Homebrew PCBs

On Sun, 18 Jan 2004 08:48:36 +1000, David Hopkins <davhop@...> 
wrote:

> Gentlemen,
> For a number of years I have been using my roll solder machine to tin my
> completed etched boards for soldering.
>
> Part of the process involves removing the tarnish from the copper before
> applying the water based flux and passing the board through the rollers.
>
> The tarnish remover was a Multicore solders PC2 Tarnish remover.
>
> Disaster struck last week, the plastic bottle sprung a leak and four 
> liters
> spread over the steel shelves and finally on to the cement.
>
> Not a pretty sight. The shelves were stripped of paint and the cement
> surface etched away.
>
> Apparently Multicore don't make this product in this country any more. 
> So I
> need a replacement.
>
> The label shows it contains Thiourea and dilute Hydrochloric acid. The
> Thiourea is 4%.
>
> Anyone know what this Thiourea is and is there a better way to chemically
> remove the tarnish.
>
> I will most likely have to make the mixture my self as  the brand names
> available in the USA are seldom available here.
>
> Any comments welcomed
>
> David
>
>

I know what thiourea is, it is considered a carcinogen and used in 
electroless tinning
a lot.. (probably the reason why they don't produce it any more)

I can't help you much with your tarnish remover problem, sorry, but i would
like it very much if you could describe how your roll tinning machine 
works.

thanks

st