A pressureless sintering interconnect process for nanometals

Abstract

This invention belongs to the field of power electronic device packaging and relates to a pressureless sintering interconnection process for nano-metals. Through steps such as stencil printing, nitrogen drying, pre-connection using a chip mounter, and pressureless sintering, a reliable connection between nano-metal solder paste and copper-clad ceramic substrates and chips is achieved. This invention eliminates the need for pressure sintering equipment, significantly reducing costs while improving production efficiency. The pressureless sintering process ensures complete sintering of the nano-metal solder paste, forming a stable connection structure. This process meets the high-temperature packaging technology requirements of the power electronic device packaging field and provides strong support for the widespread application of wide-bandgap semiconductor devices.

Description

Technical Field

[0001] This invention belongs to the field of power electronic device packaging and relates to a pressureless sintering interconnection process for nano-metals. Background Technology

[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 speed. However, their large-scale application has not yet been achieved due to high production costs and a lack of efficient and reliable high-temperature packaging technologies. Nanoscale metal particles can be sintered and connected at relatively low temperatures, and the resulting dense sintered structure retains the high melting point of the bulk metal. Nanoscale silver or copper, due to their excellent thermal conductivity and good high-temperature reliability, are widely used as interconnect materials for power device chips. To ensure a certain sintering strength and reliability, sintering pressure is usually applied during the interconnection process. However, sintering furnaces with pressure-applying capabilities are expensive and can only sinter a few samples at a time, resulting in low production efficiency. Therefore, there is a need to develop simpler, more economical, and more efficient sintering interconnection processes. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a pressureless sintering interconnection process for nano-metals that is simple, economical and effective. By using a chip mounter for pressure pre-connection, the entire nano-metal sintering process can be completed using a conventional nitrogen drying oven.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a pressureless sintering interconnection process for nanometals, comprising the following steps:

[0005] S1 employs precision stencil printing technology, which controls the pressure and speed of the squeegee to ensure that 100μm thick nano-metal solder paste is uniformly and precisely pre-coated on the designated area surface of the copper-clad ceramic substrate to form a solder paste layer of uniform thickness.

[0006] S2. Carefully transfer the ceramic substrate coated with solder paste into a nitrogen drying oven and introduce high-purity nitrogen to remove oxygen. Heat the oven to a temperature range of 130-140°C and maintain this temperature for 20 minutes to remove solvents and volatiles from the solder paste.

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

[0008] S4. Transfer the chip and substrate to a nitrogen drying furnace and introduce nitrogen gas. Heat the furnace to 250°C and perform pressureless sintering for 10-60 minutes. Then cool the furnace to room temperature.

[0009] Optionally, the nanomaterial can be a metallic material of silver, copper, or gold.

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

[0011] The beneficial effects of this invention are as follows: This invention provides a nano-metal pressureless sintering interconnect process. By increasing the bonding time and pressure, a certain degree of pre-connection is achieved, followed by a longer pressureless sintering time to achieve the ideal sintering strength. Although this method increases the sintering time, it eliminates the need for expensive pressure sintering equipment, and hundreds of samples can be sintered at a time, significantly increasing production efficiency.

[0012] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0013] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0014] Figure 1 This is a production flow diagram of the present invention;

[0015] Figure 2 This is a schematic diagram of the shear strength of specific embodiments 1 and 2 of the present invention. Detailed Implementation

[0016] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed 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 are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0017] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0018] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0019] Specific Implementation Example 1,

[0020] A pressureless sintering interconnect process for nanometals, the process is as follows: Figure 1 As shown, the specific preparation method is as follows:

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

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

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

[0024] (4) Transfer the chip and substrate to a nitrogen drying furnace and introduce nitrogen gas. Heat the furnace to 250°C and perform pressureless sintering for 60 minutes. Then cool the furnace to room temperature.

[0025] Specific embodiment 2,

[0026] A pressureless sintering interconnect process for nanometals, the process is as follows: Figure 1 As shown, the specific preparation method is as follows:

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

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

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

[0030] (4) Transfer the chip and substrate to a nitrogen drying furnace and introduce nitrogen gas. Heat the furnace to 250°C and perform pressureless sintering for 10 minutes. Then cool the furnace to room temperature.

[0031] Performance testing,

[0032] Shear strength tests were performed on the interconnect structures formed by sintering the chip and substrate together using nano-metal solder paste in Specific Embodiments 1 and 2, and the results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the shear strength of the interconnect structure formed by sintering the chip and substrate together using nano-copper solder paste in Example 3 meets the standard of GB / T4937.19-2018 (Mechanical and Climatic Testing Methods for Semiconductor Devices Part 19: Chip Shear Strength). This demonstrates that the sintering process involved in this invention has a good connection effect.

[0033] Traditional nano-metal sintering processes include four stages: stencil printing, nitrogen drying, chip mounting, and pressure sintering. Chip mounting pressure is typically below 5 MPa for 1 second, and pressure sintering takes 5–10 minutes. This invention achieves a certain degree of pre-connection by increasing the mounting time and pressure, followed by a longer pressureless sintering period to reach the desired sintering strength. While this method increases sintering time, it eliminates the need for expensive pressure sintering equipment, allowing for the sintering of hundreds of samples at a time, significantly increasing production efficiency.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A pressureless sintering interconnection process for nanometals, characterized in that, Includes the following steps: S1 employs precision stencil printing technology, which controls the pressure and speed of the squeegee to ensure that 100μm thick nano-metal solder paste is uniformly and precisely pre-coated on the designated area surface of the copper-clad ceramic substrate to form a solder paste layer of uniform thickness. S2. Carefully transfer the ceramic substrate coated with solder paste into a nitrogen drying oven and introduce high-purity nitrogen to remove oxygen. Heat the oven to a temperature of 130-140°C and maintain this temperature for 20 minutes to remove solvents and volatiles from the solder paste. S3, place the dried ceramic substrate on the pick-and-place machine track tray and preheat it to 150°C; at the same time, place the chip onto the solder paste printing area on the substrate surface, set the pick-and-place head temperature to 150°C and apply a pressure of 5~20 MPa, and hold for 5~10s to achieve pre-connection between the chip and the substrate. S4. Transfer the chip and substrate to a nitrogen drying oven and introduce nitrogen gas. Heat the oven to 250°C and perform pressureless sintering for 10-60 minutes. Then cool the oven to room temperature. By using a chip mounter for pre-connection under pressure, the entire nano-metal sintering process can be completed using a conventional nitrogen drying oven.

2. The pressureless sintering interconnection process for nanometals according to claim 1, characterized in that: Nanomaterials are metallic materials made of silver, copper, or gold.

3. The pressureless sintering interconnection process for nanometals according to claim 1, characterized in that: It is suitable for power electronic device packaging, such as SiC and GaN packaging.

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