Nanometal pressureless sintering interconnection process

Abstract

The invention belongs to the field of power electronic device packaging, and relates to a nanometal pressureless sintering interconnection process, which realizes reliable connection of nanometal soldering paste, a copper-clad ceramic substrate and a chip through the steps of steel mesh printing, nitrogen drying, chip mounter pre-connection, pressureless sintering and the like. Pressure sintering equipment is omitted, the cost is remarkably reduced, and meanwhile the production efficiency is improved; the pressureless sintering process ensures full sintering of the nano metal soldering paste, and a stable connection structure is formed; the process meets the requirement of the power electronic device packaging field on the high-temperature packaging technology, and provides powerful support for wide application of wide-band-gap semiconductor devices.

Description

Technical Field

[0001] The invention belongs to the field of power electronic device packaging and relates to a nano metal pressureless sintering interconnection process. Background Art

[0002] Wide-bandgap semiconductors represented by SiC and GaN have gradually become a research hotspot due to their advantages such as low power consumption, high thermal conductivity and high switching rate. However, due to the high production cost and the lack of efficient and reliable high-temperature packaging technology, large-scale application has not yet been achieved. Nanometal particles can be sintered and connected at a lower temperature, and the dense sintered structure after forming still retains the high melting point of the bulk metal. Nanosilver or copper is widely used as a chip interconnect material for power devices because of its excellent thermal conductivity and good high-temperature reliability. In order to ensure a certain sintering strength and reliability, it is usually necessary to apply sintering pressure during the interconnection process. However, sintering furnaces with pressurization functions are relatively expensive, and can only sinter a few samples at a time, and the production efficiency is low. Therefore, it is necessary to develop a simpler, more economical and effective sintering interconnection process. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a nano-metal pressureless sintering interconnection process, which is simple, economical and effective. The entire nano-metal sintering process can be completed by using a placement machine for pressurized pre-connection and a common nitrogen drying furnace.

[0004] To achieve the above object, the present invention provides the following technical solution: a nano-metal pressureless sintering interconnection process, comprising the following steps:

[0005] S1, using precision steel screen printing technology, by controlling the scraper pressure and speed, to ensure that the 100μm thick nano metal solder paste is evenly and accurately pre-coated on the surface of the designated area of ​​the copper-clad ceramic substrate to form a uniform thickness of solder paste layer;

[0006] S2, carefully transfer the ceramic substrate coated with solder paste to a nitrogen drying furnace, introduce high-purity nitrogen to exclude oxygen, raise the temperature to 130-140°C, maintain this temperature for 20 minutes of drying treatment to remove the solvent and volatiles in the solder paste;

[0007] S3, place the dried ceramic substrate on the track tray of the placement machine and preheat it to 150°C; at the same time, mount the chip on the solder paste printing area on the surface of the substrate, set the temperature of the placement head to 150°C and apply a pressure of 5 to 20 MPa, and maintain it for 5 to 10 seconds to achieve pre-connection between the chip and the substrate;

[0008] S4, transferring the chip and substrate to a nitrogen drying furnace and introducing nitrogen, heating to 250°C, performing pressureless sintering for 10-60 minutes, and then cooling to room temperature with the furnace.

[0009] Optionally, the nano metal material is a metal material of silver, copper or gold.

[0010] Optionally, it is applicable to the field of power electronic device packaging, especially for the packaging of wide bandgap semiconductor devices such as SiC and GaN.

[0011] The beneficial effect of the present invention is that the nano-metal pressureless sintering interconnection process of the present invention achieves a certain degree of pre-connection by increasing the patch time and pressure, and finally cooperates with a longer pressureless sintering to achieve the ideal sintering strength. Although this method increases the sintering time, it saves expensive pressure sintering equipment, and can sinter hundreds of samples at a time, greatly increasing production efficiency.

[0012] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0014] Figure 1 It is the production flow chart of the present invention;

[0015] Figure 2 It is a schematic diagram of the shear strength of specific embodiments 1 and 2 of the present invention. DETAILED DESCRIPTION

[0016] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and the features in the embodiments can be combined with each other without conflict.

[0017] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0018] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0019] Specific embodiment 1,

[0020] A nano-metal pressureless sintering interconnection process, the process is as follows Figure 1 The specific preparation method is as follows:

[0021] (1) Using steel screen printing to control the thickness, a 100 μm thick nano-metal solder paste is evenly pre-coated on the surface of the copper-clad ceramic substrate;

[0022] (2) Transfer the ceramic substrate to a nitrogen drying furnace and introduce nitrogen, raise the temperature to 130-140° C., and dry for 20 min;

[0023] (3) Place the dried ceramic substrate on the track tray of the placement machine and preheat it to 150°C; at the same time, mount the chip on the solder paste printing area on the substrate surface, set the placement head temperature to 150°C and apply a pressure of 5 MPa, and maintain it for 5 seconds to achieve pre-connection between the chip and the substrate;

[0024] (4) The chip and substrate were transferred to a nitrogen drying furnace and nitrogen was introduced. The temperature was raised to 250°C and pressureless sintered for 60 minutes, followed by cooling to room temperature in the furnace.

[0025] Specific embodiment 2,

[0026] A nano-metal pressureless sintering interconnection process, the process is as follows Figure 1 The specific preparation method is as follows:

[0027] (1) Using steel screen printing to control the thickness, a 100 μm thick nano-metal solder paste is evenly pre-coated on the surface of the copper-clad ceramic substrate;

[0028] (2) Transfer the ceramic substrate to a nitrogen drying furnace and introduce nitrogen, raise the temperature to 130-140° C., and dry for 20 min;

[0029] (3) Place the dried ceramic substrate on the track tray of the placement machine and preheat it to 150°C; at the same time, mount the chip on the solder paste printing area on the surface of the substrate, set the temperature of the placement head to 150°C and apply a pressure of 20MPa, and maintain it for 10 seconds to achieve pre-connection between the chip and the substrate;

[0030] (4) The chip and substrate were transferred to a nitrogen drying furnace and nitrogen was introduced. The temperature was raised to 250°C and pressureless sintered for 10 min. The mixture was then cooled to room temperature in the furnace.

[0031] Performance testing,

[0032] The shear strength test was conducted on the interconnection structure formed by sintering the chip and the substrate through the nano-metal solder paste in Specific Example 1 and Specific Example 2. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the shear strength of the interconnection structure formed by sintering the chip and the substrate by nano copper solder paste in Example 3 meets the standard of "GB / T4937.19-2018" (Mechanical and climatic test methods for semiconductor devices Part 19: Chip shear strength). This shows that the sintering process involved in the present invention has a good connection effect.

[0033] The traditional nanometal sintering process includes four stages: steel screen printing, nitrogen drying, chip mounting, and pressure sintering. The chip mounting pressure is usually less than 5MPa, the time is 1s, and the pressure sintering time is 5 to 10min. The present invention achieves a certain degree of pre-connection by increasing the chip mounting time and pressure, and finally cooperates with a longer period of pressureless sintering to achieve the ideal sintering strength. Although this method increases the sintering time, it eliminates the expensive pressure sintering equipment, and can sinter hundreds of samples at a time, greatly increasing production efficiency.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A nano-metal pressureless sintering interconnection process, characterized in that: The following steps are involved: S1, using precision steel screen printing technology, by controlling the scraper pressure and speed, to ensure that the 100μm thick nano metal solder paste is evenly and accurately pre-coated on the surface of the designated area of ​​the copper-clad ceramic substrate to form a uniform thickness of solder paste layer; S2, carefully transfer the ceramic substrate coated with solder paste to a nitrogen drying furnace, introduce high-purity nitrogen to exclude oxygen, raise the temperature to 130-140°C, maintain this temperature for 20 minutes of drying treatment to remove the solvent and volatiles in the solder paste; S3, place the dried ceramic substrate on the track tray of the placement machine and preheat it to 150°C; at the same time, mount the chip on the solder paste printing area on the surface of the substrate, set the temperature of the placement head to 150°C and apply a pressure of 5 to 20 MPa, and maintain it for 5 to 10 seconds to achieve pre-connection between the chip and the substrate; S4, transferring the chip and substrate to a nitrogen drying furnace and introducing nitrogen, heating to 250°C, performing pressureless sintering for 10-60 minutes, and then cooling to room temperature with the furnace.

2. The nano-metal pressureless sintering interconnection process according to claim 1, characterized in that: The nano metal material is a metal material of silver, copper or gold.

3. The nano-metal pressureless sintering interconnection process according to claim 1, characterized in that: It is suitable for the packaging of power electronic devices, especially for the packaging of wide bandgap semiconductor devices such as SiC and GaN.

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