Low stress MEMS package structure and method of packaging thereof

Abstract

The application discloses a low-stress MEMS packaging structure and a packaging method thereof. The low-stress MEMS packaging structure comprises a plane carrier, a chip, a packaging cover and a protective film. The chip is fixedly arranged on one surface of the plane carrier, and an electrode on the chip is bonded and connected with a pin on the plane carrier. The packaging cover is arranged outside the chip and is fixedly connected with one surface of the plane carrier. A cavity formed by the packaging cover and the one surface of the plane carrier is in a vacuum state. The protective film is sealed and wrapped outside the packaging cover by vacuum coating film technology and high-temperature pressure film curing technology, so that the cavity can keep the vacuum state. The low-stress MEMS packaging structure and the packaging method thereof can effectively overcome the stress influence caused by the combination of various materials, and effectively avoid the influence of external humidity, pressure and the like on the stability of the product, so that the performance of the MEMS packaging structure is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of MEMS packaging, and particularly provides a low-stress MEMS packaging structure and a packaging method thereof. BACKGROUND

[0002] With the development of MEMS packaging technology, the application of MEMS devices is more and more extensive, and the requirements for MEMS devices are also higher, such as the noise requirement, drift and the like of the MEMS devices; and with the development of electronic products, higher requirements are also put forward for the detection precision and the like by using MEMS devices.

[0003] The detection of the MEMS device is realized by micro-mechanical movement, and the mechanical stress affecting the micro-mechanical movement is one of the main factors disturbing the performance improvement of the MEMS device, and the stress source is mainly caused by the difference of the materials in contact after the MEMS is packaged, for example: the plastic encapsulation resin wrapping the MEMS chip, the solder reflow after the cover is pasted. Especially for the widely used multi-chip assembly SiP, the size of the MEMS product is getting smaller and smaller, which can reach 2mm*2mm*1.1mm, so under this size condition, the stress generated by packaging multiple materials together is particularly obvious (especially when the temperature changes), thereby causing the characteristics of the product such as sensitivity, zero drift and the like to deteriorate.

[0004] In order to solve the above technical problems, some manufacturers currently use an open-hole metal cap packaging structure, as shown in the accompanying drawings. Figure 1 However, in order to ensure the subsequent electronic assembly reflow high temperature, the metal cap must be used in the upper open-hole mode, but this will cause the product after the cover to be sealed, and the dust, humidity and the like from the outside will enter the MEMS product, thereby affecting the product characteristics, and the disadvantage of gradual deterioration of the MEMS sensor signal during long-term use cannot be avoided.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] In order to overcome the above defects, the present application provides a low-stress MEMS packaging structure and a packaging method thereof, which is reasonable and easy to implement, can effectively overcome the stress influence caused by the combination of multiple materials, and effectively avoid the influence of external humidity, pressure and the like on the product stability, greatly improving the performance of the MEMS packaging structure.

[0007] The technical scheme adopted by the present application to solve its technical problems is: a low-stress MEMS packaging structure, comprising a plane carrier, a chip, a packaging cover and a protective film, the chip is fixedly arranged on a surface of the plane carrier, and an electrode on the chip is bonded and connected with a pin on the plane carrier; the packaging cover is arranged outside the chip and is fixedly connected with a surface of the plane carrier, and a cavity formed by the packaging cover and the surface of the plane carrier is also formed in a vacuum state; and the protective film is sealed and wrapped outside the packaging cover to ensure that the cavity remains in a vacuum state.

[0008] As a further improvement of the present application, the packaging cover is a hollow cover structure made of metal material, the top of the hollow cover structure is closed, the bottom of the hollow cover structure is open, and a small hole is formed in the side wall of the hollow cover structure;

[0009] When the hollow cover structure is arranged outside the chip, the bottom opening of the hollow cover structure is fixedly connected with a surface of the plane carrier through tin paste; and when the cavity is evacuated, the air in the cavity is discharged through the small hole.

[0010] As a further improvement of the present application, two small holes are symmetrically formed in the opposite side walls of the hollow cover structure.

[0011] As a further improvement of the present application, the chip is fixedly adhered to a surface of the plane carrier by die bonding glue, and the electrode on the chip is bonded and connected with the pin on the plane carrier by gold ball bonding process;

[0012] The protective film adopts a high-temperature-resistant epoxy film, which is sealed and wrapped outside the packaging cover by vacuum film coating technology and high-temperature pressure film curing technology.

[0013] The present application also provides a packaging method of a low-stress MEMS packaging structure, comprising the following steps:

[0014] S1), providing a plane carrier, a plurality of chips are fixedly arranged on a surface of the plane carrier in an array, and electrodes on the plurality of chips are bonded and connected with pins on the plane carrier by gold ball bonding process;

[0015] S2), providing a plurality of packaging covers, and a small hole is formed in the side wall of each packaging cover;

[0016] S3), a plurality of the packaging covers are respectively arranged outside a plurality of the chips, and the bottom openings of the plurality of the packaging covers are respectively fixedly connected with a surface of the plane carrier; at this time, a rough product is obtained;

[0017] S4), a protective film is provided, and the protective film is covered on the top side of the plurality of package covers away from the plane carrier; the prototype covered with the protective film is placed into a vacuum film coating machine to perform low-temperature film pressing treatment, so that the plurality of package covers are formed into a vacuum state together with the surface of the plane carrier, and the protective film can also seal the package cover array group composed of the plurality of package covers as a whole; at this time, an intermediate product is obtained;

[0018] S5), the obtained intermediate product is placed into an oven to perform high-temperature film pressing and curing treatment, so that the protective film can completely seal each package cover while ensuring that the plurality of cavities are in a vacuum state; after the high-temperature film pressing and curing treatment is completed, a semi-finished product is obtained after cooling.

[0019] S6), the obtained semi-finished product is cut to obtain a plurality of low-stress MEMS package structures in an independent single state.

[0020] As a further improvement of the application, the package cover is a hollow cover structure made of a metal material, the top of the hollow cover structure is closed, the bottom is open, and two small holes are symmetrically arranged on the opposite side walls of the hollow cover structure.

[0021] As a further improvement of the application, when S3) is performed, tin paste is first coated on the surface of the plane carrier according to the array layout form of the plurality of chips, and then the plurality of package covers are respectively covered outside the plurality of chips, and then heating is performed to solidify the tin paste, so that the bottom openings of the plurality of package covers are fixedly connected with the surface of the plane carrier.

[0022] As a further improvement of the application, in S4), the working parameters of the vacuum film coating machine for low-temperature film pressing treatment are as follows: the working temperature is 40-60°C, and the pressure applied to the protective film is 0.5-2 Kg / cm 2 .

[0023] As a further improvement of the application, when S5) is performed, the oven is first controlled to be heated at a heating rate of (4-6°C) / min to 140-160°C, and during the heating process, the protective film in a molten state is simultaneously subjected to film pressing operation with a pressure of 0.5-2 Kg / cm 2 , so that the protective film can completely seal each package cover; after the heating and film pressing operation are completed, the intermediate product subjected to the above operation is subjected to heat preservation treatment at a temperature of 140-160°C for 2-3h, so that the protective film is fully cured; after the heat preservation treatment is completed, the semi-finished product is obtained after cooling to room temperature.

[0024] As a further improvement of the present application, the thickness of the protective film can be reduced to half of the initial thickness after the temperature rising and film pressing operation is completed.

[0025] The present application has the following advantages: ①The present application adopts the packaging structure combining the metal packaging cover and the protective film, which can effectively overcome the stress influence caused by the combination of multiple materials, and completely isolate the product cavity from the outside world, effectively avoiding the influence of external humidity, pressure and other factors on the product stability, thereby greatly improving the performance of the MEMS packaging structure. ②The present application opens a small hole on the side wall of the packaging cover, which can facilitate the vacuumization and film covering of the product on the existing vacuum film coating machine, simplifying the process operation, controlling the production cost, facilitating the production implementation, providing the basis for reflow soldering of subsequent product electronic mounting, and avoiding the influence of high temperature of reflow soldering on the product performance. ③The present application also adopts high-temperature film pressing curing treatment, which can not only ensure the sealing property of the MEMS packaging structure, but also accurately reduce the thickness of the MEMS packaging structure to the set size, thereby meeting the production requirements. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a sectional view of the existing metal cap packaging structure;

[0027] Figure 2 is a structure schematic view of the rough product obtained after S3) of the present application is completed;

[0028] Figure 3 is Figure 2 is an enlarged schematic view of the single-packaged rough structure in the rough product shown in FIG. 8;

[0029] Figure 4 is Figure 3 is a sectional view of the single-packaged rough structure shown in FIG. 9;

[0030] Figure 5 is a structure schematic view of the packaging cover of the present application;

[0031] Figure 6 is a structure schematic view of the rough product on which the protective film is pasted and covered in S4) of the present application;

[0032] Figure 7 is Figure 6 is an enlarged schematic view of the protective film pasted and covered on the single-packaged rough structure shown in FIG. 10;

[0033] Figure 8 is a structure schematic view of the low-stress MEMS packaging structure of the present application;

[0034] Figure 9 A perspective view of the low-stress MEMS packaging structure according to the present application.

[0035] The following description is made in connection with the drawings identified below:

[0036] 1 - plane carrier; 2 - chip; 3 - packaging cover; 30 - small hole; 4 - protective film. DETAILED DESCRIPTION

[0037] The advantages and effects of the present application can be easily understood by those skilled in the art from the content disclosed in the present specification.

[0038] It should be noted that the structures, proportions, sizes, etc. shown in the drawings attached to the present specification are only used to understand and read the content disclosed in the present specification by those skilled in the art, and do not define the limiting conditions for the implementation of the present application, and therefore do not have technical substantive significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application.

[0039] Embodiment:

[0040] Please refer to the drawings attached to the present specification Figure 8 and 9 , which are respectively a structural schematic view and a perspective view of the low-stress MEMS packaging structure according to the present application.

[0041] The low-stress MEMS packaging structure according to the present application comprises a plane carrier 1, a chip 2, a packaging cover 3 and a protective film 4. The chip 2 is fixedly arranged on a surface of the plane carrier 1, and the electrodes on the chip 2 are bonded and connected with the pins on the plane carrier 1. The packaging cover 3 is arranged outside the chip 2 and is fixedly connected with a surface of the plane carrier 1, and the chamber enclosed by the packaging cover 3 and the surface of the plane carrier 1 is also formed in a vacuum state. The protective film 4 is sealed and wrapped outside the packaging cover 3 to ensure that the chamber remains in a vacuum state. The MEMS packaging structure can not only effectively overcome the stress influence caused by the combination of various materials, but also completely isolate the inner cavity of the product from the outside world, effectively avoiding the influence of external humidity, pressure, etc. on the stability of the product, thereby greatly improving the performance of the MEMS packaging structure.

[0042] In the present embodiment, preferably, please refer to the drawings attached to the present specification Figure 3 to Figure 5As shown, the encapsulation cover 3 is a hollow cover structure made of metal material. The top of the hollow cover structure is closed and the bottom is open. Small holes 30 are provided on the side walls of the hollow cover structure.

[0043] After the hollow cover structure is placed over the chip 2, the bottom opening of the hollow cover structure is fixedly connected to a surface of the planar carrier 1 by solder paste; and when the chamber is evacuated using a vacuum coating machine, the air in the chamber is discharged through the small hole 30.

[0044] More preferably, two small holes 30 are symmetrically formed on the opposite two vertical walls of the hollow cover structure. Of course, during production, the number and size of the small holes 30 are determined according to actual production needs.

[0045] In this embodiment, preferably, the planar carrier 1 is one of a ceramic substrate, a silicon substrate, and an FR4 substrate, but is not limited to the above substrate materials. The planar carrier 1 can be a single-layer or multi-layer structure, and can be a single-plate structure or a multi-plate structure. The chip 2 is bonded to a surface of the planar carrier 1 by die bonding adhesive, and the electrodes on the chip 2 are bonded to the pins on the planar carrier 1 by gold wire ball bonding process. More specifically, when mounting the chips, several chips 2 are first bonded to a surface of the planar carrier 1 by die bonding adhesive (such as DAF film), and then the die bonding adhesive is cured by heating. Then, the electrodes on several chips 2 are bonded to the pins on the planar carrier 1 by gold wire ball bonding process.

[0046] In this embodiment, preferably, the protective film 4 is a high-temperature resistant epoxy film commonly used in the filter industry that can withstand baking at 200°C. The adhesive surface of the high-temperature resistant epoxy film has a certain degree of adhesion. Furthermore, the high-temperature resistant epoxy film is sealed and wrapped around the encapsulation cover 3 using vacuum coating technology and high-temperature pressing curing technology.

[0047] The present invention also provides a packaging method for the above-mentioned low-stress MEMS packaging structure, comprising the following steps:

[0048] S1) A planar carrier 1 is provided, on which a plurality of chips 2 are arrayed and fixedly mounted on one surface of the planar carrier 1, and the electrodes on the plurality of chips 2 are bonded to the pins on the planar carrier 1 by a gold wire ball bonding process. For details, please refer to the appendix. Figure 2 and 4 As shown;

[0049] S2) Provide a plurality of encapsulation covers 3, and each of the encapsulation covers 3 has a small hole 30 on its side wall (see appendix for details). Figure 5 (As shown), this is in preparation for subsequent vacuum coating;

[0050] S3), a cover corresponding to each of the packaging caps 3 is arranged outside each of the chips 2, and the bottom opening of each of the packaging caps 3 is fixedly connected to a surface of the planar carrier 1; at this time, a prototype product is obtained, which can be specifically referred to in Figs. 3 and 4. Figure 2 and 3 as shown;

[0051] S4), a protective film 4 is provided, which is a high-temperature-resistant epoxy film commonly used in the filter industry and can withstand baking at 200°C. The adhesive surface of the high-temperature-resistant epoxy film has a certain adhesion. After the protective film 4 is pasted and covered on the top side of the packaging caps 3 away from the planar carrier 1, it can be specifically referred to in Figs. 5 and 6. Then, the prototype product covered with the protective film 4 is placed into a vacuum film coating machine for low-temperature film pressing treatment, so that the chambers enclosed by each of the packaging caps 3 and the surface of the planar carrier 1 are formed in a vacuum state, and the protective film 4 can also seal and wrap the entire packaging cap array group composed of the packaging caps 3; at this time, an intermediate product is obtained. Figure 6 and 7 as shown; then, the obtained intermediate product is placed into an oven for high-temperature film pressing and curing treatment, so that the protective film 4 can completely seal and wrap each of the packaging caps 3 while ensuring that each of the chambers remains in a vacuum state, ensuring the sealing property of each MEMS packaging structure in the subsequent process; after the high-temperature film pressing and curing treatment is completed, the semi-finished product is cooled to obtain a semi-finished product.

[0052] S5), the obtained semi-finished product is cut to obtain a plurality of low-stress MEMS packaging structures in an independent single state, which can be specifically referred to in Figs. 7 and 8.

[0053] S6), the obtained semi-finished product is cut to obtain a plurality of low-stress MEMS packaging structures in an independent single state, which can be specifically referred to in Figs. 7 and 8. Figure 8 and 9 as shown.

[0054] Preferably, in the above S1), the planar carrier 1 adopts one of a ceramic substrate, a silicon substrate and an FR4 substrate, but is not limited to the above substrate materials, and the planar carrier 1 can adopt a single-layer or multi-layer structure, and the planar carrier 1 can be an integral plate structure or a multi-plate structure. In addition, when the chip is mounted, the chip adhesive (such as DAF film) is first used to bond the plurality of chips 2 to a surface of the planar carrier 1, and then heated to solidify the chip adhesive, and then the gold ball bonding process is used to bond and connect the electrodes on the plurality of chips 2 to the pins on the planar carrier 1.

[0055] Preferably, in the above S2), the packaging cover 3 is a hollow cover structure made of metal material, the top of the hollow cover structure is closed, the bottom is open, and two small holes 30 are symmetrically arranged on the opposite side walls of the hollow cover structure. Of course, the number and size of the small holes 30 are determined according to actual production needs during production.

[0056] Preferably, when performing the above S3), tin paste is first coated on a surface of the plane carrier 1 in the form of an array of a plurality of chips 2, and then a plurality of packaging covers 3 are respectively correspondingly covered outside a plurality of chips 2, and then heating is performed to solidify the tin paste, so that the bottom openings of a plurality of packaging covers 3 are fixedly connected with a surface of the plane carrier 1.

[0057] Preferably, in the above S4), the working parameters of the vacuum laminating machine for low-temperature laminating processing are: working temperature 40-60°C, pressure applied to the protective film 4 0.5-2 Kg / cm 2 ; and further preferably: working temperature 50°C, pressure 1-1.5 Kg / cm 2 .

[0058] The working mechanism of the above S4) is: after the embryonic product covered with the protective film 4 is placed in the vacuum laminating machine, the vacuum laminating machine first performs vacuumization, so that the air in a plurality of cavities is extracted through the small holes 30, and a plurality of cavities are formed in a vacuum state (the present application does not have special requirements for the vacuum degree, which is determined according to production needs); and when the temperature in the working chamber of the vacuum laminating machine rises to 40-60°C, the protective film 4 becomes soft, and under the action of air pressure with a pressure of 0.5-2 Kg / cm 2 , the protective film 4 is pressed downward, so that the top side of a plurality of packaging covers 3 and the side walls of a plurality of packaging covers 3 distributed around are wrapped (correspondingly, the small holes 30 on the side walls of a plurality of packaging covers 3 distributed around are also blocked by the protective film 4), that is, the protective film 4 wraps the whole packaging cover array group composed of a plurality of packaging covers 3, and the inside of the intermediate product is in a vacuum state.

[0059] Preferably, when performing the above S5), the oven is first controlled to rise at a temperature rising rate of (4°C-6°C) / min to 140-160°C, and in the rising process, the protective film 4 becomes a molten glue state (or semi-liquid state) while being pressed with a pressure of 0.5-2 Kg / cm 2The lamination operation is performed on the protection film 4 in a molten state to completely seal each package cover 3, and ensure the sealing of each MEMS package structure. After the lamination operation, the intermediate product is subjected to a heat preservation treatment at a temperature of 140-160℃ for 2-3h to fully solidify the protection film 4, ensure the bonding force between the protection film 4 and the package cover 3 and between the package cover 3 and the planar carrier 1, and eliminate stress. After the heat preservation treatment and cooling to room temperature, the semi-finished product is obtained.

[0060] In addition, the specific working parameters in S5) can be further preferred as follows: the oven is heated to 150℃ at a heating rate of 5℃ / min, and during the heating process, the lamination operation is performed on the protection film 4 in a molten state at a pressure of 1-1.5Kg / cm 2 The heat preservation treatment parameters are as follows: the heat preservation temperature is 150℃, and the heat preservation time is 2-3h.

[0061] In addition, after the heating and lamination operation, the thickness of the protection film 4 can be reduced to half of the initial thickness. For example, the initial thickness of the protection film 4 is 200μm, and after the heating and lamination operation, the thickness of the protection film 4 can be reduced to 100μm.

[0062] In summary, the present application has the following advantages: ①The metal package cover and the protection film are combined to form a package structure, which can effectively overcome the stress caused by the combination of multiple materials, and completely isolate the product cavity from the outside world, thereby avoiding the influence of humidity and pressure on the product stability and greatly improving the performance of the MEMS package structure. ②Small holes are formed on the side walls of the package cover, which can facilitate the vacuumization and film coating of the product on the existing vacuum film coating machine, simplify the process operation and control the production cost, facilitate the production, provide the basis for subsequent electronic mounting, and prevent the product from being affected by the high temperature of the reflow soldering. ③The high-temperature lamination solidification treatment can ensure the sealing of the MEMS package structure and accurately reduce the thickness of the MEMS package structure to a set size, which meets the production requirements.

[0063] The above embodiments only exemplarily illustrate the effects of the present application, and are not used to limit the present application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the technical principles of the present application, and these improvements and modifications should be considered within the protection scope of the present application.

Claims

1. A low-stress MEMS package structure, characterized by: The package structure comprises a plane carrier (1), a chip (2), a package cover (3) and a protective film (4), the chip (2) is fixedly arranged on a surface of the plane carrier (1), and electrodes on the chip (2) are bonded and connected with pins on the plane carrier (1); the package cover (3) is arranged outside the chip (2) and is fixedly connected with a surface of the plane carrier (1), and a cavity enclosed by the package cover (3) and the surface of the plane carrier (1) is also formed in a vacuum state; and the protective film (4) is sealed and wrapped outside the package cover (3) to ensure that the cavity is kept in a vacuum state. The package cover (3) is a hollow cover structure made of metal material, the top of the hollow cover structure is closed, the bottom is open, and a small hole (30) is formed in the side wall of the hollow cover structure. When the hollow cover structure is arranged outside the chip (2), the bottom opening of the hollow cover structure is fixedly connected with a surface of the plane carrier (1) through tin paste; and when the cavity is vacuumized, the air in the cavity is discharged through the small hole (30). The chip (2) is fixedly arranged on a surface of the plane carrier (1) by means of die bonding, and the electrodes on the chip (2) are bonded and connected with the pins on the plane carrier (1) by means of gold ball bonding process. The protective film (4) is made of high-temperature-resistant epoxy film, which is sealed and wrapped outside the package cover (3) by vacuum film coating technology and high-temperature film pressing curing technology. The high-temperature film pressing curing technology can accurately thin the thickness of the MEMS package structure to a set size.

2. The low-stress MEMS package structure of claim 1, wherein: Two small holes (30) are symmetrically formed in the opposite side walls of the hollow cover structure.

3. A packaging method of a low-stress MEMS package structure, characterized by: The method comprises the following steps: S1), providing a plane carrier (1), a plurality of chips (2) are fixedly arranged on a surface of the plane carrier (1) in an array, and electrodes on the plurality of chips (2) are bonded and connected with pins on the plane carrier (1) by means of gold ball bonding process; S2), providing a plurality of package covers (3), and a small hole (30) is formed in the side wall of each package cover (3); S3), a plurality of package covers (3) are respectively arranged outside a plurality of chips (2), and the bottom openings of the plurality of package covers (3) are respectively fixedly connected with a surface of the plane carrier (1); at this time, a rough product is obtained; S4), providing a protective film (4), covering the protective film (4) on the top side of the plurality of package covers (3) away from the plane carrier (1), and then placing the rough product covered with the protective film (4) into a vacuum film coating machine for low-temperature film pressing treatment, so that the plurality of package covers (3) and the surface of the plane carrier (1) together form a cavity in a vacuum state, and the protective film (4) can also seal and wrap the package cover array group composed of the plurality of package covers (3) as a whole; at this time, an intermediate product is obtained; S5), providing a protective film (4), covering the protective film (4) on the top side of the plurality of package covers (3) away from the plane carrier (1), and then placing the rough product covered with the protective film (4) into a vacuum film coating machine for low-temperature film pressing treatment, so that the plurality of package covers (3) and the surface of the plane carrier (1) together form a cavity in a vacuum state, and the protective film (4) can also seal and wrap the package cover array group composed of the plurality of package covers (3) as a whole; at this time, an intermediate product is obtained; S5), the obtained intermediate product is placed into an oven for high-temperature film-pressing curing treatment, so as to ensure that the cavities are kept in vacuum state and the protective film (4) can completely seal and wrap each package cover (3); after the high-temperature film-pressing curing treatment is completed, the semi-finished product is obtained after cooling; S6), the obtained semi-finished product is cut to obtain a plurality of low-stress MEMS package structures in independent single states.

4. The packaging method of a low-stress MEMS package structure according to claim 3, wherein: The package cover (3) is a hollow cover structure made of metal material, the hollow cover structure is closed at the top and open at the bottom, and two small holes (30) are symmetrically arranged on the opposite side walls of the hollow cover structure.

5. The packaging method of a low-stress MEMS package structure according to claim 3, wherein: When S3) is performed, tin paste is first coated on a surface of the plane carrier (1) according to the array layout of the plurality of chips (2), then the plurality of package covers (3) are respectively covered outside the plurality of chips (2), and then heating is performed to solidify the tin paste, so that the bottom openings of the plurality of package covers (3) are fixedly connected with the surface of the plane carrier (1).

6. The packaging method of a low-stress MEMS package structure according to claim 3, wherein: In the above S4), the working parameters of the vacuum laminator for low-temperature lamination are as follows: working temperature 40-60°C, and pressure applied to the protective film (4) 0.5-2 Kg / cm 2 .

7. The packaging method of a low-stress MEMS package structure according to claim 3, wherein: In the above S5), first, the oven is controlled to be heated to 140-160°C at a heating rate of (4-6°C) / min, and during the heating, the protective film (4) being changed into a molten state is simultaneously subjected to a film-pressing operation with a pressure of 0.5-2 Kg / cm 2 After the heating and film-pressing operation are completed, the intermediate product subjected to the above operation is subjected to a heat preservation treatment at a temperature of 140-160°C for 2-3 h, so that the protective film (4) is fully solidified. After the heat preservation treatment is completed and the product is cooled to room temperature, the semi-finished product is obtained.

8. The packaging method of a low-stress MEMS package structure according to claim 7, wherein: After the temperature rising and film pressing operations are completed, the thickness of the protective film (4) can be reduced to half of the initial thickness.

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