Good day,
    
    I'm looking for some information or suggestions regarding my SMT PWB 
    design.  We are a Military contractor who, due to extreme environmental 
    conditions, require that our SMT assemblies (single-sidded) get hard 
    bonded to a metal restraining core to control the TCE mismatch.  To 
    prevent electrical shorting of the board to the core, we require that a 
    polyimide insulating layer be bonded to the bottom of the board.  This 
    process has typically filled the PTHs with epoxy resin.  We also 
    require that the resin-filled holes be plated over with copper and then 
    solder coated.  This was done mainly because early designs (10-12 years 
    ago) had the vias embedded right in the surface mount solder pads.  
    Since then, we've fanned out the vias so they aren't directly in the 
    pads, but we still use some of them for in-circuit testing.  
    
    My problem is trying to find a mil-qualified fab house who can 
    consistently provide quality boards of this type.  If anyone has 
    experience with building boards like this or if anyone has some design 
    suggestions I'd like to hear from you.
    
    
    A picture is worth a thousand words... not much of a picture, though.
    
    		                         
    		|                       |< SOLDER	 
    		|                       |< COPPER OVER-PLATE (.001-.002")
    	        |       |	|       |< PTH PAD
    		       ||EPOXY-	||
    		       ||FILLED	||
    		       ||HOLE	||	< POLYIMIDE (TYPICALLY 6-8 LAYERS  
    		       ||	||		     APPROX .060" THICK	
    		       ||	||      	     3:1 ASPECT RATIO)	
    	        |       |       |       |       
    	                                        < POLYIMIDE COVER LAYER 
    								(.005")
    
    						< METAL RESTRAINING CORE
    
    	                                        
    
    
    Thanks,
    
    Jim M.