or bad, rework rework process microetch time control improper or other reasons will cause surface blistering; if the copper sink rework online found copper bad can directly after washing from the line of degreasing pickling is not economic erosion directly rework; the best not to remove oil, micro etching; for the plate plate electric has thickened, should now be microetching deplating, note the time control, can use one or two plates roughly calculate deplating time, ensure the deplating effect; faded by brushing machine after a group of plating polishing brush brush and then press the normal production process of copper corrosion, but micro etching time should be halved or make the necessary adjustments;


6. graphics transfer process, after the development of insufficient washing, after the development of the placement time is too long or too much dust in the workshop, etc., will cause poor surface cleaning, fiber treatment effect is slightly worse, it may cause potential quality problems;


 

(Source: internal information)

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