CN1693901A - High value speedometer - Google Patents

Abstract

The invention discloses a high-g value accelerometer. The accelerometer is composed of an acceleration sensitive beam, two circuit boards and an SOI silicon micro-solid piezoresistive chip; the acceleration sensitive beam has symmetrical steps, and the two circuit boards are symmetrically glued together. Connected to the steps, the SOI silicon micro-solid piezoresistive chip is arranged in the middle of the acceleration sensitive beam, and the silicon micro-solid piezoresistive chip is connected to the two circuit boards through wires. The invention adopts double-ended fixed acceleration-sensitive beams and silicon-isolated SOI silicon micro-solid-state piezoresistive chips to form a silicon micro-strain solid-state piezoresistive high-g sensor, which solves fuze systems such as armor-piercing, bunker penetration, ground-penetrating weapons, and aerial bombs. The high-g acceleration measurement problem. At the same time, the eutectic welding technology is adopted to solve the problem of sensor hysteresis. The accelerometer sensor has the characteristics of high measurement range, good dynamic characteristics, strong weather resistance, high measurement accuracy, and high overload, and can meet the measurement needs of high g-value acceleration of fuze systems such as armor penetration, bunker penetration, ground penetrating weapons, and aerial bombs. .

Description

High-g Accelerometers

Technical field

The invention belongs to the field of production and application of acceleration sensors, and relates to a high-g value accelerometer based on SOI technology.

Background technique

When armor-piercing, bunker penetration, ground-penetrating weapons attack targets, and aerial bombs are launched, the acceleration information generated is one of the main references for triggering the disarming of the fuze system and detonating the detonation system. With the development of new military ideas and the continuous progress of weapon technology, the test requirements for the acceleration of weapon systems are getting higher and higher, and the existing acceleration sensor devices can no longer meet the needs of modern warfare. For example, in the process of new missiles and rockets attacking targets, accelerations above g×10 ⁵ will be generated, and the acceleration measurement device is required to accurately measure the acceleration value and provide the measurement signal to the fuze control system; and when the acceleration value reaches g×10 When the value is ⁵ , the accelerometer should have an overload protection system to avoid damage to the accelerometer caused by high acceleration shocks. Most of the existing accelerometers can only withstand the acceleration below 50000g, which cannot meet the requirements. According to the data search carried out by the applicant, there are no products and related reports of high-g value accelerometers at present.

Contents of invention

The purpose of the present invention is to provide a high-g accelerometer based on SOI technology, which integrates stress sensitivity and force-electric conversion detection, and is suitable for armor-piercing, bunker penetration, ground-penetrating weapons and aerial bombs High-g acceleration measurements for isofuze systems.

The technical solution to achieve the above object is a high-g value accelerometer, which is characterized in that the accelerometer is composed of an acceleration sensitive beam, two circuit boards and an SOI silicon micro-solid piezoresistive chip; the acceleration sensitive beam has a symmetrical There are positioning grooves at both ends of the step, and two circuit boards are bonded symmetrically on the step. The SOI silicon micro-solid piezoresistive chip is set in the middle of the acceleration-sensitive beam, and the silicon micro-solid piezoresistive chip is connected to the two circuit boards through wires. .

The invention adopts double-ended fixed acceleration-sensitive beams and silicon-isolated SOI silicon micro-solid-state piezoresistive chips to form a silicon micro-strain solid-state piezoresistive high-g sensor, which solves fuze systems such as armor-piercing, bunker penetration, ground-penetrating weapons, and aerial bombs. The high-g acceleration measurement problem. At the same time, the eutectic welding technology is adopted to solve the problem of sensor hysteresis. The accelerometer sensor has the characteristics of high measurement range, good dynamic characteristics, strong weather resistance, high measurement accuracy, high overload, etc., and can meet the measurement needs of high g-value acceleration of fuze systems such as armor-piercing, bunker penetration, ground-penetrating weapons, and aerial bombs. .

Description of drawings

Fig. 1 is a schematic diagram of the installation of the high-g value accelerometer of the present invention.

Fig. 2 is a structural composition diagram of the high-g value accelerometer of the present invention.

Fig. 3 is a working principle diagram of the elastic element of the present invention.

Figure 4 Structural diagram of the acceleration sensitive beam.

Fig. 5 is a structure diagram and a photomicrograph of an SOI silicon micro-solid piezoresistive chip.

Figure 6 is a physical photo of the high-g accelerometer.

Below in conjunction with accompanying drawing and below in conjunction with accompanying drawing and the embodiment that the inventor realizes and the present invention is used for armor-piercing, bunker penetrating, ground-penetrating weapon and aerial bomb etc. fuze system uses high-g value accelerometer working principle to be described in further detail.

Detailed ways

With reference to Fig. 1, Fig. 2, a kind of high-g value accelerometer is made of acceleration sensitive beam 1, two circuit boards 2, 3 and SOI silicon micro-solid piezoresistive chip 4; Symmetrical steps are arranged on this acceleration sensitive beam 1, There are positioning grooves at both ends, and the two circuit boards 2 and 3 are bonded symmetrically on the steps. The SOI silicon micro-solid piezoresistive chip 4 is arranged in the middle of the acceleration sensitive beam 1. The SOI silicon micro-solid piezoresistive chip 4 and the two circuit boards Boards 2 , 3 are connected by leads 5 .

The high-g value accelerometer is connected and fixed with the carrier (fuze assembly) by two fixing screws 6 through two positioning grooves on a plane, so as to realize the positioning of the accelerometer. During installation, the acceleration direction is perpendicular to the length direction of the acceleration sensitive beam 1 .

Referring to Fig. 3, when the acceleration a shown in the figure perpendicular to the length direction of the acceleration sensitive beam 1 is generated, it is equivalent to the effect of generating a distributed force p on the acceleration sensitive beam, according to Newton's law:

p=ρhwa (1)

In the formula: a is the measured acceleration, the unit is m/s ² ; h, w are the height and width of the beam, the unit is m; ρ is the density of the beam material, the unit is Kg/m ³ .

The acceleration sensitive beam 1 deflects and deforms under the action of acceleration. The SOI silicon micro-solid piezoresistive chip 4 packaged at the midpoint of the acceleration-sensitive beam 1 through eutectic welding can sense the change in the stress of the acceleration-sensitive beam 1, so that the bridge of the Wheatstone bridge in the SOI silicon micro-solid piezoresistive chip 4 The arm resistance changes proportionally because:

$\frac{\mathrm{<span\; class="notranslate">\; \&Delta;R</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;\&rho;</span>}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&pi;\&sigma;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Under the excitation of a fixed power supply, the electric bridge outputs an electrical signal. The change of stress is proportional to the magnitude of the distribution force p, so the magnitude of p can be measured through the magnitude of the output signal, and the measured acceleration a can be calculated by formula (1). By changing the structural parameters (width, length and thickness) of the acceleration sensitive beam 1, accelerometers with different measurement ranges can be designed.

For the acceleration sensor, considering the requirements of the sensor accuracy index, when designing the accelerometer range, the strain detected by the SOI sensitive element at the detection point of the acceleration sensitive beam 1 is ≤500με as the calculation basis, and the width of the beam is determined by the pasted silicon piezoresistive chip Determined according to the requirements, the length and thickness parameters of the acceleration sensitive beam are calculated according to the allowable strain. Considering the packaging factor and the volume limit during installation, the structure of the designed acceleration-sensitive beam is shown in Figure 4. Under the action of the distributed force p, the middle part of the elastic beam 1 of the accelerometer produces the largest strain, which is the stress concentration point. The SOI silicon micro-solid piezoresistive chip 4 is installed in this part, which can maximize the sensitivity of the sensor.

The required SOI silicon micro-solid piezoresistive chip 4 is manufactured on the (100) silicon crystal plane by adopting SOI technology and various silicon micromachining technologies. The structure of the SOI silicon micro-solid piezoresistive chip 4 is shown in Figure 5(a), including SiO ₂ of 4000 Å, which is used to isolate the measurement circuit layer from the silicon substrate, and is epitaxially obtained by LPCVD to obtain a single crystal silicon that satisfies the piezoresistive effect Layer thickness (about 1.5~2u) and upper layer 0.1~0.3u silicon nitride stress matching layer and protective layer, where the silicon nitride layer is used to eliminate the influence of thermal stress caused by the difference in thermal expansion coefficient between silicon and SiO ₂ . The resistance strip adopts a four-fold structure and embossed form, which has the advantages of high detection sensitivity. In order to better realize the bonding operation, the back side of the SOI silicon micro-solid piezoresistive chip 4 is plated with gold.

Due to the adoption of SOI technology and titanium-platinum-gold beam lead structure, the chip can work under the condition of 200 ℃ ~ 400 ℃, which solves the influence of leakage current at high temperature and meets the requirements of pressure measurement in harsh environments such as high temperature.

The SOI silicon micro-solid piezoresistive chip 4 is packaged in the middle of the fixed support beam of the acceleration elastic element 1 by using eutectic welding technology. Among them, the upper surface of the acceleration elastic element 1 is treated with gold plating, the solder composition of eutectic welding is 98Au/2Si, and the SOI silicon micro-solid piezoresistive chip 4 is welded to the middle of the acceleration elastic element 1 under the environmental conditions of 380°C-430°C. Eutectic welding has high welding strength, smooth welding, small thermal resistance between SOI silicon micro-solid piezoresistive chip 4 and acceleration elastic element 1, and high temperature resistance.

The photomicrograph of the SOI silicon micro-solid piezoresistive chip 4 completed by the inventor according to the above technical scheme is shown in FIG. 6 . Its dimensions: 11mm(L)×7mm(W)×1.5mm(H), measuring range: g×10 ⁵ ~g×20 ⁵ ; sensitivity: 0.5μV/g, weight: 0.7g. Experiments have proved that the design purpose has been achieved.

Claims (3)

1. a high g value accelerometer is characterized in that, this accelerometer is made of acceleration sensitive beam (1), two circuit boards (2,3) and SOI silicon micro-solid piezoresistive chip (4); There are symmetrical steps on the beam (1), with positioning grooves at both ends, two circuit boards (2, 3) are symmetrically bonded on the steps, and the SOI silicon micro-solid piezoresistive chip (4) is arranged on the acceleration sensitive beam (1 ) in the middle, the SOI silicon micro-solid piezoresistive chip (4) is connected with two circuit boards (2, 3) through lead wires (5). 2. The high g value accelerometer as claimed in claim 1, is characterized in that, described SOI silicon micro-solid piezoresistive chip (4) and acceleration sensitive beam (1) are bonded on by eutectic welding or other encapsulation process Together. 3. The high-g value accelerometer according to claim 1, characterized in that, the back side of the SOI silicon micro-solid piezoresistive chip 4 is plated with gold.

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