"g. beat " @spam protected wrote in message . ..
wrote in message
ups.com...
I don't do much soldering (obviously) but which is better and is less
prone to cracking in the future? The newer Lead-free rosin core or the
63/37 tin/lead rosin core? A store in my town only stocks these two.
This for a small circuit board repair project.

Also, What can I use to cleanup the dried-up rosin residue on the PCB?

Thanks


Phillip -

NEVER use acid core solder on electronic circuits (or kiss that appliance /
project goodbye).

63 / 37 is the Eutectic of Tin and Lead metals.
Eutectic is an English word that comes from the Greek 'eutektos', meaning
'easily melted.'

The lowest temperature at which a mix of two materials will melt.
Often the temperature is an anomaly, that is, it is much lower than the
melting temperatures of only slightly different mixtures. Lead-tin solder is
an example. Lead melts at 327 C, tin at 231 C.
The lowest melting combination is 67 lead, 33 tin ( 180 C ).

Non-eutectic mixtures have a melting or softening (plastic) range. Such
mixtures do not flow well until thoroughly heated past the softening
(plastic) range. Kester solder Alloy temperature chart
http://www.kester.com/en-us/technical/alloy.aspx

g. beat


I'm a bit confused about the talk of not using acid fluxed solders in electronics. Just about all conventional solder wires formulated for electronic work, contain one or more cores of rosin based flux. As far as I am aware, this is a fundamentally acidic material when in its activated state, and in fact its being acidic is how it removes the tarnish and oxidation on the surfaces to be joined.

Recent research that I have done regarding the use of lead free solder wire for repair and rework purposes, suggests that because of the inferior wetting properties of lead free, the fluxes employed are actually more aggressive than those in leaded solder, by virtue of being *more acidic*. This is cited as being a reason that lead free soldering is considered to be potentially more injurious to health than leaded soldering, and that workshops should take steps to improve fume extraction.

I obtained this information on very good authority, directly from a recognised specialist, working for a company whose job it is to recommend on such matters. Comments please ??

Arfa