Oil pressure sensor MEMS(Micro? Electromechanical? System (micro-electromechanical system) refers to a micro-electromechanical system integrating micro-sensor, actuator, signal processing and control circuit, interface circuit, communication and power supply.
1. Features MEMS pressure sensor can realize high-precision and low-cost mass production by using design technology and manufacturing technology similar to integrated circuits, thus opening the door for low-cost large-scale use of MEMS sensors for consumer electronics and industrial process control products and making pressure control simple, easy to use and intelligent.
The traditional mechanical pressure sensor is based on the deformation of metal elastic body, and the elastic deformation of mechanical quantity is converted into electric quantity conversion output, so it can't be as small as MEMS pressure sensor, as small as integrated circuit, and the cost is much higher than MEMS pressure sensor. Compared with the traditional mechanical quantity sensor, the size of MEMS pressure sensor is smaller, and the maximum is less than one centimeter. Compared with the traditional "mechanical" manufacturing technology, its cost performance is greatly improved.
Second, the principle of MEMS pressure sensor At present, MEMS pressure sensors include silicon piezoresistive pressure sensor and silicon capacitive pressure sensor, both of which are micromechanical electronic sensors produced on silicon wafers.
Silicon piezoresistive pressure sensor adopts Whiston bridge composed of high-precision semiconductor resistance strain gauge as the measuring circuit of electromechanical conversion, which has high measuring accuracy, low power consumption and extremely low cost. If there is no pressure change, the output of the piezoresistive sensor of Whiston Bridge is zero, and there is almost no power consumption. . Lithographic plate of strain bridge of silicon piezoresistive pressure sensor.
MEMS silicon piezoresistive pressure sensor adopts the inner wall of circular stress cup silicon film with fixed periphery, and uses MEMS technology to directly carve four high-precision semiconductor strain gauges at the maximum stress on its surface to form a Whiston measuring bridge. As an electromechanical conversion measuring circuit, the physical quantity of pressure is directly converted into electric quantity, and the measuring accuracy can reach 0.0 1-0.03%FS.
Capacitive pressure sensor uses MEMS technology to fabricate diaphragm grating on silicon wafer. The upper diaphragm grid and the lower diaphragm grid form a group of capacitive pressure sensors. The upper diaphragm grid moves downward under pressure, which changes the distance between the upper diaphragm grid and the lower diaphragm grid, and also changes the capacitance between plates, that is, △ pressure =△ capacitance.
Third, the application prospect of MEMS pressure sensor MEMS pressure sensor is widely used in automotive electronics fields such as TPMS, oil pressure sensor, automobile brake system air pressure sensor, automobile engine intake manifold pressure sensor (TMAP) and diesel engine common rail pressure sensor. Consumer electronic products such as tire pressure gauge, sphygmomanometer, cabinet scale, health scale, washing machine pressure sensor, dishwasher, refrigerator, microwave oven, vacuum cleaner, air conditioning pressure sensor, washing machine level control pressure sensor, water dispenser, dishwasher, solar water heater, etc. Industrial electronic products, such as digital pressure gauges, digital flow meters, industrial ingredients weighing, etc.
Typical MEMS pressure sensor chip structure and electrical principle, the left picture shows the electrical schematic diagram, that is, the Whiston bridge composed of resistance strain gauges, and the right picture shows the internal structure of the chip. Typical MEMS pressure sensor chips can be used to produce various pressure sensor products. MEMS pressure sensor chip can be packaged in one package (MCM) with instrumentation amplifier and ADC chip, which makes it easy for product designers to design the final product with this highly integrated product.
Fourthly, design, produce and sell the design, production and sales chain of MEMS pressure sensor mold. At present, most processes of integrated circuit 4-inch wafer production line can be used for MEMS production. However, three unique MEMS process equipments need to be added: double-sided mask aligner, wet etching table and bonding machine. Manufacturers of pressure sensor products need to add expensive standard pressure detection equipment. For MEMS pressure sensor manufacturers, it is very important and urgent to develop sales experience and channels in the fields of automotive electronics and consumer electronics. In particular, in recent years, the demand for MEMS pressure sensors in the automotive electronics field has surged. For example, the annual demand of Jie Shen Electronics is about 2-3 million units.
5. The similarities and differences between 5.MEMS chip and IC are different from the traditional IC industry which focuses on two-dimensional static circuit design. Based on theoretical mechanics, MEMS designs three-dimensional dynamic products with circuit knowledge. Micron-scale mechanical design will rely more on experience, and design and development tools (Ansys) are also different from traditional IC (such as EDA). In addition to a large number of traditional IC processes, MEMS processing also needs some special processes, such as double-sided etching and double-sided lithography. Compared with traditional integrated circuits, MEMS technology is simple and there are fewer photolithography steps. Some non-standard special processes in MEMS production need to be adjusted according to the requirements of the products. Due to the close cooperation of product design, process design and production, IDM mode is superior to Fabless+Foundry mode. MEMS requires high packaging technology. The production line of traditional semiconductor manufacturers is facing elimination, even if it is used to produce LDO, the profit is very low, but if MEMS is produced, it can get higher profit. Each wafer on the line can produce 5-6k qualified MEMS pressure sensors. After each wafer is sold, the gross profit can be 7- 10 times of the cost. Switching to MEMS has little change in the process requirements of manufacturers, limited additional auxiliary equipment, low investment and high efficiency. The integrated packaging of MEMS chip and IC chip is a new trend of integrated circuit technology development and a new opportunity for traditional IC manufacturers.
Cost estimation of producing MEMS pressure sensor chip with intransitive verb The cost estimation of producing MEMS pressure sensor chip on wafer production line is shown in the table below. The newly-increased fixed expenses refer to the personnel expenses and depreciation of new equipment invested in this project (personnel: 65,438 experts +0+2 MEMS designers +4 engineers +5 technicians+12, annual expenses 1.47 million yuan, and new equipment investment of 6.5 million yuan). The existing cost refers to the cost used under the condition of 5 lithography (including the shared cost of labor, chemicals, water and electricity, spare parts, etc.). ); The material cost of silicon wafer refers to the price of double-throwing 4-inch silicon wafer.
Many of the above words also contain some technical terms. We can choose to skip the novice level and look at the introduction of some main functions. But also has application prospect. It can be seen from the application prospect that we can't lack it in the future, whether it is a big machine or a small machine, it can help the machine work better. If you are engaged in this machine, you can take a closer look, because this is a compulsory course in this field. Finally, I hope the above can bring some help to everyone.