Yousef

2 possibilities, both assuming the leads are a ferrous alloy and that what you are
seeing is really rust:
1. The cut edge of the leads is not tinning during the soldering because a) the lead
alloy is not solderable (e.g. containing nickel) and/or the flux used is insufficiently
active.
2. You are using a rotary trimming knife after soldering (many systems in the past used
solder-trim-solder)
In both cases, you have a bare alloy exposed to the aqueous process, with an active DI
water followed by a slow drying process: rusting is therefore inevitable until you
manage to ensure that the cut ends are tinned correctly.

This is a known problem.

Brian

MOTLAQY wrote:

> Dears,
>
> Below is a short description of a problem we have faced recently at our
> plant with the Through/Hole assemblies.
>
> Problem: Unacceptable formation of rust (brown to red color) on the CCA just
> after cleaning (before and after wave solder)
> Location: Exactly at the cutting edge of the T/H components leads (most of
> the T/H components)
> Process used: Semi-Aqueous cleaning (Prozone wash 45?C, Prozone/tap water
> rinse 45?C, DI water rinse 50?C, then hot air forced drying 110?C)
>
> What could be the reasons for this problem and what do you recommend to
> solve it and to prevent re-occurrence.
>
> Your expected useful response is highly appreciated in advance.
>
> Best regards,
>
> Yousef Almotlaq
> Manufacturing Engineer
>
> Advanced Electronics Company - Saudi Arabia
>
> Email [log in to unmask] <mailto:[log in to unmask]>
> Tel  + 966 1 220 1350 X 3215
> Fax + 966 1 220 1355
>
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