5.Open Joint( 空焊 )

拒收 良好情r

缺c描述 :

Solder does not connect pad and lead entirely.

ACCEPTABILITY

It is not consider to be a defect if the joint covered more than 50% of solder in the copper pad.

PROBABLE CAUSES

Solder is wicked up by the lead which removed the required amount of solder to form a solder joint
Lacked of coplanarity which result in bent lead or insufficient solder
Grain boundary cavitation

Solder sucked into vias
Incomplete outgassing causes entractment of gases generated from evaporation and decomposition chemicals used in flux or paste
Improper volume of solder
Excessive intermetallic compound

POSSIBLE PREVENTIONS

Optimize the heating profile so that it will be compatible with the chemical make-up of solder paste or flux
Allow a sufficient dwell time in the molten state
Optimize the cooling rate to balance the gas release mechanism and microstructure development
Maintain the temperature in the soldering machine to allow formation of good solder joint

Select alloy composition with high fluidity and controlled intermetallic formation
Coplanarity should be sufficient so as not to result in either bent lead or insufficient solder
During PCB design, avoid solder joint with an excessive large interface area with excessive thickness
Minimize the gas generation

Rework

The open 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.