35856Re: CRT monitor dying?
- Dec 1, 2006Jeff,
Thanks for the reply and I agree. We use the best components possible,
International Rectifier for MOSFETs and certainly Kemet for
capacitors. Same for all other parts as well; at top-line vendor's
parts are 10% more expensive than the also-rans. It makes no sense to
"save" 10% up front only to pay back 50% in rework or worse.
The biggest challange has been adapting to ROHS. We have things pretty
well worked out now but it wreaked havoc in the beginning. No matter
how you cut it, it is an inferior process compared to SnPb.
I just hope it satisfies the mud-hut and wattle mentality of the green
type's vision of Vallhala until the next 'thing'. There will always be
a next 'thing' with these anachronists until technology is eliminated.
--- In Electronics_101@yahoogroups.com, "jverive" <jverive@...> wrote:
> Indeed, the inspection procedures I mentioned were for a failure
analysis lab I used to run (before having to go on disability).
> As you have found, the high-k dielectrics (used in X7R, Y5V, and Z5U
caps, for example) are much more brittle than the low-k dielectrics
used in C0G (also known as NP0, for Negative-Positive zero, which
refers to the low thermal coefficient). However, ALL ceramic SMD caps
have the potential for thermal or stress cracks. Of the various app
notes I've read, I like those put out by KEMET. These cracks are
going to be even bigger problems with lead-free solders, and
post-assembly testing is never foolproof, and neither is optical
inspection (even if it could be automated). We had some success with
bed-of-nails testing, though these have strict mechanical requirements
to keep from causing cracks themselves. Cracked power plane decoupling
caps are notoriously hard to detect because of the low node impedance,
yet these have the greatest potential to cause nasty damage when they
eventually short out, due to the vast amount of energy available.
> I could go on and on about the difficulties in dealing with cracked
ceramic caps, but I want to keep this posting from getting too long.
> - Jeff
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