CN103196593B - Resonance type micro-machinery pressure sensor and low-stress assembling method of resonance type micro-mechanical pressure sensor chip - Google Patents

Abstract

The invention discloses a resonant pressure sensor and a low-stress assembling method for its chip, which comprises: a tube seat with a cavity for placing a sensor chip in the middle, and a plurality of bars for connecting with the sensor chip Electrically connected tube pins; sensor chip, which includes a differential detection resonant beam placed along the diagonal of the sensor chip for pressure detection; fixed bead, which is horizontally placed on the differential detection resonant beam of the sensor chip, for use The sensor chip is fixed on the tube base; the tube cap is covered on the tube base, and its edge is fixedly connected with the edge of the tube base. The resonant pressure sensor chip is mechanically fixed to realize the assembly without hard connection with the shell, and there is no residual stress after assembly, which effectively reduces the influence of mechanical stress and thermal stress caused by sensor assembly.

Description

Resonant micromachined pressure sensor and low-stress assembly method for sensor chip

technical field

The invention relates to the field of micromechanical pressure sensors and the field of sensor packaging/assembly technology, in particular to a resonant micromechanical pressure sensor and a low-stress assembly method for a sensor chip.

Background technique

Micro-Electro-Mechanical Systems (MEMS for short) technology is a cutting-edge technology based on microelectronic technology and micromechanical technology. Sensors processed by MEMS technology have technical advantages such as small size, light weight, and mass production, and have received more and more research attention.

Pressure sensors based on MEMS technology are mainly divided into three categories: piezoresistive, capacitive and resonant. Compared with the other two types of pressure sensors, the resonant pressure sensor has outstanding advantages such as high precision and good stability, and is known as a new generation of pressure sensors.

The resonant micromechanical pressure sensor is a high-precision pressure sensor, which is based on mechanical resonance technology and uses resonant elements (such as resonant beams) as sensitive elements to realize pressure detection sensors. The working principle of the resonant pressure sensor is to use the change of pressure to change the resonant frequency of the resonant oscillator, and indirectly measure the pressure by measuring the change of frequency.

Due to the extremely high sensitivity of the resonant pressure sensor, it is very sensitive to factors that cause stress changes in the resonant beam (such as ambient temperature, packaging stress, assembly stress, etc.), so the packaging and assembly of the resonant pressure sensor chip on the tube base, etc. The method and process become the main factors restricting the comprehensive performance of the sensor. Yokogawa Corporation of Japan achieves chip assembly by introducing a silicon wafer with a thickness several times that of the chip between the sensor chip and the tube holder. The British Druck Company uses a long glass tube that is several times the thickness of the sensor chip and welds the tube holder to realize chip assembly. The patent application (CN201010218423.2) realizes chip assembly through a cantilever beam structure. These methods still require processes such as bonding or welding to realize the assembly between the sensor chip and the tube base, so that the sensor chip still has assembly residual stress after assembly, and the release of residual stress and changes in ambient temperature will lead to long-term output stability of the sensor. and temperature characteristics.

The most important technical defect in the prior art: the existing sensor chip assembly method either uses long glass tubes to be welded to the tube base, or uses thick silicon wafers to bond, or uses cantilever beam structures to bond, these methods are still unavoidable The residual stress problem after the sensor chip and the tube base are assembled.

Secondary technical defects in the existing technology: the existing sensor chip assembly methods are relatively complicated, and affected by the assembly process, the residual stress of the sensor after chip assembly may be inconsistent, resulting in poor consistency of sensor performance.

Contents of the invention

The purpose of the present invention is to provide a MEMS technology-based silicon resonant pressure sensor and a low-stress assembly method for its chip, and further improve the comprehensive performance of the resonant pressure sensor.

The invention discloses a resonant pressure sensor, which includes:

A tube base, which has a cavity for placing the sensor chip in the middle, and a plurality of tube pins for electrically connecting with the sensor chip are distributed on its edge;

A sensor chip, which includes a differential detection resonant beam placed along the diagonal of the sensor chip for pressure detection;

a fixed bead, which is horizontally placed on the differential detection resonant beam of the sensor chip, for fixing the sensor chip on the stem;

The tube cap is covered on the tube base, and its edge is fixedly connected with the edge of the tube base.

The invention also discloses a low-stress assembly method for a resonant pressure sensor chip, which includes:

Step 1, machining a cavity matching the size of the sensor chip on the tube base, and embedding the sensor chip in the cavity;

Step 2. Contact the fixing bead to a corner of the sensor chip, and fix the fixing bead on the tube base with screws, so as to fix the sensor chip in the cavity of the tube base;

Step 3, electrically connecting the needles distributed on the edge of the tube base with the electrode pads on the edge of the sensor chip through the lead wires;

Step 4. Cover the tube base with a tube cap matching the tube base, and connect them together by bonding or welding.

The beneficial effects of the present invention are: (1) The resonant pressure sensor chip realizes the assembly without hard connection with the shell through mechanical fixing, and there is no residual stress after assembly, which effectively reduces the mechanical stress and thermal stress caused by the assembly of the sensor (2) Compared with the existing assembly methods, the assembly process only adopts the method of mechanical fastening, and the assembly process is simple, easy and efficient.

Description of drawings

Fig. 1 is a schematic structural view of a resonant micromechanical pressure sensor in the present invention;

Fig. 2 is a structural sectional view of a resonant micromechanical pressure sensor in the present invention;

Fig. 3 is a structural schematic diagram of a resonant pressure sensor chip in the present invention;

Fig. 4 is a flow chart of the assembly method of the resonant micromechanical pressure sensor chip in the present invention;

Fig. 5 is a graph comparing temperature characteristic curves of the assembled resonant pressure sensor according to the assembly method proposed by the present invention and the prior art.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The invention discloses a resonant micromechanical pressure sensor and a low-stress assembly method for a sensor chip.

FIG. 1 shows a schematic structural view of the resonant micro-mechanical pressure sensor, and FIG. 2 shows a structural cross-sectional view of the resonant micro-mechanical pressure sensor. As shown in FIGS. 1 and 2 , the resonant pressure sensor includes a base 1 , a sensor chip 2 that is vacuum-packaged or air-tightly packaged, a fixed bead 3 and a cap 4 .

Preferably, the tube base 1 is a TO-18 circular tube base, and 18 pins 1c are evenly distributed along the edge of the tube base for the electrical connection of the sensor chip. The middle of the stem 1 has a square cavity 1a that matches the sensor chip 2. The length and width of the cavity are slightly larger than the sensor chip by more than 0.2mm, so that the sensor chip can be placed easily, but it should not be too large to avoid the sensor chip Arbitrary movement; there is a screw hole 1b on the outside of one corner of the square cavity, which is used to fix the bead 3, and the depth of the cavity is 0.1 mm or more greater than the thickness of the sensor chip. The socket can also be a socket of other shapes, and the number of needles on it can also be set according to needs, and the shape of the cavity for placing the sensor chip can also vary according to the shape and size of the sensor chip .

Fig. 3 shows a structural diagram of the resonant pressure sensor chip. As shown in Figure 3, the resonant pressure sensor chip 2 is a square sensor chip that matches the square cavity 1a on the stem 1, which is mainly composed of two groups placed along a diagonal of the sensor chip 2 Differential detection consists of resonant beams. Wherein, one set of differential resonant beams 2a is used for pressure detection, placed at one end of a diagonal line of the sensor chip 2, and another set of differential resonant beams 2b is used for backup, placed at the opposite end of the sensor chip 2 The other end of the angular line; each group of resonant beams is fixed and connected to the sensor chip 2 through the anchor point 2d. Soldering pads 2c are also distributed on the edge of the sensor chip 2 for electrical connection between the sensor chip 2 and the tube needle 1c on the tube base 1 .

The sensor chip 2 is fixedly placed at the cavity 1a on the tube base 1, and the fixed bead 3 is a soft rubber strip with small screws 6 on both ends, which is placed horizontally on the spare part of the sensor chip 2. on the resonant beam 2b, and the sensor chip 2 is fixed on the tube base 1 through the cooperation of the small screw 6 and the screw hole 1b.

The welding pad 2c on the sensor chip is connected to the pin on the tube base 1 through the lead wire 7 .

The tube cap 4 is a circular metal tube cap matching the size of the tube base 1, which is covered on the tube base 1, and its edge is fixedly connected with the edge of the tube base 1 by glue or welding .

A magnet 5 is also bonded on the outer surface of the cap 4 for electromagnetic excitation of the sensor chip.

Wherein, the tube base 1 is made of Kovar alloy material or a material with a similar expansion coefficient to silicon material; the fixing bead 3 is made of polytetrafluoroethylene, plexiglass or other insulating materials; the sensor chip 2 has at least one A group of differential resonant beams is used for detection; if the sensor chip does not require electromagnetic excitation, it can be packaged without a magnet.

The invention also discloses a method for assembling the resonant micromechanical pressure sensor chip.

Fig. 4 shows the assembly method of the resonant micromechanical pressure sensor chip described in the present invention, which includes the following steps:

Step 1), process a square cavity 1a matching the size of the sensor chip 2 on the metal tube base 1, and process a screw hole 1b outside a corner of the square cavity 1a; preferably, the cavity 1a is deeper than the sensor Chip thickness above 0.1mm;

Step 2), embedding the sensor chip 2 into the square cavity 1a in the metal stem 1, the height of the placed sensor chip 2 is lower than the upper surface of the metal stem 1, and the sensor chip 2 The spare resonant beam 2b is located on the side of the metal socket 1 with the screw hole 1b;

Step 3), lightly touch the fixed bead 3 with small screws on both ends to one corner of the sensor chip, so that the fixed bead is placed horizontally on the spare resonant beam 2b of the sensor chip 2, and is connected to the metal via the small screw. The interaction of the screw holes 1b on the tube base 1 tightens and fixes the fixing bead 3 on the metal tube base 1, so as to fix the sensor chip 2 in the cavity 1a of the metal tube base 1;

Step 4), the electrode pads 2c distributed on the edge of the sensor chip 2 are closely connected with the tube pins 1a evenly distributed on the edge of the metal stem 1 by wire bonding technology;

Step 5), bonding the magnet 5 on the metal pipe cap 4, then tightly covering the metal pipe cap 4 on the metal pipe base 1, and connecting them together by bonding or welding.

The basic principle of the above-mentioned resonant pressure sensor chip low-stress assembly method disclosed by the present invention is to fix the sensor chip in a special socket by mechanical means, so as to realize the assembly of the sensor chip and the socket without hard connection. Since the hard connection method such as glue or welding is not used, although the sensor chip is fixed at a specific position of the tube base, it is not integrated with the tube base through hard connection, so there is no residual stress caused by the hard connection assembly of the chip, which avoids Mechanical and thermal stress on the sensor chip.

The above-mentioned assembly method proposed by the present invention can effectively reduce the temperature drift of the sensor chip, has the advantages of simple assembly structure, low cost, good stability, etc., and is suitable for low-stress assembly of sensors.

FIG. 5 shows a comparison chart of sensor temperature performance curves measured by the cantilever beam assembly method in the prior art and the above assembly method proposed by the present invention for the same resonant pressure sensor chip. It can be clearly seen from the figure that adopting the method of the present invention to assemble the resonant pressure sensor chip can effectively reduce the temperature coefficient of the sensor and improve the overall performance of the device.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. A resonant pressure sensor comprising: A tube base, which has a cavity for placing the sensor chip in the middle, and a plurality of tube pins for electrically connecting with the sensor chip are distributed on its edge; A sensor chip, which includes two sets of differential resonant beams placed along the diagonal of the sensor chip, one set of differential resonant beams is used for pressure detection, placed at one end of a diagonal line of the sensor chip, and the other set of differential resonant beams As a spare resonant beam, it is placed at the other end of the diagonal line of the sensor chip, and each group of differential resonant beams is fixedly connected to the sensor chip through anchor points; the sensor chip is fixedly placed in the cavity of the tube base Inside; The fixed bead is a soft rubber strip with screws on both ends, which is placed horizontally on the spare resonant beam of the sensor chip. There is a screw hole outside the cavity, and the fixed bead passes through the screw and the screw hole The cooperative action of fixing the sensor chip on the socket; The tube cap is covered on the tube base, and its edge is fixedly connected with the edge of the tube base. 2. The resonant pressure sensor according to claim 1, characterized in that, the fixed bead is made of polytetrafluoroethylene, plexiglass or other insulating materials. 3 . The resonant pressure sensor according to claim 1 , wherein the tube seat is made of Kovar material or a material with a similar expansion coefficient to silicon material. 4 . 4. The resonant pressure sensor according to claim 1, characterized in that there are solder pads distributed on the edge of the sensor chip, which are electrically connected to the needle through a wire. 5. The resonant pressure sensor according to claim 1, characterized in that, the resonant pressure sensor further comprises a magnet placed on the tube cap, which is used to electromagnetically excite the sensor chip. 6. The resonant pressure sensor according to claim 1, wherein the shape of the sensor chip matches the cavity, and the size of the cavity is larger than the size of the sensor chip, and its depth is larger than the cavity. the thickness of the sensor chip. 7. A low-stress assembly method for a resonant pressure sensor chip as claimed in claim 1, comprising: Step 1, machining a cavity matching the size of the sensor chip on the tube base, and embedding the sensor chip in the cavity; Step 2. Contact the fixing bead to a corner of the sensor chip, and fix the fixing bead on the tube base with screws, so as to fix the sensor chip in the cavity of the tube base; Step 3, electrically connecting the needles distributed on the edge of the tube base with the electrode pads on the edge of the sensor chip through the lead wires; Step 4. Cover the tube base with a tube cap matching the tube base, and connect them together by bonding or welding.