In article <
dgk7mo+jbtb@...>,
Andrew Mawson <
andrew@...> wrote:
> Along with my multi tank system I acquired some Mega (Seno) 600-021
> immerse tinning solution - it's rather old but I'll try it anyway !
> On the bottle it says to disolve in tap water at 50 deg C - let it
> cool
> and use at room temperature. On the Mega site it says to disolve in
> distilled (rather than tap) water. Two questions:
> a/ should it be distilled or tap water?
I've used tap water with this, or a similar, product and it works ok but I
notice there can be a slight milkiness or precipitation when mixed up and
I wondered whether this was a reaction with chemicals in the water. It may
of course depend on the purity of your tap water and it is possible that
the salts present in "hard" water may interfere with the plating process
in some way.
Generally speaking pure water of some sort is better for making up most
chemicals
> b/ what is the odd chemistry that lets it work at room temp but not at
> 50 Deg C when increasing the temp normally speeds up chemical reactions.
It is likely that the chemistry works adequatly at room temperature and
higher temperatures would lead to rapid and uneven deposition, possibly
with poor adhesion. You may even get decomposition rather than plating in
the presence of the copper.
I believe the chemistry involves Thiourea which is considered a health
hazard and the risks may be higher if it is warmer than neccessary.
The higher temperature is neccessary to get the stuff to dissolve properly
in a reasonably short time.
Stuart