Part of the customers’ miscalculation this type hole without copper as follows:
1, tin light deep plating (go) and poor ability of call tin bad;
2, abnormal PTH, hole didn’t sink copper;
3, copper plated deep plating ability is poor.
In the actual production, gradually thin hole without copper. Investigate its reason, nothing more is conductive substrate (board a copper or copper layer cloud thickens) barriers to electroplating copper deposition resistance of the coating. The following is the resistance coating production and prevention are analyzed.
In a copper or cloud thickens copper plate electric process line, during the developing process under the PCB board face not crosslinking polymerization of ink dissolved solution, contain ink polymer solution by the circulation pump spray to PCB board face and hole again, this time if the follow-up pressure water (water washing water) are unable to PCB board face and hole containing polymer ink survivor is rinsed clean, then the residual ink polymer compounds in the viscosity of hole wall to form a thin layer of resistance coating, more to the hole in the middle of the cleaning effect is worse, the greater the resistance coating appearance probability, especially through the holes. (development period of the multistage water is only a process of continuously diluted residue, aims to residue dilution) as much as possible.
Understand the sticky resistance coating polymer is causing hole electric copper layer gradually thin after the culprit, the focus of the problem is focused on hole cleaning effect to remove the sticky resistance of the coating. Suit the remedy to the case, can cure.
In addition, the premise is essential in coping with real problems facing existing production conditions, respect for customers, such as: circuits and resistance welding, dry film and the sharing of wet film developing machine, water flow rate being limited by the environmental protection, etc.
Have customers in the hope of increasing electricity pretreatment of micro erosion quantity can remove the hole resistance coating, but unfortunately not help, but fall in micro erosion caused by excessive hole without copper. The correct solution is improved imaging dried routine maintenance, at the same time figure electric pretreatment choose good acidic degreasing effect in addition to the agent.
Acid in addition agent to cooperate with customers to solve this kind of copper from the central hole to hole gradually thinning hole no copper phenomenon and the correct use of acid in addition to the agent needs to pay attention to the following items:
1, a strict acid in addition to the oil washing, require water sufficient, for it contains humectant cleaning not net could lead to more foam and nickel copper cylinder cylinder.
2, acid except oil designed for wet film, use wet film or plate of black oil, if hole not on nickel or copper plating, after treated with acid in addition to the agent. For fine line is apart from the dry film should be appropriate to reduce the open cylinder quantity, control acid in addition to the oil content is 4%, in addition to prevent too high oil content in the attack dry film result in canine teeth shape coating line edge, in addition, acid in addition to the oil to the dry film gradually thin hole without copper the result is right also.
3, the winter is peak time of this kind of problem (poor because of the low temperature, water washing), is the most effective way to improve the effect of degreasing temperature (contribution is not big, higher concentration will increase the water pressure), 30-35 degrees temperature control, low temperature is not conducive to ensure the oil removal effect; High temperature easy attacks except the oil ink and cause plating. In manual line, still should cooperate with manual swing, equipped with filter to ensure the liquid penetration in the hole. Such as customer production conditions, EC – 51 in cylinder period should be shortened to 15-20 square feet per litre.