One of the important properties of heat absorbers is thermal stability up to 250-270°C during short time heating without water. There is some contradiction with the requirement of use for 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 is 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 allowed base metal dissolution and creation of solid phase boundaries between copper and brass parts.