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September 2000

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Subject:
From:
Phil Crepeau <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 7 Sep 2000 14:29:17 -0700
Content-Type:
text/plain
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text/plain (109 lines)
hi,

well, look at it this way.  at least they know you are looking.  my cynical opinion is this: if they don't think you are looking, they'll send you everything that comes off the end of their line.

on the other hand, i think a solderability test at receiving inspection that consists of a test print and oven reflow is a terrific idea.  you'll need to get your supplier to agree that lot acceptance will be based on the results of that test.  they may not be too keen to do that.

phil

-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Thursday, September 07, 2000 2:03 PM
To: [log in to unmask]
Subject: Re: [TN] HASL Dewetting..Part II..


In a message dated 09/07/2000 2:29:55 PM Central Daylight Time, 
[log in to unmask] writes:

> seen the pictures, and rad the responses. A lot of good posts. At the risk
>  of being redundant, her's what I've run cross as root causes for this sort
>  of dewetting.
>  
>  1. LPI Solder Mask residue. Either from incomplete developing, poor rinsing
>  and dried in place, or redeposit from a poorly ventilated cure oven. Either
>  case difficult to see with naked eye prior to HASL processing.
>  
>  2. Oxidation of copper from LPI cure bake not properly removed by preclean
>  for HASL (microetch).
>  
>  3. Poor flux wetting to surface. Boards not properly dried of rinse waters
>  after pre-clean and prior to application of flux at HASL. Trying to flux 
wet
>  panels doesn't work well. Or poor flow of flux through the flux rollers.
>  
>  Hope this helps
>  
>  Bob Dube
>  
>  ES&D

Hi Bob and Everybody!

Well, had a conference call about an hour ago with our fab vendor. Not 
mentioning any names, and I'm not trying to trash anybody, but the call was 
interesting.

There were a couple of people there from their side, and me, our quality 
engineer, and purchasing manager on our side.

The conversation started by them stating that they didn't see a dewetting 
problem (I sent them the same pictures you looked at). They said that the 
reason the solder looked like that was because they use a vertical leveling 
machine, and that's the nature of the HASL process. They stated that they 
build boards for other customers and the boards all look like that and 
they've never had a complaint from any of their customers about solderability 
problems.

I was kind of dumbfounded...me and our quality engineer kind of stared at 
each other with a big question mark over our heads. What they were saying was 
180° out from the input I've gotten from everyone here. So then I asked; "You 
mean you disagree that those pictures don't show dewetting?" They replied; 
"Yes, that appearance is normal...and besides you can't say there's a problem 
with dewetting until you do a test like running the board over a wave or 
solder dipping it to see if there's really dewetting occuring." I replied; 
"We have boards here from other vendors that have been HASL'ed, and they 
don't appear like these boards do..."

So I told them that I would take a board and print it with solder paste and 
run it through our reflow oven...that I wanted to test it that way because 
that's the way it would be assembled.

I did, and the solder did cover the pads and adhere pretty much, however I 
did notice on a few pads that the solder did not flow out to the very edges 
of the pads.

So are the boards okay? Or was I "the boy who cried wolf" on this deal?

'preciate any comments...ya' live and learn.

-Steve Gregory-

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