In response to Richards question, I also have a couple of questions for the
IPC gurus.
First:
Someone here suggested that the IPC might like to consider issuing a
procedure for:-
"The Long Term Storage and Subsequent Processing of Electronic
Components and Sub-Assemblies".
The document IPC-SM-786A "Procedures for Characterising and Handling of
Moisture/Reflow Sensitive ICs" goes part way to answering this question.
Obsolescence is now a constant re-design burden on military equipment
suppliers who are desperately endeavouring to support their products over a
15 to 20 year period. Lifetime buys and long term storage under controlled
conditions is one possible answer to the problem - but at what cost in
money, space, labour resource, quality control measures, etc?
How are other areas of this business (medical appliances; comms base
stations; measurement and control systems; etc) planning to support their
product for such long periods?
Additionally, we have yet to feel the weight of the mill stone that the
current move towards the use of COTS (commercial off the shelf) equipment
may be bequeathing to this industry over the next 20 years.
I think that Ingemar's response is an excellent foundation.
Incidentally, there has also been a hot, open ended debate on the cousin of
Technet:-
[log in to unmask]
Second:
It would be most useful to have the entries in the Subject field, "RE: [TN]
............................." selected.
This would ease both the speed reading of a full 'Inbox' of mail and also
the process of sorting by subject in the Outlook s/w 'Favourites' file.
Is it therefore possible to recommend the following:-
be explicit and un-ambiguous
be short
use recognised key words (is there a defined list somewhere that I
have missed?)
be consistent throughout the thread
The subject reference for Richards e-mail is an excellent example of how to
do it.
Sorry to be picky, but I think it does help.
Thanks,
These are my opinions, not my company's.
Barry Bates
> -----Original Message-----
> From: TechNet
> Sent: 16 November 1999 12:05
> To: s=TechNet(a)IPC.ORG;o=INTERNET;p=BAE;a=GOLD 400;c=GB;
> Subject: [TN] Long term storage of electronic components
>
>
> 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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