Hi Ahne,

1. The batteries quit charging. This is part of the circuit that hooks to a
solar panel to re-charge an onboard battery.
2. Not quite sure about this one. We got sent some pictures and me being
the pessimistic kind of guy that I am disagree with. I've pulled many parts
from random boards and have yet to find even one that hasn't had the belly
pad fully wet with solder. I know that hot air removal could skew things
some, but you would think that I would have found at least one with
insufficient solder...

Steve

Not quite sure how they determined that

On Thu, Aug 13, 2015 at 2:41 PM, Ahne Oosterhof <[log in to unmask]> wrote:

> " It was told to to us that there is less than 50% coverage on the belly
> pad."
>
> 1) What occurred that made the customer look?
> 2) How was this 50% determined/detected by the customer?
>
> Ahne.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> Sent: Thursday, August 13, 2015 12:56 PM
> To: [log in to unmask]
> Subject: [TN] Crude destructive test
>
> Hi All,
>
> So here's the story; we're building a board that has a Linear Technology
> LT3652 12-pin MSOP device on it, and it has a belly or grounding pad on it.
> The board is designed with five 20-mil via's beneath it (bad idea), and
> they are through via's not cap plated or tented. So they start having
> problems with the part. The footprint on the board has the belly aperture
> much larger that the pad on the device itself. I have a 5-mil thick stencil
> because there are 20-mil pitch QFP's on the board, and I print 100% of the
> area of the belly pad on the board (which is .160" X .082"). My reflow
> profile peaked out at 228 C. and I was above reflow for 63/37 for
> 112-seconds. While I did not have a thermocouple on that part, I did have
> it nearby because there are some large D-Packs in the vicinity and I wanted
> to be sure I was getting adequate reflow on those.
>
> So the complaint is that we're getting insufficient solder on the belly
> pad. It was told to to us that there is less than 50% coverage on the belly
> pad. We x-rayed many boards and while we could see that sometimes the vias
> didn't fill, we saw evidence of solder on almost 100% of the area of the
> pad. We could tilt the board and under high magnification see beneath the
> part and tell that solder had wet to the belly pad on the part, but what we
> could not tell was how much it actually covered the pad. We removed parts
> with hot air and could not find one part that did not have solder wet to
> 100% of the pad.
>
> So my boss asked me to take a board and physically pry one off to see what
> it looked like. So I got a heavy exacto blade and slipped it beneath the
> edge of the part and pried. The corner broke and then the top half part
> with all the guts split off, a couple of leads in the corners broke off
> too, but the belly pad stayed on the board. I was able to get the exacto
> blade under a corner of the belly pad and I could slowly peel it away from
> the solder joint, and this is what it looked like:
>
> http://stevezeva.homestead.com/LT3652_Belly_Pad.jpg
>
> So I saw a few small voids (which was not unexpected), but to my untrained
> eye I don't see much wrong. I do wonder a little about me being able to
> peel away the belly pad like that, should I have been able to do that? Or
> does the solder fracture along the intermetallic layer when you apply
> peeling forces like that?
>
> Thanks in advance for any input...
>
> Steve
>
> --
>
>
> This email and any attachments are only for use by the intended
> recipient(s) and may contain legally privileged, confidential, proprietary
> or otherwise private information. Any unauthorized use, reproduction,
> dissemination, distribution or other disclosure of the contents of this
> e-mail or its attachments is strictly prohibited. If you have received this
> email in error, please notify the sender immediately and delete the
> original.
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
>

-- 


This email and any attachments are only for use by the intended 
recipient(s) and may contain legally privileged, confidential, proprietary 
or otherwise private information. Any unauthorized use, reproduction, 
dissemination, distribution or other disclosure of the contents of this 
e-mail or its attachments is strictly prohibited. If you have received this 
email in error, please notify the sender immediately and delete the 
original. 


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________