What was the duration and ramp times on your 1812  capacitor tests?
 ----------
From: TechNet-request
To: TechNet
Subject: Re: ASSY:FAB:Des: Joint Cracking LCCCC
Date: Friday, September 13, 1996 11:45AM

Bob,

I have seen serious cracking in tests on 1812 capacitors in -55 to +125C 
test.
They are a good bit smaller and the TCE mismatch not so bad so I am not at
all surprised at what you are seeing.

I would treat 1206's as the limit in kit that is going to see those sorts of
temperatures (-55) regularly in service, unless measures are taken to reduce
the problem.

David Whalley


>I have been looking at some 20 pin Leadless Ceramic Chip Carriers which 
have
>exhibited cracks. They are mounted on standard FR4 and thermal cycled 
between
>-55 +80 for 1000 hours.
>
>Cracking is a problem with this device as we know but not at these low lead
>counts. Many uses in their design rules make 28 pin devices the limit and
then
>incorporate the use of matched substrate to reduce differential expansion.
>
>I would appreciate any feed back on failure that people have seen on 
testing
of
>low lead count devices or even feed back on where people see the limit on 
pin
>count and the need for special substrates.

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************