5. Crossings and passages

5.1 Electrical crossings

Electrical feedthroughs must ensure electrical insulation and vacuum tightness at the same point. In industrial vacuum, this requirement can be easily met by using plastic materials (Plexiglas, polycarbonate, etc.) and elastomer seals, but in high vacuum and ultra-high vacuum, the use of these materials is not recommended, or even strictly forbidden. The insulating materials used are glass, porcelain and alumina.

Joining these insulators to stainless steel or copper is tricky, mainly because of the different coefficients of thermal expansion. Brazed joints can be made by interposing one or more intermediate alloys or glasses (Dilver-P, or Kovar ). We strongly advise users to use commercially available materials or, in the case of special...