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Dispensing machine dispensing process common defects and solutions
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Dispensing is used in a wide range of applications, from airplanes to small clothes and toys. It can be said that as long as the glue arrives, then the dispensing process and the dispenser are required. Below, we talk about the common defects and solutions of the dispensing machine.
1, drawing / trailing
Phenomenon: drawing/tailing, common defects in dispensing
Cause: The inner diameter of the dispensing machine is too small, the dispensing pressure is too high, the distance between the plastic nozzle and the PCB is too large, the adhesive is out of date or the quality is not good, the adhesive viscosity is too high, and it cannot be removed from the refrigerator. Return to room temperature, too much dispensing, etc.
Solution: change the nozzle with larger inner diameter, reduce the pressure of dispensing, adjust the height of “stop”, change the glue, select the glue type suitable for viscosity, and return to room temperature after removal from the refrigerator (about 4h), adjust the dispensing the amount.
2, the nozzle is blocked
Phenomenon: The amount of the glue nozzle is less than that of the glue.
Cause: The pinhole is not completely cleaned, the patch glue is mixed with impurities, there is a hole blocking phenomenon, and the incompatible glue is mixed.
Solution: Change the clean needle, change the quality of the patch glue, the patch rubber grade should not be mistaken.
3, hole hit
Phenomenon: only the dispensing action, no glue amount.
Cause: The bubbles are mixed and the nozzle is clogged.
Solution: The glue in the syringe should be deaerated (especially the glue installed by itself) and treated according to the nozzle clogging method.
4, component offset
Phenomenon: The solidified component is displaced. In severe cases, the component leads are not on the pad.
Cause: The amount of glue applied to the patch is not uniform (for example, the glue on the chip is more than one). When the patch is applied, the component is displaced, the adhesive force of the patch is lowered, and the PCB is placed for too long after dispensing. Semi-cured.
Solution: Check whether the glue nozzle of the dispenser is clogged, remove the uneven rubber, adjust the working state of the placement machine, change the glue, and the PCB placement time should not be too long (less than 4h) after dispensing.
5, after curing, the component bonding strength is not enough, after the wave soldering will fall off
Phenomenon: After curing, the bonding strength of the components is not enough, lower than the standard value, and sometimes the film will appear when touched by hand.
Cause: The process parameters are not in place after curing, especially the temperature is not enough, the component size is too large, the heat absorption is large, the curing light is aging, the glue is not enough, and the component/PCB is polluted.
Solution: adjust the curing curve, especially to improve the curing temperature. Usually, the peak curing temperature of the thermosetting adhesive is critical. It is easy to cause the falling film to reach the peak temperature. For the light-curing adhesive, it should be observed whether the curing light is aging. There is blackening, the amount of glue, and whether the PCB/component is contaminated.
6. After the curing, the component pins are floating/displaced.
Phenomenon: After curing, the component leads float or shift. After wave soldering, the solder will enter the pad, and in short cases, short circuit and open circuit will occur.
Cause: The patch adhesive is not uniform, the amount of patch glue is too much, and the components are offset when the patch is applied.
Solution: adjust the dispensing process parameters of the dispenser, control the amount of dispensing, and adjust the process parameters of the patch.
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