Kevin:
 
Double check the preheat profile.  Your cap manufacturer should have the profile recommendations.  Typically, there are two criteria: rate of rise during preheat and maximum temperature change when the caps hit the wave.  Assuming that the caps are'nt damaged going in, it sounds like the temperature change between the preheat and the wave may be excessive.
 
Don Vischulis
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kevin Stokes
Sent: Thursday, August 16, 2001 2:26 PM
To: [log in to unmask]
Subject: [TN] To wave or not to wave, that is the question...

Old problem: mounting ceramic capacitors to the bottom side of an assembly and your customer wants you to wave them on.

We are having problems with 0805 0.22 uF and 0.1 uF caps going through wave and cracking during the process.  We are following all of the standard protocols (preheat, etc.).  My understanding is that 0805s are typically capable of handling this process.

Anyone got any ideas short of moving the cap to the top or doing a double sided reflow?

Kevin

Kevin Stokes
Reliability Manager
Kimball Electronics Group
(812) 634-4207