Michitaka Shimazoe

A special silicon diaphragm pressure sensor with high output and high accuracy

Abstract A conventional silicon diaphragm sensor cannot be used in a low pressure range that requires high output and high accuracy. This disadvantage arises from a large pressure-induced deflection of the diaphragm, which is known as the balloon effect. In order to solve this problem, a silicon diaphragm with a center boss has been developed. In this sensor, an annular groove is formed in the back surface of the diaphragm and diffused piezoresistive gagues are formed radially adjacent to the outer and inner edges of the groove on the top surface. Experimental results are explained by a two-cantilever model. The accuracy of this sensor (0.17% of full scale) is ten times better than that of a conventional one in the low pressure range (5 to 100 kPa full scale) and is the same under front and back pressures. These characteristics are achieved in a wide temperature range, from −40 to 120 °C.

Differential Pressure/Pressure Transmitters Applied with Semiconductor Sensors

The optimum design for silicon diaphragm-type pressure sensors and that for a sensing body of the transmitters have been considered. Three types of sensors, which have different section shapes, have been developed for measuring wide-range pressure with high sensitivity and good linearity. The transmitters of the range from 0-100 Pa up to 0-50 MPa with an accuracy of 0.2 percent have been developed. For a differential pressure transmitter a three-metal diaphragm structure has been devised to protect the sensor from an overpressure. The characteristics of the transmitters are high accuracy, high reliability, and long-term stability.

Cantilever-type displacement sensor using diffused silicon strain gauges

Abstract Two kinds of alloys have been developed as cantilever and solder materials which are suitable for semiconductors. The cantilever material is an ironnickelcobalt ternary alloy that has a high elasticity with a tensile strenght of 1GPa, and a low thermal expansion coefficient 50 × 10 −7 /K. The material for the solder is goldcoppergermanium ternary eutectic alloy that has a tensile strength of 1.1 GPa. Two strain gauges were diffused in parallel on a silicon pellet, and the pellet was bonded by the alloy solder on each surface of the cantilever, taking into account linearity and temperature effect. It was confirmed that the linearity was less than ±0.1% and a zero-point shift was under ±0.1% after 10 7 repeated stresses. The temperature effect was less than ±05% over a range of 230 – 390K using a non-linear compensation.