Perhaps I am just weird, but I rarely damage
circuit boards or components
when de-soldering.
You do not know it, but you are.
ICs, and to a lesser extent transistors, are made to be soldered
*once*, and in a well controlled heated environment. Heating up an IC
pin often will stress the die and introduce cracking in the silicon,
as the chip expands in a non-uniform manner. Most of the time these
microscopic cracks do not immediately kill the device, but they will
reduce the expected lifetime of the chip. Basically, the reliability
plummets due to these "latent failures" caused by thermal stress.
You've made simialr comments before, and problably you are technically
correct. If tyhis was something that was safety critical (military,
mediacl, etc), then differnet rules would apply.
However, apoplying it to normal elecrtornci stuff and/or classic
computers sounds more like either an IC manufacturer tryint to sell more
components, or an equipment manufactueer giving yet another bogus reason
not to supply a proper service manual (yes, I have heard that one).
Put it this way... I've desoldered hundreds, maybe thousands of ICs in my
lifetime. Most of the itme I don't resodler them, I do put in a
turned-pin socket (yes, Iknow sockets are supposed to reduce
relaibility, I've never had problems with turned-pin ones). Yes, some of
the ICs I've removed have later failed. So have ICs I've not been
anywhere near. Statisitcally, I can't see a significant difference
between them. It's certainly not the case that every IC I've desodlered
has fialed within 5 years or anything like that.
And yes, Iv'e deosldered and re-used SMD parts (SOICs, PQFPs, etc) with
no problems. They don;t seen unreliable
Plketny of service manuals (at least when they;re not boardswapper
guides) suggest desoldring parets for testing. I don't think any tell you
never to reuse said parts.
As I said, if a life depends on it, then different rules apply. For
classic computers, I'd not worry about it at all.
-tony
