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Causes of foaming on the surface of plate copper plating

Jun 29, 2018

The fact that the surface of the circuit board is blistering is actually a problem of poor bonding strength on the surface of the board, and the surface quality of the board surface is further extended. This includes two aspects: a. The cleanliness of the board surface; b. The surface micro-roughness (or surface energy) problems; all board surface blistering problems can be summarized as the above reasons. Bonding between the coating is poor or too low, in the subsequent production process and assembly process is difficult to resist the production process The resulting plating stress, mechanical stress and thermal stress, etc., eventually caused different degrees of separation between the coatings.


Here are some of the factors that may cause poor board quality in the production process:


1. Substrate processing problems; especially for some thin substrates (usually less than 0.8mm), because the substrate rigidity is not good, brushing machine brush plate should not be used, this may not be able to effectively remove the substrate production and processing During the process to protect the surface of the copper foil foil oxidation and special treatment of the protective layer, although the layer is thinner, the brush plate easier to remove, but the use of chemical processing there is greater difficulty, so important attention in the production and processing control, so as not to cause the board surface The problem of blistering caused by poor adhesion between the substrate copper foil and the chemical copper; this problem also occurs when the thin inner layer is blackened, with poor browning and browning, uneven color, and partial dark brown. The problem of not being superior;


2. The surface of the board surface is poorly treated due to oil stains or other liquids contaminated by dust during machining (drilling, laminating, milling, etc.);


3. Bad copper brush plate: The pressure of the copper plate is too large, causing the hole deformation to brush out the copper fillet of the hole or even the hole leaking the substrate. This will cause damage during the copper plating and soldering process. Hole blistering phenomenon; even if the brush plate does not cause leakage of the substrate, but the excessive brush plate will increase the copper roughness of the hole, so the copper foil at this point in the process of micro-etching roughening can easily cause excessive over-coarsening phenomenon. , There will be a certain quality of hidden dangers; Therefore, we must pay attention to strengthening the control of the brush plate process, can be adjusted by the wear scar test and water film test brush plate process parameters to the best;


4. Washing problem: Because the heavy copper electroplating treatment requires a large amount of chemical treatment, all kinds of acid-base non-polar organic medicines have many solvents, and the board surface is not washed cleanly, especially the adjustment of the degreasing agent by the sink copper will not only cause cross-contamination. , At the same time, it will also cause local poor treatment of the board or poor processing results, non-uniform defects, resulting in some problems with the binding force; therefore, we must pay attention to strengthening the control of water washing, mainly including the flow of washing water, water quality, washing time , And the control of the plate dripping time and other aspects; particularly low winter temperatures, water washing effect will be greatly reduced, but also pay attention to the strong control of washing;


5. Micro-etching in copper pre-treatment and in graphic electroplating pre-treatment; excessive micro-etching will cause pores to leak through the substrate and cause blistering around the orifice; insufficient micro-etching will also result in insufficient bonding force and cause blistering. Therefore, we must strengthen the control of micro-etching; generally, the depth of micro-etching of the pre-treated copper is 1.5—2 micrometers, and the micro-etching of the pre-plated pattern is 0.3—1 micrometers. The best conditions are through chemical analysis and simplicity. The test weighing method controls the thickness of microetching or the erosion rate; under normal circumstances, the surface of the board after microetching is bright in color, uniform pink, and there is no reflection; if the color is not uniform, or there is reflection, there is a quality risk in the process; Strengthen the inspection; In addition, the copper content of the microetching bath, the bath temperature, the load, and the content of the micro-etching agent are all items to pay attention to;


6. The activity of the sink copper is too strong; the content of the three components in the newly opened cylinder or bath of the sink copper solution is too high, especially if the copper content is too high, the bath activity will be too strong, the chemical copper deposit will be rough, and the hydrogen Copper oxides and other defects in the chemical copper layer caused by the inclusion of too much coating quality degradation and poor adhesion defects; can be properly taken as follows can be: reduce the copper content, (supplemented into the bath water) includes three major groups Points, appropriate increase in the content of complexing agents and stabilizers, appropriate to reduce the bath temperature;


7. Oxidation of the board surface occurs during the production process; if the board is oxidized in the air, it may not only cause no copper in the hole, rough board surface, but also may cause blistering on the board surface; the time for storing the copper board in the acid liquid If it is too long, oxidation may occur on the surface of the board, and the oxide film is difficult to remove; therefore, the copper board must be thickened in a timely manner in the production process, and it is not suitable to store it for too long. Generally, the copper plating must be thickened within 12 hours at the latest. complete;


8. The copper rework is poor; some reworked boards with copper or pattern transfer may cause blisters on the board due to poor plating, improper rework methods, improper control of the microetch time during rework, or other reasons; Copper plate rework If it is found on line, it can be directly reworked from the line after removing the oil and then pickling without microetching. It is better not to re-remove the oil and micro-etching. For plates that have been board thickened, If the microetching groove is out of plating now, pay attention to time control. You can use a one or two plates to roughly estimate the out-plating time to ensure the out-plating effect. After the out-plating, apply a brushing machine to a group of soft-brushes and then press the normal brush. Production process sinks copper, but the corrosion etching time is halved or necessary adjustments are made;


9. In the process of graphic transfer, insufficient washing after development, too long time after development or too much dust in the workshop will cause poor cleanliness of the board surface, and the fiber processing effect is somewhat poor, which may cause potential quality problems;


10. The acid bath should be replaced promptly before copper plating. Too much contamination in the bath or too high copper content will not only result in cleanliness of the board surface, but also cause defects such as rough board surface;


11. Organic contamination in the electroplating tank, especially oil contamination, is more likely to occur for auto lines;


12. In addition, in the absence of warming in the production of some tanks in winter, special attention should be paid to the charging of the plates during the production process, especially for plating tanks with air agitation, such as copper and nickel; the best for nickel cylinders in winter Add a warming water washing tank before nickel plating (water temperature is about 30-40 degrees), to ensure that the initial deposition of nickel layer is dense.


In the actual production process, there are many reasons that cause blistering on the board surface. The author can only do a brief analysis. The blistering phenomenon caused by different factors may occur for different manufacturers' equipment and technology levels. The specific conditions must be analyzed in detail and cannot be generalized. The analysis of the above reasons, regardless of order of importance and importance, is based on a brief analysis of the production process. In this series, it only provides everyone with a solution to the problem and a broader perspective. I hope to everyone's process production and problems. Solve the problem, you can play a role in attracting!

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