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Brief Discussion on the Causes of Blistering of Copper Plating on Circuit Board

Jan 16, 2018

Board blistering is one of the more common quality defects in board production because of the complexity of circuit board manufacturing processes and the complexity of process maintenance, especially in chemical wetting, which makes prevention of board blistering imperfections difficult. The author based on many years of practical experience in production and service experience, based on the circuit board now sinking copper plating foaming causes of a brief analysis, hoping to help colleagues in the industry!


Waffle board surface is actually the problem of poor adhesion of the board, and then extended is the surface quality of the board, which contains two aspects:


1, the problem of board cleanliness;

2, the surface of the micro-roughness (or surface energy) problems; board all the board on the issue of foaming can be summarized as the above reasons. Poor bonding between the coating or too low, in the follow-up production and processing and assembly process In the production process is difficult to resist the coating stress, mechanical stress and thermal stress, etc., eventually resulting in different degrees of separation between the coating.


    Now it may be in the production and processing of some of the factors that cause poor quality board summarized as follows:


    1. Substrate processing problems; especially for some thinner substrates, (generally 0.8mm below), because the substrate less rigid, should not be used brush plate brush machine, it may not be able to effectively remove the substrate production and processing In the process to prevent oxidation of the surface of the copper foil and special treatment of the protective layer, although the thin layer, the brush plate easier to remove, but the use of chemical treatment there is a big difficulty, so important in the production process control, so as not to cause the board The problem of blistering of the board due to the poor adhesion between the base copper foil and the chemical copper; this problem occurs when the thinner inner layer is blackified, and there is also blackening and browning, uneven color, partial dark brown Not inferior problem


    2. The surface of the plate in the machining (drilling, laminating, milling, etc.) caused by the process of oil or other liquid contamination of the surface contamination of dust pollution phenomenon;


    3. Shen copper brush plate bad: Shen copper plate before grinding plate pressure is too large, resulting in distortion of the hole brush hole copper foil or even orifice leakage substrate, so that in the process of plating copper plating tin spray welding will result Hole blisters phenomenon; even if the brush does not cause leakage of substrate, but excessive brush will increase the rough copper aperture, and therefore roughening in the process of micro-roughening prone to excessive roughening phenomenon , There will be some hidden dangers of quality; therefore, we should pay attention to strengthening the control of the brush plate process, the wear plate test and the water film test will brush plate process parameters adjusted to the best governance;


    4. Washing problems: Because the copper plating process to go through a lot of chemical treatment, all kinds of acid-base electrodeless organic solvents and other drugs more, the surface is not washed, especially copper adjustment degreaser, will not only cause cross-contamination , At the same time it will also result in partial treatment of the plate surface or treatment of poor, uneven defects, resulting in some binding problems; therefore, we should pay attention to strengthen the control of the washing, including the cleaning water flow, water quality, washing time , And board dripping time and other aspects of control; special winter temperatures are lower, the washing effect will be greatly reduced, but also pay attention to the strong control of the washing;


    5 copper immersion pre-treatment and graphics in the pre-treatment of micro-etching; micro-erosion will lead to excessive leakage of the substrate hole, causing the bubble around the orifice phenomenon; lack of micro-etching will also result in insufficient binding, triggering foaming ; So to strengthen the control of micro-etching; general immersion copper pretreatment depth of 1.5 --- 2 microns etching, micro etching before the pattern plating 0.3 --- 1 micron, the best conditions through chemical analysis and simple Test gravimetric method to control the thickness of micro-etching or etching rate; under normal circumstances after the micro-etching the board bright color, uniform pink, no reflective; if the color is uneven, or reflective of pre-processing process there are quality problems; Strengthen the inspection; other micro-etching tank copper content, bath temperature, load, micro-etchant content are all items to be noticed;


    6. Shen copper liquid activity is too strong; sink copper liquid tank or tank newly opened high content of three components, especially the copper content is too high, will result in bath activity is too strong, chemical copper deposition rough, hydrogen, Asia Copper oxide and other chemical copper layer inclusions too much caused by poor quality coating properties and poor adhesion defects; can be properly taken as follows: Copper content can be reduced, (to the bath to add pure water), including the three groups Points, appropriate to improve the complexing agent and stabilizer content, appropriate to reduce the temperature of the bath;


    7. Plate surface oxidation occurred in the production process; such as Shen copper plate in the air oxidation, not only may result in holes without copper, rough surface, may also cause the board surface blistering; Shen copper plate in acid storage time Too long, the board will also be oxidized, and this oxide film is difficult to remove; so in the production process Shen copper plate in a timely manner thickened, should not be stored too long, generally within 12 hours to thickening copper complete;


    8. Poor copper rework; some copper or graphics after the turn of the rework plate in the rework process because of poor plating, rework method is not right or rework process control of the eroded time, or other reasons will cause the board bubble; Rework of copper If you find online copper bad can be washed directly from the line after degreasing pickling direct rework without corrosion; best not to re-degreasing, micro-etching; plate has been thickened plate should be Now micro-etching tank fade plating, pay attention to time control, you can first roughly use one or two plates to measure the fade plating time, to ensure the fade plating effect; after fade plating application brush plate machine after a group of soft grinding brush light brush and then press normal production Copper sinking process, but the eclipse etching time to halve or make the necessary adjustments;


    9. Graphic transfer process after the development of insufficient washing, after the development time is too long or too much dust in the workshop, etc., will result in poor board cleanliness, fiber treatment effect is slightly worse, it may cause potential quality problems;


    10. Before copper immersion acid tank should pay attention to timely replacement, too much pollution in the bath, or copper content is too high, not only will cause board cleanliness problems, but also cause defects such as rough surface;


    11. Plating tank appears organic pollution, especially oil, appear more likely in the automatic line;


    12. In addition, some factories in the winter production of the bath did not warm the case, but also pay special attention to the production process of plate charged into the slot, especially with air agitation plating bath, such as copper and nickel; nickel cylinder winter is best In the nickel plus a heated wash tank, (water temperature at 30-40 degrees), to ensure the initial deposition of nickel dense compact.


    In the actual production process, causing a lot of reasons for the surface of the bubble, the author can only do a brief analysis, for different manufacturers of equipment technology may have different reasons for the phenomenon of bubbles, the specific circumstances to be specific analysis, can not be generalized, ; The above analysis of the reasons, regardless of the primary and secondary importance and basic analysis in accordance with the production process to do a brief analysis, in this series out, just to provide you with a solution to the problem of the direction and a broader perspective, hoping to everyone's production and problems Solution, can play a valuable role!


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