ISSN:
0954-0911
Source:
Emerald Fulltext Archive Database 1994-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The trendtowards higher density, higher frequency, higher power active devices in placing increasinglydifficult demands on device packaging. Materials with high thermal conductivities are replacingthe traditional ceramics in hermetic, high power packages, and MCM/ hybrid modules. Thermally enhanced plastic packages more frequently feature heat sinks embedded in thepackage for direct attachment of the power devices. Today's challenge inelectronic packaging is to dissipate the heat from the source, the device itself, without affectingits electrical performance or reliability. The material directly contacting the device is the dieattach medium. On lower power packages, the die bond line is not usually the highest thermalresistance in the thermal path. With highly conductive substrates and heat sinks, the die attachmaterial now becomes the critical element directly in series with the highly conductive substrate. Fundamental limitations in thermal properties of about 3 W/mK exist inpresent-day organic adhesives, primarily of the thermosetting type. Thisthermal conductivity (k) does not meet the current demands of thermally enhancedplastic laminate packages, MCMs, or direct die attach to heat spreaders or heat sinks. This paper describes the development, properties and application ofelectrically conductive thermoplastic adhesive pastes having thermal conductivity values as highas 35 W/mK, and able to produce thin, void-free bond lines for maximum thermaltransfer. The key material variables are isolated and evaluated for their impact of the k value. DOEs (design of experiments) were run to optimise the combination of the keyvariables, namely size/shape of the filler and the volume fraction to produce the highest kwithout sacrificing other functional properties such as adhesion. The effect of polymer chemistry(thermoset and thermoplastic) was also studied. The properties of the newlydeveloped, enhanced conductivity thermoplastic adhesives are compared with other materialtechnologies and examples of current applications reviewed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1108/09540919710195172
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