This application relates in general to electronic circuitry, and in particular, to conductivity of heat in electronic circuitry.
Thermal management materials with high thermal conductivity, high thermal diffusivity, machineability and low coefficient of thermal expansion (“CTE”) at low cost are desirable. For many electronic applications it would be beneficial if the material was not electrically conductive so that electronic components could be assembled directly onto the high thermal conductivity material. However, materials with high thermal conductivity are also typically electrically conductive. For example, carbon-based materials, such as graphite and graphene, typically have high thermal conductivity and are also electrically conductive. It would be desirable to have high thermal conductivity ceramic dielectric layers on graphitic substrates (i.e., a pure graphite substrate or a graphite-metal composite substrate) for fabrication of a high-performance circuit board through printing copper (“Cu”) circuit traces on the top of the ceramic dielectric layers.
Besides providing high thermal performance and sufficient dielectric strength, the dielectric layers should also possess a strong, adhesion with graphitic substrates, be compatible with Cu paste printing and curing processes that require a curing temperature over 400° C., and possess a strong adhesion with the Cu printed circuit traces.
In order to create effective dielectric ceramic layers that combine good adhesion to both graphitic substrates and printed Cu, and strong insulating capability, multiple ceramic layer structures on graphitic substrates are implemented in embodiments of the present invention.
Generally, compared with polymeric dielectric layers (e.g., epoxy, silicone, polyimide), ceramic-type dielectric layers (e.g., made with ceramic powders, such as aluminum nitride (“AlN”), boron nitride (“BN”), silicon carbide (“SiC”), etc.) have much higher thermal conductivity and a lower CTE that matches well with typical semiconductor materials (e.g., Si, GaN, GaAs).
In embodiments of the present invention, different kinds of printing pastes or inks are utilized in various combinations, some of which are more specifically described herein, to develop multiple ceramic dielectric layers on graphitic substrates. The pastes or inks may comprise a high thermal conductivity powder (e.g., AlN, BN, SiC, or graphite micron powders) and a nonorganic binder. Water may be used as a vehicle to adjust the viscosity. The pastes or inks are further described in Table 1.
A SiCl/BN/SiC/Graphitic-waier structure 100 in accordance with embodiments of the present invention is illustrated in cross-section in
The Cu traces 105 on the ceramic dielectric layer are configured to be solderable. As shown in
An AlN/Graphite/Graphitic-wafer structure 400 in accordance with embodiments of the present invention is illustrated in cross-section in
This application claims priority to U.S. Provisional Application Ser. No. 61/603,479, which is hereby incorporated by reference herein.
Filing Document | Filing Date | Country | Kind |
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PCT/US2013/027717 | 2/26/2013 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2013/130418 | 9/6/2013 | WO | A |
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