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SMT焊接不良及图片说明2--不規則/斷裂的錫點)

放大字体  缩小字体 发布日期:2009-11-04  浏览次数:304
核心提示:2.Disturbed/Fractured Solder Joint( 不規則 / 斷裂的錫點 )拒收         &nbs

2.Disturbed/Fractured Solder Joint( 不規則 / 斷裂的錫點 )

拒收                                              良好情況

缺點描述 :

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.

 
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