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High-Temperature Electronic Packaging
Pages 51-60

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From page 51...
... For example, microwave packaging will have to meet additional requirements such as impedance matching, low dielectric loss at microwave frequencies, low sensitivity of dielectric and conductors to temperature changes, and low capacitance of interconnect to the backside of radio frequency ground plane. One approach to providing hermetic electronic packaging suitable for operation at higher temperatures is to rely on existing packaging technology such as either the use of single metal packages 51 with electrical feedthroughs isolated by glass beads or the use of multilayer ceramic packages (single or multichip)
From page 52...
... The most attractive ceramic package for use in high-temperature applications is the aluminum-nitride package; however, the most often used is the less costly alumina. Ceramic packages are manufactured using a cofired tape process and have an advantage over metal packages because they can avoid the use of expensive fragile glass-to-metal seals.
From page 53...
... When using such a substrate material, less stress between the substrate and chip is generated during the temperature excursions encountered in the manufacture and operation of the substrate assembly. It should be noted that SiC has a high dielectric constant and high dissipation factor limiting its use as a substrate.
From page 54...
... The microstructurally toughened interracial a&esion also assures that the cofired multilayer substrate maintains the high thermal conductivity and mechanical strength of typical monolithic A1N (Chiao et al., 1991~. Thin-film metallizations have also been successfully used at high temperatures.
From page 55...
... . Hard solders provide electrically conductive paths and have high thermal conductivity but are difficult to rework.
From page 56...
... The tendency for silver migration and the effect of thermal cycling on the long-term adhesion of this system over extended temperature ranges has not yet been studied, however. Polymer die attach is normally not practical for use at temperatures above 250 °C where a nonconductive attachment is needed.
From page 57...
... Recent advances in organic dielectrics have allowed some application of organic, printed circuit boards in high-temperature environments, primarily for reduced cost. Polyimide printed circuit boards patterned with nickel, nickel-plated copper, or nickel-plated tin are common combinations.
From page 58...
... SUMMARY Although high-temperature wide bandgap devices are being developed, they can only be successfully implemented into commercial applications if the packaging technology is developed in parallel to provide a cost and performance advantage. Novel approaches should be examined based on the existing knowledge of advanced packaging technologies, especially multichip modules.
From page 59...
... The use of existing high-density multichip module designs can leverage the development of high-temperature electronic systems by careful selection of the material systems used. 59 There is not an upper temperature that should be feared by packaging engineers any more than by the device physicist (Johnson, in press)


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