Hello Richard,
we store some components for more than 20 years (spare parts for military purpose). My idea is that storage depends on the condition of the part. If you have a good tinning and underplate of the solder areas, I think the parts can be just protected from human handling, humidity and dust for many years. That's our experience. The very thin oxides that will grow are easily broken by the flux and heat during soldering. And if you have gold plated solder lands, the storage will be even more free from problems.

However, this about GOOD tinning or goldplating. As you know, the reality is not always such. Sometimes we get components with a bad tinning directly on an oxidized nickel plating! And this nickel plating may have a very bad adhesion on the bulk material. What you get is depending on what serious company you deal with. So, Richard, you have to figure out what quality your components have before deciding what storage you need. If the customer pays for nitrogene cabinets or vacuum sealed bags, then do it, such a storage is certainly excellent, otherwise it can be an expensive story! But, still you need an analysis of the condition of the finish, otherwise you will open the nitrogene cabinet after 5 years and perhaps find a still unuseful part.

Good Luck

Ingemar



Hello again,

Our company manufactures PCB's for use in military equipment to conform
with ANSI-J001B standard.

Every once in a blue moon, a customer asks us to do something that isn't
entirely normal, at least in the normal electronics manufacturing world.
We can mostly solve the problem or cater for the request, but in this
case we need to do more research.

We have been asked to store all the components (including bare boards)
for a military project spanning 5 years. I had previously been
researching into moisture sensitive components, as some of you may know,
and was not entirely surprised to be given this project.

We will be doing solder tests every 12 months to check for solderability.
We will probably be doing a bake every 12 months too. The idea behind
such a wide gap between bakes being to avoid as much as possible the
formation of intermetallics, which would compromise the quality of
manufacture.

The storage cabinets we are looking at claim a dryness giving a -15deg.C
dewpoint with 5%RH. What temperature did they say? Good question.

I would like to store the components at room temperature, unless you
reckon that the intermetallics are a major problem, where we might
consder researching into something lower.

Have any of you out there stored components fo such a long time? What
procedures did you follow / intend to follow? How effective were these
measures? What do you recommend?

Thankyou for reading this e-mail,

Best Regards,

Richard Tilbrook,
Student Engineer

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