We use the following general guidelines in our ceramic-to-metal designs.

  • Place ceramic in compression rather than tension.
  • Maximum solid metal pin diameter is .060" where pin is brazed directly to ceramic ID.
  • Choose a metal such as Kovar with the most closely matched expansion to the ceramic when possible.
  • The metal selected to be bonded to the outside diameter of a ceramic should have a thermal expansion > Al2O3.
  • The outside metal member should be of the thinnest cross-section thickness possible to take up expansion mismatch.
  • The selected metal should be as ductile as the design permit.
  • Service temperature must be considered in allowing of expansion-contraction stresses.
  • When internal conductors > .060" are required, a metal tubing with a .010" wall will yield totakeup expansion mismatch.
  • Avoid butt seals. If impossible, use the thinnest ductile metal available.
  • Step braze subassembly techniques should be considered.
  • Consult the factory for installation criteria for all Specialty Seal Group hermetic seals