Micro-electro-mechanical systems (MEMS) need to be protected from environmental influences and yet still be able to exchange electrical signals – demands that HermeS® meets. These are actually glass wafers with integrated conductor feedthroughs that are manufactured using simple processes and connected to thousands of MEMS to seal them tightly for decades. HermeS® was developed by the NEC SCHOTT Components Corporation.
Borofloat® 33, a glass that displays the same thermal expansion as silicon from room temperature to over 300 degrees Celsius, is used as the glass substrate. Even when subjected to severe heat, inside the engine compartment of an automobile, for instance, no cracks occur between the glass substrate and the MEMS. When it comes to the metal that is used for the feedthroughs, tungsten is the material of choice because it is very stiff and can be manufactured to have exact dimensions and be extremely thin. In addition, it suits the thermal expansion of Borofloat® 33 just perfectly and maintains the pressure that is exerted on the wire after it has been melted in.
The most important quality criterion for the glass wafer is the exactness with which the feedthroughs can be placed. With HermeS®, this is ± 20 micrometers and is measured optically. This allows for substrates with several 10,000s of metal feedthroughs.
HermeS® wafers are available in 4-inch and 6-inch sizes. As of 2010, SCHOTT is planning to offering 8-inch wafers too. With even smaller diameters and pitch distances, these wafers are most appropriate for high volume industrial applications, especially in the field of sensors and optical devices. This means that customers are able to combine a high level of integration and miniaturization of the MEMS packaging designs with superior electrical properties and hermeticity.
Yet another advantage of packaging components in glass is that, unlike metal, it is transparent and visual inspections can be performed on the MEMS and adjustments made using laser light, even after it has been packaged.
Business Unit Electronic Packaging
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