Phil: The Tin Research Institute published the "Photographic	
			Guide to Soldering Quality" back in the late 70's or	
			early 80's.This contained a reference to pumice 
			abrasive cleaners and dewetting.		
		      The Spiliotis article from '78 as mentioned in an 
			earlier post also discusses dewetting related to	
			pumice clean.					
		      In a nutshell the pumice becomes embedded in the	
			surface of the copper which results in poor solder	
			wetting during subsequent processing.I believe when	
			this work was done it related to electroplated Sn/Pb	
			and not HAL.					
									
		     I have copies of both articles although they're getting	
		       pretty crumbly.					
									
						Regards			
						Michael Barmuta		
						Staff Engineer		
						Fluke Corp.		
						Everett Wa.		
						(206)356-6076
On Wed, 18 Sep 1996 07:53:20 -0700 [log in to unmask] wrote:

> From: [log in to unmask]> Date: Wed, 18 Sep 1996 07:53:20 -0700
> Subject: Dewetting & Pumice Scrub
> To: [log in to unmask]
> 
> Technetters 
> 
> In the mid 1970's Paul Davis of Tin Research wrote an article on dewetting 
as
> result of pumice scrub.  Does anyone have a reference to where this was
> published.  Also does anyone have any input as to dewetting as result of
> pumice scrub in relation to a sequence of: (1) pumice scrub, (2)apply 
solder
> mask, (3) hot air level, (4)solderability test and dewet..
> 
> Another question on dewetting.  Has anybody seen dewetting as a result of a
> white residue on the lands and board which was analyzed as lead carbonate?
>  And another:where does the lead carbonate come ?
> 
> Phil Hinton 
> Hinton PWB Engineering 
> [log in to unmask] 
> 
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