failing ic's. Is this a regular occurence?

[oram]

So had a 556 fail today straight out the bag. Was wondering if this happens often. I was staring and testing the circuit for about 3 hours before i'd changed the IC. It was reading around 9v on all pins but  - out. Does anyone know what physically happens inside the chips when breakdown occurs?

cheers

Oram

[mth5044]

Was it socketed? If you soldered it to the board, it might have failed due to prolonged heating.

[GibsonGM]

Was it socketed? If you soldered it to the board, it might have failed due to prolonged heating.

My guess.    When breakdown occurs, the thin layers of dielectric and/or PN junctions pop.     Like hitting a soap bubble with a propane torch.   Happens fast, and is final.   

That said, it's NOT common to ruin chips unless you've wired something wrong, or mishandled it...is this a CMOS chip that's static sensitive??

Only other thing could be a bad lot from the manufacturer, again not too common.

[oram]

it was socketed.

Not sure about cmos... chip reads ne556n...didn't arrive in static sensitive bag...handled the replacement which worked fine.

cheers for insight

[GibsonGM]

NE = Manufacturer, Signetics
556N;   N = the pinout,  plastic DIP

If your voltages are ok, then I'd really have to guess you got a bad lot of parts!!    Do you know for a fact the circuit is good, or do you have a known-good one to put a 556 in to see?

[amptramp]

There has been a big problem with counterfeit parts in the electronics industry, enough that GIDEP (government - industry data exchange program) alerts about it have been going on since the 1980's.  We once got a DIP device marked 74LS74 but it was a 16-pin part!  Unless you have some kind of supplier quality assurance, this is just a fact of life that you have to deal with.

[oram]

*GibsonGM

yeah circuit was good, replaced ic and everything was fine...but then of course i tinkered before changing the ic and voltage noting wasn't my first step. So possibly the circuit was bad before changing the ic. A familiar circuit though, but then familiarity breeds laziness. I had continuity tested all pats of the vero first so pretty sure i'd not shorted it.

*Posted by: amptramp

Cheers. Was wondering at what stage in fault finding the ic may get changed. facts of life i can deal with.

[GibsonGM]

Hey, at least it worked out!  I hate when you think the part is the 'wrong thing', and can't really prove it.  ESP. if they're CMOS (static).   In your case, it ended well )

Can't WAIT to get a few bad IC's some day...oh man!