Al/SiC carriers for microwave integrated circuits by a new technique of pressureless infiltration
Materials with high thermal conductivity and thermal expansion coefficient matching with that of Si or GaAs are being used for packaging high density microcircuits due to their ability of faster heat dissipation. Al/SiC is gaining wide acceptance as electronic packaging material due to the fact that its thermal expansion coefficient can be tailored to match with that of Si or GaAs by varying the Al:SiC ratio while maintaining the thermal conductivity more or less the same. In the present work, Al/SiC microwave integrated circuit (MIC) carriers have been fabricated by pressureless infiltration of Al-alloy into porous SiC preforms in air. This new technique provides a cheaper alternative to pressure infiltration or pressureless infiltration in nitrogen in producing Al/SiC composites for electronic packaging applications. Al-alloy/65vol% SiC composite exhibited a coefficient of thermal expansion of 7/spl times/10/sup -6/ K/sup -1/ (25/spl deg/C-100/spl deg/C) and a thermal conductivity of 147 Wm/sup -1/K/sup -1/ at 30/spl deg/C. The hysteresis observed in thermal expansion coefficient of the composite in the temperature range 100/spl deg/C-400/spl deg/C has been attributed to the presence of thermal residual stresses in the composite. Thermal diffusivity of the composite measured over the temperature range from 30/spl deg/C to 400/spl deg/C showed a 55% decrease in thermal diffusivity with temperature. Such a large decrease in thermal diffusivity with temperature could be due to the presence of micropores, microcracks, and decohesion of the Al/SiC interfaces in the microstructure (all formed during cooling from the processing temperature). The carrier showed satisfactory performance after integrating it into a MIC.
Reduction of Die-Bonding Interface Thermal Resistance for High-Power LEDs Through Embedding Packaging Structure
Thermal management is a key issue for high-power light-emitting diodes (LEDs). In this study, a novel packaging structure was proposed to reduce the die-bonding interface thermal resistance and provided a new idea for LED heat-dissipation. The LED chip was embedded into a square groove at the lead-frame substrate. The gap between the edges of the LED chip and square groove was filled with boron nitride/silicone composite. So the heat generated from the chip could be dissipated from the side surfaces to the substrate. The experimental results show that the heat-dissipation ability of LEDs has been significantly improved by the new embedding packaging structure. The die-bonding interface thermal resistance can be reduced by more than 20%. The junction temperature rise can be reduced by 14%. Due to the fully embedding of LED chip in the square groove, the light intensity distribution is slightly shrunk and the light output power is slightly reduced by about 8%.
Aluminum Silicon Carbide (AlSiC) Thermal Management Packaging For High Density Packaging Applications
High-density microelectronics require packaging materials and systems that provide superior thermal management and highly functional interconnection schemes for component performance and reliability. Aluminum Silicon Carbide (AlSiC) metal matrix composite (MMC) packages have a unique set of material properties that are ideally suited to thermal management performance, and a functionality that supports high density interconnection microelectronic packaging applications. Furthermore, the AlSiC fabrication and processing technology provides these high performance attributes cost-effectively. The AlSiC coefficient of thermal expansion (CTE) value is compatible with direct IC device attachment allowing for the maximum thermal dissipation into the high thermal conductivity (170 – 200 W/mK) AlSiC package. Additionally, the low material density of AlSiC (3 g/cm 3 ) makes it ideal for weight sensitive applications such as airborne, spaceborne, or portable devices. The AlSiC material and functional electronic packaging geometries are cost-effectively produced using Ceramics Process Systems (CPS) QuickSet™/QuickCast™ net-shape (without machining) fabrication process. Functional packaging features such as feedthrus, sealrings and substrates are incorporated in AlSiC during fabrication using the CPS Concurrent Integration™ technique eliminating the need for additional assembly and brazing (or soldering) operations. The ideal material properties coupled with AlSiC fabrication and Concurrent Integration™ process provide low-cost high performance functional thermal management packaging solutions. This paper will illustrate the AlSiC material/packaging capabilities through examples of High-Density Interconnect (HDI) electronic packaging, which will be discussed in terms of the ultimate component reliability. In addition the AlSiC packaging cost-efficiency will be illustrated through an outline of the AlSiC material/packaging fabrication process which will be contrasted to traditional fabrication and packaging assembly techniques.