TW202200527A - Composite substrate including a ceramic substrate and an aluminum-based silicon carbide substrate stacked on each other from the top to the bottom - Google Patents

Abstract

The present invention provides a composite substrate, which includes a ceramic substrate and an aluminum-based silicon carbide substrate stacked on each other from the top to the bottom, and the ceramic substrate and the aluminum-based silicon carbide substrate are hot-compressed with active metal solder therebetween to form a joint surface, wherein the aluminum-based silicon carbide substrate contains 50-83 vol% of SiC composition, and the active metal solder is the one selected from the group consisting of silver, copper, titanium, zinc and aluminum. The composite substrate only requires selecting an aluminum-based silicon carbide substrate with an appropriate SiC composition. When subjected to high temperature hot pressing, it can make use of its own characteristics of high heat resistance and low thermal expansion to be directly compressed together with the ceramic substrate through active metal solder to form a continuous and dense joint interface with good overall heat dissipation. As a result, the process is simplified, the strength of the joint and yields are improved, the cost is cheaper. Moreover, the heat dissipation effect and impact resistance can be improved. It has superior performance in mechanical properties such as resisting impact and vibration as well as product reliability, and it is also more applicable to the automotive field.

Description

Composite substrate

The present invention provides a composite substrate, especially an AlSiC substrate with appropriate SiC composition, which can be directly bonded with a ceramic substrate by thermocompression through active metal solder to form a continuous and dense bonding interface with good overall heat dissipation effect to simplify the process. Process, improve the strength and yield of bonding, and the cost is cheaper.

According to the press, ceramics have good mechanical strength, and have good heat resistance, chemical stability, oxidation resistance, electrical insulation, compactness and optical properties, etc., and their properties can also be changed by composition. Ceramics are widely used in electronic devices, optoelectronic and semiconductor components packaging, automotive, communications, aerospace technology, chemical and other industries, and ceramic substrates made of ceramic materials are due to the high thermal conductivity and heat resistance of the ceramic material itself. Good performance, high insulation, high strength, and thermal matching with wafer materials, it is very suitable as a packaging substrate for power devices. Usage requirements.

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 practical applications, ceramic materials are often bonded to metal (such as aluminum or copper) heat dissipation elements or circuits, and the bonding methods include diffusion bonding. , brazing and welding, and in the process of joining metal and ceramic substrates by brazing, it is difficult to wet the ceramic material with general alloy solder, which will result in insufficient bonding strength between the alloy solder and the ceramic material. In this case, the pre-metallization method and the active brazing method can be used to improve its wettability. The soldering 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 and produce a wetting effect to achieve the purpose of bonding. , and because the operation of the process is very simple, it is widely used in ceramic packaging and metallization.

However, the traditional 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 connect one side of the ceramic substrate to copper metal through an active metal brazing (AMB) material ( Abbreviated as active metal solder), after welding to form the AMB substrate, the copper layer is selectively etched to produce the copper metal circuit layout, while the other side of the ceramic substrate is passed through thermal conductive adhesive (such as adhesive or resin, etc.) or other surfaces. Treatment [such as metallization (such as nickel, gold, tin, etc.) or anodizing treatment, etc.] and thermocompression bonding with the aluminum metal substrate to form a composite substrate, which can be absorbed by the working wafer mounted on the copper metal circuit on the surface of the ceramic substrate. The heat energy generated by the load is transferred to the aluminum metal substrate through the bonding interface or absorbed by the aluminum metal substrate in the form of heat conduction, thereby reducing the thermal shock caused by the excessive heat energy accumulated on the ceramic substrate or affecting the operation performance of the working chip.

However, the ceramic substrate is bonded to the aluminum metal substrate with adhesive or resin. Although it can be performed at low temperature, the thermal stress problem generated during the bonding process is reduced, but the resin has a poor heat conduction effect, which will hinder heat conduction at the interface. , so that the overall thermal resistance of the composite substrate increases after bonding, and the interface will peel off due to aging after long-term use, and the resin cannot Wetting on the ceramic substrate will cause problems such as poor heat dissipation and interface gaps; and if the ceramic substrate is bonded to the aluminum metal substrate by surface treatment, such as electroless plating, high temperature sintering, evaporation, sputtering and other metallization Treatment, the surface-treated material contains complex chemical composition, and there are many variables such as shrinkage and expansion. After thermocompression bonding, it is easy to find poor interface bonding force, poor compactness, easy oxidation, or difficult to control the thickness of the metallized layer, etc. problem. In other words, the choice of resin or surface treatment is not an ideal choice for composite substrates, especially not conducive to the development of the automotive field where high thermal conductivity is also important for external heat dissipation and impact resistance. It is also an important issue and problem that the industry has long wanted to improve. where.

Therefore, in view of the above-mentioned deficiencies, the inventor collected relevant information, through various evaluations and considerations, and with years of experience in the industry, continued trial production and modification, and then the invention patent for designing such a composite substrate was born.

The main purpose of the present invention is that the composite substrate replaces the aluminum metal substrate with an aluminum-based silicon carbide substrate composed of an appropriate proportion of SiC, and utilizes its higher heat-resistance temperature and heat-resistance coefficient than the traditional metal substrate, and the thermal expansion change is small and difficult to occur. High temperature deformation has the characteristics of high heat resistance and low thermal expansion. When subjected to high temperature hot pressing, active metal solder can be directly pressed with the ceramic substrate to form a continuous and dense joint interface with good overall heat dissipation effect, which can not only simplify the process, but also And improve the strength and yield of bonding, the cost is cheaper, and the heat dissipation effect and impact resistance can be improved. Compared with traditional composite substrates, it has superior performance in mechanical properties such as shock and vibration resistance and product reliability, and is more applicable. in the automotive field.

The secondary purpose of the present invention is that the active metal solder selected for the composite substrate is any one selected from the group consisting of silver, copper, titanium, zinc and aluminum, and the active metal is used to have The high activity of the aluminum-based silicon carbide substrate can improve the wetting reaction of the ceramic after the solder is melted, so that the aluminum-based silicon carbide substrate can be directly hot-pressed with the ceramic substrate without any metallization surface treatment, and finally form no interface gap or interface peeling. The thermal resistance of the active metal solder is much lower than that of the resin used in the traditional bonding interface, so the heat conduction effect is better, and the heat generated by the heat source can be quickly transferred to the aluminum through the ceramic substrate and the active metal solder. The silicon carbide-based substrate is released to the outside to reduce heat accumulation on the ceramic substrate, and the overall heat dissipation effect is better.

Another object of the present invention is that the bonding interface of the composite substrate, the lack of metallized surface treatment contains the problems of poor interface bonding force and poor compactness caused by the complex chemical composition, shrinkage and expansion and other variability factors, and the aluminum-based silicon carbide substrate is passed through the aluminum-based silicon carbide substrate. After the active metal solder and the ceramic substrate are directly thermocompressed, a continuous and dense bonding interface can be formed. Compared with the traditional composite substrate, the interface gap or interface peeling caused by thermal expansion and deformation can effectively improve its impact resistance strength and product reliability. more superior.

1: Ceramic substrate

2: Aluminum-based silicon carbide substrate

3: Active metal solder

L: load

[Fig. 1] is a schematic view of the structure of the composite substrate of the present invention.

[Fig. 2] is a data table of the composition of the active metal solder of the present invention.

[FIG. 3] is a schematic view of the composite substrate of the present invention during thermocompression bonding.

[FIG. 4] is the test data and the joint surface effect judgment table of the embodiment of the present invention.

In order to achieve the above-mentioned purpose and effect, the technical means and structure adopted by the present invention, the preferred embodiments of the present invention are described in detail in the drawings and the structure and function are as follows, so as to be fully understood.

Please refer to Figures 1 to 4, which are the schematic diagram of the structure of the composite substrate of the present invention, the data table of the composition of the active metal solder, the schematic diagram of the composite substrate during thermocompression bonding, and the data and the effect of the bonding surface tested in the examples. As can be clearly seen from the figure, the composite substrate of the present invention includes a ceramic substrate 1 and an aluminum-based silicon carbide (AlSiC) substrate 2 that are stacked up and down, and a system is formed between the ceramic substrate 1 and the aluminum-based silicon carbide substrate 2 A joint surface is formed by thermocompression bonding with active metal solder (abbreviation for active metal brazing (AMB) material) 3, wherein the upper ceramic substrate 1 comprises a ceramic base and a metal layer structure on at least one surface thereof, the ceramic base The material is preferably implemented as silicon nitride (Si ₃ N ₄ ), but not limited to this, 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 made of high/low temperature co-fired ceramics (HTCC/LTCC), direct copper cladding (DBC), direct copper electroplating (DPC) or active metal brazing (AMB) and other technologies, a copper metal layer is attached to the upper surface of the ceramic substrate, and then the copper metal layer is etched to form a copper metal circuit, so that chips, semiconductors or power devices can be mounted or packaged on the ceramic substrate 1, and It is electrically connected to copper metal lines by soldering, wire bonding, etc.

In this embodiment, the lower layer of the above-mentioned composite substrate is an aluminum-based silicon carbide substrate 2, and its characteristics mainly depend on the volume percentage (vol%, that is, the composition content), distribution and particle size of SiC. The aluminum-based silicon carbide substrate 2 contains 50~83vol% SiC composition, preferably 63vol%, and because it contains more than 50vol% SiC composition, its heat resistance temperature and heat resistance coefficient are higher than those of traditional metal substrates Or the ceramic substrate is high, and the thermal expansion change is small, which is not easy to be deformed at high temperature, so that the aluminum-based silicon carbide substrate 2 itself has the characteristics of high heat resistance and low thermal expansion, which can replace the aluminum metal substrate and directly connect with the ceramic substrate 1 through the active metal solder 3. Thermocompression bonding is performed to form a composite substrate.

As shown in Figures 2 and 3, the active metal solder 3 used in the embodiment of the present invention mainly has three composition ratios, wherein the solder A contains 70 vol % silver (Ag), 28 vol % copper (Cu) and 2vol% titanium (Ti), solder B contains 10vol% silver (Ag), 85vol% copper (Cu) and 5vol% titanium (Ti), and solder C contains 80vol% zinc ( Zn) and 20vol% aluminum (Al), these solders are prepared by using active metals (such as titanium, zinc) and metals such as silver, copper, and aluminum. The wetting reaction to the ceramic, so the ceramic surface can be bonded to the metal without metallization.

When the ceramic substrate 1, the aluminum-based silicon carbide substrate 2 and the active metal solder 3 are thermocompressed, a vacuum heating furnace or a furnace can be used to heat the active metal solder 3 to a sintering temperature above the melting point (such as preferably 580°C~865°C). ℃ temperature range), as shown in the data table in Figure 4, the sintering temperature can be 865 ℃, 510 ℃ or 580 ℃, etc. depending on the composition of the solder, and after the active metal solder 3 is melted and held for a period of time, it can be It is fully filled between the ceramic substrate 1 and the aluminum-based silicon carbide substrate 2 for wetting reaction, and the predetermined load L can be respectively 0.58kgf/cm ² (0.075Mpa), 1.17kgf/cm ² (0.11Mpa) or 0.21kgf /cm ² (0.028Mpa) for thermocompression bonding, or a heating rod can be used to heat the load L (such as a thermocompression head), and the thermocompression head can directly press the ceramic substrate 1 to heat the active metal solder 3 to achieve a predetermined sintering As the active brazing temperature or temperature holding time increases, the aluminum-based silicon carbide substrate 2 can be used to have high heat resistance and low thermal expansion characteristics, so that when it is subjected to high temperature hot pressing, it can pass through the active metal solder 3 and ceramics. The substrates 1 are pressed together to form a composite substrate with a dense joint surface, and from the microscopic metallographic structure of the joint interface of the composite substrate, it can be observed that the alloy solder of the active metal solder 3 can effectively fill the ceramic substrate 1 and the aluminum-based carbonization. The surface pores of the silicon substrate 2 have good wettability, so that the ceramic substrate 1 and the aluminum-based silicon carbide substrate can be closely bonded, and the bonding interface between the two is seamless, and it is not easy to flex and deform. Any interfacial gap or interfacial peeling of the composite substrate.

Specifically, the test data of Examples 1 to 10 of the composite substrate of the present invention shown in FIG. 4 can be observed, wherein the ceramic base material selected for the upper ceramic substrate 1 of the composite substrate structure is silicon nitride (Si ₃ ) with a thickness of 0.32 mm. N ₄ ), the lower layer aluminum-based silicon carbide (AlSiC) substrate 2 is composed of silicon carbide (SiC) with a thickness of 3.00 mm and a content ratio of 50%, 63% and 83%, respectively, and through the active metal solder 3 different compositions A composite substrate with a joint surface is formed by thermocompression bonding under different load L and sintering temperature according to the proportions (such as solders A to C).

According to the results of judging the effect of the joint surface in Examples 1 to 4, it can be found that under the same load L (eg 0.58kgf/cm ² ) and sintering temperature (eg 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 joint surface effect is judged to be good, but according to Examples 5 to 7, it can be found that the sintering temperature (such as 865 ℃) ) remains unchanged, as the load L increases from 0.58kgf/cm ² to 1.17kgf/cm ² , the SiC composition content of the aluminum-based silicon carbide substrate 2 is 50% or the aluminum-based silicon carbide substrate 2 is pre-metallized surface treatment (such as surface electroplating), regardless of the composition ratio of solder A or solder B, the effect of the joint surface is judged to be poor.

In addition, according to the results of the judgment of the joint surface effect in 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 composition ratio of the solder C is selected, the lower load L is 0.21 kgf/cm ² , and the sintering temperature was 580°C for thermocompression bonding, and the joint effect was judged to be good. However, when the sintering temperature was lowered to 510°C and the load L was unchanged, the joint effect was judged to be poor. Therefore, the present invention The active metal solder 3 of the embodiment has three different solder compositions, which can be selected with an aluminum-based silicon carbide substrate 2 with a SiC composition content ranging from 50% to 83%, and by adjusting the load L and sintering temperature of the thermocompression bonding process , can be applied to the composite substrate of the present invention.

When the composite substrate of the present invention is mounted or packaged with heat sources such as chips, semiconductors or power devices on the upper ceramic substrate 1, the heat generated by the heat source and the copper metal circuit can be absorbed by the ceramic substrate first, and the heat generated by the active metal solder 3 can be quickly transferred to the The lower aluminum-based silicon carbide substrate 2 is absorbed and released to the outside world. Since the thermal resistance value of the active metal solder 3 selected in this embodiment is much lower than that of the resin used for traditional bonding, the heat conduction effect is better, and The aluminum metal substrate is replaced by an aluminum-based silicon carbide substrate 2 with an appropriate SiC composition, without the need for metallized surface treatment (such as surface electroplating copper, electroless nickel plating, etc.), the active metal solder 3 can be directly hot-pressed with the ceramic substrate 1 Bonding, a continuous and dense bonding interface with good overall heat dissipation effect is formed, which not only simplifies the composite substrate process, but also improves the strength and yield of the bonding, making the cost cheaper, and at the same time, it can improve the heat dissipation effect and impact resistance. The composite substrate has significantly superior performance in resisting impact load and vibration and other mechanical properties and product reliability, and is also 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, The active metal solder 3 can be directly pressed together with the ceramic substrate 1 to form a dense bonding interface, and finally a composite substrate without any interface gap or interface peeling can be formed, and the active metal solder is selected from silver, copper, titanium, zinc. And any one of the group composed of aluminum, because the bonding interface of the composite substrate does not contain resin, the thermal conduction effect is better, which can reduce the heat accumulation on the ceramic substrate, and the overall heat dissipation effect is better; In addition, the bonding interface The lack of metallized surface treatment on the surface contains problems such as poor interface bonding force and poor compactness caused by variable factors such as complex chemical composition, shrinkage expansion, etc. Compared with traditional composite substrates, interface gaps or interface peeling caused by thermal expansion deformation are more common. Its impact resistance strength has excellent performance in resisting impact and vibration and other mechanical properties and product reliability.

The above detailed description is only for describing a preferred feasible embodiment of the present invention, but the embodiment is not intended to limit the scope of the patent application of the present invention, and all other equivalent changes and modifications are completed without departing from the technical spirit disclosed in the present invention. Changes should be included in the patent scope covered by the present invention.

To sum up, the above-mentioned composite substrate of the present invention can indeed achieve its effect and purpose when used, so the composite substrate of the present invention is an invention with excellent practicability. , I hope that the Jury Committee of the Jun Bureau can approve this case as soon as possible to protect the inventor's hard work.

1: Ceramic substrate

2: Aluminum-based silicon carbide substrate

3: Active metal solder

Claims (9)

A composite substrate includes a ceramic substrate and an aluminum-based silicon carbide substrate stacked up and down, and a joint surface formed by active metal solder is contained between the ceramic substrate and the aluminum-based silicon carbide substrate, and the aluminum-based silicon carbide substrate is It is composed of silicon carbide (SiC) with a volume percentage of 50~83vol%, and the active metal solder is selected from silver (Ag), copper (Cu), titanium (Ti), zinc (Zn) and aluminum (Al). any of the groups. The composite substrate of claim 1, wherein the ceramic substrate comprises a ceramic base and a metal layer structure formed on at least one surface of the ceramic base. The composite substrate of claim 2, wherein the ceramic base material is silicon nitride (Si ₃ N ₄ ), titanium nitride (TaN), aluminum nitride (AlN), beryllium oxide (BeO), aluminum oxide (Al ₂ O ₄ ) or silicon carbide (SiC). The composite substrate of claim 2, wherein the metal layer structure is a copper metal layer attached to the upper surface of the ceramic substrate, and then a copper metal circuit is formed by etching. The composite substrate of claim 1, wherein the aluminum-based silicon carbide substrate contains a SiC composition with a volume percentage of 63 vol%. The composite substrate of claim 1, wherein the active metal solder contains 70 vol % Ag, 28 vol % Cu, and 2 vol % Ti. The composite substrate of claim 1, wherein the active metal solder contains 10 vol % of Ag, 85 vol % of Cu and 5 vol % of Ti. The composite substrate of claim 1, wherein the active metal solder contains 80 vol % Zn and 20 vol % Al by volume. The composite substrate of claim 1, wherein the active metal solder is formed of The joint surface is formed by thermocompression bonding.

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