Dewetting or Non-wetting Causes Print E-mail
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Written by Paul Lotosky   
Saturday, 01 August 2009 00:00

Wave Soldering TroubleshootingWhen the solder doesn’t stick, first check the pad.

Dewetting is a condition that results when molten solder coats a surface and then recedes, leaving irregularly shaped mound(s) of solder separated by areas that are recovered with a thin film of solder and with the basis metal unexposed.

Non-wetting is a condition in which there is partial adherence of molten solder to a surface it has contacted, and the basis metal remains exposed.

While we usually list in this space the primary process setup areas to check, dewetting and non-wetting typically are board-related due to pad surface contamination.

Fig. 1

Other things to look for in the process include:

  • Solder temperature too low.     
  • Preheat too high or low.    
  • Excess or insufficient flux blow-off.
  • Solder wave height low.     
  • Flux not making contact.    
  • Flux contamination.    
  • Board pallet too hot.
  • Flux applied unevenly.    
  • Flux SP GR too low.    
  • Conveyor speed too fast or slow.
  • Board not seated properly.    
  • Flux SP GR too high.    
  • Solder contamination.    
  • Other things to look for with the assembly include:
  • Board or component contamination.    
  • Improper board handling.    
  • Other things to look for with the board design include:
  • Oxidation.    
  • Contamination.

Paul Lotosky is global director - customer technical support at Cookson Electronics (cooksonelectronics.com) This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

 

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