CN113809016B - Composite substrate - Google Patents

Abstract

The invention discloses a composite substrate, comprising a ceramic substrate and an aluminum-based silicon carbide substrate stacked up and down, and a bonding surface is formed by hot pressing the ceramic substrate and the aluminum-based silicon carbide substrate through active metal solder, wherein the aluminum-based silicon carbide substrate contains 50-83 vol% SiC, and the active metal solder is selected from any one of the group consisting of silver, copper, titanium, zinc and aluminum. This composite substrate only needs to select an aluminum-based silicon carbide substrate with a suitable SiC composition, and utilizes its own high heat resistance and low thermal expansion characteristics. When subjected to high temperature hot pressing, the active metal solder can be directly pressed together with the ceramic substrate to form a continuous and dense bonding interface with good overall heat dissipation effect, so as to simplify the process, improve the bonding strength and yield, and make the cost cheaper. At the same time, the heat dissipation effect and impact resistance can be improved, and the mechanical properties such as impact resistance and vibration resistance and product reliability have excellent performance, and are more suitable for the automotive field.

Description

Composite substrate

Technical Field

The present invention relates to a composite substrate, and more particularly to an AlSiC substrate having an appropriate SiC composition, which can be directly hot-pressed and bonded to a ceramic substrate by active metal solder to form a continuous and dense bonding interface with good overall heat dissipation effect, thereby simplifying the manufacturing process, improving the bonding strength and yield, and making the cost lower.

Background technique

Ceramics have excellent mechanical strength, and have good heat resistance, chemical stability, oxidation resistance, electrical insulation, density and optical properties. They can also be applied to different processes by changing their properties through composition. Therefore, ceramics are widely used in electronic devices, optoelectronics and semiconductor component packaging, automobiles, communications, aerospace technology, chemical industry and other industries. Ceramic substrates made of ceramic materials are very suitable as packaging substrates for power devices because of the high thermal conductivity, good heat resistance, high insulation, high strength, and thermal matching with chip materials of the ceramic materials themselves. The heat generated by heat sources (such as chips, semiconductor devices) can be exported from the ceramic substrate to meet the use requirements of high-power electronic devices.

Common ceramic substrate materials include aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), beryllium oxide (BeO), silicon carbide (SiC), etc. In order to obtain better thermal and electrical properties, mechanical strength, air tightness and smaller dimensional changes, in actual applications, ceramic materials are often joined with metal (such as aluminum or copper) heat dissipation components or circuits. The joining methods include diffusion bonding, brazing and welding. In the process of joining metal and ceramic substrate by brazing, it is difficult for ordinary alloy solder to wet the ceramic material, which will result in insufficient bonding strength between the alloy solder and the ceramic material. In this case, pre-metallization and active brazing methods can be used to improve wettability. The pre-metallization method is to metallize the joint surface of the ceramic material before brazing, while the active brazing method is to add a trace amount of active metal (such as titanium, zirconium, etc.) to the alloy solder (such as nickel, copper, silver, etc.) to prepare an active metal solder, which can react with the ceramic material to produce a wetting effect and achieve the purpose of bonding. Moreover, since the process operation is very simple, it is widely used in ceramic packaging and metallization.

However, the conventional method of bonding a ceramic substrate to an aluminum metal substrate [such as an aluminum-based metal plate or a heat sink, etc.] is generally to first weld one side of the ceramic substrate to copper metal through an active metal brazing (AMB) material (referred to as active metal solder) to form an AMB substrate, and then selectively etch the copper layer to produce a copper metal circuit layout, while the other side of the ceramic substrate is thermally pressed to the aluminum metal substrate through a thermal conductive glue (such as an adhesive or resin, etc.) or other surface treatments [such as metallization (such as nickel plating, gold, tin, etc.) or anodizing treatment, etc.] to form a composite substrate, so that the copper metal circuit on the surface of the ceramic substrate can carry a working chip to absorb the heat energy generated by the load, and transfer it to the aluminum metal substrate through the bonding interface in the form of heat conduction or be absorbed by the aluminum metal substrate to dissipate heat, thereby reducing the thermal shock caused by excessive heat energy accumulated in the ceramic substrate or affecting the operating performance of the working chip.

However, the ceramic substrate uses adhesive or resin to bond with the aluminum metal substrate. Although it can be done at low temperature, reducing the thermal stress problem generated during the bonding process, the resin has a poor heat conduction effect, which will hinder heat conduction at the interface, resulting in an increase in the overall thermal resistance of the composite substrate after bonding. Long-term use will also cause interface peeling due to aging, and because the resin cannot wet on the ceramic substrate, it will cause problems such as poor heat dissipation and interface gaps. In addition, if the ceramic substrate uses a surface treatment method to bond with the aluminum metal substrate, such as chemical plating, high-temperature sintering, evaporation, sputtering and other metallization treatments, the surface treatment materials have complex chemical compositions and many variable factors such as shrinkage and expansion, resulting in problems such as poor interface bonding force, poor density, easy oxidation or difficult to control the thickness of the metallization layer after hot pressing bonding. In other words, whether choosing resin or surface treatment is not an ideal option for composite substrates, especially not conducive to the development of the automotive field that requires high thermal conductivity to dissipate heat and impact resistance at the same time, and it is also an important topic and problem that the industry has long wanted to improve.

Summary of the invention

Therefore, in view of the above shortcomings, the inventor collected relevant information, evaluated and considered various aspects, and used the years of experience accumulated in this industry to continuously test and modify, and finally designed this composite substrate.

The main purpose of the present invention is to replace the aluminum metal substrate with an aluminum-based silicon carbide substrate with an appropriate content of SiC in the composite substrate, and utilize its higher heat resistance temperature and heat resistance coefficient than the traditional metal substrate, and the small thermal expansion change is not easy to deform at high temperature, and has the characteristics of high heat resistance and low thermal expansion. When subjected to high temperature hot pressing, it can be directly pressed with the ceramic substrate through active metal solder to form an overall good heat dissipation effect and continuous and dense bonding interface, which can not only simplify the process, and improve the strength and yield of the bonding, but also be cheaper. At the same time, it can improve the heat dissipation effect and impact resistance. Compared with traditional composite substrates, it has superior performance in mechanical properties such as resistance to impact and vibration and product reliability, and is more suitable for the automotive field.

A secondary purpose of the present invention is that the active metal solder used in the composite substrate is selected from any one of the group consisting of silver, copper, titanium, zinc and aluminum, and the high activity of the active metal can be used to improve the wetting reaction of the solder to the ceramic after melting, so that the aluminum-based silicon carbide substrate can be directly hot-pressed and bonded with the ceramic substrate without metallization surface treatment, and finally a composite substrate without any interface gap or interface peeling is formed. In addition, because the thermal resistance of the active metal solder is much lower than that of the resin used in the traditional bonding interface, the heat conduction effect is better, and the heat generated by the heat source can be quickly thermally conducted to the aluminum-based silicon carbide substrate through the ceramic substrate and the active metal solder for external release, so as to reduce the heat accumulation on the ceramic substrate, and the overall heat dissipation effect is better.

Another purpose of the present invention is to solve the problems of poor interface bonding strength and poor density caused by the lack of metallized surface treatment, complex chemical composition, shrinkage and expansion and other variable factors at the bonding interface of the composite substrate. A continuous and dense bonding interface can be formed after the aluminum-based silicon carbide substrate is directly hot-pressed with the ceramic substrate through active metal solder. Compared with the interface gap or interface peeling caused by thermal expansion deformation commonly seen in traditional composite substrates, it can more effectively improve its impact resistance and product reliability.

In order to achieve the above object, the present invention adopts the following technical means:

The present invention discloses a composite substrate, comprising a ceramic substrate and an aluminum-based silicon carbide substrate stacked up and down, and a bonding surface formed by an active metal solder is contained between the ceramic substrate and the aluminum-based silicon carbide substrate, wherein the aluminum-based silicon carbide substrate contains 50 to 83 vol% of silicon carbide (SiC) by volume, and the active metal solder is selected from any one of the group consisting of silver (Ag), copper (Cu), titanium (Ti), zinc (Zn) and aluminum (Al).

Preferably, the ceramic substrate comprises a ceramic base and a metal layer structure formed on at least one side surface of the ceramic base.

Preferably, the ceramic substrate material is silicon nitride (Si ₃ N ₄ ), tantalum nitride (TaN), aluminum nitride (AlN), beryllium oxide (BeO), aluminum oxide (Al ₂ O ₄ ) or silicon carbide (SiC).

Preferably, the metal layer structure is a copper metal layer attached to the upper surface of the ceramic substrate, which is then etched to form a copper metal circuit.

Preferably, the aluminum-based silicon carbide substrate contains 63 vol% SiC.

Preferably, the active metal solder contains 70 vol% Ag, 28 vol% Cu and 2 vol% Ti.

Preferably, the active metal solder contains 10 vol% Ag, 85 vol% Cu and 5 vol% Ti.

Preferably, the active metal solder contains 80 vol% Zn and 20 vol% Al.

Preferably, the joint surface formed by the active metal solder is formed by thermal compression bonding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a composite substrate of the present invention;

FIG2 is a data table showing the composition of active metal solder of the present invention;

FIG3 is a schematic diagram of a composite substrate of the present invention during thermal compression bonding;

FIG. 4 is a table showing the test data and the joint surface effect determination table of the embodiment of the present invention.

Symbol Description

1: Ceramic substrate

2: Aluminum-based silicon carbide substrate

3: Active metal solder

L: Load

Detailed ways

In order to achieve the above-mentioned purpose and effect, the technical means and structure adopted by the present invention are illustrated in detail with reference to the preferred embodiment of the present invention, and its structure and function are as follows, so as to facilitate a complete understanding.

Please refer to Figures 1 to 4, which are respectively a schematic diagram of the structure of the composite substrate of the present invention, a data table of the composition of the active metal solder, a schematic diagram of the composite substrate during hot pressing bonding, and data tested in the embodiment and a bonding surface effect determination table. It can be clearly seen from the figures that the composite substrate of the present invention includes a ceramic substrate 1 and an aluminum-based silicon carbide (AlSiC) substrate 2 stacked up and down, and the ceramic substrate 1 and the aluminum-based silicon carbide substrate 2 are hot-pressed and bonded by an active metal solder [the abbreviation of active metal brazing (AMB) material] 3 to form a bonding surface, wherein the upper ceramic substrate 1 includes a ceramic substrate and a metal layer structure on at least one side of the surface thereof. The ceramic substrate material is preferably silicon nitride (Si ₃ N ₄ ), but is not limited thereto, and can also be tantalum nitride (TaN), aluminum nitride (AlN), beryllium oxide (BeO), aluminum oxide (Al ₂ O ₄ ) or silicon carbide (SiC), etc., and the metal layer structure is a copper metal layer attached to the upper surface of the ceramic substrate through high/low temperature co-fired ceramics (HTCC/LTCC), direct copper bonding (DBC), direct electroplated copper (DPC) or active metal brazing (AMB) and other technologies, and then etching is performed on the copper metal layer to form a copper metal circuit, so that chips, semiconductors or power devices can be mounted or packaged on the ceramic substrate 1, and electrically connected to the copper metal circuit through solder, wire bonding, etc.

In the present embodiment, the lower layer of the composite substrate is an aluminum-based silicon carbide substrate 2, and its characteristics are mainly determined by the volume percentage (vol%, i.e., the content of the composition), distribution and particle size of SiC, etc., which can be adjusted by changing the content of the composition. Since the aluminum-based silicon carbide substrate 2 contains 50-83 vol% SiC, preferably 63 vol%, and because it contains more than 50 vol% SiC, its heat resistance temperature and heat resistance coefficient are higher than those of traditional metal substrates or ceramic substrates, and its thermal expansion change is small and it is not easy to deform at high temperature, so that the aluminum-based silicon carbide substrate 2 itself has the characteristics of high heat resistance and low thermal expansion, and can replace the aluminum metal substrate, and can be directly hot-pressed with the ceramic substrate 1 through the active metal solder 3 to form a composite substrate.

As shown in FIGS. 2 and 3 , there are three main composition ratios of the active metal solder 3 used in the embodiment of the present invention, wherein solder A contains 70 vol% silver (Ag), 28 vol% copper (Cu) and 2 vol% titanium (Ti) by volume, solder B contains 10 vol% silver (Ag), 85 vol% copper (Cu) and 5 vol% titanium (Ti) by volume, and solder C contains 80 vol% zinc (Zn) and 20 vol% aluminum (Al) by volume. These solders are prepared using active metals (such as titanium, zinc) and metals such as silver, copper, and aluminum. Since the active metals are highly active, they can improve the wetting reaction of the solder to the ceramic after it is melted, so that the ceramic surface does not need to be metallized to achieve the purpose of bonding with the metal.

When the ceramic substrate 1, the aluminum-based silicon carbide substrate 2 and the active metal solder 3 are heat-pressed, a vacuum heating furnace or a melting furnace can be used to heat the active metal solder 3 to a sintering temperature above the melting point (e.g., preferably a temperature range of 580°C to 865°C). As shown in the data table of FIG. 4 , the sintering temperature can be 865°C, 510°C or 580°C, etc., depending on the composition ratio of the solder. After the active metal solder 3 is melted and kept at the temperature for a period of time, it can be fully filled between the ceramic substrate 1 and the aluminum-based silicon carbide substrate 2 for wetting reaction. Then, the predetermined load L can be 0.58kgf/cm ² (0.075Mpa), 1.17kgf/cm ² (0.11Mpa) or 0.21kgf/cm ² (0.028Mpa) for hot pressing bonding, or a heating rod can be used to heat the load L (such as a hot pressing head), and the hot pressing head can be used to directly hot press the ceramic substrate 1 to heat the active metal solder 3 to a predetermined sintering temperature. As the active brazing temperature or the temperature holding time increases, the aluminum-based silicon carbide substrate 2 itself can be used to have the characteristics of high heat resistance and low thermal expansion. When it is subjected to high-temperature hot pressing, the active metal solder 3 and the ceramic substrate 1 can be pressed together to form a composite substrate with a dense bonding surface. From the microscopic metallographic structure of the bonding interface of the composite substrate, it can be observed that the alloy solder of the active metal solder 3 can effectively fill the surface pores of the ceramic substrate 1 and the aluminum-based silicon carbide substrate 2, and has good wettability, so that the ceramic substrate 1 and the aluminum-based silicon carbide substrate can be tightly bonded, and there is no gap in the bonding interface between the two, and it is not easy to bend and deform, and finally a composite substrate without any interface gap or interface peeling is formed.

Specifically, the test data of Examples 1 to 10 of the composite substrate of the present invention are shown in FIG4 , wherein the ceramic base material selected for the upper ceramic substrate 1 of the composite substrate structure is silicon nitride (Si ₃ N ₄ ) with a thickness of 0.32 mm, and the lower aluminum-based silicon carbide (AlSiC) substrate 2 is composed of silicon carbide (SiC) with a thickness of 3.00 mm and a content of 50%, 63% and 83% respectively, and hot pressing bonding is performed by different composition ratios of active metal solder 3 (such as solders A to C) at different loads L and sintering temperatures to form a composite substrate with a bonding surface.

According to the results of the determination of the bonding surface effect of Examples 1 to 4, it can be found that under the same load L (such as 0.58 kgf/cm ² ) and sintering temperature (such as 865°C), no matter whether the composition ratio of solder A or solder B is selected, as long as the SiC composition content of the aluminum-based silicon carbide substrate 2 is higher than 50% (such as 63% or 83%), the bonding surface effect is determined to be good. However, according to Examples 5 to 7, it can be found that under the condition of the sintering temperature (such as 865°C) being unchanged, as the load L increases from 0.58 kgf/cm ² to 1.17 kgf/cm ² , when the SiC composition content of the aluminum-based silicon carbide substrate 2 is 50% or the aluminum-based silicon carbide substrate 2 undergoes a pre-metallization surface treatment (such as surface electroplating), no matter whether the composition ratio of solder A or solder B is selected, the bonding surface effect is determined to be poor.

In addition, according to the results of the determination of the bonding surface effect of Examples 8 to 10, it can be found that when the SiC composition content of the aluminum-based silicon carbide substrate 2 is 63% and the solder C composition ratio is selected, the thermal compression bonding is performed at a lower load L of 0.21 kgf/ ^cm2 and a sintering temperature of 580°C, and the bonding surface effect is determined to be good. However, when the sintering temperature is reduced to 510°C and the load L remains unchanged, the bonding surface effect is determined to be poor. Therefore, the three different solder compositions of the active metal solder 3 of the embodiment of the present invention can be selected in combination with the aluminum-based silicon carbide substrate 2 with a SiC composition content between 50% and 83%, and by adjusting the load L and sintering temperature of the thermal compression bonding process, they can all be applied to the composite substrate of the present invention.

When the composite substrate of the present invention is equipped with or encapsulated with a heat source such as a chip, a semiconductor or a power device on the upper ceramic substrate 1, the heat generated by the heat source and the copper metal circuit can be first absorbed by the ceramic substrate, and then quickly heat-conducted to the lower aluminum-based silicon carbide substrate 2 through the active metal solder 3 for absorption, and then released to the outside. Since the thermal resistance of the active metal solder 3 selected in this embodiment is much lower than that of the resin used in the traditional bonding, the heat conduction effect is better, and the aluminum-based silicon carbide substrate 2 with a suitable SiC composition replaces the aluminum metal substrate. Without metallization surface treatment (such as surface electroplating copper, chemical nickel plating, etc.), it can be directly hot-pressed and bonded with the ceramic substrate 1 through the active metal solder 3, and finally a continuous and dense bonding interface with good overall heat dissipation effect is formed, which can not only simplify the composite substrate manufacturing process, but also improve the bonding strength and yield, making the cost cheaper, and at the same time improve the heat dissipation effect and impact resistance. Compared with the traditional composite substrate, it has significantly superior performance in mechanical properties such as resistance to impact load and vibration and product reliability, and is more suitable for the automotive field.

Therefore, the present invention mainly provides a composite substrate that replaces the aluminum metal substrate with an aluminum-based silicon carbide substrate 2 composed of SiC with an appropriate content ratio, and utilizes its high heat resistance and low thermal expansion characteristics. When subjected to high temperature hot pressing, it can be directly pressed together with the ceramic substrate 1 through the active metal solder 3 to form a dense bonding interface, and finally form a composite substrate without any interface gap or interface peeling, and the active metal solder is selected from any of the group consisting of silver, copper, titanium, zinc and aluminum. Since the bonding interface of the composite substrate does not contain resin, the heat conduction effect is better, the heat accumulation on the ceramic substrate can be reduced, and the overall heat dissipation effect is better; in addition, the bonding interface lacks metallization surface treatment and contains complex chemical composition, shrinkage and expansion and other variation factors caused by poor interface bonding force, poor density and other problems. Compared with the traditional composite substrate that is often caused by thermal expansion deformation and interface gaps or interface peeling, it can more effectively improve its impact resistance, and has superior performance in mechanical properties such as resistance to impact and vibration and product reliability.

The above detailed description is only for a preferred feasible embodiment of the present invention, but the embodiment is not used to limit the scope of the patent application of the present invention. All other equivalent changes and modifications that do not deviate from the technical spirit disclosed by the present invention should be included in the patent scope covered by the present invention.

Claims (8)

1. A composite substrate comprises a ceramic substrate and an aluminum-based silicon carbide substrate which are stacked up and down, wherein a joint surface formed by active metal solder is contained between the ceramic substrate and the aluminum-based silicon carbide substrate, the aluminum-based silicon carbide substrate contains 63-83 vol% of silicon carbide (SiC), and the active metal solder contains 70vol% of Ag, 28vol% of Cu and 2vol% of Ti.

2. A composite substrate comprises a ceramic substrate and an aluminum-based silicon carbide substrate which are stacked up and down, wherein a joint surface formed by active metal solder is contained between the ceramic substrate and the aluminum-based silicon carbide substrate, the aluminum-based silicon carbide substrate contains 63-83 vol% of silicon carbide (SiC), and the active metal solder contains 10vol% of Ag, 85vol% of Cu and 5vol% of Ti.

3. A composite substrate comprises a ceramic substrate and an aluminum-based silicon carbide substrate which are stacked up and down, and is characterized in that a joint surface formed by active metal solder is contained between the ceramic substrate and the aluminum-based silicon carbide substrate, the aluminum-based silicon carbide substrate contains 63-83 vol% of silicon carbide (SiC), the active metal solder contains 80vol% of Zn and 20vol% of Al, and the sintering temperature is 580 ℃.

4. The composite substrate of any one of claims 1-3, wherein the ceramic substrate comprises a ceramic base and a metal layer structure formed on at least one side surface of the ceramic base.

5. The composite substrate of claim 4, wherein the ceramic base material is silicon nitride (Si ₃N₄), tantalum nitride (TaN), aluminum nitride (AlN), beryllium oxide (BeO), aluminum oxide (Al ₂O₄), or silicon carbide (SiC).

6. The composite substrate of claim 5, wherein the metal layer structure is formed by attaching a copper metal layer to the upper surface of the ceramic substrate and etching the copper metal layer to form a copper metal line.

7. The composite substrate according to any one of claims 1 to 3, wherein the aluminum-based silicon carbide substrate contains 63vol% silicon carbide (SiC).

8. A composite substrate according to any one of claims 1 to 3, wherein the bonding surface formed by the active metal solder is formed by thermocompression bonding.