Graham

Sprague, about 1975, issued a statement about elcos and solvents. They
had researched the effects and concluded that a) a few micrograms of all
halogenated solvents entering an elco would cause failure within 0 to 6
months; b) aqueous and alcohol cleaning was safe and c) that only the
Sprague series xxx was safe as this range was epoxy-sealed and was
obligatory for mission-critical apps; all other elcos would allow
solvent vapours to enter.

However, this does sound more like attack of the rubber seal, where the
aluminium case is swaged over it.

I suggest you contact the supplier(s) and ask for epoxy sealed types.

Brian

Graham Naisbitt wrote:
> Good evening Techies
>
> We have a customer who has discovered a "black deposit" underneath an
> electrolytic capacitor that has caused a circuit failure. They conformally
> coat the assembly using a classic AR coating and claim that the coating
> softens the seal on the capacitor. We are awaiting the results of a surface
> analysis they are running to determine what the "black deposit" might be.
>
> We believe that the solvents in the coating might be attacking the capacitor
> seal causing the leakage, but cannot understand why this should happen on
> components from a reputable supplier. The customer has changed the component
> supplier, but the problem seems even more severe.
>
> The end product is safety critical Class 3 - folks may die if the product
> fails.
>
> Can you good folks maybe shed some light on what might be done to overcome
> the problem?
>
> Change the seal on the capacitor and if so, what type of seal should be
> used?
>
> Anyone with similar experience?
>
> --
> Regards Graham Naisbitt
>
> [log in to unmask]
>
> Cell: 079 6858 2121
> Office: +44 (0)1252 813706
>
> Concoat Limited - Engineering Reliability in Electronics
>
> Web: www.concoat.co.uk  and  www.concoatsystems.com
>
> ---------------------------------------------------
> Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
> information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
> -----------------------------------------------------
>
>

---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------