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  • Analysis on the reasons of PCB shallow thin hole without copper
    Date :2017-4-24

    PCB manufacturing process is prone to shallow copper problems, some customers of this type of hole without copper misjudgment is as follows:
    1, agent (go) tin deep plating ability is poor and bad call tin;
    2, PTH anomaly, the hole is not deposited copper;
    3, the deep copper plating ability is poor.


    In the actual production, gradually thin hole without copper. The reason for this is that there is no barrier layer on the conductive substrate (board a copper or thick copper layer) to prevent the deposition of copper plating. Following the analysis of the production and prevention of this resistance coating.


    In a heavy electric copper or copper line process under the developing process of PCB surface without crosslinking polymerization of ink dissolved in the developer, the developer containing polymeric ink by the circulating pump sprayed again to PCB surface and the hole, if subsequent pressure washing (including washing water) to the remnants of PCB the surface and hole containing polymer ink wash ink, polymer PCB will then trapped in the hole wall proofing anti stick to form a thin layer of resistance coating, more to Kong Zhongyang, the cleaning effect is worse, the greater the probability of resistance coating appears very small, Kong You. The multistage washing of the developing section is only a process of continuously diluting the residue, with the aim of diluting the residue as much as possible.


    It is pointed out that the focus of the problem is to ensure the cleaning effect in the hole to remove the anti adhesion coating after the understanding of the polymer anti sticking coating is the main cause of the thin copper layer in the hole. Suit the remedy to the case, can cure.


    In addition, the premise of dealing with the reality of the problem is to face up to and respect the customer's existing production conditions, such as: line and resistance welding, dry film and wet film common developer, water flow by environmental restrictions.


    Customers had hoped to increase the size of the pre treatment of micro etching to remove the internal resistance of the coating, but unfortunately not help, but fell over the micro erosion caused by excessive copper. The correct solution should be to strengthen the maintenance of the development of the dry process, while the pre treatment of the oil removal effect of the excellent selection of acidic degreasing agent.


    EC-51 acidic degreasing agent can cooperate with customers to solve this kind of hole copper from the hole to the center of the gradual thinning of the Kong Wu copper phenomenon, the correct use of EC-51 acidic degreasing agent should pay attention to the following matters:
    1, EC-51 washing requirements slightly strict, requiring full washing, because it contains the wetting agent cleaning is not clean may lead to copper and nickel cylinder has more foam.
    2, EC-51 designed for wet film, the use of wet film or black oil plate, if the hole is not plated with nickel or copper, can be solved with EC-51 treatment. On fine pitch dry film should be appropriate to reduce the amount of opening cylinder, controlling the content of EC-51 was 4%, in addition to attack to prevent high oil content of dry film line caused by caniniform coating, in addition, the EC-51 of the dry film gradually thin hole without copper effect is good.
    3, winter is the high incidence of such problems (because of low temperature, poor water), the most effective way to improve the oil removal efficiency is rising (increased concentration contribute little, will increase the pressure, water temperature control) 30-35, low temperature is not conducive to ensure oil removing effect; high temperature susceptible to oil removal the attack caused Plating Ink agent. PCB in the manual line, but also with the manual swing, add filters to ensure that the hole through the liquid. If the customer production conditions are bad, EC-51 cylinder cycle should be shortened to 15-20 square feet / L.


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