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|High Voltage, High Impedance Resistors Small Sized for Medical Applications|
|Keywords: high ohmic resistor network , high voltage resistors, alumina substrate|
|Actually the requests for specialized resistor networks for medical applications require several development steps to cope with higher functionality at size restricted layouts. Applications for other commercial use are guided by a subset of these requirements - this paper deals only with the first named issue. To reach the restrictions for weight and size can directly translated to smallest available chips size and highest specific (square's) ohmic values. Special packaging issues come along for implant and hand held devices: flip chip mounting with solder balls. All of these requirements are met by RMT's latest developed resistor network. The design is based on the high impedance material CrSi which offers a factor 4 higher sheet resistance between 500 and 1500 ohm/square compared with the standard NiCr; the higher TCR by a factor of 5 doesn't have much influence due to the constant environment temperature of use. Designed line width is just above 8μm, to meet size requests. These layers can be manufactured on different substrates like alumina, fused silica and Si – wafers. The maximum voltage applied to the resistor network is taken into account at the applied layout rules and has to be tested and qualified separately. Packaging requests led to a flip chip arrangement with standard solder balls; a passivation layer was realized; possible solutions are: polyimide, a SiOx – layer and a hermetic housing. Other chip connecting possibilities are wire bonding and conductive adhesive bonding, but will require more space. The customer's manufacturing technique and logistic may use tape and reel or chip tray delivery optimized for mounting.|
|Dr. Wolfgang Tschanun MBA, Head of Micro Systems Technology
Reinhardt Microtech AG
Wangs, St. Gallen, CH - 7323,