Microcertec - Ceramic to Metal Nrazed Assemblies

Applications

Ceramic-to-metal brazed assemblies are particularly suited for use in such severe environments as, for instance :

• airborne electronics for the aerospace - civilian and military,
• defense devices,
• medical and analytical instruments,
• high-energy physics, high and very high vacuum,
• the nuclear industry.

PNL INNOTECH has a thorough experience in those various fields that allows the company to address every kind of application in line with it own requirements.

Products

The product range that PNL INNOTECH can offer is not restricted to the here below list since the company mainly manufactures customized ceramic to metal brazed assemblies. For instance :

• high-voltage feedthroughs for the mass spectrometry, ion guns
• electrical feedthroughs for medical implants – cochlear and heart pace makers
• hermetic packages for airborne electronics, analytical tools and devices for the oil industry,
• high-voltage hermetic connectors for the nuclear industry,
• high-voltage insulators for electron tubes

Materials

Not all advanced ceramics can be brazed. There are mainly :

• aluminium oxide (alumina, saphirre,rubi) and beryllium oxide,
• and to a lower extent aluminium nitride, silicon nitride, silicon carbide, boron carbide, zirconia…

The metal associated with the ceramic must have a close CTE – coefficient of thermal expansion – in order to minimize residual stresses in the joint that would lead to rupture. The following metals are most commonly used :

•  kovar, copper, titanium, nickel-iron, stainless steel, molybdenum, niobium, platinum…

The braze alloy to be used will depend upon various parameters : final temperature of use of the product, nature of the metal to be joined, several metals of different kinds to be brazed. The following alloys Ag-Cu, Ag-Cu-Pd, Ag-Cu-Au, Au-Cu, Au-Ni, Ag, Au, Cu are typical and cover a range of temperatures from 780°c to 1100°c.

A ceramic to metal assembly can be done in various ways, but all of them require that a metal interlayer be deposited so that the adhesion of the subsequent brazing will be possible :

• sintered thick layer of molybdenum-manganese, only with oxide ceramics (alumina, beryllium oxide..)
• thick layer of a reactive metal that chemically reacts
• thin layer of W-Ti for instance deposited by PVD process.

PNL INNOTECH can offer these three technologies. The choice for one of these will depend  upon the brazed assembly design to be manufactured, the conditions of use or the cost requirements.

We primarily use the following materials to manufacture the here above products :

• high-purity alumina - 94 to 99.8 % (aluminium oxide)
• aluminium nitride (AlN)
• Macor®
• silica, quartz
• MgO & Y-TZP zirconia (zirconium oxide)