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Filler materials: welding, brazing, soldering


Fusion joining techniques produce permanent joints. Soldered joints and some brazed joints can be disassembled with care.
Welding is a common fabrication method for metals used in spacecraft. Brazing usually refers to joining with alloys of copper, silver and zinc and should be used instead of soldering when stronger joints and an increase in temperature resistance is specified. Soldered joints are used for electrical and thermal conducting paths and for low mechanical strength joints. Soldering is commonly referred to as "soft-soldering" in which ow-melting point alloys, such as tin-lead or indium-based materials are used.

There are a large number of welding filler materials available. Forms (e.g. wires and rod) vary depending on the welding technique used. Selection of the correct filler rod is largely dictated by the metals being joined, notably alloy composition. Filler materials, welding procedures and post-weld processes are detailed in aerospace standards and specifications.

Comments on weld filler materials also apply to braze metals and processes. An added complication is that braze fillers are generally very different from the parent weld materials andso galvanic couples andother corrosion effects also need consideration.
Solder alloys that are acceptable for use inelectronic assemblies inspace, and their associated fluxes and process chemicals (e.g. solvents and cleaning baths), were subject to intense evaluation, see Table A-7 and Table A-8 (from ECSS-Q-70-08).
Solder alloys consist of the tin-lead and indium-lead alloys defined in ECSS-Q-70-08 and ECSS-Q-70-38. They are procured according to these specifications, they define purity levels and, where necessary, fluxes of suitable formulation for the assembly of spacecraft electronics.


Soft Solder, Sn60 (Space Quality)
Soft Solder, Sn63 (Space Quality)
Soft Solder, Silver-loaded (Space Quality)
Tin-Silver Eutectic Solder, (Space Quality)