Morning All!
Well, I'm starting work on Monday! WOO-HOO! (broken toe and all) Actually,
my toe feels fine. It's been a few days now since I broke it, and the blood
from the break has had a chance to migrate up to the surface of the skin and
it looks worse now than when I first broke it. I won't post any pictures
though, don't want to make anybody cringe ;^)
I do have some cross-section photos that clearly illustrate what Dwight was
talking about. It's obvious that he's been there, done that, and got his
t-shirt...
http://stevezeva.homestead.com/files/uVia_Bubble.jpg
http://stevezeva.homestead.com/files/Uvia_Bubble_2.jpg
Steve
----- Original Message -----
From: "Dwight Mattix" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, August 27, 2009 1:18 PM
Subject: Re: [TN] Via-in-pad blowing bubbles
> As described by others plating defects can cause the solder void. However
> a more common problem we see is failure of the uVia to wet out. I've got
> pics of both conditions going back years now.
>
> This due to a final shape of an otherwise well formed and plated uVia. The
> via needs to wet out. If it doesn't wet, the air will be held in by the
> surface tension of the liquidus solder. The temp will finally rise enough
> for the air pressure to overcome the surface tension. That's when the
> solder ball expands and forms a bridge to an adjacent ball.
>
> In order to wet out consistently, the uVia final shape should be a bit
> more open at the top than at the bottom. If the via sidewalls are too
> near vertical or if the plating has a cornice where plating closed down
> narrower at the knee of the via it will cause voiding. The liquid solder
> forms a meniscus that hangs up on the knee of plating.
>
> Simple fix? Specify solder copper filled uVias in outerlayers. Tougher
> fix? Agree on an acceptability spec with your suppliers for final uVia
> shape. Many of the top tier high volume offshore uVia fabs already have a
> uVia shape standard that's been applied to them by a large OEM or two
> (:-)) who've gone before you.
>
>
> At 06:34 PM 8/26/2009, Chris Mahanna wrote:
>>Hello netters-
>>
>>Have we a term for vias-in-pad blowing solder ball bubbles to the point of
>>bridging?
>>Regardless, is there a unique cure for the problem?
>>I wonder because- how does one get just enough pressure to blow the large
>>bubble, but not blow-out? Bad luck?
>>Or is it not that unusual, and just usually gets screened before it gets
>>to me?
>>
>>Chris
>>
>>
>>---------------------------------------------------
>>Technet Mail List provided as a service by IPC using LISTSERV 15.0
>>To unsubscribe, send a message to [log in to unmask] with following text in
>>the BODY (NOT the subject field): SIGNOFF Technet
>>To temporarily halt or (re-start) delivery of Technet send e-mail to
>>[log in to unmask]: SET Technet NOMAIL or (MAIL)
>>To receive ONE mailing per day of all the posts: send e-mail to
>>[log in to unmask]: SET Technet Digest
>>Search the archives of previous posts at: http://listserv.ipc.org/archives
>>Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
>>for additional information, or contact Keach Sasamori at [log in to unmask] or
>>847-615-7100 ext.2815
>>-----------------------------------------------------
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> for additional information, or contact Keach Sasamori at [log in to unmask] or
> 847-615-7100 ext.2815
> -----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
