TECHNET Archives

October 2012

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Phil Nutting <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Phil Nutting <[log in to unmask]>
Date:
Fri, 5 Oct 2012 12:15:07 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (111 lines)
Victor,

I have one photo and the detail is insufficient to determine answers to your questions, but it looks like solder that has fully reflowed and been trapped under the part.  I have not had the luxury to get up close and personal with any of these failed boards.

Phil

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Friday, October 05, 2012 12:09 PM
To: [log in to unmask]
Subject: Re: [TN] solder splash under SMT caps

Are these only solder splashes are can it contain fluid from the cap itself? Solder skeletal or un-reflowed solder spheres, solder paste.?   A picture is worth one thousand words, even x-ray.

Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Toby Carrier
Sent: Friday, October 05, 2012 10:52 AM
To: [log in to unmask]
Subject: Re: [TN] solder splash under SMT caps

What are the size of the solder splash in comparison to the area? Are there numerous small splashes or just one large slpash? Are you finding the splashes under every 2225 capacitor, or just a certain area of capacitors?

Toby


On Fri, Oct 5, 2012 at 9:55 AM, Phil Nutting <[log in to unmask]>wrote:

> Here is my question for today.
>
> We have an SMT board that measures 16 inches by 17 inches be 0.062 
> thick (it is well supported in the end application) with 32 voltage 
> multiplier circuits so the board develops 12.5kV.  On the 2225 
> capacitors we had failures (arcing) under the parts and our customer 
> removed some caps only to find solder splashes.  We used the standard 
> IPC pad configuration for a
> 2225 part (3.7mm gap) with no solder mask under the capacitor, ENIG 
> finish and I suspect tin/lead paste.  I have a photo I will post if 
> Steve Gregory is still offering his site.
>
> Our customer wants us to use a specific capacitor by AVX and the AVX 
> pad layout of 4.6mm gap. Our contract manufacturer wants us to open up 
> the gap between pads by 1mm (essentially the 4.6mm recommended by AVX).
>
> My theory on this failure is the following; (could be any one or a 
> combination of any items listed below) Too much solder paste Incorrect 
> reflow pre-heat Incorrect liquidus temp
>
> I have read John Maxwell's white paper and see that he recommends a 
> larger space, but he didn't see significant performance enhancement 
> above the 1808 part.  Refer to 
> http://johansondielectrics.com/technical-notes/application-notes/new-i
> mpact-of-pad-design-and-spacing-on-ac-breakdown-performance.html
> .
>
> I agree that this greater distance will help with arcing, but will it 
> help with the solder splash?
>
> Will separating the pads have that much affect that the solder will be 
> drawn out to the outside visible pads?
>
> Inquiring minds want to know....
>
> Phil Nutting
> Design for Manufacturing Engineer
> Kaiser Systems, Inc.
> 126 Sohier Road
> Beverly, MA 01915
> Phone: 978-922-9300 x1310
> Fax: 978-922-8374
> e-mail: [log in to unmask]<mailto:[log in to unmask]>
> www.kaisersystems.com<http://www.kaisersystems.com>
> www.linkedin.com/in/philnutting<http://www.linkedin.com/in/philnutting
> >
>
>
> ________________________________
> Note: All the information contained in this e-mail and its attachments 
> is proprietary to Kaiser Systems, Inc. and it may not be reproduced 
> without the prior written permission of sender. If you have received 
> this email in error, please immediately return it to sender and delete 
> the copy you received.
>
>
> ______________________________________________________________________
> 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] 
> ______________________________________________________________________
>



--
Toby


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

ATOM RSS1 RSS2