Do parts and PCBs have a shelf life? Well, yes and no. I have some 7400 series logic chips in DIP form that I bought back in 1980. Every now and then, I pull one out and put it into a proto board to test some circuit idea I’ve got. They still work thirty years later. I haven’t taken any special care in storage either. Some are stuck into anti-static foam. Some are not. All are sitting in a mini-parts bin without any moisture protection. I guess they do get a little shielding from light, but basically, they’re just hanging out. They’ve been, at various times, in the attic, in the basement, in the garage or in the house.
That may seem like good evidence refuting a shelf like for parts. And today’s parts are even more robustly designed to start with. Still though, if I use any of those parts, it’s generally in a proto board or a socket. Sometimes I have to straighten the leads a bit. A lot of things don’t matter so much at low temperatures, low speeds, low volumes and large geometries.
It’s different when you have fine pitch parts being picked up and placed by a robot and then run through a 10-zone reflow oven. Oxidation that doesn’t matter for a socketed prototype can interfere with the solder adhesion. Bent pins or missing BGA balls can prevent the part from fitting. Moisture absorbed over time can make the chip act like a popcorn kernel when in the reflow oven.
That’s not to say that you can’t use old parts for a prototype these days. Just give them a good inspection before sending them off for assembly. And, if they’re moisture sensitive parts or have been stored in high-humidity areas, consider having your assembly house bake them before assembly. The same goes for raw PCBs too. Overly moist PCBs can delaminate during reflow. Some PCB finishes such as immersion sliver and OSP can tarnish or degrade over time too.
Duane Benson
Archaeologists, we are not
Electrolytic capacitors assuredly have a shelf life. I only order as many as I need, and throw away any that are indeterminately 10 years old.
Old carbon composition resistors can go out of tolerance over decades, but I’ve never been bit by that one.
Huh. That was supposed to be 10 followed by a plus sign. The plus sign must have been stripped out by your html sanitizer. The above sentence is much less clear without it, so amend “10 years old” to “of unknown age or over ten years old”.
I’ll bet they’re using the heck out of those same computers, TV’s, radios, etc. to get their word out and solicit donations! Not to mention (gasp) BULK mailings!
As a scuba diver I appreciate their efforts to save the world’s land, waters and it’s creatures…. but they can be a little hypocritical sometimes too without a doubt!
I think that comment is on the wrong post Darrell 🙂
Back OT I have loads of components in my damp cellar that I plan on using when I’m retired and actually have time to do so 🙂
During manufacture I have seen ancient components used on boards that were years old, stored on open shelves cleaned and soldered on yet still work fine.
So is this shelf life thing a rumour put out by the component manufacturers just to make us buy more? lol