Heat treatment, vacuum-tight brazed joints and EB welding for heat sinks, busbars and vacuum components.
Copper scores with excellent thermal and electrical conductivity and is therefore ideal for components that need to safely conduct high energy and heat flows. Listemann realizes vacuum-tight solder joints and coordinated Heat treatments for thermally highly stressed components – from power electronics, cooling plates and heat exchangers to vacuum-compatible apparatus and feedthroughs. Thanks to flux-free vacuum processes, clean, low-particle joining zones with high tightness and reproducible quality are created.
Vacuum-brazing (Cu-Cu, Cu-steel, Cu-Ni, Cu-ceramic via active solder)
EB welding for selective, deeply penetrating seams
Dimensional Heat treatments for property control
Cooling channel plates, heat sinks, high-current rails/busbars
Vacuum and process technology with high sealing requirements
Hybrid assemblies (copper-steel, copper-ceramic)
Vacuum-brazing allows us to join copper with partner materials such as steel, nickel-based alloys and ceramics (using activated brazing alloys and suitable interlayers). Typical gap dimensions in the range of 0.02-0.08 mm ensure capillary flow; defined temperature-time profiles minimize pores and intermetallic brittle phases. For hybrid composites (e.g. Cu-steel), we use diffusion barriers to prevent brittle phases and increase thermal shock resistance. Electron beam welding (EBW) is also an option for highly stressed areas, provided the geometry and heat input allow it.
Heat treatment of copper alloys (e.g. low-stress, property- or structure-oriented) stabilizes dimensional stability, reduces residual stresses and improves long-term reliability under thermal cycling. For vacuum and process-critical applications, we prefer to use oxygen-free copper (OF/OFHC) to avoid hydrogen-induced damage and ensure maximum purity. Surfaces are degreased, lightly oxide-removed and finely roughened before joining and then handled without particles.
Intermetallic brittle phases can be reliably avoided by using suitable solders or diffusion barriers (e.g. nickel) as well as closely controlled temperature-time profiles.
Yes, copper can be soldered with ceramic if activated solders are used and the surfaces are clean in a vacuum and suitable roughness and gap dimensions are ensured.
Depending on the temperature and medium, silver-, copper-, gold- or nickel-based solders are suitable for copper, whereby the selection is always made on a project-specific basis according to tightness, strength and operating conditions.
When Vacuum-brazing copper, a uniform gap of around 0.02 to 0.08 millimeters is generally recommended, as this supports the capillary flow and enables a high level of tightness.
Pore formation is reduced by planning homogeneous temperature fields, controlled heating and holding times, suitable solder feed points and defined degassing phases.
Oxygen-free copper reduces the risk of hydrogen-induced damage and is therefore particularly suitable for vacuum and high-purity applications.
The permissible operating temperatures depend on the solder system used; silver solders often cover medium temperatures, while nickel- or gold-based solders allow higher continuous temperatures.
The service life under thermal cycles is improved by ductile solders, stress-relieving interlayers, adapted geometries and validated cooling ramps.
Phone: +41 52 245 18 55
Mobile: +41 77 442 46 91
t.bachmann@listemann.com
Phone: +423 375 90 12
Mobile: +423 78 05 401
t.bitschnau@listemann.com
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