Ken, I think no one dare to give such a promis. Now, we use all sizes of ceramic components on thick brass-backed boards. I guess we consume hundreds of thousands a year without too severe problems. Reason: you have to design for matching the CTE-diff. Small pads and high 'pedestals' of solder use to be the basic rule, with considerations for this and that. If these boards were exposed to even more environmental stress, maybe things would start to happen, but fortunately, our product is either hardworking or standby-ing, never switched off, so they survive pretty well despite the somewhat crazy design (ceramic and brass together).
'Design for reliability' is of special value in your case. If you are not familiar with FEA and solder joint CAD simulation tools, I can give the adress to a guy who is doing such jobs day and night since years back. You never get a straightforward result from the machine brain, rather indications about what to avoid and what way to use, then the equations have to be mated with experience (non-linear material properties, is one such factor that gives the machine grey hair).
Good Luck
Ingemar
Ericsson Microwave Systems



     Hi, Technetter,

     Could anyone advise what the maximum size of ceramic SMD capacitor
     that can be used reliably on copper based substrate is? The main
     concern is the CTE difference between that kind of capacitor and the
     metal substrate. The sevice temperature range of the assembly is -40
     to 130degC. Are there any literature/standard talking about this?
     Thanks.

     Regards,
     Ken

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