G'day Bob,



13 Dec 96 07:56, Bob Lawrence wrote to Rod Gasson:



 BL>>> It's basically impossible to replace a surface-mount micro

 BL>>> anyway.



 RG>> Gee, now you tell me.



 BL>   It's basically impossible to do brain surgery with a sharp stick,

 BL> too.



Gee now you tell me.  ;-)



 RG>> I've had to replace 3 such micro's in as many weeks... one on a

 RG>> Panasonic VCR, the other on an NEC, and the 3rd one on a

 RG>> Phillips.



 BL>   Was that before or after the brain surgery?



That's irrelevant, I obviously still need the surgery else I'd never

have taken on the jobs in the first place.



 RG>> Not bad for something that is 'basically impossible to replace'

 RG>> and rarely fail.



 BL>   Oddly, getting it off is the hard part.



.  I never seem to have much trouble getting it off. What's

this have to do with changing SMmicros though?



 BL> If you can flow it off and

 BL> leave a little solder behind, the new one goes in okay... but if you

 BL> fuck it the first time you're dead!



Yup. No second chances with these things (well, sometimes you *may*

get a second chance, but rarely a 3rd).



 BL> Three out of three is very good.



I've had lots of experience.



 BL> And I'd give odds that you've left something unsoldered...



I'll give odds on that you'd be hard pushed to tell the chip(s) had

ever been replaced.  I really do have this down to a fine art.



 BL> replace those than normal bits, but those 50-thou micros with leads

 BL> all around are mongrels! I just don't have the knack...



Tis an aquired skill.  I actually did a six week rather intensive

training course on soldering techniques, etc a few years back. I went

at the companies expense, thinking it was gunna be a good bludge,

after all, I'd been soldering for years.  Boy was I wrong, I never

knew there was so much to know/learn about such a 'simple' task.



My confidence and ability to change these SMD's sure improved though.

The only thing I don't like about them is the ever present doubt that

the fault isn't caused by the micro after all, 'cos as you rightly

stated, they do tend to be very reliable. I seem to get more than most

though, 'cos I still take on 'bastard' jobs for other companys - and

naturally, these kinds of faults are bastards.

I make 'em pay though. :-)



Cheers,

Rod



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