Dennis,
     I had a quick look at your companies web site. I take it that hermetic
sealing is something that you want to get into to extend your product
range. I used to be involved with this in a previous job. We used two basic
technologies, high temperature solder, or a glass frit.
The solder was 80/20 gold tin eutectic. This melts at around 320C. We used
these on ceramic packages and kovar lids. The sealing areas on the packages
and lids are metallised with 60 micro inches minimum of gold as the top
layer. The solder was applied as a preform tacked to the lid by the lid
manufacturer. The lid was placed on the package with a clip and passed
through an N2 atmosphere belt furnace to seal. The use of all gold surfaces
meant that no flux was needed.
The other method used a glass frit on ceramic lids. These melted in a 440C
air atmosphere belt furnace to seal to ceramic packages. These required no
nitrogen inerting and no extra metallisation, but at the cost of increased
temperature exposure. This technology will have moved on since and lower
temperatures are probably possible.

Testing for hermiticity is also required. We based our tests on Mil std
883. There may be ANSI replacements for these. Take a look at the EIA/JEDEC
web site at http://www.jedec.org.Two tests are used, gross leak to find big
holes and fine leak for small. A number of different methods are used. For
gross leak we immersed parts in a fluorocarbon under pressure, then placed
them in a heated bath of another fluorocarbon of higher boiling point. Any
fluorocarbon in the package would evaporate and bubble out. For small holes
we placed parts in a pressurised helium chamber, then into a helium
detector. Any helium inside the package would leak out and be detected.

     I would recommend that you talk to package and lid suppliers. Kyocera,
NTK technical ceramic, Indium Corp and Williams spring to mind. They
probably all have web sites as a first point of contact.

regards,
Jeremy Drake
Celestica Ltd
Kidsgrove
Stoke on Trent
England.

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################