We have found a factor that is not to be found in any standard or paper,
namely, the size of the components. If you have e.g. a mobile telephone
card, all components are the tiniest that are to be found on the market.
With that follow extremly small solder pads equal to extremly small solder
volumes. Such card are more sensitive to solder tarnish than board with
much bigger components. Therefore, Ericsson have a storage maximum of a
couple of weeks only. I have never seen a investigation of that condition.
Nor any calculations or rules.
Inge
--------------------------------------------------
From: "Bill Belanger" <[log in to unmask]>
Sent: den 16 April 2010 10:14
To: <[log in to unmask]>
Subject: Re: [TN] PCB Shelf life
> Hello Angel,
>
> As a former PCB fabricator, I'm not sure that the base material has a
> shelf
> life. It's usually quite stable, and lasts a very long time in the field.
>
> Solderability, however, is a different story. Some surface finishes can
> preserve solderability for many years, such as HASL (Hot Air Solder
> Level),
> which essentially coats any exposed copper with solder. Others, such as
> immersion tin and OSP (Organic Solderability Preservative), measure their
> shelf life in months, weeks or days.
>
> Hope this helps,
>
> Bill Belanger
>
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