Clayton,

What is the lead plating? Copper corrosion products, primarily sulfides and
chlorides (not oxides), have been known to migrate into the package as well
as migrate between leads (causing increased current leakage or an electrical
short). In order for migratory corrosion products to appear, you need
chlorides and sulfides in the environment. This can be from leftover fluxes
and other chemicals on the board or it can be from industrial gases (you'd
be suprised how much chlorine gas you breathe in everyday).

The corrosion products can only migrate into the package if there is a
delamination between the encapsulant and the lead. Have you conducted
acoustic microscopy of the component after reflow?

If you want to qualify the components, you will need to run them through a
typical solder reflow (with flux) and then subject it to either HAST or
mixed flowing gas (MFG). As a general rule of thumb, if your cleaning
process is thorough, your use environment is benign (controlled office) and
your required lifetime is less than five years, these imperfections should
not be a problem. However, if you have leftover flux on the board, you could
see leakage problems in as little as six months.

Craig


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Clayton Gardner
Sent: Monday, March 12, 2001 8:13 PM
To: [log in to unmask]
Subject: [TN] Exposed Copper


Hi All

Can you please comment on the following

Is there any associated/documented risk, if there are small plating
imperfections on copper leaded SO08 components leaving a small section of
exposed copper as the lead exits the component body??

We use IPC 610 Class 2 for this product.  Our customer has concerns about
the exposed copper leading to corrosion and entering the component body.

Any help or info you can provide would be muchly appreciated.

Thanks

Clayton Gardner
Engineering Manager
AEMS
11-13 Fiveways Blvd
Keysborough VIC  3173
AUSTRALIA

Ph 61 3 9701 5499
Fx 61 3 9701 5422

email: [log in to unmask]

web:  www.aems.net.au

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