Patent Application
20170114455
A thermally conductive composition can include an electrically conductive filler. An electrically conductive filler can increase the thermal conductivity of the thermally conductive composition. An electrically conductive filler can also decrease the dielectric breakdown voltage of the thermally conductive composition.
A decrease in the dielectric breakdown voltage of a thermally conductive composition can cause failures. For example, a relatively low dielectric breakdown voltage of a thermally conductive composition that couples a heat-generating component of an electronics device to a heat-dissipating structure can cause an electrical short circuit in the electronics device.
In general, in one aspect, the invention relates to a thermally conductive composition having an electrically conductive filler with a ceramic coating selected to maintain a relatively high dielectric breakdown voltage of the thermally conductive composition while maintaining a relatively high thermal conductivity of the thermally conductive composition.
In general, in another aspect, the invention relates to a method for forming a thermally conductive composition. The method can include: forming a ceramic coating on an electrically conductive filler for the thermally conductive composition; and mixing the thermally conductive composition including the electrically conductive filler with the ceramic coating such that the ceramic coating provides a relatively high dielectric breakdown voltage of the thermally conductive composition while maintaining a relatively high thermal conductivity of the thermally conductive composition.
Other aspects of the invention will be apparent from the following description and the appended claims.
Embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements.
Reference will now be made in detail to the various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Like elements in the various figures are denoted by like reference numerals for consistency. While described in conjunction with these embodiments, it will be understood that they are not intended to limit the disclosure to these embodiments. On the contrary, the disclosure is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.
In one or more embodiments, a thickness of the ceramic coating 14 is controlled to provide the relatively high dielectric breakdown voltage of the thermally conductive composition 10. The thickness of the ceramic coating 14 can be varied to vary the dielectric breakdown voltage of the thermally conductive composition 10.
In one or more embodiments, the thickness of the ceramic coating 14 is controlled to maintain the relatively high thermal conductivity of the thermally conductive composition 10. The thickness of the ceramic coating 14 can be varied to vary the thermal conductivity of the thermally conductive composition 10.
In one or more embodiments, the thickness of the ceramic coating 14 is controlled in response to a desired balance between the relatively high dielectric breakdown voltage and the relatively high thermal conductivity of the thermally conductive composition 10. For example, the thickness of the ceramic coating 14 can be increased to increase the dielectric breakdown voltage of the thermally conductive composition 10 at the expense of some of the thermal conductivity of the thermally conductive composition 10. Conversely, the thickness of the ceramic coating 14 can be decreased to increase the thermal conductivity of the thermally conductive composition 10 at the expense of some of the dielectric breakdown voltage margin of the thermally conductive composition 10.
In one or more embodiments, the electrically conductive filler 12 a metal. Example metals for the electrically conductive filler 12 include aluminum, copper, and silver.
In one or more embodiments, the electrically conductive filler 12 is an electrically conductive non-metal material. Example non-metals for the electrically conductive filler 12 include carbon fiber, carbon nanotube, and graphite.
In one or more embodiments, the ceramic coating 14 is formed on a surface of the electrically conductive filler 12 using a chemical vapor deposition (CVD) process. Examples of the ceramic coating 14 include an aluminum oxide coating, a silica coating, and a zinc oxide coating.
In one or more embodiments, the electrically conductive filler 12 is mixed in a layer 15 with a polymer resin 16. Examples of the polymer resin 16 include silicone rubber, epoxy, polyurethane, and polyacrylate.
The thickness of the ceramic coating 14 in one or more embodiments can range between 0.1 micrometers and 20 micrometers. The preferred range of the thickness of the ceramic coating 14 in one or more embodiments can be between 0.5 micrometers and 5 micrometers.
In one example embodiment of the thermally conductive composition 10, the electrically conductive filler 12 is aluminum and the ceramic coating 14 is a 3-micrometer thick layer of aluminum oxide. The aluminum oxide layer can be prepared through a fluidized bed chemical vapor deposition (FBCVD) process using aluminum acetylacetonate as precursor.
The thickness of the ceramic coating 14 can be controlled by controlling one or more of the FBCVD process parameters. The FBCVD process parameters that can be controlled can include bed temperature, carrier gas flow rate sent through the vaporizer line, and coating duration.
In one or more embodiments, the thickness of the ceramic coating 14 is selected so that it yields a relatively high thermal conductivity between a surface 17, the intervening mixture of the polymer resin 16 and the electrically conductive filler 12 with the ceramic coating 14, and a surface 18 of the thermally conductive composition 10 while maintaining a relatively high dielectric breakdown voltage across the thermally conductive composition 10 between the surfaces 17 and 18.
A surface 21 of the heat-generating component 20 thermally couples to the surface 17 (
The relatively high dielectric breakdown voltage between the heat-generating component 20 and the heat-dissipating structure 22 avoids damage to and failure of the thermally conductive composition 10 when a relatively large voltage differential exists between the heat-generating component 20 and the heat-dissipating structure 22. In one or more embodiments, the thermally conductive composition 10 provides a dielectric breakdown voltage above 5 kilovolts per millimeter while also providing a thermal conductivity of up to 8 watts per meter-kelvin.
At step 310, a ceramic coating is formed on an electrically conductive filler for the thermally conductive composition. The ceramic coating can be formed by a CVD process.
At step 320, the thermally conductive composition including the electrically conductive filler with the ceramic coating is mixed such that the ceramic coating provides a relatively high dielectric breakdown voltage of the thermally conductive composition while maintaining a relatively high thermal conductivity of the thermally conductive composition. The electrically conductive filler with the ceramic coating can be mixed in a polymer resin.
The CVD precursors and parameters can be controlled to control the thickness of the ceramic coating in response to a desired dielectric breakdown voltage of the thermally conductive composition. The CVD precursors and parameters can be controlled to control the thickness of the ceramic coating in response to a desired thermal conductivity of the thermally conductive composition. The CVD precursors and parameters can be controlled to control the thickness of the ceramic coating in response to a desired balance between the dielectric breakdown voltage and the thermal conductivity of the thermally conductive composition.
While the foregoing disclosure sets forth various embodiments using specific diagrams, flowcharts, and examples, each diagram component, flowchart step, operation, and/or component described and/or illustrated herein may be implemented, individually and/or collectively, using a range of processes and components.
The process parameters and sequence of steps described and/or illustrated herein are given by way of example only. For example, while the steps illustrated and/or described herein may be shown or discussed in a particular order, these steps do not necessarily need to be performed in the order illustrated or discussed. The various example methods described and/or illustrated herein may also omit one or more of the steps described or illustrated herein or include additional steps in addition to those disclosed.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the invention as disclosed herein.
