On Fri, 12 Jan 96 11:05:23 CST Nancy Nelson wrote:

> From: Nancy Nelson <[log in to unmask]>
> Date: Fri, 12 Jan 96 11:05:23 CST
> Subject: OSP Questions
> To: [log in to unmask]
> 
>      Can anyone tell me where to get Data on a "Silver Nitrate Test" to 
>      check thickness on OSP's.
>      
>      Has anyone arrived on an acceptable thickness range on OSP's at this 
>      time?
>      
>      Thanks in Advance for any response
>      
>      Nancy Nelson PCA Eng. Services
>      Dell Computer 
>      512.728.0016
>      Fax 512.728.3653
> 
                                                                          
 	Nancy: 	 A silver nitrate test doesn't actually "check thickness".	
		It is a tool that can be used to verify the presence and 
		integrity of the coating.Silver nitrate of a known normality	
		(0.01-0.10N) is placed by dropper on the board and held for	
		a given time (10-60sec.).This is rinsed dried and inspected.	
		A discolored or darkened appearance of the copper MAY indi-	
		cate an insufficient coating.				
									
		There isn't any one acceptable thickness,it really depends	
		on the type of OSP being used and your assembly process	
		and chemistries.If possible work with the PCB supplier and	
		their OSP vendor.They should be able to give you a starting	
		point to test from.Then determine what thicness works best	
		for your application.					
							    		
		  Assuming your PCB supplier has the capability to do quan-	
		atative thickness testing(typically I.R.or U.V.)you can	
		establish an acceptable thickness range with them.	
									
		Since the formation of the OSP coating thickness is pretty	
		much self limiting,thin coating will probably be more of a	
		concern.By empirically testing boards below and within the 
		specification with silver nitrate at a given normality and	
		time you could arrive at a spot test for coating integrity.	
									
		If possible the best test is to run an unpopulated PCB thru	
		your processes.						
									
					Regards				
					Michael Barmuta			
					Staff Engineer			
					Fluke Corp.			
					(206)356-6076