Hi,
Will putting a packet of Silica Gel into a box of carbon film resistors help prolong the life? Or will it do anything for the resistors?
Thanks.
No, the resistors will still age and change value slightly given enough time.
ok, so it wont help at all, not worth doing? I remember buying a kit of resistors once that had the packets in the box, so I thought it did something.
I haven't ordered any silica gel yet, so maybe I will just hold off.
How long do you want them to last. 100years?
I have 20+ year old resistors in plastic drawers that still look ok. Some might even be 50+ years old.
The oxidised wires of the old ones only make them a bit harder to solder.
Who cares. I think I will never use them anymore, because I moved to SMD resistors, and only use through-hole for testing/breadboarding.
I think SMD has a shorter shelf life. Reflow soldering might be harder when connections are oxidised.
Don't know. The 5 year old SMD resistors and capacitors still flow ok.
Leo..
Well the kits I am making are going to a warehouse where they wait to be sold. I don't know what conditions they will be exposed to and I want to make sure the kit is okay when the customer gets it.
So I was thinking about putting in one of those packets into each kit. But if it won't help anything, I will just save the money.
Desiccant has its place not generally resistors.
Ic and semiconductors can suffer from popcorning when soldered which is why they arrive in sealed plastic pouches.
They absorb moisture over time.
Oxidation is another issue that a desiccant will not solve, need inert gas packing for that.
If your kits involve soldering be aware that PCB will deteriorate in storage, they can become unsolderable within months.
Might be useful to prevent corrosion in very humid areas of the world, but not generally needed.
Fingerprints are bad, so handle parts that are not used instantly with tools or gloves.
Pack in a sealed (antistatic?) plastic bag, like they do with loose lots of SMD chips.
Kitchen type freezer bag sealers are cheap.
That also stops/slows environmental exposure problems.
Leo..
okay, thanks for the tips. I'm not making any IC kits right now, but I might in the future. I do a lot of other components.
So I was thinking about putting in one of those packets into each kit. But if it won't help anything, I will just save the money.
Humidity is a concern regarding the solderability of a component. Generally, manufacturers provide a 1-2 year shelf life for components with relatively benign conditions. In this case, the shelf life has nothing to do with the degradation of the component itself but of the terminal or leads.
If the component contains any plastic, then it is a matter of preventing the epoxy from absorbing humidity which will turn into steam during soldering. This effect is sometimes known as tombstoning.
Wawa:
How long do you want them to last. 100years?
I have 20+ year old resistors in plastic drawers that still look ok. Some might even be 50+ years old.
The oxidised wires of the old ones only make them a bit harder to solder.
Who cares. I think I will never use them anymore, because I moved to SMD resistors, and only use through-hole for testing/breadboarding.
I think SMD has a shorter shelf life. Reflow soldering might be harder when connections are oxidised.
Don't know. The 5 year old SMD resistors and capacitors still flow ok.
Leo..
About half of my resistors are from the 1970s. They work fine - I live in Arizona so they have no corrosion on the leads. All the old ICs, sockets, dip switches, anything else I had stuck in a big sheet of conductive foam however has badly blackened leads. A bit of scraping fixes them though. I tossed all the older caps, cause they were stupidly BIG!
Old thru hole parts can often have leads cleaned up with pink pencil eraser, or 300 grit sand paper so not much leg material is removed.
Silica gell is used in industry mainly due to air transport to prevent condensing humidity problems as pressure changes. This would normally cause tarnishing on the leads of components. It is also used with sealed packages with semiconductors so that a part may go through a solder oven without having to be baked for 24 hours to prevent moisture popping that can move the component as they are flow soldered.
adele:
Well the kits I am making are going to a warehouse where they wait to be sold.
That's a new twist compared to your other thread about making up a kit for your own projects. Not that it matters.... interesting though.
When I worked in Malaysia we used to pack everything with silica gel but then the humidity was always between 90 and 100%. Unless you are somewhere tropical it shouldn't be necessary.
If you are going to be using a warehouse you should check on the conditions there before signing the contract.
Russell.
Use metal film or metal oxide resistors? Less sensitive to environmental conditions and better
overall, probably completely unaffected by storage conditions (other than for solderability of
the leads).