If only a few micrograms of acid (complex) hides in pores and voids (which are plenty of on a board), you have a lot of traps that can hide for days, weeks, months before they activate. We have seen comparable issues with leakage from wet capacitors. It's unbelievable what microscopic amounts of this stuff can cause. Especially if it creeps under the conformal coating or sneeks in under the underfills. I have a short, but very good article from Lucent/Bell about microscopic contaminations and what problems they can cause in long time aspect. If it's of general interest, I  can send it to H.H. Steve Gregory I.

Inge

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: den 28 augusti 2008 09:31
To: [log in to unmask]
Subject: Re: [TN] what damage can a battery leakage do on a TTL/CMOS controller card 1990 vintage

Nasty, but what kind of battery to start with? The chemistry of different types can vary enormously.

Inge's advice is probably the safest and surest. Prevention is surely better than cure: never keep batteries in equipment longer than the "sell-by" date, whether used or not.

If the cleaning is done rapidly after the leak occurs, it should be OK, but I would scrap anything that has had more than a week's contact with the battery residues. Why remove the chips?

Brian

Anil kher wrote:
> Hi all
>
>
>
> Need advise. This has happenned twice in the last 2 months. The
> battery leaked all over the card (S-M - CNC 45 card no. 45.01.02.3)
> The m/cs did not start the next day.
>
>
>
> If the card is  powered after a few years of storage the battery
> starts leaking and within a few days it is all over the PCB.
>
>
>
> We removed the chips and cleaned in Hot water / air agitn and againa
> nd again. Baked bare card and reloaded chips. NADA. Solvent extarct of
> bare PCB all perfect.
>
>
>
> Advise if we should change all chips - some TTL, some cmos, memory,
> eproms, etc.
>
>
>
>
>
> Anil
>
>
>
> Micro Interconnexion Pvt. Ltd
>
> D3-12 A, Corlim Ind. Estate
>
> Corlim, ILHAS, GOA
>
> INDIA - 403110
>
> Tel: +91-832-2284337
>
> Fax: +91-832-2284209
>
> alt. E-mail: [log in to unmask]
>
>
>
> LEADERS IN GOLD PLATED PCBs
>
>
>
>
>
>
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