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New for December 2010! Not that long ago, microwave work almost always entailed hermetically-sealed modules. In the classic thousand-dollar X-band T/R module, maybe 10% of the cost was the housing.

Hermetic housings are usually an alloy of steel, one of the most popular "blends" is kovar. Kovar has two key propertiess that make it useful in hermetic housings: it forms an oxide that allows molten glass to seal to it hermetically, and it has low thermal expansion that is nearly the same as popular microwave semicondutors (GaAs, InP) as well as ceramics use in thin-film networks and thick film substrates.

Hermetic housings must be weldable (to install a lid or cover), and provide a means for electrical signals to enter and exit. The signals penetrate the housing in feedthroughes. Feedthroughs come in two classes, ceramic, and glass. Covers can be welded with laser or seam welders.

In glass feedthroughs, borosilicate glass has been developed specifically to adhere to housing materials.

More to come!


Author : Unknown Editor