PCB News - Ceramic circuit board and MEMS sensor

Ceramic PCB are ideal packaging materials for a new generation of large-scale integrated circuits and power electronic modules. It is widely used in our lives and has a variety of applications. Today we will discuss one of the practical applications of ceramic circuit boards-MEMS sensors.

What is a MEMS sensor?

MEMS sensor is a typical sensor device based on micro-electromechanical system. It refers to a device or system that can be manufactured in batches and integrates microstructures, microsensors, microactuators, and signal processing and control circuits. Its characteristic size is generally in the range of 0.1 μm to 100 μm. MEMS integrates many cutting-edge achievements of today's science and technology. MEMS sensors can not only perceive the measured parameters and convert them into signals that are convenient for measurement, but also analyze, process, identify and judge the obtained signals, so they are vividly called It is a smart sensor.

Wide application of MEMS

Applied in automotive electronics

MEMS pressure sensors are mainly used to measure air bag pressure, fuel pressure, engine oil pressure, intake pipe pressure and tire pressure. This sensor uses monocrystalline silicon as a material, and uses MEMS technology to fabricate a force-sensitive diaphragm in the middle of the material. Then, impurities are diffused on the diaphragm to form four strain resistors, and then the strain resistors are connected by a Wheatstone bridge. Circuit to obtain high sensitivity. MEMS pressure sensors for vehicles have several common forms such as capacitive, piezoresistive, differential transformer, and surface acoustic wave.

The principle of MEMS accelerometers is based on Newton’s classical laws of mechanics. It usually consists of a suspension system and a detection mass. The acceleration is detected by the offset of the micro-silicon mass block. It is mainly used for automobile airbag systems, anti-skid systems, and car navigation. Systems and anti-theft systems, among which, capacitive MEMS accelerometers have the characteristics of high sensitivity and minimal temperature influence, and are the mainstream products in MEMS micro-accelerometers. Micro gyroscope is a kind of angular rate sensor, mainly used for GPS signal compensation of car navigation and car chassis control system. There are mainly vibration type and rotor type. The most widely used is the vibrating gyroscope, which uses the Coriolis effect generated when a vibrating mass of monocrystalline silicon or polycrystalline silicon is rotated by a base to sense the angular velocity. For example, when a car is turning, the system uses a gyroscope to measure the angular velocity to indicate whether the steering wheel is in place, and actively applies appropriate brakes on the inner or outer wheels to prevent the car from leaving the lane. Usually, it forms an active control with a low accelerometer. system.

Applied to smart wearable devices

In the daily training of athletes, MEMS sensors can be used to measure 3D human movements, record every movement, and coaches analyze the results and compare them repeatedly in order to improve athletes' performance. With the further development of MEMS technology, the price of MEMS sensors will also decrease, which can also be widely used in public gyms. In terms of skiing, the pressure sensor, acceleration sensor, gyroscope, and GPS in 3D motion tracking allow users to obtain extremely accurate observation capabilities. In addition to providing snowboard movement data, it can also record the user's location and distance. The same is true for surfing. The 3D motion tracking installed on the surfboard can record information such as wave height, speed, surfing time, paddleboard distance, water temperature and calories consumed.

Applied in the field of intelligence

Now, more and more MEMS sensors are applied to mobile phones to improve the user experience of mobile phones. High-end mobile phones are generally equipped with several MEMS products such as acceleration sensors, pressure sensors, gyroscopes, silicon microphones, fingerprint sensors, distance sensors, ambient light sensors, and magnetic sensors. Let's talk about one of the applications-the application in mobile photography. Mobile phone photography brings us the convenience of taking pictures wherever we go, but in the face of complex environments and diverse photo scenes, human hands will inevitably shake when taking pictures, such as walking, running, lying down and taking pictures, or extending hands or hands. Holding the selfie stick to take a selfie, no matter what kind of shaking, it will cause the blurry distortion of the picture. Before MEMS was applied to mobile phone photography, the camera of the mobile phone was mainly used to realize the anti-shake method (referred to as the lens anti-shake technology) by moving the lens group by the voice coil motor. Big limitations. With the successful application of MEMS sensors in mobile phone photography, another high-end anti-shake technology in the market: multi-axis anti-shake has been successfully transplanted to mobile phones, that is, using mobile image sensors to compensate for shaking. During the shooting process, Through the gyroscope to sense the instantaneous jitter in the photographing process, relying on sophisticated algorithms, calculate the range of movement that the motor should make and quickly compensate within one hundredth of a second. With the technical advantages of MEMS fast and precise control, the mobile phone can still show clear and sharp pictures even when the device is shaken by a large amplitude.

Applied in automotive electronics

Stone ceramic PCB, the thermal expansion coefficient of ceramic and chip is close, and the ceramic does not contain organic components and has a long service life. Even in the environment of high temperature, high pressure, high vibration, and high chemical corrosion of the car, it can still protect the normal operation of the equipment and effectively extend it The product life cycle reduces maintenance costs and further improves product quality.

Applied to mobile devices and smart wearable devices

Aluminum nitride ceramic PCB have high thermal conductivity (thermal conductivity 180 W/(mK) ~ 260 W/(mK)), which can effectively meet the high heat dissipation requirements of MEMS sensors. At the same time, the ceramics produced by Stone The circuit board line/spacing (L/S) resolution can be 20μm, and it supports customization, which can better realize the integration and miniaturization of MEMS sensor devices, so as to meet the light and thinness of current mobile devices and smart wearable devices Hard demand.