Leadless pressure-sensitive core and sintering preparation process thereof
Through a one-step sintering forming process of leadless pressure-sensitive core, conductive paste is used to inject into the electrode through holes, which solves the problems of high sintering temperature and poor connection performance in the prior art, and achieves efficient and stable leadless pressure-sensitive Core preparation.
Patent Information
- Application Number
- CN202411294100.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2024-12-20
AI Technical Summary
The existing leadless pressure sensor sintering process has high temperature of glass slurry and complicated steps, unstable sealing and mechanical connection performance between the chip and the glass base, and small needle insertion hole diameter, resulting in poor electrical connection performance.
Adopt a leadless pressure-sensitive core structure, including end cap, shell and tube base and lead needle. Through a one-step sintering molding process, conductive paste is used to inject into the electrode through holes to achieve stable connection between the lead needle and the chip and reduce the sintering temperature. , and continuously heat-raising sintering is performed in the fixture.
The preparation process of leadless pressure-sensitive core is simplified, the sintering temperature is reduced, the sealing and mechanical properties are improved, the stability and reliability of electrical connection are ensured, and the problem of difficulty in inserting the needle is avoided.
Smart Images
Figure CN119159077A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of pressure sensor preparation, and in particular relates to a leadless pressure-sensitive core and a sintering preparation process thereof. Background Art
[0002] As the most widely used sensor in the sensor field, pressure sensors have been developed for nearly half a century. In order to adapt to various environmental requirements, various types of pressure sensors have been born, and they are rapidly developing in the direction of intelligence, miniaturization, and high reliability, supporting the needs of all aspects of daily life and industrial fields. Since daily life and industrial sites often face various high and low temperature environments, harsh environments such as corrosion, vibration, impact, radiation, and the requirements of integration, precision, and intelligence of equipment, high requirements are placed on the high temperature resistance, reliability, and miniaturization of sensors.
[0003] The chip of the pressure sensor uses a pressure-sensitive chip, which mainly uses the pressure-sensitive properties of semiconductor silicon. When subjected to stress, the energy band changes, resulting in a change in resistance. Four varistors are connected to form a Wheatstone bridge. When stress is applied, the resistance value changes, and a pressure difference appears at the output end. The pressure difference is measured to obtain the corresponding stress. The chip is electrostatically bonded to the substrate glass and then fixed to the base through a sintering process. The leadless pressure sensor is different from the common oil pressure sensor in that it does not need to be filled with silicone oil, so it can withstand higher temperatures.
[0004] Leadless pressure sensors have the advantages of miniaturization and high reliability. They are usually integrated into a device in a miniaturized manner to ensure a compact structural design. In order to protect the sensor components from the external environment, a shell and protective layer made of special materials are usually used. The existing leadless pressure sensors are mainly composed of pressure-sensitive chips, bonding glass, glass substrates, protective shells, etc.
[0005] At present, the common sintering process is as follows: the glass base is sintered with the protective shell, and then the glass-bonded chip and the glass base are sintered together through glass paste, and then the lead pins coated with silver paste (or metal glass melt) are inserted into the holes of the bonding glass, sintered and solidified to achieve electrical connection with the chip. Such operation often makes it difficult to insert the lead pins, or the mechanical and electrical connection performance is poor. If the lead pins coated with silver paste (or metal glass melt) are inserted into the holes of the bonding glass first, and then the chip and the glass base are sintered together. Such operation will result in poor mechanical connection between the glass base and the chip, or it will be difficult for the lead pins to pass through the vias on the glass base. Moreover, during the sintering process, the sensor assembly is simply placed horizontally on a flat plate and placed in a furnace for sintering, and the sintering effect is difficult to guarantee.
[0006] Another common method is to directly fix the lead pins (binding posts) on the glass base, and then turn the sensitive chip upside down on the glass base, which has been coated with glass slurry. After installation, put the whole thing directly on the perforated bracket and put it into the furnace for sintering. This method requires the lead pins (binding posts) to be kept flush and highly aligned with the hole of the chip, otherwise it will affect the electrical connection between the section and the chip, and has high requirements for the process. Summary of the invention
[0007] The technical problem to be solved by the present invention is that the existing leadless installation process has the problems of high sintering temperature of glass paste and complicated sintering steps, and the sealing performance and mechanical properties between the chip and the glass base are easily affected by the paste composition, packaging steps, and chip structure; at the same time, since the hole diameter of the lead pin inserted into the chip is too small, it is difficult to introduce the conductive paste or the metal glass melt into the hole, resulting in the electrical connection performance and mechanical properties between the lead pin and the chip being unstable. A leadless varistor core with a simple structure, low sintering temperature, and good sealing performance and a sintering preparation process thereof are provided. To achieve the above purpose, the present invention can adopt the following technical solutions:
[0008] A leadless varistor core comprises an end cover, a tube shell base and a lead pin, wherein the end cover is sealed and connected to the top of the tube shell base, a plurality of pressure holes are opened on the end cover, the inner side of the tube shell base is a cavity structure, and a support base is provided at the bottom of the cavity, a varistor chip is provided on the support base, and the lead pin sequentially penetrates the bottom of the tube shell base and the support base and is sintered and fixed to the varistor chip.
[0009] As a further improvement of the present invention, a guide needle extension portion is reserved after the guide needle passes through the support base.
[0010] As a further improvement of the present invention, the pressure-sensitive chip includes a silicon wafer and a chip base, and the chip base is bonded to the silicon wafer through anodic bonding.
[0011] As a further improvement of the present invention, one side of the silicon wafer is etched with deep pits, and the other side of the silicon wafer is plated with circuits and electrodes; the chip base is etched with shallow grooves to protect the circuit; the chip base is provided with electrode through holes, and the lead pins are sintered together with the electrodes on the silicon wafer through the electrode through holes.
[0012] As a further improvement of the present invention, the electrode through hole is divided into two sections, the upper section has a diameter larger than the lower section, and the electrode through hole is filled with conductive slurry to achieve sintering connection between the lead pin and the electrode.
[0013] As a further improvement of the present invention, the end cap, the tube shell base and the lead pin are all made of metal alloy and are surface treated; the support base is made of glass or ceramic, and the chip base is made of glass or ceramic.
[0014] As a general technical concept, the present invention also provides a sintering preparation process applicable to the above-mentioned leadless varistor core, comprising the following steps:
[0015] Step S1, sintering and connecting the tube shell base, the lead pin and the support base through glass slurry to obtain the tube shell;
[0016] Step S2, bonding the chip base to the silicon wafer through anodic bonding to obtain a pressure-sensitive chip;
[0017] Step S3, flip-chip sintering the pressure-sensitive chip obtained in step S2 and the tube shell obtained in step S1 to obtain a core base by using a fixture;
[0018] Step S4, welding the core base obtained in step S3 to the end cover to obtain a leadless pressure-sensitive core;
[0019] Step S5: performing a performance test on the leadless varistor core.
[0020] As a further improvement of the present invention, the clamp comprises a fixed cover plate, a fixed flat plate and a base which are arranged in sequence; the fixed cover plate is provided with a through hole, the fixed flat plate is provided with a protrusion, and the top of the protrusion is provided with a groove;
[0021] When in use, first place the varistor chip in the groove, and inject conductive slurry into the electrode through-hole of the chip base, then turn the tube shell upside down on the outside of the protrusion, and cover the fixed cover plate on the fixed flat plate, and fix the tube shell in the fixture through the through-hole; finally, fix the fixed cover plate, fixed flat plate and base with fasteners, and put them into a tubular furnace for sintering and fixing.
[0022] As a further improvement of the present invention, the components of the glass slurry include SiO2, oxide and dispersion; the oxide includes at least one of PbO, B2O3, ZnO, P2O5 or MgO; and the dispersion includes at least one of pineneol, acetone or ethanol.
[0023] As a further improvement of the present invention, the components of the conductive paste include silver powder, adhesive, curing agent, silane coupling agent and diluent, the viscosity of the conductive paste is lower than 10Pa·s, and the sintering temperature is lower than 450°C; when in use, the conductive paste is injected into the electrode through hole by a micro-sampler, the tube shell base with lead pins is turned upside down on the pressure-sensitive chip, and heated and cured.
[0024] Compared with the prior art, the advantages of the present invention are:
[0025] The leadless varistor core and the sintering preparation process thereof of the present invention effectively simplify the preparation process of the leadless varistor core by adopting a one-step sintering molding method, avoids cumbersome processes, and shortens the development time. Under the premise of ensuring good sealing performance, the sintering temperature is lower. Moreover, all sintering processes can be solved in the fixture by continuous heating, without the need for separate treatment, reducing the operation steps and saving process time. Furthermore, the lead pins are pre-sintered and fixed, avoiding the defect that the leads / lead pins are difficult to pass through the supporting base. At the same time, a micro-injector is used to introduce the conductive slurry into the electrode through-holes of the chip, and the lead pins and the chip are sintered together to achieve good electrical connection. Finally, a pressure sensor with a streamlined structure, stability and reliability is obtained through the sintering preparation process of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 It is a schematic diagram of the cross-sectional structure principle of the leadless pressure-sensitive core in a specific embodiment of the present invention; there is no chip in the figure;
[0027] Figure 2 It is a schematic diagram of the cross-sectional structure principle of the leadless pressure-sensitive core in a specific embodiment of the present invention; there is a chip in the figure;
[0028] Figure 3 It is a schematic diagram of the cross-sectional structure principle of a chip in a specific embodiment of the present invention;
[0029] Figure 4 It is a schematic diagram of the structural principle of the clamp in a specific embodiment of the present invention;
[0030] Figure 5 for Figure 4 Schematic diagram of the cross-section structure principle in the AA direction;
[0031] Figure 6 It is a schematic diagram of the preparation process of the leadless pressure-sensitive core in a specific embodiment of the present invention;
[0032] Legend: 1. End cap; 2. Shell base; 3. Lead pin; 4. Support base; 5. Extension; 6. Silicon wafer; 61. Deep pit; 7. Chip base; 71. Electrode through hole; 72. Shallow groove; 8. Pressure hole; 9. Clamp; 91. Fixed cover plate; 911. Through hole; 921. Protrusion; 922. Groove; 92. Fixed plate; 93. Base. DETAILED DESCRIPTION
[0033] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.
[0034] In the description of the present invention, it should be understood that the terms "side", "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.
[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.
[0036] Example 1
[0037] like Figures 1 to 3 As shown, the leadless varistor core of the present invention comprises an end cap 1, a tube shell base 2 and a lead pin 3. The end cap 1 is sealed and connected to the top of the tube shell base 2, and a plurality of pressure holes 8 are provided on the end cap 1. The inner side of the tube shell base 2 is a cavity structure, and a support base 4 is provided at the bottom of the cavity, and a varistor chip is provided on the support base 4. The lead pin 3 passes through the bottom of the tube shell base 2 and the support base 4 in sequence and is sintered and fixed to the varistor chip.
[0038] like Figure 1 As shown, the lead pin 3 passes through the support base 4 and a reserved extension portion 5 is provided to facilitate sintering connection between the lead pin 3 and the pressure sensitive chip. During the packaging process, if the lead pin 3 is too long and difficult to operate, the lead pin 3 can be shortened.
[0039] like Figure 3 As shown, the pressure-sensitive chip mainly consists of two parts: a silicon wafer 6 and a chip base 7. The chip base 7 is bonded to the silicon wafer 6 by anodic bonding.
[0040] Furthermore, a deep pit 61 is etched on one side of the silicon wafer 6, and a circuit and an electrode are plated on the other side of the silicon wafer 6. A shallow groove 72 is etched on the chip base 7 to protect the circuit. An electrode through hole 71 is provided on the chip base 7, and the lead pin 3 is sintered together with the electrode on the silicon wafer 6 through the electrode through hole 71.
[0041] like Figure 2As shown, there is a sintering surface a between the support base 4 and the tube shell base 2, there is a sintering surface b between the chip base 7 and the support base 4, there is a welding surface c between the perforated cover plate 1 and the tube shell base 2, and there is a bonding surface d between the silicon wafer 6 and the chip base 7.
[0042] like Figure 3 As shown, the electrode through hole 71 is divided into two sections, the upper section has a larger diameter than the lower section, to prevent overflow during subsequent pouring of conductive paste. The conductive paste is poured into the electrode through hole 71 to achieve sintering connection between the lead pin 3 and the electrode, and to ensure reliable mechanical and electrical properties between the lead pin 3 and the varistor chip.
[0043] In this embodiment, the end cap 1, the tube shell base 2 and the lead pin 3 are all made of metal alloys with special surface treatment. The support base 4 is made of glass or ceramic. The chip base 7 is made of glass or ceramic.
[0044] Example 2
[0045] like Figure 6 As shown, the leadless varistor core sintering preparation process of the present invention comprises the following steps:
[0046] Step S1: After all parts are processed, the tube shell base 2, the lead pins 3 and the support base 4 are sintered and connected by glass paste to obtain a tube shell.
[0047] Step S2, bonding the chip base 7 to the silicon wafer 6 by anodic bonding to obtain a bonded pressure-sensitive chip.
[0048] Step S3, the varistor chip obtained in step S2 is connected to the tube shell obtained in step S1 by flip-chip sintering through a fixture 9 to obtain a core base.
[0049] Step S4, welding the core base obtained in step S3 to the end cap 1 to obtain a leadless pressure-sensitive core. Further, the core base and the end cap 1 can be welded together by electron beam welding or laser welding to form a complete core.
[0050] Step S5: performing a performance test on the leadless varistor core.
[0051] like Figure 4 and Figure 5 As shown, the clamp 9 includes a fixed cover plate 91, a fixed flat plate 92 and a base 93 which are arranged in sequence. The fixed cover plate 91 is provided with a plurality of through holes 911, and the fixed flat plate 92 is provided with a plurality of protrusions 921, and each protrusion 921 has a groove 922 at the top. Furthermore, the clamp 9 should have the characteristics of good corrosion resistance, good temperature resistance, good thermal conductivity and low linear expansion coefficient.
[0052] When in use, first place the pressure-sensitive chip in the groove 922, and inject the conductive slurry into the electrode through-hole 71 of the chip base 7 through a micro-injector; then, turn the tube shell upside down on the outside of the protrusion 921, and cover the fixed cover plate 91 on the fixed flat plate 92, and fix the tube shell in the fixture 9 through the through-hole 911; finally, fix the fixed cover plate 91, the fixed flat plate 92 and the base 93 through fasteners, and put them into a tubular furnace for sintering and fixing.
[0053] In step S1 of this embodiment, the components of the glass paste include SiO2, oxides and dispersion liquid. The oxides include at least one of PbO, B2O3, ZnO, P2O5 or MgO. By adding oxides to SiO2 to form a eutectic structure, the melting temperature of the glass can be effectively reduced. The dispersion liquid includes at least one of pineneol, acetone or ethanol.
[0054] In this embodiment, SiO2 and oxide are mixed to form glass powder, the phase change temperature of the glass powder is about 350°C, and the melting temperature is about 450°C. Pinyl alcohol is added to the glass powder as a dispersion liquid to form a glass slurry. The glass slurry is mainly used for "tube shell sintering". When used, the glass slurry is applied to the bonding part, first heated to the evaporation point of the dispersion liquid, and then heated to the melting point of the glass after the dispersion liquid evaporates, and then kept warm for a period of time and cooled.
[0055] In step S3 of this embodiment, high-temperature inorganic glue is used in the sintering process of the pressure-sensitive chip and the shell. The high-temperature inorganic glue is a two-component adhesive mainly composed of an inorganic ceramic material (such as Al2O3 or aluminosilicate) and a modified curing agent. It is used for bonding between the chip and the shell base 2. It requires long-term resistance to high temperatures of 300°C, and the thermal expansion coefficient is required to be as small as possible, keeping it close to the thermal expansion coefficients of ceramics, glass, and silicon wafers. In addition, it is also required to be oil-resistant, acid-resistant, alkali-resistant, and water-resistant. When the high-temperature inorganic glue is relatively viscous, it can be diluted. The high-temperature inorganic glue is mainly used for "sintering of pressure-sensitive chips and shells". When in use, mix the two components evenly, add an appropriate amount of diluent, use a spatula or scraper to brush the colloid onto the pressure-sensitive chip and the supporting base 4, and bake and cure at high temperature.
[0056] In this embodiment, the components of the conductive paste include silver powder, adhesive (epoxy resin or other), curing agent (amine, anhydride), silane coupling agent (optional, can reduce viscosity, increase viscosity, and improve mechanical strength) and diluent. The viscosity of the conductive paste is lower than 10Pa·s, but the viscosity cannot be too low, which will affect the conductivity and mechanical properties after sintering. The sintering temperature is lower than 450°C. Among them, the silver powder is in the form of flakes, and the conductivity and adhesion of the flakes are relatively good; the particle size of the silver powder is small enough, preferably in the micron level. If the particle size of the silver powder is too small, the viscosity of the paste will increase due to the increase in specific surface area. The solid content of the paste is between 60% and 70%; too low a solid content affects the conductivity, and too high a solid content affects the mechanical strength.
[0057] When in use, the conductive paste is injected into the electrode through hole 71 by a micro-sampler, and 1 / 3 to 1 / 2 of the hole is enough, and the tube shell base 2 with the lead pin 3 is turned upside down on the pressure-sensitive chip and heated to cure. Specifically, during the sintering process, it can be heated under vacuum first to discharge the gas inside the hole, and then sintering is performed to ensure reliable electrical and mechanical connection between the lead pin and the electrode of the chip.
[0058] In this embodiment, a flip-chip sintering method is adopted to achieve rapid alignment of the lead pin 3 and the varistor chip, thereby realizing a highly reliable seal between the varistor chip and the tube shell. The clamp is made of metal, ceramic or graphite material, which can effectively prevent the tube shell and the clamp from sintering together, thereby improving the safety of sintering.
[0059] In this embodiment, by adopting a one-step sintering molding method, the preparation process of the leadless pressure-sensitive core is effectively simplified, the complicated process is avoided, and the development time is shortened. Under the premise of ensuring good sealing performance, the sintering temperature is lower. Moreover, all sintering processes can be solved in the fixture 9 by continuous heating, without the need for separate treatment, reducing the operation steps and saving process time. Furthermore, the lead pin 3 is pre-sintered and fixed, avoiding the defect that the lead wire / lead pin is difficult to pass through the support base. At the same time, a micro-injector is used to introduce the conductive slurry into the electrode through hole 71 of the chip, and the lead pin 3 is sintered together with the chip to achieve a good electrical connection. Finally, a pressure sensor with a streamlined structure, stability and reliability is obtained through the sintering preparation process of the present invention.
[0060] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can use the above disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the spirit and technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention still fall within the scope of protection of the technical solutions of the present invention.
Claims
1. A leadless pressure-sensitive core, characterized in that: The invention comprises an end cover (1), a tube shell base (2) and a lead pin (3); the end cover (1) is sealedly connected to the top of the tube shell base (2); a plurality of pressure holes (8) are provided on the end cover (1); the inner side of the tube shell base (2) is a cavity structure, and a support base (4) is provided at the bottom of the cavity; a pressure-sensitive chip is provided on the support base (4); and the lead pin (3) penetrates the bottom of the tube shell base (2) and the support base (4) in sequence and is sintered and fixed to the pressure-sensitive chip.
2. The leadless pressure-sensitive core according to claim 1, characterized in that: After the guide needle (3) passes through the support base (4), an extension portion (5) is reserved.
3. The leadless pressure-sensitive core according to claim 2, characterized in that: The pressure-sensitive chip comprises a silicon chip (6) and a chip base (7), and the chip base (7) is bonded to the silicon chip (6) through anodic bonding.
4. The leadless pressure-sensitive core according to claim 3, characterized in that: One side of the silicon wafer (6) is etched with a deep pit (61), and the other side of the silicon wafer (6) is plated with a circuit and an electrode; the chip base (7) is etched with a shallow groove (72) for protecting the circuit; the chip base (7) is provided with an electrode through hole (71), and the lead pin (3) is sintered together with the electrode on the silicon wafer (6) through the electrode through hole (71).
5. The leadless pressure-sensitive core according to claim 4, characterized in that: The electrode through hole (71) is divided into two sections, an upper section and an lower section, and the diameter of the upper section is larger than the diameter of the lower section. Conductive paste is poured into the electrode through hole (71) to achieve sintering connection between the lead pin (3) and the electrode.
6. The leadless pressure-sensitive core according to any one of claims 3 to 5, characterized in that: The end cover (1), the tube shell base (2) and the lead pin (3) are all made of metal alloy and are surface treated; the support base (4) is made of high temperature resistant glass or ceramic, and the chip base (7) is made of glass or ceramic.
7. A sintering process for preparing a leadless varistor core according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step S1, sintering and connecting the tube shell base (2), the lead pin (3) and the support base (4) by glass slurry to obtain a tube shell; Step S2, bonding the chip base (7) to the silicon wafer (6) by anodic bonding to obtain a pressure-sensitive chip; Step S3, using a fixture (9) to flip-chip sinter and connect the pressure-sensitive chip obtained in step S2 and the tube shell obtained in step S1 to obtain a core base; Step S4, welding the core base obtained in step S3 to the end cover (1) to obtain a leadless pressure-sensitive core; Step S5: performing a performance test on the leadless varistor core.
8. The sintering preparation process according to claim 7, characterized in that: The clamp (9) comprises a fixed cover plate (91), a fixed flat plate (92) and a base (93) which are arranged in sequence; the fixed cover plate (91) is provided with a through hole (911), the fixed flat plate (92) is provided with a protrusion (921), and the top of the protrusion (921) is provided with a groove (922); When in use, the pressure-sensitive chip is first placed in the groove (922), and a conductive paste is injected into the electrode through hole (71) of the chip base (7); then the tube shell is turned upside down on the outside of the protrusion (921), and the fixed cover plate (91) is covered on the fixed flat plate (92), and the through hole (911) fixes the tube shell in the fixture (9); finally, the fixed cover plate (91), the fixed flat plate (92) and the base (93) are fixedly connected by fasteners, and placed in a tube furnace for sintering and fixing.
9. The sintering preparation process according to claim 8, characterized in that: The components of the glass paste include SiO2, oxides and dispersion liquid; the oxides include at least one of PbO, B2O3, ZnO, P2O5 or MgO; the dispersion liquid includes at least one of pineneol, acetone or ethanol.
10. The sintering preparation process according to claim 8, characterized in that: The components of the conductive paste include silver powder, adhesive, curing agent, silane coupling agent and diluent. The viscosity of the conductive paste is lower than 10 Pa·s and the sintering temperature is lower than 450° C. When in use, the conductive paste is injected into the electrode through hole (71) by a micro-sampler, and the tube shell base (2) with the lead pin (3) is placed upside down on the pressure-sensitive chip and heated for curing.