Hi Bill,
It looks bad.The solder on those pads is heavy contaminated prior to wave
soldering.
You should examine unprocessed boards.This kind of appereance might be
results of lot of things:
- incident splash of chemicals corrosive to tin/lead ( for example those
based on sulfuric acid) somewhere between HASL and your assembly line.
- unwashed chemicals from HASL precleaning line
- poor etch resist removal ( tin or tin/lead from pattern plating)
-dross in HASL pot 
- rework ? ( results of unwashed aggresive flux used for rework)
I do not think,that this is results of LPI residues - if those are present
on the pads,the result is lack of coverage
Edward

Edward Szpruch
Eltek , Manager of Process Engineering
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel  ++972 3 9395050 , Fax  ++972 3 9309581
e-mail   [log in to unmask]

> -----Original Message-----
> From: Stephen R. Gregory [SMTP:[log in to unmask]]
> Sent: ä àåâåñè 02 2001 17:45
> To:   [log in to unmask]
> Subject:      Re: [TN] Process Problem vs Board Problem
> 
> Hi Bill! 
> 
> In looking at the pictures, I must say that the HASL does look kind of 
> strange. It almost looks like the HASL is just adhered in that ring around
> 
> the pad, and the rest of the pad and barrel almost looks like tin with no 
> HASL covering?!? 
> 
> Do you remember if the boards looked the same back when you had no
> problems 
> as they do now? 
> 
> Maybe somebody else has a clue... 
> 
> -Steve Gregory- 
> 
> 
> 
> 
>       Technetters' 
> 	
>       I've recently run into a problem with Wavesoldering some circuit
> boards 
>       where I am having problems getting topside solder joints. The
> process that 
>       I'm running has the topside of the board at 195-200 F just prior to
> the 
>       solder wave. My conveyor speed is 4.0 fpm. My fluxer is a spray
> fluxer. The 
>       board is a .062 - 6 layer board that has an aluminum heat sink on
> it. I feel 
>       that my process is set correctly. 
> 	
>       The original process that previously used on these boards was very 
>       successful when we used an OA water soluble flux. This process was
> on that I 
>       qualified many years ago to  J-Std-001A for Class 3 assemblies. 
> 	
>       On these circuit boards, I'm trying to use a No Clean Lo Activity
> level flux 
>       that is water washable. Because I have new equipment for
> wavesoldering, I 
>       was hoping to not have to do a re-qualification process for our
> level 3 
>       assemblies. Because our new equipment has much better controls than
> our old 
>       equipment I thought that it would be easy to solder these boards
> with an LO 
>       active flux. Well, my initial pass has been a disaster so far. There
> are 
>       three pictures that I'm looking for comments on. They are located on
> Steve's 
>       Webpage at http://stevezeva.homestead.com. (A thousand thanks go out
> to 
>       Steve Gregory for providing a site for posting the pictures.) Two of
> the 
>       pictures, called Bare Pad and Bare Pad2 show a condition that I can
> describe 
>       but I don't know if this condition has a name. In those pictures,
> there is a 
>       heavier coat of solder on the pad, but it seems to form a concentric
> ring on 
>       the pad.The extremities of the pads, both toward the outside and the
> inside, 
>       show a tinned surface but it appears to be much thinner. To me, it
> seems 
>       like these thin areas do not readily solder. It seems like this thin
> area is 
>       barrier that can only be overcome with a very strong OA flux. This
> may 
>       explain why I did not have a problem before. The other picture shows
> another 
>       condition that I see in various places on the bare board where there
> are 
>       protrusions on the inside of the PTH's. This appears to be trapped
> volitiles 
>       that were being expulsed during the HASL process. 
> 	
>       I'm trying to determine if I have a board problem or a process
> problem. 
> 	
>       Is it unreasonable for me to think that this board can be soldered
> with a 
>       no-clean (but water washable) LO activity level flux? 
> 	
>       Any help or comments would be greatly appreciated. 
> 	
>       Bill Kasprzak 
>       Moog Inc., Electronic Assembly Engineering 
> 	
> 
> 
> 
> 

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