Bridge strain gauge structure

Abstract

FIELD: instrument making.SUBSTANCE: invention can be used as sensitive elements for creating sensors (S) of mechanical parameters for various purposes. The bridge strain gauge structure (BSGS) without a substrate comprises four semiconductor strain gauges (SGS), four contact pads, SiO2 oxide on the back side of the structure and lead-out conductors connected to each other monolithically, while depending on the design of the BSGS, the middle of their parallel located SGS threads or diagonally located contact pads of the bridge are connected to each other by shunting jumpers that reinforce the structure and increase its strength, the jumpers are made in one piece simultaneously with the elements of the BSGS, from the same semiconductor material, while the width of each jumper exceeds the width of the SGS thread by 3 times, and the thickness of SiO2 on the back side of the structure is increased and is 0.8…1.2 mcm.EFFECT: increase in the strength, rigidity and reliability of BSGS, simplification of work with them, a reduction in the thickness of the adhesive layer and, as a result, a reduction in the error of sensors from elastic imperfections of the adhesive.2 cl, 10 dwg

Description

[0001] The invention relates to instrument engineering and can be used in the manufacture of durable and reliable sensing elements (SE) for creating sensors (S) for force and other mechanical parameters. Known SES are constructed on bridges of discrete semiconductor strain gauges (SST) on substrates made of organic materials, which are attached to the elastic elements (EE) of the sensors using adhesives [1]. Disadvantages include: the difficulty of handling discrete SSTs due to their small size and fragility, the labor-intensive selection of four SSTs with similar parameters in a Wheatstone bridge, and the difficulty of securing and mounting them on the EE for the same reasons.

[0002] The closest in technical essence to the declared one are bridge strain gauge structures (BSG) without a supporting substrate, containing four PTRs, as a rule, made of bulk Si p +type with a specific resistance l = 0.02 Ohm cm, monolithically combined into bridges [2]. Despite all the advantages of MTS, due to their small size, there is one serious drawback due to their fragility, low strength, and the difficulty of working with them. The dimensions of the structures are: overall dimensions of 3 ... 6 mm, thickness of 20 ... 25 μm, oxide thickness on the back side of the structure - 0.5 ... 0.8 μm, PTR thread width of 100 ... 150 μm. Therefore, MTS require delicate, delicate handling, which complicates work with them during welding of leads, precise installation and gluing on the UE and their assembly (almost like shoeing a flea).

[0003] The objectives of the invention are: increasing the strength, rigidity and reliability of MTS, simplifying work with them, reducing the thickness of the adhesive layer and, as a result, reducing the error D from elastic imperfections of the adhesive.

[0004] The stated objectives are achieved by the fact that, depending on the design of the MTS, the centers of their parallel PTR threads or diagonally located contact pads of the bridge are connected to each other by shunting jumpers, reinforcing the structure and increasing its strength; the jumpers are manufactured in one piece simultaneously with the MTS elements, from the same semiconductor material, while the width of each jumper exceeds the width of the PTR thread by 3 times, and the thickness of SiO2 on the back side of the structure is increased and is 0.8 ... 1.2 μm; and by the fact that, after fixing the MTS on the elastic element of the sensor, all shunting jumpers must be electrically and, in places remote from the PTR threads, mechanically disconnected from the bridge by breaking them and completely removing the remains of the jumpers at the breaks, in order to exclude possible conductivity.

[0005] Figure 1 shows various types of MTS designs: options a, b, c - for UE operating under tension-compression, bending, torsion and shear; g - for membrane pressure sensors; d - for use in UE with stress concentrators in the form of holes.

[0006] Fig. 2 shows the same structures equipped with shunt jumpers that increase the strength and rigidity of the MTS; the dotted line also indicates the places where the jumpers should be removed. For better understanding and clarity, on one of the sheets with figures, the places where the jumpers should be removed (dotted line) are painted in red. Designations adopted in the figures, where all dimensions are given in µm: 1-PTR; 2 - contact pads for welding the leads; 3 - leads made of gold wire ϕ 30...50; 4 - shunt jumpers; length, width and thickness of the PTR thread: l=3000-4000; B=100...150; thickness 20...25; thickness of the SIO2 oxide (not shown in the Figures) on the back side of the MTS is 0.8...1.2 µm; nominal resistance of the PTR Rн=100...150 Ohm≅R1 ≅R2≅R3≅R4; overall dimensions of the PTR bridges without terminals (A×A)→A=3000…5500; B1=300-width of the shunt jumpers; maximum internal opening of the concentrator D=5000; max membrane diameter D1=6000, max MTS length for this diameter L=5500, its max width B2=1100 (for smaller membrane diameters D1=3000,4000 the structure is made without shunts); Epit=5…7 V-supply voltage; Uout=40…100 mV-output signal; - crystallographic directions and (111) - crystallographic plane in the anisotropic material Si. The sensor with the RE, on which the MTS is fixed, and, using a burr or a diamond cutter, all the shunt jumpers are broken, and a voltage E is applied to the bridge, operates as follows. When the sensor is loaded with the measured parameter (force, pressure, acceleration, etc.), the RE is deformed, while two STRs of the bridge are stretched, and the other two STRs are compressed, in this case: the first two increase the resistance by +ΔR, and the other two decrease its value by -ΔR. As a result, a signal Uout proportional to the measured parameter is formed at the output D. The advantages of using the proposed MTS are as follows:

[0007] • the strength, rigidity and reliability of the MTS are increased by introducing shunting jumpers into its design that are monolithically connected to it, reinforcing and strengthening the entire structure;

[0008] • The working conditions of the MTS operator are improved by increasing their strength, rigidity and reliability;

[0009] • the values ​​of elastic imperfections D are reduced due to the absence of a substrate;

[0010] • Reducing the thickness of the adhesive layer for gluing MTS by increasing the thickness of SiO2.

[0011] Sources of information used:

[0012] 1. "Semiconductor strain gauges" ed. M. Dina, 1965, p. 125.

[0013] 2. Bazhin Yu.M., Tsyvin A.A. “The state of semiconductor electrical strain gauges and prospects for its development”, journal “Instruments and control systems” No. 1, pp. 17-20, 1976.

Claims

1. A bridge strain gauge structure (BSG) without a substrate, containing four semiconductor strain gauges (SSG), four contact pads, SiO2 oxide on the back side of the structure and lead-out conductors connected to each other monolithically, characterized in that, depending on the design of the BGS, the middles of their parallel-arranged SSG threads or diagonally-arranged contact pads of the bridge are connected to each other by shunting jumpers that reinforce the structure and increase its strength, the jumpers are manufactured in one piece simultaneously with the BGS elements, from the same semiconductor material, wherein the width of each jumper exceeds the width of the SSG thread by 3 times, and the thickness of SiO2 on the back side of the structure is increased and is 0.8...1.2 μm.

2. The MTS according to paragraph 1, characterized in that, after securing the MTS on the elastic element of the sensor, all shunt jumpers must be electrically and, in places remote from the PTR threads, mechanically disconnected from the bridge by breaking them and completely removing the remains of the jumpers in the breaks, in order to eliminate possible conductivity.

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