What Is High or Low Temperature Solder?

Most printed circuit boards and electronic components are soldered using standard melting point alloys.  The Tin/Lead alloys most commonly used are Sn63/Pb37 and Sn60/Pb40 with melting points of 361°F (183°C) and 370°F (188°C) respectively. 

The Lead-Free solder alloys SAC305 and Sn99.3/Cu0.7 have melting points of 430°F (221°C) and 441F (227°C) respectively. While higher than the Sn63 alloy, lead-free solders are not considered high-temperature solders.

HIGH-TEMPERATURE SOLDER

Since pure Tin melts at 450°F (232°C) and pure Lead at 621°F (327°C), high-temperature solders contain mostly Lead.  For instance, the Sn10/Pb88/Ag2 alloy containing 88% Lead has a 570°F (299°C) melting point.

APPLICATIONS for HIGH-TEMP SOLDERS

Components that will operate in very hot environments, such as in avionics, automotive and downhole oil and gas wells can benefit from higher temperature solders.

LOW-TEMPERATURE SOLDER

Low temperature solders have melting points ranging from 117°F (47°C) to 320°F (160°C).  These solder alloys contain Tin blended with a variety of metals such as Bismuth, Indium, Cadmium, etc.

APPLICATIONS for LOW-TEMP SOLDERS

Components or substrates like flex circuits that are heat sensitive are good candidates for lower temperature solders.  Step soldering, or 2^nd side soldering using low-temp solder can be accomplished without disturbing previously soldered components that were attached using standard lead-free alloys. 

Soldering at lower temperatures also reduces the thermal energy needed, extending the equipment life, and reducing overall electrical usage.

 SOLDER ALLOY MELTING POINTS  (°F)