I have just compiled these bits of info from wiki and others but I thought others would be just as interested::
solder
63/37: melts at 183 °C (361.4 °F) (eutectic: the only mixture that melts at a point, instead of over a range)
60/40: melts between 183–190 °C (361–374 °F)
50/50: melts between 185–215 °C (365–419 °F)
Lead-free solder alloys melt around 250 °C (482 °F), depending on their composition.
Other common solders include low-temperature formulations (often containing bismuth), which are often used to join previously-soldered assemblies without un-soldering earlier connections, and high-temperature formulations (usually containing silver) which are used for high-temperature operation or for first assembly of items which must not become unsoldered during subsequent operations.
the eutectic alloy of 63% tin and 37% lead eutectic: the only mixture that melts at a point, instead of over a range
A eutectic formulation has several advantages for soldering; chief among these is the coincidence of the liquidus and solidus temperatures, i.e. the absence of a plastic phase. This allows for quicker wetting out as the solder heats up, and quicker setup as the solder cools. A non-eutectic formulation must remain still as the temperature drops through the liquidus and solidus temperatures. Any differential movement during the plastic phase may result in cracks, giving an unreliable joint. Additionally, a eutectic formulation has the lowest possible melting point, which minimizes heat stress on electronic components during soldering.
solder is drawn into the joint by capillary action and to bond to the materials to be joined by wetting action.
Soldering is distinguished from brazing by use of a lower melting-temperature filler metal; it is distinguished from welding by the base metals not being melted during the joining process
Soft soldering is characterized by the melting point of the filler metal, which is below 400 °C (800 °F).[1]
Flux
the primary purpose of flux is to prevent oxidation of the base and filler materials.
Secondarily, flux acts as a wetting agent in the soldering process, reducing the surface tension of the molten solder and causing it to better wet out the parts to be joined.
Traditional rosin fluxes are available in non-activated (R), mildly activated (RMA) and activated (RA) formulations. RA and RMA fluxes contain rosin combined with an activating agent, typically an acid, which increases the wettability of metals to which it is applied by removing existing oxides. The residue resulting from the use of RA flux is corrosive and must be cleaned off the piece being soldered. RMA flux is formulated to result in a residue which is not significantly corrosive, with cleaning being preferred but optional.
Mildly activated (Type RMA) Formula 186 was developed for difficult-tosolder applications where a more active flux than plain rosin is required, but where highly activated fluxes are considered potentially conductive.
Fully activated rosin (Type RA) Formula 1544 is characterized by excellent wetting action that permits soldering even on such metals as brass and nickel, which are extremely difficult to solder with ordinary rosin.
solder
63/37: melts at 183 °C (361.4 °F) (eutectic: the only mixture that melts at a point, instead of over a range)
60/40: melts between 183–190 °C (361–374 °F)
50/50: melts between 185–215 °C (365–419 °F)
Lead-free solder alloys melt around 250 °C (482 °F), depending on their composition.
Other common solders include low-temperature formulations (often containing bismuth), which are often used to join previously-soldered assemblies without un-soldering earlier connections, and high-temperature formulations (usually containing silver) which are used for high-temperature operation or for first assembly of items which must not become unsoldered during subsequent operations.
the eutectic alloy of 63% tin and 37% lead eutectic: the only mixture that melts at a point, instead of over a range
A eutectic formulation has several advantages for soldering; chief among these is the coincidence of the liquidus and solidus temperatures, i.e. the absence of a plastic phase. This allows for quicker wetting out as the solder heats up, and quicker setup as the solder cools. A non-eutectic formulation must remain still as the temperature drops through the liquidus and solidus temperatures. Any differential movement during the plastic phase may result in cracks, giving an unreliable joint. Additionally, a eutectic formulation has the lowest possible melting point, which minimizes heat stress on electronic components during soldering.
solder is drawn into the joint by capillary action and to bond to the materials to be joined by wetting action.
Soldering is distinguished from brazing by use of a lower melting-temperature filler metal; it is distinguished from welding by the base metals not being melted during the joining process
Soft soldering is characterized by the melting point of the filler metal, which is below 400 °C (800 °F).[1]
Flux
the primary purpose of flux is to prevent oxidation of the base and filler materials.
Secondarily, flux acts as a wetting agent in the soldering process, reducing the surface tension of the molten solder and causing it to better wet out the parts to be joined.
Traditional rosin fluxes are available in non-activated (R), mildly activated (RMA) and activated (RA) formulations. RA and RMA fluxes contain rosin combined with an activating agent, typically an acid, which increases the wettability of metals to which it is applied by removing existing oxides. The residue resulting from the use of RA flux is corrosive and must be cleaned off the piece being soldered. RMA flux is formulated to result in a residue which is not significantly corrosive, with cleaning being preferred but optional.
Mildly activated (Type RMA) Formula 186 was developed for difficult-tosolder applications where a more active flux than plain rosin is required, but where highly activated fluxes are considered potentially conductive.
Fully activated rosin (Type RA) Formula 1544 is characterized by excellent wetting action that permits soldering even on such metals as brass and nickel, which are extremely difficult to solder with ordinary rosin.
