Rick,

We have gone through exhaustive studies, and had Kemit visit 
our facility to share what they know about cracked ceramic caps.

Some of the root causes of cracking can be:

	1. Pick and Place placement force.
	2. Mechanical stress from board twist and flex after
           reflow. ( mat'l handling )
	3. Stress during the reflow process.

Kemit has many papers on this subject.

What it boils down to is the larger pkgs are more susceptible to these
forces.

Therefore we have been,for the last 2 years, designing out all ceramic
caps larger than the 1210 pkg. In some cases this means putting caps in 
parallel or in series to get the required value for the design.

Good luck,

Dan Shea([log in to unmask])
The Foxboro Co.


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Date: Fri, 15 Dec 1995 11:34:57 -0600 (CST)
From: Phoenix International <phoeintl@sentry>
To: IPC Technet <[log in to unmask]>
Subject: Cracking X7R capacitors

What have companies done to address the cracking problem of multi-layer 
cermaic chip capacitors? We see cracking problems with 0.1 and 0.01 
microfarad X7R ceramic caps. The defect is more a mechanical stress crack 
and not a thermal stress crack.

We understand some companies prohibit this type of component from being 
included in product design. Does anyone have ideas how a company can 
successfully use these components? Are there alternative components that 
can be used to replace the X7R capacitor?

Suggestions, comments and horror stories welcomed.

Thanks.   Rick Vernon, Phoeinx International


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