Vacuum Brazed Stainless Steel and Gold-Plated Stainless-Steel Pins to Ceramic

Brazing stainless-steel and gold-plated stainless-steel pins to ceramic is a well-established joining method in the production of electronic assemblies, sensor components, and hermetic feedthroughs. These joints combine the mechanical strength of metal with the electrical insulation and thermal stability of ceramic, but achieving consistent results requires careful control of materials and process conditions.

Ceramic materials do not naturally wet with conventional brazing alloys and therefore require surface metallization, most commonly a molybdenum-manganese layer followed by nickel plating. This metallized surface allows the filler metal to bond reliably to the ceramic during brazing. Stainless steel pins, while mechanically robust, form stable surface oxides that can interfere with wetting if not processed in a controlled atmosphere. When gold-plated pins are used, the gold layer improves wetting and corrosion resistance, but the brazing temperature and dwell time must be limited to avoid excessive dissolution of the plating into the filler alloy.

Vacuum furnace brazing provides the controlled environment needed for this type of metal-to-ceramic joining. The oxygen-free atmosphere prevents oxide formation on stainless steel surfaces and eliminates the use of flux, which is particularly important for electronic and hermetic applications. Uniform heating within the vacuum furnace reduces thermal gradients across the assembly, helping to protect the ceramic from cracking and ensuring stable filler metal flow. Typical vacuum levels in the range of 10^-4 to 10^-5 mbar are sufficient to produce clean, well-bonded joints.

For most standard applications using metallized ceramic and gold-plated stainless-steel pins in a vacuum furnace, a brazing cycle around 800-820 °C with a 5-8 minute dwell is a proven starting point when using silver-based alloys. Final optimization should always be done based on joint geometry, ceramic type, and performance requirements.

Process control plays a significant role in joint reliability. Heating and cooling rates must be matched to the ceramic and metal combination to minimize residual stress caused by differences in thermal expansion. Proper joint design, including consistent braze gaps and accurate pin positioning, further improves mechanical strength and long-term stability. Finished assemblies are commonly inspected using visual examination, leak testing, and electrical checks, depending on the application requirements.

For applications where cleanliness, repeatability, and reliability are essential, Normantherm vacuum furnace brazing remains the preferred solution for joining stainless steel and gold-plated pins to ceramic. With controlled thermal cycles and a stable vacuum environment, high-quality joints can be produced consistently for demanding industrial and electronic applications.