A couple of years back we did some work for a Japanese customer who was insistent that 
vias shouldn't be tented.  This was apparently to avoid reliability problems if 
process chemicals became trapped by the tenting.  I've always tented vias, except for 
prototype boards with via holes large enough for mod. wires, and never seen this 
happen.  We did however have problems with solder shorts to un-tented vias under 
(non-BGA) ICs on the boards for Japan, as we'd thought might happen.  As a compromise, 
on the next revision of the board we left the vias untented but put in a via-to-(pad 
or via) clearance rule at double the basic board spacing and this stopped the problems 
- at the expense of routability.

Under BGAs, I'd always tent vias as any risk of shorts is too great a risk given the 
cost/difficulty of inspection and rework.

Regards

Andy Gulliver

> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> Sent: 23 August 2001 12:34
> To: Protel EDA Forum
> Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: Re: [PEDA] Antwort: tenting vias;what Intel says
> 
> 
> In a message dated 8/23/2001 4:03:21 AM Eastern Daylight Time, 
> [EMAIL PROTECTED] writes:
> 
> > [EMAIL PROTECTED]
> 
> Here's an excerpt from one of Intel's datasheet concerning the 
> tenting of BGA 
> vias:
> 
> "Intel recommends tenting the via’s on the
> bottom side of the board to minimize heat transfer to the balls during 
> reflow. Tenting via’s on the top-side of
> the board to minimize the risk of solder-wicking is optional and 
> left to the 
> customer’s discretion. It should be
> noted that tenting on both sides allows no relief for trapped gasses."
> 

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* To post a message: mailto:[EMAIL PROTECTED]
*
* To leave this list visit:
* http://www.techservinc.com/protelusers/leave.html
*                      - or email -
* mailto:[EMAIL PROTECTED]?body=leave%20proteledaforum
*
* Contact the list manager:
* mailto:[EMAIL PROTECTED]
*
* Browse or Search previous postings:
* http://www.mail-archive.com/proteledaforum@techservinc.com
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Reply via email to