Analysis of The Causes of Blistering On The Surface of Copper Immersion Plating on PCB Boards (2)

5. Micro-etching in copper pretreatment and pattern electroplating pre-treatment. Excessive micro-etching will cause the orifice to leak the substrate and cause foaming around the orifice. Insufficient micro-etching will also cause insufficient bonding force and cause foaming. Therefore, it is necessary to strengthen the control of micro-etching. Generally, the depth of micro-etching in the pre-treatment of copper sinking is 1.5-2 microns, and the micro-etching in the pre-treatment of pattern plating is 0.3-1 microns. The micro-etching thickness or corrosion rate is controlled by the test weighing method. Under normal circumstances, the surface of the board after micro-etching is bright in color, uniform pink, without reflection. If the color is uneven, or there is reflection, it means that there is a quality risk in the pre-process. Pay attention to strengthen the inspection, in addition, the copper content of the micro-etching tank, the temperature of the bath, the load, the content of the micro-etching agent, etc. are all items to be paid attention to.

6. The surface of the board is oxidized during the production process. If the copper immersion board is oxidized in the air, it may not only cause no copper in the hole, the board surface is rough, but also may cause the board surface to blister. If the storage time of the immersion copper board in the acid solution is too long, the surface of the PCB board will also be oxidized, and this oxide film is difficult to remove. Therefore, the copper immersion board should be thickened in time during the production process, and it should not be stored for too long. Generally, the copper plating should be thickened within 12 hours at the latest complete.

7. Poor rework of copper sinking. Some reworked boards after sinking copper or graphics are transferred due to poor de-plating during the rework process, incorrect rework methods or improper control of micro-etching time during the rework process, or other reasons will cause the board surface to foam, sink. Rework of copper plate if the poor copper sinking is found on the line, it can be directly removed from the line after washing with water, and then pickled directly without corrosion. It is best not to re-degrease, micro-etch. Now the micro-etching tank is de-plating, pay attention to time control, you can roughly measure the de-plating time with one or two sheets to ensure the de-plating effect. After de-plating, apply a set of soft grinding brushes after de-plating, and then press the normal production. Process copper sinking, but the etching time should be halved or adjusted as necessary.

8. Organic pollution in the electroplating tank, especially oil pollution, is more likely to occur for automatic lines.

9. The pickling tank should be replaced in time before copper plating. Too much pollution in the tank liquid or too high copper content will not only cause problems with the cleanliness of the board surface, but also cause defects such as roughness of the board surface.

10. Insufficient water washing after development, too long storage time after development or too much dust in the workshop, etc., will cause poor cleanliness of the board surface and poor fiber treatment effect, which may cause potential quality problems.

11. In addition, when the tank liquid is not heated in the production of some factories in winter, special attention should be paid to the electrification of the board in the production process, especially the plating tank with air agitation, such as copper-nickel. It is best for nickel tanks in winter. Before nickel plating, add a warm water washing tank (the water temperature is about 30-40 degrees) to ensure that the initial deposition of the nickel layer is good.

In the actual production process, there are many reasons for the blistering of the board surface. We can only make a brief analysis. For different manufacturers’ equipment and technical levels, there may be blistering caused by different reasons. The specific situation should be analyzed in detail, and cannot be generalized. The above-mentioned reason analysis is not divided into priority and importance, basically according to the production process flow to do a brief analysis, in this series, just to provide you with a problem-solving direction and a broader vision, the specific situation depends on the site situation.