SMT焊接不良及图片说明2--不t/嗔训腻ac)_资讯

SMT焊接不良及图片说明2--不t/嗔训腻ac)

日期:2009-11-04 10:21 点击:424

2.Disturbed/Fractured Solder Joint( 不t / 嗔训腻ac )

拒收 良好情r

缺c描述 :

It is characterized by stain marks and dull color on the surface or by a rough gritty appearance.

PROBABLE CAUSES

Mechanical shock during solidification
Solder temperature too high
Solder and flux contamination
Pallet skip

Inappropriate preheat temperature and conveyor speed
Board and components contamination

POSSIBLE PREVENTIONS

Check the conveyor for any vibration source
Remove assemblies from machine before solder solidifies or delay removal of PCB after soldering
Ensure that the the solder and preheat temperature are set accordingly to the manufacturers’ specifications

Minimise contamination from solder, flux, board and components
Maintain a appropriate conveyor speed so that the heat transfer to the board during the process is not too excessive or deficient

REWORK

Disturbed solder joint is desoldered with the help of a chisel-shaped soldering tip and solder wick.The solder wick should be pressed into the corner long enough to let the heat travel into the gap underneath the component so that the solder is sucked out.The joint is resoldered back by placing the solder iron against it long enough such that the transfer of heat is sufficient enough before placing the solderwire close to the tip of the iron.