Conformal Coating:
     
     Conformal coating is a material which is applied to boards to 
     encapsulate them and protect them from the environment.  Conformal 
     coating requires rework kits to be available to assembly and test 
     lines and can be difficult and messy to work with.  I have had these 
     kits made for me by the conformal coat supplier.  Use conformal 
     coating only if it is absolutely necesarry.
     
     Four types of conformal coat:
                             
     Acrylics:  Fair contamination resistance.  High Mech hardness. Will    
     absorb moisture if not in a breathing environment.  General Purpose.   
     Cheapest.
     
     Polyurethanes:  High contamination resistance.  High mechanical        
     hardness. Good, general purpose, cost effective coat.
     
     Epoxies:  High contamination resistance. Very high mechanical          
     hardness.  Hard to rework due to material toughness.
     
     Urethanes:  Highest contamination resistance.  Lowest mechanical       
     hardness.  Material is soft and rubbery.  Rework is messy. Most        
     costly.
     
     Be careful with rework, an improperly cured mask can yield problems    
     later.
     
          Frank Hinojos
          Watkins-Johnson Co.
                     
     
     
     ______________________________ Reply Separator 
     _________________________________
     Subject: CONFORMAL COATING
     Author:  "Tamir Ben-Shoshan" 
     <[log in to unmask]> at INTERNET
     Date:    6/12/97 5:01 PM
     
     
     Hi,
     
     I need some information about the conformal coating used for   
     assemblies insulation, and if the possibility of rework exist in this 
     technology.
     
     Thanks, Tamir
     
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