Completely released – ROSE-L mission in space

Christian Lausch, the responsible development engineer in the Airbus Mechanic & Mechatronic Development Engineering department, and his colleague Harald Arlt, who has been with Airbus for 14 years, put all their expertise into developing a functioning lightweight construction solution. The original idea was to use vapor phase soldering – in principle, this would have been possible. The disadvantage was that the 2.2 m long board would have had to be segmented, which would have resulted in a loss of strength. However, it was also clear that the later application would “see” space and therefore be exposed to considerable temperature fluctuations and external influences. Unlike satellite electronics packed “on board”, for example, which are still surrounded by a protective shell even in space. The Airbus experts therefore decided against the vapor phase soldering process, as the application they were looking for had to offer the greatest possible resistance. The search continued – and they found what they were looking for in the existing machinery in the company´s own clean room production facility, which had been used until recently to produce flight electronics (circuit boards and onboard systems). After this production was relocated internally, the machines were returned to Development Engineering. Among them was an ECOSELECT 2 mini-wave selective soldering system – after a brief analysis it was clear: width fits, height fits, perhaps Airbus could use it to produce the required assemblies measuring 2.2 m x 0.3 m and only 0.4 mm thick in conjunction with a low-temperature solder?

This was the time to get in touch with the soldering machine manufacturer Ersa – and to obtain an assessment of whether the planned project was feasible. Things quickly got rolling, and in January 2021, work began on the specification of a test setup for a feasibility study, with an initial series of tests taking place at Ersa from March onwards, including slots and strips, solder joint geometry, workpiece carrier plus hold-down device, solder selection, soldering parameters and motion sequence. In September, a second series of tests started at Airbus – with a new test board with four rings in the original design, a new product carrier for the ring design including hold-down device and ring slots in different geometries. At the beginning of January 2022, the final soldering tests were carried out in Wertheim using a tin-bismuth solder. These were successful, paving the way for Ersa to be commissioned to convert the ECOSELECT 2 system, including the design and construction of a suitable 2.4 m long product carrier. “The challenge was enormous, as we were not dealing with a classic through-hole plated PCB, but a 0.4 mm thin high-tech CFRP substrate, fully copper-coated, without solder resist. The length of the slots at 20 mm raised a number of questions as to whether this could actually be soldered in a single process. We have already soldered a wide variety of geometries. But this project was also new territory for us. We knew from other projects that the solder tends to flow anywhere with large copper surfaces – just not to the planned location. But we actually managed to do it in close cooperation with the Airbus team,” says Jürgen Friedrich, Head of Application Technology at Ersa, who has been with the company for over 25 years. In July 2022, Ersa finally completed the plant conversion at Lake Constance, which included switching from tin-lead to tin-bismuth. One of the major challenges here was adapting the system control for processing the 2.4 m long product carrier in a single pass. Ersa thus supplied a complete system for an unusual application and successfully commissioned it on site.