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November 1999

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Subject:
From:
Ryan Grant <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 16 Nov 1999 08:06:23 -0700
Content-Type:
text/plain
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text/plain (93 lines)
Richard,
        Why bake every 12 months?  Moisture absorption only presents a problem
during reflow, where you can delaminate the component.  Provided you
bake before assembly, the length of time between bakes becomes
irrelevant.  In addition, if you store the components at 5%RH, they
should be able to be stored indefinitely without absorbing a significant
amount of moisture.



                        Thanks

Ryan Grant
Process Development Engineer
MCMS
(208) 898-1145
FAX (208) 898-2789
[log in to unmask]

>-----Original Message-----
>From:  Richard Tilbrook [SMTP:[log in to unmask]]
>Sent:  Tuesday, November 16, 1999 5:05 AM
>To:    [log in to unmask]
>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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