4.Insufficient Solder-component side( 零件面錫不足 )
拒收 良好情況
缺點描述 :
Solder joint is flat and does not show a proper meniscus.
ACCEPTABILITY
For unclinched terminals : If the joint is cover with more than 75% of solder and the area of the copper pad without solder is less than 25%, then it is not consider to be a defect.
For IC’s clinched terminals : If the joint is at least cover with 50% of solder and the area of the copper pad without solder is less than 50%, then it is not consider to be a defect.
PROBABLE CAUSES
- Solder temperature too high
- Solder wave too high
- Solder wave uneven
- Solder is contaminated
- Preheat temperature too high or too low
- Flux is contaminated
- Flux specific gravity too high or too low
- Flux no longer active
- Flux not making contact
- Flux foamhead low
- Fluxer uneven
- Flux blow-off excessive
- Pallet too hot
- Internal plane
- Large unfilled holes
- Hole to lead ratio large
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- Conveyor speed too high
- Conveyor angle too high
- Board not seated right
- Defective fixture and pallet design
- Component contamination
- Component leads too short
- Board contamination due to insufficient board cleaning
- Excessive mask(Temp)
- Masking in holes
- Ink in holes
- Misregistration of mask
- Improper board handling
- Cracks in circuit path
- Large plane on component and solder side
- Weight distribution
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POSSIBLE PREVENTIONS
- Ensure that the solder pot temperature is set accordingly to the specifications
- Ensure that the solder wave angle is set at a height according to the specifications
- Check for solder and flux from contamination
- Raise the preheat temperature to the correct value
- Set the flux specific gravity to a more appropriate value
- Maintain the concentration of the flux
- Adjust the height of the fluxer
- Weight distribution should be correct
- Flux foamhead should be kept at the correct level
- Ensure that the fluxer is even
- Reduce the temperature of the pallet or the formhead may collapse
- Keep track of the conveyor speed to allow adequate heat transfer required for soldering
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- Adjust the board to allow adequate contact between the board and the hot solder
- Avoid minimum contact on the solder side of the board
- Avoid minimum contact with the components’ leads
- Handle the board properly to avoid damage on the surface of the board
- Use the board before the expiry date of the protective agent coated on the board
- Check for cracks in circuit path
- Ensure that there are little or no large plane on component and solder side
- Ensure that there are little or no large unfilled holes
- Hole to lead ratio should be correct
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REWORK
The joint is heated by placing the chisel-shaped soldering tip against it long enough such that the transfer of heat is sufficient enough to melt the joint before placing the solderwire close to the tip of the iron.Sufficient amount of solder is allowed to be deposited onto the joint to create good wetting.
