PCB News - PCB manufacturer: introduction of manual solder paste coating process

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Manual dispensing equipment is used for small batch smt patch production or model prototype and functional machine research and development stages of new products, as well as dripping solder paste or placement glue when repairing and replacing components in production.

Preparation solder paste

Install the needle copper solder paste, put it into the adapter connector, change the lock, and place it vertically on the syringe holder. According to the size of the smt chip processing pad, choose the plastic tapered needle tip with different inner diameters.

Adjust the amount of dripping

Turn on the compressed air source and open the dispenser. Adjust the air pressure, adjust the time control knob, control the dripping time, press the continuous dripping method, step on the switch, and the solder paste will drip out continuously until the switch is released to stop. Repeatedly adjust the amount of solder paste dropped. The amount of solder paste dripping is determined by air pressure, degassing time, solder paste viscosity and the thickness of the needle tip. Therefore, the detailed parameters should be set according to the detailed situation, and the parameters are mainly adjusted according to the amount of solder paste dripping on the smt processing pad. After the amount of solder paste dripping is adjusted properly, it can be dripped on the SMT PCB board.

dripping operation

Place the smt PCB board flat on the workbench, hold the needle tube, make the angle between the needle tip and the smt PCB board approximately 45°, and perform the drip operation.

Common shortcomings and solutions

Smearing is a common phenomenon in the dripping process, that is, when the needle is moved away, a thin line or "tail" occurs on the top of the solder joint. The tail may collapse and directly contaminate the pad, causing bridging, solder balls, and false soldering.

One of the reasons for tailing is that the process parameters of the dispenser are not adjusted properly, such as the inner diameter of the needle is too small, the dispensing pressure is too high, the distance between the needle and the smt PCB board is too large, etc.; the other reason is butt welding The function of the paste is not well understood, and the solder paste is not compatible with the application process. Perhaps the quality of the solder paste is not good, the viscosity has changed or it has expired. Other reasons may also cause wire drawing/tailing, such as electrostatic discharge to the board, bending of the circuit board, or insufficient board support. For the above reasons, you can adjust the process parameters, replace the needle with a larger inner diameter, reduce the pressure, and adjust the height of the needle from the smt PCB board; check the factory date, function and use requirements of the solder paste used, and whether it is suitable for the coating of this process.