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PCB manufacturing dispensing defects causes and solutions  

336 Published by FASTPCBA 10月 23,2019

PCB manufacturing dispensing defects causes and solutions  

  1. Reasons for drawing and tailing defects:
  2. The inner diameter of the nozzle is too small
  3. Dispensing pressure is too great
  4. The distance between the nozzle and the PCB is too large.
  5. The adhesive glue expires or the quality is not good.
  6. The adhesive glue is too high
  7. Failure to return to room temperature after removal from the refrigerator
  8. Too much adhesive glue

Solution

  1. Change the nozzle with larger inner diameter
  2. Reduce the dispensing pressure
  3. Adjust the “stop” height,
  4. Replace the adhesiveglue
  5. Select the rubber type suitable for viscosity
  6. Return to room temperature after removing from the refrigerator (about 4h)
  7. Adjust the amount of dispensing

 

  1. Analysis of the cause of the nozzle clogging
  2. The needle hole is not completely cleaned
  3. Mixed impurities in the adhesive glue
  4. There is a hole blocking phenomenon
  5. Incompatible glue mixing

 

Solution

  1. Change the clean needle
  2. Change the high quality adhesiveglue
  3. Timely inspection and cleaning of dispensing needles
  4. SMD rubbermark should not bemistaken

 

  1. Analysis of the reasons for component shift
  2. The amount ofadhesiveglue is uneven
  3. Component shift during mounting
  4. The adhesive has low initial adhesion
  5. PCB placement time is too long after dispensing
  6. Glue semi-curing

 

Solution

  1. Check if the nozzle is clogged
  2. Eliminate uneven dispensing
  3. Adjust the working state of the placement machine and replace the adhesive glue with appropriate viscosity.
  4. PCB placement time should not be too long after dispensing (less than 4h)
  5. Increase drying temperature and time

 

  1. Analysis of the reasons for the component drop
  2. The curing process parameters are unfulfilled
  3. The temperature is not enough
  4. The component size is too large
  5. Large heat absorption
  6. Photocuring lamp aging
  7. The amount of adhesive glue is not enough
  8. Component or PCB is contaminated

 

Solution

  1. Adjust the curing curve
  2. Increase the curing temperature
  3. Increase the peak curing temperature of the thermosetting adhesive and select the appropriate component
  4. Increase the peak temperature
  5. Observe whether the photocuring light is aging, whether the tubeis black or not, and replace it in time.
  6. Increase the amount of glue
  7. Observe the component/PCB in time for contamination and clean it

 

  1. Component pins are floating or shifted

Cause Analysis:

  1. Uneven patch adhesive

B Excessive adhesive glue

  1. Chipcomponent offset

solve

  1. Adjust the dispensing process parameters
  2. Control the amount of dispensing
  3. Adjusting the dispensing process parameters
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