7.Solder Ball( 錫球 )
拒收 良好情況
缺點描述 :
Solder balls adhere to PCB. Solder balls which appear around the pad or at the side of chips. This causes short circuit and low insulation to the joint.
PROBABLE CAUSES
- Solder temperature too high
- Solder wave height too low
- Solder wave is uneven
- Preheat temperature too low
- Flux is contaminated
- Flux specific gravity too low
- No flux blow-off
- Conveyor speed too high
- Slumping of solder paste during pre-heating
- Excessive paste
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- Defective fixture and pallet design
- Board contamination due to insufficient board cleaning
- Epoxy glass exposure
- Defective mask material and excessive mask (temperature)
- Moisture in laminate
- Rough plated through hole
- Paste is push out of place during insertion
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POSSIBLE PREVENTIONS
- Ensure that the solder pot temperature is set accordingly to the standard specification stated
- Solder wave height should not be too high and should be flowing evenly as PCB travels across.
- PCB must be preheated to the required temperature to avoid sudden temperature ramp.
- Check for flux contamination and the specific gravity must stay within manufacturer’s specification
- Ensure that there is no flux blow-off
- Adjust the insertion pressure
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- Conveyor speed must be adjusted to a optimum rate
- Ensure elimination of defective fixture
- PCB must be free of contaminants
- During fabrication, there should not be any hole
- or pad misregistration and rough plated hole
- Moisture should be eliminated in laminate
- Mask material should be in good condition
- Epoxy glass material must not be exposed
- Make the solder deposit smaller
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REWORK
Solder balls can be removed by touching it with the well-tinned tip of soldering iron.
