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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Wed, 9 Jul 2014 17:08:46 -0600
Content-Type:
text/plain
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text/plain (1 lines)
Hi George!

Got your *.pdf posted, it's here:

http://stevezeva.homestead.com/XRF_HASL_Thickness.pdf

Thanks, and I know there will be others that really appreciate the information that you share with the group.

Steve 

-----Original Message-----
From: Wenger, George M. [Contractor] [mailto:[log in to unmask]] 
Sent: Wednesday, July 9, 2014 4:24 PM
To: Steve Gregory
Cc: TechNet E-Mail Forum
Subject: RE: [TN] HASL Plated PCB Matter

Hi Steve,

I know the attachment to this email will be stripped off by TN but I assume that since your email is also on the distribution you will get the attachment and might be able to post it for others to see.

The first slide in the attachment one of Roberto's photos and since I didn't know if this was vertical or horizontal HASL I put two images on the slide indicating what I think was the HASL direction and the air Knife directions.  You are correct that this does look like "typical HASL"  One of the problems with HASL is you can't look at a HASL surface finish on a pad and be certain if it is solderable or not.  I've always over simplified HASL by saying you can have FLAT HASL by blowing hard with the HASL machine air knives or you can have SOLDERABLE HASL by not blowing hard with the HASL machine air knives but you then typically have topography issues which effect fine pitch component solder paste printing and placement.  The real trick with HASL is to blow hard enough with the air knives to level the HASL surface finish but not blow TOO HARD to remove all of the solder and leave IMC.  That means the PCB fabricator doing the HASL surface finish has to pay lots of attention to his HASL process.

I assume from Roberto's photos that Location I marked as Location #1 is solderable because there looks like thick solder in that area.  The Location I marked as Location #2 may or may not be solderable.  If you do an XRF measurement in that area and fine you have 20 to 50 micro-inches of solder the chances are you have IMC and will have solderability issues.  If the XRF measurement indicates you have over 50 micro-inches of solder the features will probably be solderable.  My preference has always been that I want at least 100 micro-inches of solder on a HASL feature to insure that it will be solderable.  

The second slide in the attachment is a really old analysis of a SnPb HASL board where there were solderable and non-solderable areas on a HASL feature.

My suggestion to Roberto is if he is concerned he should do XRF measurements because they are easy, non-destructive, and give almost just as much good information as doing a solderability test.

Regards,
George
George M. Wenger
Failure Signature & Characterization Lab LLC
609 Cokesbury Road, High Bridge, NJ 08829
(908) 638-8771 Home  (732) 309-8964 Mobile E-mail [log in to unmask] [log in to unmask]

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Wednesday, July 09, 2014 1:30 PM
To: [log in to unmask]
Subject: Re: [TN] HASL Plated PCB Matter

Hi Ricardo,

I finally have your pictures posted. Sorry it took me so long, I can usually post things much sooner than this, but I was tied-up all day with jury duty yesterday, and when I came into work today it's been hectic.

So here are your photos:

http://stevezeva.homestead.com/HASL1.jpg

http://stevezeva.homestead.com/HASL2.jpg

To me, this looks pretty typical of the HASL that I see, you don't ever get perfectly flat pads with HASL.

Steve 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ricardo Moncaglieri
Sent: Tuesday, July 8, 2014 10:16 AM
To: [log in to unmask]
Subject: [TN] HASL Plated PCB Matter

Dear Colleagues,
I´m working in the aerospace industry at INVAP SE - ARGENTINA and my rol is QA Electronic Service Manager.
Would like to know your comments on following matter:
 
Have requested to a new PCB provider some HASL plated pcb specimens in order to verify its quality and found out what enclosed pictures show:
100% of plated pads have its plating drained or slided off toward the same direction from left to right affecting coplanarity.
As per our visual inspection at first conclusion we stated that it is an Indicator Process (not necessary dewetting related issue) and could be caused between others, from:
1) Pb % degraded.
2) Low air flow temperature trend.
3) Angle of impact of air flow.
 
We asked the provider to define cause of this issue. We didnt do a metallographic analisys to verify Cu6Sn5 presence to confirm intermetallic fusion.
 
We run the J-STD-003 test "C" to verify solderability and it is 100% Ok well wetted, furthermore we soldered a desoldering ribbon (previously tin plated) directly to a pad without using of Flux nor solder and verified that its adherence is very good which indicates pad surface would be well plated.
 
As per your experience: Do you agree with us on our conclusions specially that it seems to be not a strictly dewetting matter?
 
Appreciate too much your feedback on such a matter.
 
Brgds, Ricardo Moncaglieri





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