6.Skip( 缺a )

拒收 良好情r

缺c描述 :

No solder on pad or component metallization.

PROBALBLE CAUSES

Wave did not overcome surface tension of solder
Surface tension of solder too high
PCB or pallet was put under too much pressure when put into the finger conveyor or not given enough room to expand during warm-up and has bowed prior to entrance into the solder pot.

Gas accumulated at joint
Geometric orientation of components causing shadowing of joints
Pallet warpage
Wave not even or level
Conveyor not parallel to solder surface

POSSIBLE PREVENTIONS

Change the direction of PCB entering into the solder pot
Dry flux properly in the preheat zone
Check pallet and make sure it is place correctly on belt or chain
Adjust finger pressure and groove pallet fixture to allow for expansion

Adjust the wave height
Adjust conveyor
Use flux with lower solid contents
Apply less flux
Better curing of adhesive
Drill holes in order to let gas escape

REWORK

The skip joint is soldered by using a chisel-shaped soldering tip placed against it long enough such that the transfer of heat is sufficient enough before placing the solderwire close to the tip of the iron.