Silicon Carbide Particulate Reinforced Aluminum Matrix Composites (AlSiC)
Aluminum silicon carbide AlSiC(SICP/Al or Al/SiC, SiC/Al) is a kind of particle reinforced metal matrix composite material, using Al alloy as the matrix, according to the design requirements, in a certain form, proportion and distribution state, using SiC particles as reinforcement, to form a clear interface of multi-phase composite materials, both a single metal does not have the comprehensive superior performance.
AlSiC research and development earlier, the theoretical description is more perfect, there are varieties to take the lead in realizing the scale industrialization of electronic packaging materials, to meet the semiconductor chip integration along Moore's law to improve the chip heat, the service life of the decline and electronic packaging "thin and small" development needs. Especially in aerospace, microwave integrated circuits, power modules, military RF system chips and other packaging analysis is extremely prominent, has become an important trend in the application and development of packaging materials.
There are several kinds of reinforcements for packaging metal matrix composites, of which SiC is the most widely used one, because it has excellent thermal properties, mature technology for particle abrasives, and relatively low prices; on the other hand, particle reinforcements are isotropic and most conducive to net shaping. According to the two-phase ratio or the heat treatment state of the composite material, the thermal physical and mechanical properties of the material can be designed, so that the AlSiC characteristics mainly depend on the volume fraction (content) and distribution and particle size of SiC, as well as the Al alloy composition. According to meet the performance requirements of chip packaging. Among them, the volume fraction of SiC is particularly important. In practical application, AlSiC is in direct contact with the chip or ceramic substrate, and CTE is required to match as much as possible. Therefore, the volume fraction of SiC vol is usually 50%-75%.
In addition, AlSiC can integrate a variety of electronic packaging materials, which can be used as package integration and develop other functions and uses. The Cu-based packaging material blocks (Cu-diamond, Cu-graphite, Cu-BeO, etc.) with high performance and fast heat dissipation were successfully embedded in SiC preforms, and the integrated packaging substrate was fabricated by metal Al infiltration. In the process of AlSiC coexistence and integration, these expensive fast heat dissipation materials can be set up in the most needed parts, reducing costs and expanding production scale. AlSiC flip chip systems embedded with fast heat dissipation materials are being tested and evaluated. In addition, materials such as alloy 48, Kovar and stainless steel can be integrated concurrently. Such materials or plug-ins, leads, sealing rings, substrates, etc. can be inserted into SiC preforms before infiltration. In the AlSiC composite forming process, the concurrent integration can be economically completed to facilitate laser connection of optoelectronic device packages.
The high silicon aluminum alloy SiAl packaging material with uniform internal structure, excellent performance and Si content as high as 70wt%(weight percentage) was prepared by spray deposition technology. The CTE of the high silicon aluminum alloy is matched with Si and GaAs, and can also be used in the packaging of radio frequency, microwave circuits and aerospace electronic systems, and developed into a lightweight metal packaging material. Aluminum silicon carbide (AlSiC) metal matrix thermal management composite material is a special packaging material for electronic components, mainly refers to the aluminum and high volume fraction of silicon carbide composite into a low density, high thermal conductivity and low expansion coefficient of packaging materials to solve the thermal failure of electronic circuits.
Performance characteristics of AlSiC
AlSiC has high thermal conductivity (180~240W/mK) and adjustable thermal expansion coefficient (6.5~9.5 × 10-6/K). Therefore, on the one hand, AlSiC's thermal expansion coefficient is well matched with semiconductor chip and ceramic substrate, which can prevent fatigue failure and even directly mount power chip on AlSiC substrate. On the other hand, the thermal conductivity of AlSiC is ten times that of Kovar alloy, the heat generated by the chip can be dissipated in time. In this way, the reliability and stability of the entire component is greatly improved.
AlSiC is a composite material, its thermal expansion coefficient and other properties can be adjusted by changing its composition, so the product can be flexibly designed according to the specific requirements of users, and can be truly tailored, which is not possible with traditional metal materials or ceramic materials.
AlSiC has a density comparable to aluminum, is much lighter than copper and Kovar, and is less than Cu/W 1/5, making it particularly suitable for portable devices, aerospace and other weight-sensitive applications.
The specific stiffness (stiffness divided by density) of AlSiC is the highest among all electronic materials: 3 times that of aluminum, 5 times that of W-Cu and Kovar, and 25 times that of copper. In addition, AlSiC has better shock resistance than ceramics, so it is an optional material in harsh environments (large vibrations, such as aerospace, automobiles, etc.).
AlSiC can be processed in large quantities, but the processing technology depends on the content of silicon carbide, and can be processed by electric spark, diamond, laser, etc.
AlSiC can be plated with nickel, gold, tin, etc., and the surface can be anodized.
The metallized ceramic substrate can be soldered to the plated AlSiC substrate, and the printed circuit board core can be bonded to the AlSiC with an adhesive or resin.
AlSiC itself has good gas tightness. However, hermeticity after packaging with metal or ceramic depends on proper plating and soldering.
The physical and mechanical properties of AlSiC are isotropic.
The significance of using AlSiC material can greatly improve the packaging performance of integrated circuits, the use of aluminum silicon carbide material for electronic packaging, so that the thermal expansion of the package body and the chip is consistent, and play a good thermal conductivity function, to solve the thermal failure of the circuit;
Bulk use of AlSiC materials can reduce packaging costs. Effectively improve the packaging technology level of my country's aerospace, military, microwave and other power microelectronics fields, improve functions, reduce costs, and accelerate the advancement of my country's aerospace and military products. For example, in the past to Kovar (Kovar) material as a device packaging shell, if replaced by aluminum silicon carbide shell, the weight can be reduced to the original 1/3, while the thermal conductivity is increased by ten times.
The successful development of AlSiC packaging materials indicates that Chinese enterprises are no longer a pure blue collar and processor in the packaging field, but have their own packaging leading products with independent technology core, filling the domestic gap, which is a great technological progress in the packaging field; the superior performance makes AlSiC have a broader market space than W-Cu, Mo, BeO, Kovar, Mo-Cu, AlN, AlSi, Al2O3 and other current packaging materials. (Source: Xi'an Chuangzheng New Materials Co., Ltd.)
According to the structural design requirements, making the reinforcement material SiC evenly distributed in the matrix is also one of the key technologies in the manufacture of aluminum silicon carbide materials. Especially in the low volume aluminum silicon carbide stirring method, vacuum pressure infiltration method, powder metallurgy method, the agglomeration of SiC particles, and the uniform distribution of SiC particles of different sizes is a difficult point.View Details