CN114132885A - Leadless packaging structure and method of high-temperature-resistant sensor - Google Patents
Leadless packaging structure and method of high-temperature-resistant sensor Download PDFInfo
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- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/0032—Packages or encapsulation
- B81B7/007—Interconnections between the MEMS and external electrical signals
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
- B81C1/00261—Processes for packaging MEMS devices
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
- B81C1/00261—Processes for packaging MEMS devices
- B81C1/00301—Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
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Abstract
The invention discloses a leadless packaging structure and a leadless packaging method for a high-temperature-resistant sensor. The invention solves the problem of reliable disintegration and even failure of the conventional metal lead bonding packaging technology in a high-temperature environment on the one hand, and simplifies the packaging lead mode on the other hand, has simple operation, high yield and high reliability in practical use, is suitable for batch production, has low cost and has high cost performance. Meanwhile, the invention improves the working stability and long-term reliability of the sensor in a high-temperature environment by selecting and simplifying the packaging material, and the sensor chip has the advantage of good dynamic response characteristic by adopting flush packaging.
Description
Technical Field
The invention relates to a high-temperature-resistant sensor, in particular to a leadless packaging structure and a leadless packaging method of the sensor.
Background
The high temperature resistant sensor has very important application in many industries and fields, such as a high temperature resistant pressure and vibration sensor for detecting the high temperature pressure and vibration in an aircraft engine, a high temperature resistant pressure sensor for measuring the pressure of a loop of a high temperature reactor of a nuclear power station, and a high temperature pressure and vibration sensor for monitoring the operation safety of a high temperature industrial reaction kettle and a smelting tower.
Therefore, the high-temperature-resistant sensor can normally work in a high-temperature environment, and the key problems are that: (1) the sensor chip can normally work in a high-temperature environment, and (2) the sensor packaging structure can normally play roles of supporting, electric connection, sealing and the like in the high-temperature environment. With the progress of the technology, the sensor chip material capable of normally working at high temperature is continuously discovered, and the first key problem of the high-temperature-resistant sensor is effectively solved. However, the sensor packaging structure often involves the combination and the fixed connection of multiple materials, and the problems of inconsistent thermal expansion of heterogeneous materials, high-temperature oxidation of materials, softening and falling of connecting pieces and the like are easily caused at high temperature, so that the supporting structure of the sensor chip fails, the electric connection is short-circuited or broken, even the sensor chip is broken, and the like, and the performance of the sensor is deteriorated or even permanently fails.
The most important ring in the sensor package is to form an effective electrical connection between the electrode of the sensor chip and the electrode on the package structure, so that the signal measured by the sensor chip can be smoothly transmitted. The current common packaging method is to use metal wire bonding for connection. For example, chinese patent CN105236343A discloses a dielectric isolation type pressure sensor package structure, in which a pressure sensor package module with a MEMS chip is connected with a lead wire by wire bonding. The connection mode has a simple structure and is convenient to operate, but when the connection mode is used in a high-temperature environment, bonding points between the leads and the sensor packaging module and between the leads and the wires are easy to fall off due to high-temperature softening, and the risk of failure exists.
In order to solve the problems of metal wire bonding, chinese patent CN102928150A discloses a leadless packaged metal film pressure sensor, in which a sensor chip is connected with a glass sealing cover in a bonding manner, and the leadless packaged metal film pressure sensor is manufactured by forming a through hole corresponding to a lead pad of the sensor chip on the glass sealing cover, a conductive metal material filled in the through hole, and a conductive metal lead pin inserted into the through hole filled with the conductive metal material, and performing vacuum annealing. The packaging mode that adopts in this patent has effectively solved the not high temperature resistant problem of metal wire bonding formula encapsulation, but has two aspects of problem in actual operation: (1) due to the small size of the MEMS chip, the sizes of the lead bonding pad and the corresponding through hole are very small (in micron order), the whole through hole is difficult to be effectively filled with the conductive metal material due to the micropore effect, bubbles and holes exist in the through hole filled with the conductive metal material, and the lead bonding pad, the conductive metal material and the conductive metal pin cannot be fully contacted or even are not contacted at all; (2) although the purpose of annealing is to sinter the conductive metal material, so that the lead pad, the conductive metal material and the conductive metal pin can be fixedly connected and form good electrical connection, the conductive metal material can generate thermal deformation and volatile bubbles in the actual sintering process, so that the volume of the conductive metal material after annealing is reduced, the bubbles exist inside the conductive metal material, and even the lead pad, the conductive metal material and the conductive metal pin are disconnected due to the fact that the thermal expansion coefficients of different materials are inconsistent. Due to the above two problems, the success rate of actually obtaining a package structure is not high.
Chinese patent CN109781334A discloses a leadless package structure of piezoresistive sensor, in which the conductive paste (composed of silver, glass, organic binder and solvent) has a problem of generating thermal stress after sintering and curing, and in order to make the conductive paste after sintering and curing stably function as a connection structure, noble metal gold is further used as a transition layer, and the thermal stress is reduced by utilizing the good ductility of gold. However, the transition layer cannot solve the problems of thermal deformation and volatile bubbles generated in the actual sintering and curing process of the conductive paste. In addition, the size of the through hole through which the valve pin penetrates still needs to be limited to a small range, so the reliability of the connection structure is still affected by the micro-porous effect. Meanwhile, PbO-ZnO-B is also used in the patent2O3System-based glass paste formationThe softening point of the glass system can be adjusted according to the lead content, and can be in PbO-ZnO-B according to the requirement2O3Based on the addition of low expansion coefficient and negative expansion materials, e.g. PbTiO3Cordierite, eucryptite, spodumene, quartz glass and the like form the composite glass slurry, the thermal expansion coefficient is adjusted, and the chemical stability and the mechanical strength are improved. However, the slurry has high viscosity, and the application mode and range are limited.
Disclosure of Invention
The invention provides a leadless packaging structure and a leadless packaging method of a high-temperature-resistant sensor, and aims to solve the technical problems of the existing high-temperature-resistant sensor packaging structure.
In order to achieve the purpose, the invention adopts the following technical scheme:
the utility model provides a leadless packaging structure of high temperature resistant sensor, this leadless packaging structure includes sensor chip, is used for supporting sensor chip's sensor housing and sets up the metal pin on sensor housing, the metal pin passes through the high temperature resistant conducting layer and links to each other with sensor chip's metal electrode, and this metal electrode is external on sensor housing surface or place sensor housing in.
Preferably, the sensor housing comprises a substrate and a chip packaging groove arranged on the substrate, the sensor chip is connected with the sensor housing through a sealing layer arranged at the bottom of the chip packaging groove, and the sensor chip is flush with the surface of the sensor housing.
Preferably, the sealing layer is formed by curing a high temperature resistant adhesive applied to the bottom of the chip package socket.
Preferably, the high-temperature-resistant adhesive comprises PbO-ZnO-B2O3The thermal expansion coefficient of the sealing layer of the glass paste of the system is between that of the sensor shell and that of the sensor chip.
Preferably, the sensor housing further comprises a channel disposed on the substrate, and the channel is connected to the bottom of the chip packaging groove.
Preferably, the sensor housing further includes a through hole disposed on the substrate, and a conductive sealing block is disposed in the through hole and filled between a portion of the metal pin located in the through hole and an inner wall of the through hole.
Preferably, the conductive sealing block is formed by curing a conductive glass paste injected into the inner space of the sensor housing along the through hole to bond a portion of the metal pin located in the through hole (bond the portion to the sensor housing).
Preferably, the conductive glass paste comprises PbO-ZnO-B as a component2O3Glass paste of the system and a nano conductive material.
Preferably, the base body is columnar, the chip packaging groove is formed in one end face of the base body, one end of the through hole is located in the other end face of the base body, and the other end of the through hole extends to the end face of the base body, wherein the chip packaging groove is formed in the end face of the base body.
Preferably, the through hole of the sensor shell is connected with the bottom of the chip packaging groove, and the high-temperature-resistant conducting layer is arranged between the metal pin and the metal electrode of the sensor chip in a superposition mode (namely the metal electrode is internally arranged); or the through hole of the sensor shell is arranged outside the chip packaging groove at the position on the end face of the base body, and the high-temperature-resistant conducting layer is arranged between the metal pin and the metal electrode of the sensor chip in a direct writing mode (namely the metal electrode is arranged externally).
Preferably, the high temperature conductive layer is formed by coating and curing a modified slurry containing a binder, a high temperature antioxidant and a nano conductive material (i.e., the binder is modified by the high temperature antioxidant and the nano conductive material), or the high temperature conductive layer is formed by coating and curing a modified slurry containing a binder, a high temperature antioxidant, a toughening agent and a nano conductive material (i.e., the binder is modified by the high temperature antioxidant, the toughening agent and the nano conductive material).
Preferably, the component of the adhesive comprises PbO-ZnO-B2O3The glass paste, i.e., the adhesive, of the system may be the above-mentioned high-temperature-resistant adhesive.
Preferably, the sensor housing further comprises an annular groove provided on a side surface of the base body.
A leadless packaging method of a high-temperature-resistant sensor comprises the following steps:
1) processing a chip packaging groove and a through hole on a substrate to obtain a sensor shell;
2) respectively and correspondingly bonding the metal pin and the sensor chip with the sensor shell through the through hole and the chip packaging groove, and then curing, and forming a high-temperature-resistant conducting layer which simultaneously covers the metal pin and the metal electrode of the sensor chip by using preset slurry (such as the modified slurry) which stretches across two sides of the junction position of the sensor shell and the sensor chip in the curing process to obtain a high-temperature-resistant sensor leadless packaging structure with an external metal electrode;
or, the metal pin is bonded with the sensor shell through the through hole, and before the sensor chip is bonded with the sensor shell through the chip packaging groove, slurry for forming the high-temperature-resistant conductive layer (for example, slurry identical to the preset slurry) is placed into the chip packaging groove, so that the metal pin and the metal electrode of the sensor chip are butted with the high-temperature-resistant conductive layer through curing, and the high-temperature-resistant sensor leadless packaging structure with the built-in metal electrode is obtained.
Preferably, the step 1) further comprises the following steps: and processing a cavity channel connected with the bottom of the chip packaging groove on the substrate.
Preferably, in the step 2), the conductive glass paste is injected into the through hole, and a gap between a part of the metal pin located in the through hole and the inner wall of the through hole is filled with the conductive glass paste, so that the metal pin is bonded to the sensor housing.
Preferably, in the step 2), the high-temperature-resistant adhesive is applied to a certain area of the bottom of the chip packaging groove (when the end surfaces of the through holes are located at the bottom of the chip packaging groove, since a high-temperature-resistant conductive layer needs to be formed in the area where the end surfaces are located, the high-temperature-resistant adhesive is applied to the bottom surface of the chip packaging groove except for the area; when the end face of the through hole is positioned outside the chip packaging groove, the bottom surface of the chip packaging groove is coated; the connecting part of the cavity channel and the bottom of the chip packaging groove is not coated), the sensor chip is placed into the chip packaging groove and is contacted with the coated high-temperature-resistant adhesive until the sensor chip is flush with the surface of the sensor shell, and therefore the sensor chip is bonded on the sensor shell.
The invention has the beneficial effects that:
in the high-temperature-resistant sensor packaging structure provided by the invention, the leadless packaging is realized by introducing the conducting layer which accords with the temperature grade of the sensor application, the reliability of the electric connection between the metal pin in the packaging structure and the metal electrode of the sensor chip is improved, and the defect of the existing packaging structure in the aspect of thermal stability is fundamentally overcome; meanwhile, the packaging mode of the sensor chip is flexible, the process difficulty of the packaging method is low, and the yield is high.
Furthermore, the sensor chip and the sensor shell are packaged in a flush mode, for the pressure sensor, the sensor chip is directly contacted with a measured high-temperature medium, the attenuation influence of a tube cavity effect on the dynamic performance of the sensor is avoided, the problems of response time lag and frequency distortion caused by the tube cavity effect are solved, and the sensor has higher response speed and higher resonant frequency.
Furthermore, the packaging materials directly connected with the sensor chip are few in types (only a few materials with the same glass paste component, such as a sensor shell material, cured high-temperature-resistant adhesive glue and the like are involved), so that the thermal expansion coefficients of the packaging materials and the sensor chip material are easy to match (the thermal expansion coefficients of the packaging materials and the sensor chip material are very close), and the possibility of thermal stress mismatch between heterogeneous materials is reduced; meanwhile, the packaging can be completed through one-time curing, and the process steps are simplified.
Furthermore, the thermal expansion coefficient of the high-temperature resistant adhesive after curing is between that of the traditional sensor shell and the sensor chip, so that the internal thermal expansion stress between the sensor shell and the sensor chip can be effectively relaxed, and the high-temperature stability and the thermal stress damage resistance of the sensor chip are improved.
Further, the invention takes the cavity (such as a channel structure and the like) at the bottom of the chip packaging groove and the through hole for adhering the metal pin as a stress relief structure of the sensor shell for thermal expansion, and reduces the internal stress caused by the thermal expansion difference between the sensor shell and the sensor chip.
Furthermore, the through hole arrangement mode adopted by the invention (especially when the end face of the through hole is positioned outside the chip packaging groove) is beneficial to increasing the aperture of the through hole, so that the metal pin can be more reliably fixed by using the packaging material (such as cured conductive glass paste) based on the glass paste with stronger viscosity.
Drawings
FIG. 1 is a schematic view of the entire structure (a) of the refractory sensor package and its longitudinal structure (b) in example 1;
FIG. 2 is a schematic view of a sensor housing (a) and its longitudinal sectional structure (b) in embodiment 1;
FIG. 3 is a schematic view of a metal lead in example 1;
FIG. 4-1 is a schematic view of a sensor chip (a) and its longitudinal sectional structure (b) in example 1;
FIG. 4-2 is a schematic diagram showing the shape and size matching between the cured high temperature resistant adhesive (a) and the backside (b) of the sensor chip in example 1;
fig. 5 is a schematic view of the whole structure (a) and the sensor housing (b) of the refractory sensor package of embodiment 2;
fig. 6 is a schematic view of a package structure of a metal pin, conductive glass paste (a) and a direct-write conductive silver paste (b) in embodiment 2;
fig. 7 is a schematic view of a package structure of the high temperature resistant adhesive (a) and the sensor chip (b) in embodiment 2;
fig. 8 is a schematic view of a state that the conductive glass paste is injected into the circular channel (the dark color region is the package structure after the conductive glass paste is cured, i.e. the conductive sealing block); wherein: (a) example 1, (b) example 2;
in the figure: 1-a sensor housing; 2-metal pins; 3-a conductive sealing block; 4-a conductive layer; 5-a sensor chip; 6-sealing layer; 101-a through hole; 102-chip package slot; 103-lumen tract; 104-an annular groove; 501-a metal electrode; 502-cavities; 503-metal wires; 504-semiconductor sensitive resistance.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. The examples are given solely for the purpose of illustration and are not intended to limit the scope of the invention.
Aiming at the problems existing in the prior leadless package (especially for the package of a high temperature resistant sensor with the grade of more than 600 ℃) when a conductive metal material is poured and sintered into a fine package through hole, such as high operation difficulty and low yield (due to air resistance and pore effect inside a micropore, the package through hole is difficult to be filled with the conductive metal material, and a pore structure is easy to generate inside the conductive metal material in the curing process, and finally, a metal pin can not be well electrically connected with a lead pad on a sensor chip); the invention provides a leadless packaging structure of a high-temperature-resistant sensor, in the packaging of the high-temperature-resistant sensor, on one hand, the electric connection packaging of a metal pin and a metal electrode of a sensor chip is carried out in modes of direct writing of conductive silver paste and the like, and on the other hand, the sensor chip and a sensor shell are packaged in a flush mode through high-temperature-resistant adhesive glue, so that the packaging success rate of the high-temperature-resistant sensor is improved, and the packaging structure is stable and reliable, the packaging process is simple to operate, and the leadless packaging structure has strong industrial application value.
Example 1
As shown in fig. 1, the overall package structure of the high temperature sensor includes a sensor housing 1, a metal pin 2, and a sensor chip 5. A part of the metal pin 2 is fixed inside the sensor shell 1 through a conductive sealing block 3 formed by cured conductive glass slurry, and the sensor chip 5 is fixed on the upper end face of the sensor shell 1 in a embedding manner through a sealing layer 6 formed by cured high-temperature-resistant adhesive glue; wherein, sensor chip 5 is openly up to metal pin 2's upper end, the electrically conductive glass thick liquids of solidification, sensor chip 5's front all flushes with sensor housing 1's up end, and metal pin 2's lower extreme stretches out to sensor housing 1's lower extreme off-plate, and sensor chip 5's the back is relative with the passageway or the inner chamber structure that are located sensor housing 1 inside. High-temperature-resistant conducting layers 4 which are formed by curing direct-writing conductive silver paste and are continuously distributed in a strip shape are attached to the junction positions and the corresponding areas on two sides of the front surface of the sensor shell 1 and the front surface of the sensor chip 5, and a circuit structure on the front surface of the sensor chip 5 is connected with the upper ends of the metal pins 2 and the cured conductive glass paste through the high-temperature-resistant conducting layers 4.
As shown in fig. 2, the sensor housing 1 is formed by processing a cylindrical base body, and a circular through hole 101, a chip package groove 102, a chip package groove bottom channel 103 and an annular groove 104 are specifically processed on the base body.
The chip packaging groove 102 is located in the middle of the upper end face of the sensor shell 1 and is mainly used for placing the sensor chip 5, the length and width of the chip packaging groove 102 (the chip packaging groove 102 is rectangular in fig. 2 a) or the diameter of the chip packaging groove 102 is matched with the sensor chip 5, the edge of the sensor chip 5 can be in close contact with the side wall of the chip packaging groove 102 after the sensor chip 5 is installed, the depth of the chip packaging groove 102 is slightly larger than the thickness of the sensor chip 5, a space is reserved for coating high-temperature-resistant adhesive with certain thickness at the bottom of the chip packaging groove 102, and the front face of the sensor chip 5 can be flush with the upper end face of the sensor shell 1.
The channel 103 is located below the bottom of the chip packaging groove 102 and is communicated with the chip packaging groove 102. The main functions of the cavity 103 are: (1) as a stress relief structure for thermal expansion of the sensor housing 1, thermal stress transmitted to the sensor chip 5 is reduced. (2) For the pressure sensor, if the channel 103 directly penetrates the lower end surface of the sensor housing 1 and communicates with the outside (as shown in fig. 2b, that is, a channel structure is adopted), the corresponding pressure sensor can be used as a gauge pressure sensor, and if the channel 103 does not penetrate the lower end surface of the sensor housing 1 (that is, an inner cavity structure is adopted), the corresponding pressure sensor can be used as an absolute pressure sensor through vacuum packaging.
The circular through hole 101 completely penetrates through the upper end surface and the lower end surface of the sensor shell 1, and the through hole is mainly used for installing a metal pin 2 of the sensor; the number and relative positions of the circular through holes 101 of the sensor housing 1 are generally determined according to the circuit structure of the front surface of the sensor chip 5, for example, in fig. 2a, the 5 circular through holes 101 are arranged in two rows at intervals, and the arrangement positions of the circular through holes 101 on the end surface of the sensor housing 1 are all located outside the chip packaging groove 102.
The function of the annular groove 104 includes: (1) the annular sealing ring is placed so that after the sensor is installed in a tested pipeline, a good sealing effect is formed between the sensor and the inner wall of the pipeline, and the detection accuracy is guaranteed; (2) the sensor is fixed as a positioning clamping groove.
The up end and the lower terminal surface of sensor housing 1 do not have edges and corners (for example, realize through the edge machining radius angle at the upper and lower terminal surface of base member), avoid sharp-pointed right angle to draw on the one hand and hinder people or other objects, and on the other hand, when pressure sensor used in some pipe, chamber, the cylindric structure of taking the radius angle is favorable to the flow and the outward diffusion of air current, liquid stream, can not produce the swirl because of there being sharp-pointed right angle, influences actual measurement precision.
It should be noted that when the materials of the sensor housing 1 and the sensor chip 5 are selected, materials having the same or similar thermal expansion coefficients are selected, so that thermal expansion matching under a high-temperature environment is realized, and small thermal stress inside the sensor and good high-temperature stability of the sensor are ensured. For example, the sensor housing 1 has a thermal expansion coefficient of 4.1 × 10-6AlN, an insulating material at/° C, and a thermal expansion coefficient of 3.7X 10 for manufacturing the MEMS chip used for the sensor chip 5-6SiC material/° c.
As shown in fig. 3, the metal pins 2 are generally in the form of cylindrical slender bar structures (also called metal pins), and the specific number and relative positions thereof are consistent with the number and relative positions of the circular through holes 101 provided in the sensor housing 1. Namely, a metal pin 2 is fixedly installed in a circular through hole 101 by using a conductive sealing block 3 formed by curing conductive glass paste.
As shown in fig. 4-1 and 4-2, the sensor chip 5 is an MEMS miniaturized chip processed by a micro-nano manufacturing process. For example, in the case of the sensor chip 5 shown in fig. 4-1a, the front side of the circuit structure includes 5 metal electrodes 501, and one end of the metal wire 503 is tightly connected to the metal electrodes 501, and the other end is tightly connected to the semiconductor sensitive resistor 504. If the sensor chip 5 is a pressure sensor chip, a cavity 502 is formed on the back surface of the chip, the shape of the cavity 502 may be rectangular (including square), circular (fig. 4-2b), or other shapes, and the size of the cavity 502 and the relative position between the cavity and the semiconductor sensitive resistor 504 are determined according to the arrangement rule of the pressure sensor sensitive films and the sensitive resistors. If the sensor chip 5 is a vibrating sensor chip, the back side of the chip should be correspondingly machined with mass and cantilever structures. The number and the position of the metal electrodes 501 and the semiconductor sensitive resistors 504 on the front surface of the sensor chip 5 can be changed according to actual needs. The number and the positions of the circular through holes 101 located outside the sensor chip 5 can be determined according to the number and the positions of the metal electrodes 501 on the front surface of the sensor chip 5. In addition, when the cavity 502 is formed in the back surface of the sensor chip 5, the cavity 103 located below the bottom of the chip packaging groove 102 is opposite to the back surface of the sensor chip 5, and the opening at the upper end of the cavity 103 is aligned to the opening of the cavity 502 through matching, so that the shape and the size of the opening are consistent, the chip packaging groove 102 is used for stably supporting the area of the back surface of the sensor chip 5 except the area corresponding to the cavity 502, the reliability of the sensor packaging structure is improved, only the area corresponding to the cavity 502 on the sensor chip 5 is movable, and other areas are fixed, so that the sensor chip 5 can perform measurement according to a preset theoretical state, and the measurement accuracy is ensured.
The high-temperature-resistant adhesive is a high-temperature adhesive and has good electrical insulation performance at high temperature. The high-temperature resistant adhesive is PbO-ZnO-B2O3The system is a glass paste mainly, except that PbO-ZnO-B is formed2O3The components of the system can also be mixed with lead titanate (PbTiO)3) Cordierite, eucryptite, spodumene, quartz glass (SiO)2) Is constituted as a component.
With PbO-ZnO-B2O3The formula of the glass slurry (namely the high-temperature resistant adhesive) mainly comprises the following components in percentage by mass:
①PbO：73％～77％
②B2O3：7％～13％
③ZnO：8％～13％
④PbTiO3cordierite, eucryptite, spodumene, quartz glass: 0 to 5 percent.
The high-temperature resistant adhesive needs to be cured at high temperature through sintering to form a sealing layer 6, and the specific use description is as follows:
1) coating high-temperature-resistant adhesive glue on the bottom of the chip packaging groove 102; in addition to controlling the coating thickness, it should be noted that the refractory adhesive is applied to form a complete sealing ring between the backside of the sensor chip and the bottom of the chip packaging groove, and cannot enter into the cavity 502 on the backside of the sensor chip 5, so as to avoid affecting the movable structures (such as sensitive film, mass, etc.) inside the sensor chip 5, that is, the refractory adhesive applied to the bottom of the chip packaging groove 102 should have a shape and size matching the shape and size of the backside of the sensor chip 5.
2) Curing
Raising the temperature from room temperature to 270 ℃ at the speed of 2 ℃/min, and keeping the temperature for 25 minutes; then uniformly raising the temperature to 550 ℃ within 135 minutes, and keeping the temperature for 5 minutes; then uniformly reducing the temperature to 540 ℃ within 10 minutes, and keeping the temperature for 20 minutes; then reducing the temperature from 540 ℃ to 495 ℃ within 20 minutes, and keeping the temperature for 20 minutes; then reducing the temperature from 495 ℃ to 455 ℃ within 20 minutes, and keeping the temperature for 20 minutes; then the temperature was decreased to room temperature at a rate of 2 deg.C/min.
The procedure is adopted to sinter the coated high-temperature-resistant adhesive, so that the sealing layer 6 obtained by sintering has no quality defects such as holes, cracks and the like, and the sintering strength and compactness are ensured.
After the high-temperature resistant adhesive is cured, the thermal expansion coefficient of the high-temperature resistant adhesive is between that of the sensor shell 1 and that of the sensor chip 5 (namely 3.7 multiplied by 10)-6From/° C to 4.1X 10-6Between/° c), and the thermal expansion coefficients of the three are very close, so that the back surface of the sensor chip 5 can be tightly fixed in the chip packaging groove 102 of the sensor housing 1, and the bonding and sealing effects are achieved; can also be used as a thermal expansion transition layerAnd the thermal expansion internal stress between the sensor shell 1 and the sensor chip 5 is relaxed, and the high-temperature stability and the thermal stress damage resistance of the sensor chip are improved.
The conductive glass paste is high-temperature resistant conductive paste obtained through blending, namely the conductive glass paste is formed by further mixing nano conductive silver powder on the basis of the components contained in the high-temperature resistant adhesive, and the mass fraction of the mixed nano conductive silver powder can be optimized according to the actual conductivity of the conductive glass paste after curing.
The specific use of the conductive glass paste is as follows:
1) filling in
And injecting conductive glass slurry into the circular through hole of the sensor shell by using a needle tube injector, and filling a gap between the part of the metal pin placed in the through hole and the inner wall of the through hole.
2) High temperature curing
The sintering procedure was referenced to the high temperature resistant bond paste described above.
The conductive glass paste after curing (i.e., the conductive sealing block 3) has the following main characteristics: (1) the high-temperature-resistant rubber has the characteristic of high temperature resistance, and is good in stability and not easy to denature when used in a high-temperature environment for a long time; (2) the conductive film has conductivity, low resistance value and small degree of change of the resistance value along with temperature change; (3) coefficient of thermal expansion of 3.7X 10-6From/° C to 4.1X 10-6The temperature is lower than the temperature of the sensor shell, and the temperature is lower than the temperature of the sensor shell; (4) the bonding nature is strong, the adhesion is good, can firmly fix metal pin in the circular through-hole of sensor housing.
The direct-writing conductive silver paste is a multi-component mixed paste composed of the high-temperature-resistant adhesive and a modifier (including not only nano conductive silver powder, but also components such as a toughness agent like micro-nano metal fibers, a high-temperature antioxidant like ferric oxide powder and the like). Forming physical connection between the metal electrode 501 on the front surface of the sensor chip 5 and the upper end (flush with the upper end surface of the sensor shell 1) of the corresponding metal pin 2 by 3D printing or spraying the direct-writing conductive silver paste, and then performing high-temperature curing on the direct-writing conductive silver paste forming the physical connection (referring to a sintering program)The high-temperature resistant adhesive), a functionalized structure layer can be formed, wherein the functionalized structure layer is tightly adhered to a plane which is formed by the upper end of the metal pin 2, the corresponding metal electrode 501, the upper end surface of the sensor shell 1 positioned between the metal pin and the functionalized structure layer, the conductive glass slurry (the upper end of the conductive sealing block 3) solidified on the periphery of the metal pin 2 and the corresponding area on the front surface of the sensor chip 5. The functional structure layer has high temperature resistance and low resistance value conductive property (also called as high temperature resistance conductive layer 4), and has a thermal expansion coefficient similar to that of the sensor shell and the chip material (namely 3.7 multiplied by 10)-6From/° C to 4.1X 10-6Between/° c), while avoiding the problem of oxidation failure (conductivity loss due to surface oxidation) occurring at high temperature and the problem of breakage occurring at the interface of the sensor housing and the sensor chip, so that a stable electrical connection can be formed between the metal pin 2 and the metal electrode 501 on the front surface of the sensor chip 5.
In the high-temperature working environment of the sensor, the high-temperature-resistant conductive layer 4 formed by curing the direct-writing conductive silver paste has good conductivity, toughness and high-temperature oxidation resistance, and provides stable and reliable electric connection between the sensor chip 5 and an external circuit connected to the metal pin 2. Meanwhile, the conductive sealing block 3 formed by curing the conductive glass paste adopted by the invention has an additional function of ensuring reliable electrical connection between the metal electrode 501 on the front surface of the sensor chip 5 and the metal pin 2. Although the metal pin 2 and the metal electrode 501 of the sensor chip 5 are indirectly connected through the cured direct-writing conductive silver paste, even if an open circuit occurs between the cured direct-writing conductive silver paste and the metal pin 2, the electrical connection reliability of the sensor is not affected, because the glass paste used for bonding the metal pin 2 in the circular through hole is conductive after being cured, an electrical signal can be transmitted to the cured conductive glass paste through the cured direct-writing conductive silver paste and then transmitted to the metal pin 2.
The overall packaging structure of the high-temperature-resistant sensor of the embodiment can be obtained by adopting the following packaging process flow:
1) processing sensor shell
2) Bonding sensor chip and metal pin
Inserting 5 metal pins 2 into corresponding circular through holes 101 of the sensor shell 1 processed in the step 1 (the upper ends of the 5 metal pins are flush with the upper end face of the sensor shell 1), and injecting conductive glass slurry into the circular through holes 101 containing the metal pins 2 at the lower end face of the sensor shell 1, wherein the injection amount of the conductive glass slurry is based on the fact that the conductive glass slurry can fully contact the metal pins 2 and the circular through holes 101 (fig. 8 a); high-temperature-resistant adhesive glue is coated at the bottom of the chip packaging groove 102 of the sensor shell 1, then the sensor chip 5 is placed in the high-temperature-resistant adhesive glue, the sensor chip 5 is tightly embedded into the chip packaging groove 102, and the front surface of the sensor chip 5 is flush with the upper end surface of the sensor shell 1.
3) The direct-writing conductive silver paste is used to form physical connection between the metal electrode 501 on the front surface of the sensor chip 5 and the corresponding metal pin 2 on the outer side.
4) Fixing the embedded sensor chip 5 on the corresponding end face of the sensor shell 1 through high-temperature curing (namely, firmly fixing the sensor chip 5 in the chip packaging groove 102); the conductive sealing block 3 formed by high-temperature curing not only seals one end of the circular through hole 101 close to the sensor chip 5, but also enables the cured conductive glass paste to be tightly and reliably combined with the metal pin 2 (so as to realize electric connection), and fixes the metal pin 2 in the circular through hole 101 (i.e. fixes the metal pin 2 and the sensor shell 1 together); the 5 flat high temperature resistant conductive layers 4 formed by the high temperature curing realize the electrical connection between the metal pin 2 and the metal electrode 501.
Example 2
The above embodiment 1 is directed to the sensor chip being relatively friendly to the working environment, for example, the chip is not directly contacted with moisture, dust or corrosive substances. Embodiment 2 is proposed in consideration of protecting the circuit structure on the front surface of the sensor chip with the package structure if the sensor chip operates in an environment containing moisture, dust, or corrosive substances.
As shown in fig. 5a, the main difference between the overall package structure of the high temperature sensor of this embodiment and embodiment 1 is: the sensor chip 5 is reversely buckled in the chip packaging groove 102, namely the back of the sensor chip 5 faces upwards, the arrangement positions of the circular through holes 101 on the end face of the sensor shell 1 are all located inside the chip packaging groove 102, namely the upper ends of the circular through holes 101 are also communicated with the chip packaging groove 102, and the positions of the groove bottom cavities 103 are unchanged, namely the cavities 103 are surrounded in the middle of the sensor shell 1 by the circular through holes 101.
The overall packaging structure of the high-temperature-resistant sensor of the embodiment can be obtained by adopting the following packaging process flow:
1) processing sensor shell
As shown in fig. 5b, 1 chip package groove 102 matching the size and shape of the sensor chip 5 and 1 channel (as chip package groove bottom channel 103) extending from the bottom of the chip package groove 102 to the lower end face of the cylindrical substrate are processed on the upper end face of the cylindrical substrate; referring to a circuit structure on the front surface of the sensor chip 5 which needs to be placed in the chip packaging groove 102, 5 circular through holes 101 which have the same diameter, penetrate through the cylindrical substrate and can be opposite to the metal electrode 501 of the sensor chip 5 are processed on the cylindrical substrate; on the side of the cylindrical base 1 annular groove 104 is machined.
2) Adhesive metal pin
As shown in fig. 6a and 8b, the metal pin 2 is bonded in the circular through-hole 101 by the conductive glass paste according to step 2) of example 1.
3) As shown in fig. 6b, a direct-writing conductive silver paste is coated on the end surface of each metal lead 2 at the bottom of the chip packaging groove 102 and inside the edge of the corresponding circular through hole 101 (at the upper end of the conductive glass paste filling area).
4) As shown in fig. 7, a high temperature resistant adhesive is applied to the bottom of the chip packaging groove 102 except for the direct-writing conductive silver paste application area and the other area except the channel structure opening, and the sensor chip 5 is placed into the chip packaging groove 102 in such a manner that the back surface (with the cavity 502) faces upwards (the sensor chip 5 is inverted), and the metal electrodes 501 are respectively aligned with the direct-writing conductive silver paste application areas, so that the sensor chip 5 is tightly embedded into the chip packaging groove 102, and the front surface of the sensor chip 5 is flush with the upper end surface of the sensor housing 1.
5) After sintering, the sensor chip 5 and the metal pin 2 are firmly fixed on the sensor housing 1 along with the complete curing of the conductive glass paste in the circular through hole 101, the direct-writing conductive silver paste in the chip packaging groove 102, and the high-temperature-resistant adhesive, and the high-temperature-resistant conductive layer 4 between the metal pin 2 and the opposite end of the metal electrode 501 (and the conductive sealing block 3) is formed.
The following are specifically mentioned: (1) the positions of each metal pin 2, the conductive sealing block 3 formed after the conductive glass paste is cured, the high-temperature-resistant conductive layer 4 formed after the direct-writing conductive silver paste is cured and the metal electrode 501 of the sensor chip 5 are in one-to-one correspondence and are positioned on the same axis, so that complete electric connection can be formed after the sensor is packaged; (2) the depth of the chip packaging groove 102, the coating thickness of the high-temperature-resistant adhesive and the direct-writing conductive silver paste and the thickness of the sensor chip 5 are matched, so that the back surface of the sensor chip is flush with the upper end surface of the sensor shell after the sensor is packaged.
The sensor chip flip-chip package adopted by the embodiment has the advantages that: (1) the circuit structure on the front side of the sensor chip 5 is effectively protected from being invaded by water vapor, dust and corrosive substances in the external environment, the service life of the sensor is long, and the environmental adaptability is strong; (2) for the pressure sensor, the measured medium applies pressure to the back of the sensor chip 5, so that the stability of the electric connection between the metal electrode 501 on the front surface of the sensor chip 5, the conductive sealing block 3 formed after the conductive glass slurry is cured and the metal pin 2 and the high-temperature-resistant conductive layer 4 formed after the direct-writing conductive silver slurry is cured can be effectively promoted, and the connection stability can be higher along with the long-time use of the sensor.
In a word, the high-temperature-resistant leadless packaging structure and the packaging process thereof solve the problem of reliability disintegration and even failure of the conventional metal lead bonding packaging technology in a high-temperature environment, simplify the packaging lead mode, have simple operation, high yield and high reliability in practical use, are suitable for batch production, have low cost and have high cost performance. Meanwhile, the invention improves the working stability and long-term reliability of the sensor in a high-temperature environment by selecting and simplifying the packaging material, and the sensor chip has the advantage of good dynamic response characteristic by adopting flush packaging.
Claims (10)
1. The utility model provides a leadless packaging structure of high temperature resistant sensor which characterized in that: the leadless packaging structure comprises a sensor chip (5), a sensor shell (1) used for supporting the sensor chip (5) and a metal pin (2) arranged on the sensor shell (1), wherein the metal pin (2) is connected with a metal electrode (501) of the sensor chip (5) through a high-temperature-resistant conducting layer (4), and the metal electrode (501) is externally arranged on the surface of the sensor shell (1) or internally arranged in the sensor shell (1).
2. The leadless package structure of high temperature sensor as claimed in claim 1, wherein: the sensor shell (1) comprises a base body and a chip packaging groove (102) formed in the base body, a sensor chip (5) is connected with the sensor shell (1) through a sealing layer (6) arranged at the bottom of the chip packaging groove (102), and the sensor chip (5) is flush with the surface of the sensor shell (1).
3. The leadless package structure of high temperature sensor as claimed in claim 2, wherein: the sealing layer (6) is formed by solidifying the high-temperature resistant adhesive glue coated on the bottom of the chip packaging groove (102); the high-temperature resistant adhesive comprises PbO-ZnO-B2O3Glass paste of the system.
4. The leadless package structure of high temperature sensor as claimed in claim 2, wherein: the sensor shell (1) further comprises a cavity (103) arranged on the base body, and the cavity (103) is connected with the bottom of the chip packaging groove (102).
5. The leadless package structure of high temperature sensor as claimed in claim 2 or 4, wherein: the sensor shell further comprises a through hole (101) formed in the base body, a conductive sealing block (3) is arranged in the through hole (101), and the conductive sealing block (3) is filled between the part, located in the through hole (101), of the metal pin (2) and the inner wall of the through hole (101).
6. The leadless package structure of high temperature sensor as claimed in claim 5, wherein: the conductive sealing block (3) is formed by solidifying conductive glass slurry injected into the inner space of the sensor shell (1) along the through hole (101); the conductive glass paste comprises the components of PbO-ZnO-B2O3Glass paste of the system.
7. The leadless package structure of high temperature sensor as claimed in claim 5, wherein: the substrate is columnar, the chip packaging groove (102) is formed in one end face of the substrate, one end of the through hole (101) is located on the other end face of the substrate, and the other end of the through hole (101) extends to the end face of the substrate, wherein the chip packaging groove (102) is formed in the end face of the substrate.
8. The leadless package structure of claim 7, wherein: the through hole (101) of the sensor shell (1) is connected with the bottom of the chip packaging groove (102), and the high-temperature-resistant conducting layer (4) is arranged between the metal pin (2) and the metal electrode (501) of the sensor chip (5) in a superposition mode; or the through hole (101) of the sensor shell (1) is arranged outside the chip packaging groove (102) at the position on the end face of the base body, and the high-temperature-resistant conducting layer (4) is arranged on the metal pin in a direct-writing mode(2) And a metal electrode (501) of the sensor chip (5); the high-temperature resistant conducting layer (4) adopts PbO-ZnO-B2O3The glass paste is a modified paste containing a glass paste as a main component, and the modified paste is coated and cured.
9. The leadless package structure of claim 7, wherein: the sensor housing (1) further comprises an annular groove (104) arranged on a side face of the base body.
10. A leadless packaging method of a high temperature resistant sensor is characterized in that: the method comprises the following steps:
1) processing a chip packaging groove (102) and a through hole (101) on a substrate to obtain a sensor shell (1);
2) respectively correspondingly bonding the metal pin (2) and the sensor chip (5) with the sensor shell (1) through the through hole (101) and the chip packaging groove (102), then curing, and forming a high-temperature-resistant conducting layer (4) which covers the metal pin (2) and the metal electrode (501) of the sensor chip (5) simultaneously by using a preset slurry which stretches across two sides of the junction position of the sensor shell (1) and the sensor chip (5) in the curing process to obtain a high-temperature-resistant sensor leadless packaging structure with an external metal electrode;
or the metal pin (2) is bonded with the sensor shell (1) through the through hole (101), slurry for forming the high-temperature-resistant conducting layer (4) is placed into the chip packaging groove (102) before the sensor chip (5) is bonded with the sensor shell (1) through the chip packaging groove (102), and therefore the metal pin (2) and the metal electrode (501) of the sensor chip (5) are butted with the high-temperature-resistant conducting layer (4) through curing, and the high-temperature-resistant sensor leadless packaging structure with the built-in metal electrode is obtained.
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| CN202111307080.1A CN114132885A (en) | 2021-11-05 | 2021-11-05 | Leadless packaging structure and method of high-temperature-resistant sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114615798A (en) * | 2022-04-01 | 2022-06-10 | 广州三则电子材料有限公司 | Zero-shrinkage hole-filling conductive slurry and preparation method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114615798A (en) * | 2022-04-01 | 2022-06-10 | 广州三则电子材料有限公司 | Zero-shrinkage hole-filling conductive slurry and preparation method thereof |
| CN114615798B (en) * | 2022-04-01 | 2022-11-29 | 广州三则电子材料有限公司 | Zero-shrinkage hole-filling conductive slurry and preparation method thereof |
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