TECHNET Archives

July 2013

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:
John Maxwell <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Maxwell <[log in to unmask]>
Date:
Sun, 14 Jul 2013 20:23:11 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (35 lines)
Hi Steve,
Absolutely, solder mask between pads are the leading cause of drawbridges to be precise for 0402 sized chips It only gets worse when we go to smaller case sizes. I actually got best of conference at SMTAI in I believe 91 for my paper on designing assemblies for sub miniature chips. Covered it then and we are still designing boards with solder mask in all the wrong places:-)  I stared then get rid of it then and followed up with a couple of papers a few years back when I was at Johanson Dielectrics for HV parts. 


Regards,

John Maxwell

On Jul 14, 2013, at 8:02 PM, stephen gregory <[log in to unmask]> wrote:

> Hi all,
>  
> Have any of you ever had thick solder mask cause you tombstones? I'm thinking that maybe that has happened to me. We built a board last week that we built before without any problems. It does have quite a few 0402's. We had a few random tombstones last build, but not anything like we had this time! Tombstones all over the board! Nothing changed from the last build except the datecode on the PCB's. They were supplied to us from our customer.  
>  
> I'm pretty sure that the board was double masked. The fab drawing calls out for SMOBC, and then when you look farther down in the notes section it calls out for a matte black mask. It looked to me that there may have been a green LPI first put down, then a matte black mask put over top of it. 
>  
> I don't have pictures now, but I'll get some tomorrow. I've found some links that talk about mask causing tombstones:http://blog.screamingcircuits.com/2007/11/soldermask-and.html
> http://communities.mentor.com/mgcx/message/2726
>  
> So I know it can happen. I just want to check with you guys to find out if it happens often.
>  
> Thanks!
>  
> Steve
> 
> ______________________________________________________________________
> 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