Neither pure copper nor solid gold can be anodically bonded to glass. It is only the gold coating on the copper which allows
a joint to be built up as a result of the copper ions diffusing into the gold layer, but not many of them being able to migrate
into the glass. To encapsulate microstructures produced by the LIGA technique, anodic bonding of gold-coated copper to Corning
0211-type glass was studied. For demonstration purposes, a glass platelet made of Corning 0211 was anodically bonded to a
LIGA linear actuator consisting of electroplated copper coated with 1 μm of gold. A better understanding about the decisive
parameters in anodic bonding was obtained by varying the bonding temperature and the thickness of the gold layer. Glass can
be bonded on to the entire surface of gold layers 0.5–1 μm thick at temperatures as low as 300 °C; however, when the systems
cool to room temperature, stress-induced cracks arise in the glass. On the other hand, thicker gold layers of 2.5 to 10 μm
thickness require higher bonding temperatures for the same period of heating, but prevent the occurrence of such cracks because
of their higher ductility.
Received: 11 December 1997/Accepted: 11 March 1998