CN112440025B

CN112440025B - Double-sided micro-nano composite preformed soldering lug for electronic device and low-temperature interconnection method

Info

Publication number: CN112440025B
Application number: CN201910823706.0A
Authority: CN
Inventors: 刘磊; 王文淦; 邹贵生
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2019-09-02
Filing date: 2019-09-02
Publication date: 2022-02-18
Anticipated expiration: 2039-09-02
Also published as: CN112440025A

Abstract

The invention provides a double-sided micro-nano composite preformed soldering lug for an electronic device and a low-temperature interconnection method. The double-sided micro-nano composite preformed soldering lug comprises an intermediate layer and porous micro-nano films positioned on two sides of the intermediate layer; the porous micro-nano film is a metal film or an alloy film. The invention also provides a low-temperature interconnection method, which realizes the low-temperature interconnection of the to-be-connected parts through the double-sided micro-nano composite preformed soldering lug. The invention can solve the problems that the LT-TLPB technology has too long connection time and the joint can not meet the service temperature of a high-performance power device. The porous micro-nano film does not need to introduce organic components, and a series of problems caused by the organic components in the metal micro-nano particle soldering paste are solved from the source.

Description

Double-sided micro-nano composite preformed soldering lug for electronic device and low-temperature interconnection method

Technical Field

The invention relates to a double-sided micro-nano composite preformed soldering lug for an electronic device and a low-temperature interconnection method, and belongs to the technical field of electronic materials.

Background

In order to meet the severe requirements of the current power electronic industry on the device performance and the bearing capacity of the service environment, a new generation of high-performance power electronic device represented by a silicon carbide-based power device generally has the characteristic of being capable of working at a high temperature of 300 ℃ or above. Generally, such high performance power electronic devices are often manufactured in the form of rectangular patches, and thus the material for connecting these devices with the electronic module substrate is also generally required to be manufactured as a thin film or formed after a certain process.

In the field of conventional electronic packaging, tin-based solders are a widely used type of chip interconnection material, however, most of the tin-based solders have a melting point lower than 300 ℃, which makes it a great challenge to connect the aforementioned new generation of high-performance power electronic devices by using conventional solder soldering technology. At present, methods for realizing the aforementioned patch interconnection of high-performance power electronic devices are roughly classified into three categories: high-temperature solder, transition liquid phase connection technology and sintering metal nano-particles are adopted.

Low Temperature Transient Liquid Phase Bonding (LT-TLPB) was first traced to Leonard Bernstein in 1966. As shown In fig. 1, this method melts an intermediate layer (usually Sn, In, or In — Sn alloy In — Bi alloy, etc.) having a low melting point by heating, and reacts it with a high-melting base metal to be joined, such as Cu, Ag, Au, Ni, etc., to form a joint comprising an intermetallic compound having a high melting point. Because the intermetallic compound obtained by the LT-TLPB technology generally has a higher melting point, the joint has relatively better capability of bearing heat load.

Taking the Cu-Sn system as an example, the basic features of the LT-TLPB technology can be described in detail by the procedures given in the literature (C.Hang, Y.Tian, R.Zhang, and D.Yang, "Phase transformation and grain orientation of Cu-Sn interfacial complex reduced low temperature binding process," Journal of Materials Science: Materials in Electronics, vol.24, No.10, pp.3905-3913,2013). As shown in FIG. 2, the solid-solid diffusion of Cu/Sn atoms occurs at the interface between the Sn intermediate layer and the upper and lower Cu base materials at the start of heating, and the rate is relatively slow, and it is found from a Cu-Sn binary phase diagram that a small amount of Cu should be present at the interface₆Sn₅And (4) forming. When the heating temperature reaches the melting point of Sn, the intermediate layer starts to melt, and more Cu is formed between Cu and Sn through the relatively fast solid-liquid diffusion₆Sn₅As shown in fig. 2 (a). With the lapse of time, as shown in (b) of FIG. 2, liquid Sn is gradually consumed, and Cu₆Sn₅Grow into the interior of the joint until the upper and lower sides contact each other and merge into larger crystals. Proceeding to this stage (c) of FIG. 2, according to the interfacial reaction process described in 2.3.2, at Cu-Cu₆Sn₅Cu and Cu will be generated at the interface₆Sn₅Reaction to form Cu₃Process of Sn, at this time Cu₆Sn₅Will be consumed and Cu₃Sn is perpendicular to Cu-Cu₆Sn₅The interface grows continuously in the form of fine columnar crystals toward the inside of the joint. After a sufficient holding time, Cu in the joint₆Sn₅All is converted into Cu₃Sn, the joint structure is homogenized in the form of (d) in fig. 2.

At present, although the LT-TLPB technology is applied to partial high-temperature electronic devices, the connection process still has the following problems:

1. the connection efficiency is low. All the ideal joints for LT-TLP connection are intermetallic compounds formed after phase transformation, so the corresponding connection time is required to ensure that the substrate metal and the middle layer metal are fully diffused and isothermal solidification and tissue homogenization are completed, otherwise, low-melting-point phases remain in the joints, and the high-temperature performance of the joints is seriously influenced. However, prolonged incubation will result in excessive heat input to other devices in the packaged module, potentially leading to failure of the entire module due to overheating of the devices. Furthermore, according to the prediction of the diffusion kinetics theory, the complete LT-TLPB process takes at least tens of minutes, and longer when the interlayer thickness is greater than 10 μm. Therefore, the connection efficiency is an important factor for restricting the development of the LT-TLPB connection technology.

2. The joint presents a hole sufficient to cause failure of the crack. In the LT-TLPB connection, although the joint after the tissue homogenization and the connection parent metal have good thermal expansion coefficient matching degree, the difference of the thermal expansion coefficients between the intermediate layer and the parent metal in the connection process is large, and thermal stress is easily generated in the long-time high-temperature connection process, so that the connection joint after final cooling is cracked. In addition, the joint gradually changes from a liquid phase to a solid phase in the connection process, the coagulated tissue shrinks and a certain number of holes are generated, and the kirkendall effect in diffusion can also generate enough holes at the interfaces of two sides of the joint to cause failure. Therefore, how to avoid the generation of such malignant holes is also one of the hot spots of the current related researches.

The metal micro-nano particle sintering connection technology is a process for sintering particles to form an interconnection joint with high temperature resistance at a temperature obviously lower than the melting point of an interconnection material by fully utilizing the size effect shown by a metal or alloy material with the size in the order of micron or nanometer. The technology is fundamentally different from the traditional brazing welding in principle, so that the patch interconnection process is more consistent with the development trend of low-temperature connection and high-temperature service: the surface size effect enables the micro-nano particles to be sintered and connected at a temperature far lower than the melting point of the micro-nano particles, and the basic requirement of low-temperature connection is met; the joint obtained by sintering is of a porous structure, the melting point of the joint is close to that of the corresponding block material, and high-temperature service can be realized at the moment. The formation process of the joint does not include the generation process of intermetallic compounds which is similar to the inevitable generation process in the transition liquid phase connection technology, so that the problem of low-melting-point structure in the joint caused by insufficient phase change reaction can be effectively prevented.

At present, the sintering process of the metal micro-nano particles can be described by using a classical powder sintering theory. Among these, the literature (foal, theory of powder sintering; metallurgical industry press, 1998) states that the particle systems consisting of powdered materials always tend to reduce the free energy of their surface during the sintering process, and this tendency is considered to be the main driving force for the sintering process. Specifically, the growth of the sintering neck and the flattening of the particle surface are all concrete manifestations of the progress of the sintering process, while the relevant section of the literature (y.n. zhou, microand nanojoining. elsevier,2008) describes the experimental phenomenon of silver nanoparticles sintering to form the connection joints, in line with the aforementioned theory.

At present, micro-nano particles for high-temperature electronic interconnection are mainly nano copper particles and nano silver particles. Since the corresponding bulk materials have relatively high melting points, excellent electrical and thermal conductivity and lower cost compared with gold and platinum, most of the micro-nano particles currently reported and used as commercial products are made of silver, copper, and mixed particles or alloys of the silver and the copper.

Generally, chemical synthesis methods are common methods for preparing metal micro-nano particles in the technology, and the obtained particles are generally spherical and flaky, because such particles often can exert the surface size effect of nanoparticles better, and the preparation cost of chemical synthesis is relatively low on the premise of mass production. In addition, spherical/flaky nano-copper particles prepared by a chemical method also have similar characteristics, and thus have received attention from researchers.

In actual use, a solder paste printing method is mainly adopted. Mixing organic matters with different functions with the prepared nano-particles to prepare paste with certain viscosity, distributing the nano-particles at certain positions of a substrate by a screen printing or mask plate printing method, then placing a chip, applying auxiliary pressure and heating to volatilize the organic matters and sinter the nano-particles, thus obtaining the joint meeting the performance requirements. The sintering process of the solder paste method can be visualized as fig. 3, while the organic species and their relationship with the nanoparticles, which are common in solder paste, are shown in fig. 4.

In fig. 4, Thinnder (thinner) can ensure the viscosity and printability of the solder paste, Binder (Binder) can alleviate the cracking of the solder paste caused by the liquid tension when the organic matter is decomposed; dispersant can form an organic shell layer on the surface of the nano-particles to prevent spontaneous agglomeration in an unsintered state.

At present, a soldering paste based on a metal micro-nano particle sintering principle is commercially available, most researches are developed aiming at the characteristics of the soldering paste, and according to the research results, the following problems exist in the current metal micro-nano particle soldering paste sintering technology:

1. the presence of organic components in the solder paste makes it difficult to further lower the sintering temperature. At present, the decomposition temperature of a part of organic matters in the organic components for preparing the soldering paste is higher than 200 ℃, and a part of organic matters with the decomposition temperature higher than the sintering temperature are also contained in the formula of part of the soldering paste, so that the sintering temperature of the corresponding soldering paste is generally not lower than the minimum temperature at which the organic components are decomposed, and the sintering temperature of the soldering paste is generally maintained between 200 ℃ and 300 ℃ due to the current situation, and is difficult to further reduce.

2. The decomposition and evaporation of organic components in the soldering paste in the sintering process can cause the generation of macrocracks in the connecting layer, so that the depth control of the evaporation process of organic matters is needed when the large-size chip is sintered, and special equipment such as an infrared heating furnace is needed.

3. The general solder paste needs to be printed on site when in use, and the decomposed organic matter needs to be preheated, so that the sintering process time is more likely to exceed 30min although shorter than that of the LT-TLPB technology.

The literature (b.feng et al, "compatible Bilayer of deposited Nanoparticles from Room-Temperature organic Nano-Architecture for Device integration," ACS applied materials & interfaces,2019.) states that a thin layer of micro-Nano particles can be prepared directly on the surface of a Device or substrate using pulsed laser deposition techniques, the thin layer being free of organic components and the micro-Nano particles in the thin film having a variety of particle sizes, and the joint obtained after sintering has a similar microstructure to the joint obtained by sintering solder paste. At present, the technology has already been patented.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a double-sided micro-nano composite preformed soldering lug for an electronic device, which makes innovations on a soldering lug preparation method and a preforming method by utilizing the basic principle of sintering micro-nano particles, effectively reduces the temperature required by a connection process and realizes a more convenient patch interconnection process.

In order to achieve the aim, the invention provides a double-sided micro-nano composite preformed soldering lug for an electronic device, which comprises an intermediate layer and porous micro-nano films positioned on two sides of the intermediate layer; the porous micro-nano film is a metal or alloy film.

The double-sided micro-nano composite preformed soldering lug is a three-layer structure material formed by compounding an intermediate layer and two layers of porous micro-nano films, and is shown in figure 5. Preferably, the porous micro-nano film has a skeleton structure formed by contacting or fusing (partially fusing) and combining micro-sized and/or nano-sized particles with each other.

In the double-sided micro-nano composite preformed soldering lug, preferably, micro-nano particles in the porous micro-nano film basically keep the appearance characteristics of a spherical shape or an ellipsoidal shape. The micro-nano particles are combined with each other to form a moderate sintering neck to form a skeleton structure, but the micro-nano particles (or most of the micro-nano particles) are not completely fused, but still keep the shapes of the micro-nano particles, but are not completely fused with each other.

In the double-sided micro-nano composite preformed soldering lug, the thickness of the middle layer is preferably 5-200 microns, and more preferably 10-50 microns.

In the double-sided micro-nano composite preformed soldering lug, the intermediate layer is preferably made of metal or alloy; more preferably, the metal includes silver, copper, gold, palladium, platinum or iron, and the alloy includes invar or an alloy composed of two or more metals of silver, copper, gold, palladium, platinum and iron, but is not limited thereto. The intermediate layer may be a foil made of the above-mentioned metal or alloy.

In the double-sided micro-nano composite preformed soldering lug, the porous micro-nano film comprises micron-sized particles and nano-sized particles with various particle sizes, as shown in fig. 6 (fig. 6 is a photo obtained by placing the film in liquid and performing ultrasonic dispersion). Preferably, the size of the micro-nano particles in the porous micro-nano film is 10 nanometers to 20 micrometers.

In the double-sided micro-nano composite preformed soldering lug, the size of the porous micro-nano film can be determined according to the requirement.

In the double-sided micro-nano composite preformed soldering lug, preferably, the density of the porous micro-nano film is 5-85%. The specific compactness can be determined according to the requirement and regulated by controlling the preparation process, for example, the unsintered soldering lug can be regulated by deposition and other processes. In addition, the density of the sintered porous micro-nano film can be regulated and controlled by controlling the auxiliary pressure, temperature and sintering time in the sintering process.

In the double-sided micro-nano composite preformed soldering lug, the material of the porous micro-nano film preferably includes one or an alloy of two or more metals of platinum, rhenium, palladium, iridium, rhodium, zirconium, copper, aluminum, titanium, nickel, silver, gold, tin and indium, but is not limited to the above materials.

In the double-sided micro-nano composite preformed soldering lug, the thickness of the porous micro-nano film is preferably 20-80 μm.

The invention also provides a mask frame body for preparing the double-sided micro-nano composite preformed soldering lug, which comprises a frame body base, a first frame body part and a second frame body part, wherein:

the frame body base is a hollow base and is provided with a fixing piece for fixing the first frame body part and the second frame body part;

the first frame body part is a hollow part, wherein the hollow part is provided with a grid;

the second frame body part is a hollow part, wherein the hollow part is provided with a grid;

the first frame body part and the second frame body part can clamp and fix the middle layer, are placed in the frame body base and are fixed through the fixing part.

According to the specific embodiment of the invention, the mask frame body is an intermediate layer for fixing the double-sided micro-nano composite preformed soldering lug so as to be placed into pulsed laser deposition equipment for deposition and preparation of the porous micro-nano film. The overall shape and size of the mask frame body and the shape and size of each component part can be adjusted according to the double-sided micro-nano composite preformed soldering lug to be prepared.

In the mask frame, the frame base is used for placing and fixing the first frame part and the second frame part which clamp the middle layer, and the middle of the frame base is hollow so as to facilitate deposition. The first frame body part and the second frame body part are used for clamping and fixing the middle layer, namely the unfolded middle layer is clamped between the first frame body part and the second frame body part, then the three parts are integrally placed into the frame base and are fixed through the fixing part on the frame base, and the first frame body part, the second frame body part and the hollow part of the frame base are mutually matched in size so as to prepare the film through deposition. The fixing member on the base of the frame body can adopt any form capable of realizing fixing, such as a clamp, a buckle, a bolt and the like.

The shapes and sizes of the mask frame body, the frame body base, the first frame body portion, and the second frame body portion may be selected as needed, and are preferably rectangular or square, and the hollow portion is also preferably shaped accordingly.

The mask frame body provided by the invention can be easily turned in the preparation process, and after the deposition of one side surface of the middle layer is finished, the mask frame body is directly turned, so that the deposition of the other side surface can be carried out.

In the mask frame, the first frame portion and the second frame portion are preferably identical in shape and size. The first frame part and the second frame part have the same shape and size, so that the mask frame body is convenient to mount and clamp, but the mask frame body can also be made into a form with two parts with different shapes and sizes.

The invention also provides a preparation method of the double-sided micro-nano composite preformed soldering lug for the electronic device, which is characterized in that porous micro-nano films are formed on the surfaces of two sides of the middle layer in a pulse laser deposition mode, and then the double-sided micro-nano composite preformed soldering lug for the electronic device is obtained.

According to embodiments of the present invention, the intermediate layer may be formed by conventional plastic forming methods, such as rolling, multiple forging, etc., or by powder metallurgy. The porous micro-nano film is prepared by adopting a laser vapor deposition method, and the size distribution of the obtained porous particle film can be controlled by adjusting the technological parameters of laser and controlling the gas atmosphere in the deposition process. In addition, the porous nano-film can also be prepared by means of solder paste printing.

In the above production method, preferably, the pulsed laser deposition has a target pitch of 15 to 250 mm.

In the above preparation method, preferably, the pulsed laser deposition has an average laser power of 25W to 2000W.

In the above production method, preferably, the deposition pressure of the pulsed laser deposition is 0.02Pa to 1.5 kPa.

The preparation method provided by the invention can be carried out through the mask frame body, and comprises the following specific steps:

clamping the middle layer by using the first frame part and the second frame part and fixing the middle layer in the frame base;

placing the mask frame body into pulse laser deposition equipment for pulse laser deposition, and forming a porous micro-nano film on the surface of one side of the middle layer;

and turning over the mask frame, putting the mask frame into pulse laser deposition equipment again for pulse laser deposition, and forming a porous micro-nano film on the surface of the other side of the middle layer to obtain the double-sided micro-nano composite preformed soldering lug for the electronic device.

The flow of the above preparation method is shown in FIG. 7. The shape and size of the projection of the material along the thickness direction can be controlled by the mask frame body during deposition, so that the mounting requirement of an actual device can be better met. The assembly structure of the mask frame and the film-like intermediate layer is shown in fig. 8 b. The shapes of the internal grids of the first frame part and the second frame part can be adjusted according to actual needs, and the manufacturing method of the internal grids comprises but is not limited to numerical control machining, rapid forming and the like. The mask frame body can be turned over in the deposition process, namely the first frame body part and the second frame body part can be separated from the frame body base after being assembled, and can be turned over from the state that the first frame body part is arranged below and the second frame body part is arranged above to the state that the first frame body part is arranged above and the second frame body part is arranged below to be inserted into the frame body base again, so that the porous micro-nano films can be deposited on two sides of the middle layer respectively.

The invention also provides a low-temperature interconnection method, which realizes the low-temperature interconnection of the to-be-connected parts through the double-sided micro-nano composite preformed soldering lug for the electronic device.

In the above low-temperature interconnection method, preferably, the method includes the steps of:

placing the double-sided micro-nano composite preformed soldering lug between two pieces to be connected, and applying auxiliary pressure to enable the soldering lugs to be attached;

heating to 100-400 ℃ and preserving heat for 0.5-120 minutes to fully densify particles in the porous micro-nano film in the double-sided micro-nano composite preformed soldering lug, and generating metallurgical bonding with an interface of a to-be-connected piece to complete low-temperature interconnection.

In the low-temperature interconnection method, when the overall temperature of the to-be-connected piece and the double-sided micro-nano composite preformed soldering lug is within the temperature range (180-350 ℃), the auxiliary pressure can be removed at any time within the heat preservation time range (0.5-120 minutes) according to actual requirements. Preferably, the auxiliary pressure is 0.5MPa to 30 MPa.

In the above-described low-temperature interconnection method, preferably, the low-temperature interconnection is performed in an atmospheric environment or a specific atmosphere, preferably, the specific atmosphere includes one or a combination of two or more of oxygen, formic acid vapor, nitrogen, and argon.

In the above-described low-temperature interconnection method, preferably, the member to be connected includes, but is not limited to, one or a combination of two or more of a semiconductor chip, a metal plate, a ceramic substrate having a metallized portion, a printed circuit board, a bulk metal, and the like.

The technical scheme of the invention can solve the problems that the LT-TLPB technology has too long connection time and the joint still cannot meet the service temperature of a high-performance power device. The porous micro-nano film prepared by the invention does not need to introduce organic components, and a series of problems caused by the organic components in the metal micro-nano particle soldering paste are solved from the source.

The shape of the projection of the porous micro-nano film obtained by the technical scheme of the invention in the thickness direction is controllable, and the connection requirements of devices with different sizes can be met.

The invention provides a technical scheme for preparing a composite interconnection material comprising a compact middle layer and multiple-particle-diameter micro-nano particle thin film layers on two sides by adopting a pulse laser deposition technology, a device to be connected does not need to be used as a substrate in the preparation process, the obtained composite material does not contain organic components, and the projection shape along the thickness direction can be controlled by a mask method.

The invention also provides a preparation method of the composite interconnection material and a corresponding low-temperature electronic interconnection method. Wherein, the size distribution of the micro-nano particles can be controlled by adjusting the deposition air pressure. The technical scheme can guide the completion of the manufacture of the micro-nano particle preformed soldering lug with various particle sizes, the soldering lug does not contain organic components, the soldering lug can be directly sintered at 180 ℃ to be connected with a patch-shaped high-performance power electronic device, a preheating step is omitted in the sintering process, and the shortest sintering time can be as low as 30 s. The sintered connecting layer is of a porous structure, the shear strength can reach 40-60MPa, and pores can be adjusted according to use requirements, so that the use requirements of different devices or specific working conditions are met.

Drawings

FIG. 1 is a schematic diagram of the LT-TLPB connection process.

FIG. 2 is a schematic view of the LT-TLPB process for connecting a Cu base material with Sn as an intermediate layer.

FIG. 3 is a schematic diagram of the low-temperature sintering of nano-solder paste under the assistance of pressure, wherein (a) is coating solder paste, preheating and pressurizing; (b) organic components are decomposed in the heating process; (c) sintering and growing nano metal particles at low temperature; (d) forming a metallurgical bond between the connecting layer and the interface.

Fig. 4 is a graph of the organic species and their relationship to nanoparticles, which are common in solder pastes.

Fig. 5 is a schematic structural diagram of a double-sided micro-nano composite preformed soldering lug of the invention.

Fig. 6 is a scanning electron microscope image of metal micro-nano particles with various sizes contained in the porous micro-nano particle film.

Fig. 7 is a schematic diagram of a preparation process of the double-sided micro-nano composite preformed soldering lug of the invention.

Fig. 8a is a top view of the mask frame provided in example 1.

Fig. 8b is a schematic cross-sectional view taken along line a-a of fig. 8 a.

Fig. 8c is a side view of the mask frame provided in example 1.

Fig. 8d is a schematic structural view of the first frame portion and the second frame portion of the mask frame provided in embodiment 1.

Fig. 8e is a schematic view of a frame base structure of the mask frame provided in embodiment 1.

Fig. 9 is a schematic view of the resulting pre-formed solder tab after deposition.

FIG. 10 is a graph showing the relationship between the shear strength and the sintering temperature of the joint of the chip and the silver-plated ceramic substrate obtained in example 2.

FIG. 11 is a scanning electron micrograph of a multilayer composite structure of the connection joint obtained by sintering at 250 ℃.

Fig. 12 shows the particle condition and particle size distribution variation results of the micro-nano particle films deposited under different air pressures.

Fig. 13 shows the strength results of the connection joints formed after sintering of the porous micro-nano films obtained under different deposition gas pressures.

Fig. 14 shows the variation of joint strength with sintering temperature when a semiconductor chip and a metallized substrate are connected by a double-sided composite tab using a silver foil containing array holes as an intermediate layer.

FIG. 15 is a cross-sectional micro-topography of a bonding layer after sintering at 250 ℃ using a double-sided composite tab with an array hole-containing silver foil as an intermediate layer.

Description of the main reference numerals

Frame base 1 first frame part 2 second frame part 3 fixing 4 grid 5 middle layer 6

Detailed Description

The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.

Definition of terms:

micro-nano particles: refers to the sum of particles that are in the micrometer and nanometer dimensions.

Preforming a soldering lug: the film-shaped material which enables two plane materials to be connected by means of mechanisms such as diffusion, melting, intermolecular force and the like has a determined geometrical shape through processing before the connection process is carried out, and the shape is not obviously changed in the connection process.

Low-temperature interconnection: this refers to a bonding process where the ambient temperature is significantly below the melting point of the bonding material. For example, sintering nano-silver particles at 200 ℃ for bonding can be included in the low temperature interconnect category because the melting point of silver is 960 ℃.

The preparation method of the double-sided micro-nano composite preformed soldering lug for the electronic device can be carried out according to the following steps:

1. selecting and preparing an intermediate layer according to the mounting requirements of the device, and designing the shape and size of the mask frame body according to the appearance of the device;

2. clamping the middle layer by using a mask frame body and placing the middle layer into a pulse laser deposition chamber provided with a metal target;

3. vacuumizing the deposition chamber, filling inert gas and controlling the deposition pressure in the chamber to be a constant value;

4. starting a laser system, and depositing a metal micro-nano particle film;

5. turning over the mask frame body by adopting a mechanical or manual method, and depositing a metal micro-nano particle film;

6. and splitting the mask frame body to obtain a cuttable double-sided micro-nano composite preformed soldering lug.

Example 1

The embodiment provides a mask frame for preparing the double-sided micro-nano composite preformed soldering lug, and the structure of the mask frame is shown in fig. 8a and 8 c. The mask frame comprises a frame base 1, a first frame part 2 and a second frame part 3; wherein the content of the first and second substances,

the frame base 1 is a square hollow base and is provided with a fixing piece 4 for fixing the first frame part and the second frame part, as shown in fig. 8 e;

the first frame part 2 and the second frame part 3 are identical in size and structure, and are square hollow parts as shown in fig. 8d, and the hollow parts are provided with grids;

the first frame part 2 and the second frame part 3 can clamp and fix the intermediate layer 6, and then are placed inside the frame base 1 and fixed by the fixing part 4, as shown in fig. 8 b.

Example 2

The embodiment provides a method for preparing a double-sided micro-nano composite preformed soldering lug by using a pure silver foil as an intermediate layer and depositing nano silver particles through pulse laser, which comprises the following steps:

selecting silver foil with thickness of 0.01mm and purity of 99.99% as intermediate layer, cutting, and mounting at the designated position of the mask frame shown in FIGS. 8 a-8 e;

the assembled mask frame body is adhered to a base and placed into a pulse laser deposition cavity, and the pure silver micro-nano particle film is deposited by adopting the following process parameters: the deposition pressure is 500-650Pa, the distance between the target and the intermediate layer is 35-40mm, the laser power is 78W, the inert gas atmosphere during deposition is argon atmosphere, and the deposition time is 20 minutes;

after deposition is finished, standing the mask frame body for 1 minute, cooling the mask frame body, manually turning the mask frame body for 180 degrees, and depositing another layer of pure silver micro-nano particle film according to the same technological parameters;

the photo of the multilayer composite double-sided micro-nano composite preformed soldering lug obtained after the frame body is removed is shown in fig. 9.

The double-sided micro-nano composite preformed soldering lug is connected with a SiC power diode chip, and the method specifically comprises the following steps:

cutting the deposited double-sided micro-nano composite preformed soldering lug into a square of 2.45mm multiplied by 2.45mm along the mask pattern;

the ceramic substrate is placed between a semiconductor power chip and a ceramic substrate with silver-plated surface, auxiliary pressure (15MPa) is applied, the ceramic substrate is heated to 180 ℃, heat preservation is carried out for 30 minutes, and sintering is carried out, so that the connection between the chip and the ceramic substrate with silver-plated surface can be realized.

The sintering temperature was respectively modified to 200 deg.C, 250 deg.C, 300 deg.C, and the above steps were repeated.

The relationship between the shear strength and sintering temperature of the joint of the chip and the silver-plated ceramic substrate is shown in fig. 10.

The test results for shear strength shown in fig. 10 indicate that: the joint strength of the double-sided micro-nano composite preformed soldering lug of the embodiment can reach 40-60MPa under the pressure auxiliary sintering condition at 250 ℃, and the connection strength of more than 80MPa can be obtained by increasing the sintering temperature. This shows that the double-sided micro-nano composite preformed soldering lug of the embodiment can realize a good structure of an electronic element and obtain higher connection strength.

Scanning electron micrographs (i.e., the microstructure of the cross section obtained after sintering at 250 ℃) of the multilayer composite structure of the connection joint obtained after sintering at 250 ℃ are shown in FIG. 11. As can be seen from fig. 11: the microstructure of the connecting layer formed by the double-sided micro-nano composite preformed soldering lug in the sintering process is uniform and dense, and the problem of nonuniform densification is avoided.

Example 3 adjusting the deposition gas pressure to control the particle size distribution of the nanoparticles obtained

Taking a micro-nano particle film composed of pure silver particles as an example, depositing by adopting a target base distance of 89mm and using an ultrafast laser source with a pulse width of 12ps, wherein the deposition pressure is respectively 50Pa, 500Pa and 1000Pa, and other parameters are the same as those in example 2. Fig. 12 shows the distribution variation of particle size in the micro-nano particle film obtained by deposition under different air pressures.

As can be seen from fig. 12, the thickness of the obtained connection layer increases with the deposition gas pressure, which indicates that a more porous structure can be obtained under the condition of high deposition gas pressure. Meanwhile, the third row of the particle size distribution statistical table in fig. 12 shows that the particle size of the particles inside the connection layer can be gradually reduced by increasing the deposition gas pressure, which means that the particle size inside the connection layer can be effectively controlled by adjusting the gas pressure during the deposition process.

The experiment shows that the particle size and the spatial structure of the obtained micro-nano particle film can be effectively controlled by adjusting the deposition air pressure on the premise that the target base distance is fixed and the technological parameters of the laser are not changed.

The particle size in the porous micro-nano film directly affects the densification degree of the connecting layer and the interface connection strength between the connecting layer and the device to be connected, the final effect is reflected in the strength of the obtained sintered joint, and the strength results of the connecting joint formed after sintering the porous micro-nano film obtained under different deposition pressures are shown in fig. 13.

As can be seen from fig. 13, the appropriate deposition pressure can effectively improve the shear strength of the sintered connection layer. For the micro-nano particle film made of pure silver particles, the deposition pressure is preferably controlled between 300Pa and 500 Pa.

Example 4

The embodiment provides a double-sided micro-nano composite preformed soldering lug with a copper foil as an intermediate layer, wherein the copper foil with the thickness of 0.05mm and the purity of 99.99% is selected as the intermediate layer, the double-sided micro-nano composite preformed soldering lug is prepared by the same method as the embodiment 2, a semiconductor power chip and a ceramic substrate with silver-plated surface are sintered under the auxiliary pressure of 15MPa at the temperature of 250 ℃, the sintering time is 30 minutes, and the strength of a connecting layer is shown in table 1.

TABLE 1 shear strength of double-sided composite solder tabs prepared using copper foil as interlayer

Sample numbering	1	2	3	Average shear strength
					Shear strength (MPa)	32.56	31.57	29.26	31.13

As can be seen from the average shear strength of the tie layer given in Table 1, the solder fillet is in strength compliance with the American military Standard MIL-STD-883K.

Example 5

The embodiment provides a double-sided micro-nano composite preformed soldering lug with an array hole pure silver foil as an intermediate layer, wherein a silver foil with the thickness of 0.01mm and the purity of 99.99% is selected as the intermediate layer, a through hole array with the diameter of 100 micrometers is processed by laser at a corresponding position, the double-sided micro-nano composite preformed soldering lug is prepared by adopting the same deposition method as the embodiment 2, and the double-sided micro-nano composite preformed soldering lug is sintered for 30 minutes at different temperatures (180 ℃,200 ℃, 250 ℃ and 300 ℃) under the auxiliary pressure of 15MPa to connect a semiconductor power device chip and a metal substrate (silver plating on the surface of the chip and silver plating on the surface of the metal substrate), and the change condition of the strength of a connecting layer along with the sintering temperature is shown in figure 14.

As can be seen from fig. 14: with the increase of the sintering temperature, the strength of the connecting layer also shows a trend of increasing, and it is noted that under the condition of the connecting temperature of 180 ℃, the strength is 18MPa, which is also higher than the specification of MIL-STD-883K of the American military standard. Therefore, the soldering lug can realize a low-temperature sintering connection process below 200 ℃.

The microstructure of the cross section of the connecting layer at a sintering temperature of 250 ℃ is shown in FIG. 15. From the cross-sectional morphology of the sintered soldering lug shown in fig. 15, the micro-nano particles in the array holes also form a uniform porous structure after sintering, and a good connection structure is formed between the particles and the intermediate layer.

Claims

1. A double-sided micro-nano composite preformed soldering lug for an electronic device comprises an intermediate layer and porous micro-nano films positioned on two sides of the intermediate layer; the porous micro-nano film is a metal film or an alloy film;

the porous micro-nano film has a skeleton structure formed by contacting or fusing and combining micro-sized and/or nano-sized particles with each other to form a proper sintering neck;

the size of the micro-nano particles in the porous micro-nano film is 10 nanometers to 20 micrometers.

2. The double-sided micro-nano composite preformed solder paste according to claim 1, wherein micro-nano particles in the porous micro-nano film retain spherical or ellipsoidal appearance characteristics.

3. The double-sided micro-nano composite preformed soldering lug according to claim 1, wherein the thickness of the middle layer is 5-200 microns.

4. The double-sided micro-nano composite preformed soldering lug according to claim 3, wherein the thickness of the middle layer is 10-50 microns.

5. The double-sided micro-nano composite preformed soldering lug according to claim 1 or 3, wherein the material of the middle layer is metal or alloy.

6. The double-sided micro-nano composite preformed solder lug of claim 5, wherein the metal comprises silver, copper, gold, palladium, platinum or iron, and the alloy comprises invar or an alloy consisting of two or more metals selected from the group consisting of silver, copper, gold, palladium, platinum and iron.

7. The double-sided micro-nano composite preformed soldering lug according to claim 1, wherein the density of the porous micro-nano film is 5-85%.

8. The double-sided micro-nano composite preformed soldering lug according to claim 2, wherein the density of the porous micro-nano film is 5-85%.

9. The double-sided micro-nano composite preformed soldering lug according to any one of claims 1, 2, 7 and 8, wherein the material of the porous micro-nano film comprises one or an alloy consisting of more than two metals of platinum, rhenium, palladium, iridium, rhodium, zirconium, copper, aluminum, titanium, nickel, silver, gold, tin and indium.

10. The double-sided micro-nano composite preformed soldering lug according to any one of claims 1, 2, 7 and 8, wherein the thickness of the porous micro-nano film is 20-80 μm.

11. The double-sided micro-nano composite preformed soldering lug according to claim 9, wherein the thickness of the porous micro-nano film is 20-80 μm.

12. The method for preparing the double-sided micro-nano composite preformed soldering lug for the electronic device according to any one of claims 1 to 11, wherein porous micro-nano films are formed on the surfaces of two sides of the middle layer in a pulse laser deposition mode, so that the double-sided micro-nano composite preformed soldering lug for the electronic device is obtained.

13. The method of claim 12, wherein the pulsed laser deposition has a target base distance of 15-250 mm.

14. The method of claim 12, wherein the pulsed laser deposition has a laser average power of 25W-2000W.

15. The method of claim 13, wherein the pulsed laser deposition has a laser average power of 25W-2000W.

16. The production method according to any one of claims 12 to 15, wherein the deposition gas pressure of the pulsed laser deposition is 0.02Pa to 1.5 kPa.

17. The production method according to any one of claims 12 to 15, wherein the production method is performed by a mask frame body having the following structure:

this mask framework includes framework base, first framework portion, second framework portion, wherein: the frame body base is a hollow base and is provided with a fixing piece for fixing the first frame body part and the second frame body part; the first frame body part is a hollow part, and the hollow part is provided with a grid; the second frame body part is a hollow part, and the hollow part is provided with a grid; the first frame body part and the second frame body part can clamp and fix the middle layer, are placed in the frame body base and are fixed through the fixing part;

the method comprises the following specific steps:

18. The manufacturing method according to claim 17, wherein the first frame portion and the second frame portion are identical in shape and size.

19. The manufacturing method according to claim 16, wherein the manufacturing method is performed by a mask frame body having the following structure:

the method comprises the following specific steps:

20. The manufacturing method according to claim 19, wherein the first frame portion and the second frame portion are identical in shape and size.

21. A low-temperature interconnection method, which is used for realizing the low-temperature interconnection of the parts to be connected through the double-sided micro-nano composite preformed soldering lug for the electronic device as claimed in any one of claims 1 to 11.

22. The low temperature interconnect method of claim 21, wherein the method comprises the steps of:

23. The low temperature interconnection method of claim 22, wherein the auxiliary pressure is 0.5MPa-30 MPa.

24. The low temperature interconnection method of any one of claims 21 to 23, wherein the to-be-connected component comprises one or a combination of two or more of a semiconductor chip, a metal plate, a ceramic substrate with metallization, a printed circuit board, a bulk metal.