Increasing of Thermal Stability of Solar Absorbers Soldered by Low Temperature Solders

One of important properties of heat absorbers is thermal stability up to 250 -270°C during short time heating without water. There is some contradiction with requirement of use low tin based solders for absorber foil brazing. The combined brazing of frame with copper-phosphorus brazing alloy and further soldering with 97Sn3Cu or 99Sn1Cu alloys have been described in this work. Metallographic analysis and micro X-ray analysis were carried out on copper sheet – brass tube samples. To increase thermal stability the joint formation in different conditions of gap and time – temperature relations was investigated. Optimal conditions allow to base metal dissolution and creation of solid phase boundaries between copper and brass parts.