Thermally conductive encapsulant material for a capacitor assembly
A capacitor assembly that comprises a housing, a capacitor element that is hermetically sealed within the housing, and a thermally conductive material that at least partially encapsulates the capacitor element is provided. The capacitor element includes a sintered anode body, a dielectric overlying the anode body, and a solid electrolyte overlying the dielectric. The thermally conductive material has a thermal conductivity of about 1 W/m-K or more as determined in accordance with ISO 22007-2:2014.
1. A capacitor assembly comprising:
a housing;
a capacitor element that is hermetically sealed within the housing, wherein the capacitor element includes a sintered anode body, a dielectric overlying the anode body, and a solid electrolyte overlying the dielectric; and
a thermally conductive material that completely encapsulates the capacitor element, wherein the thermally conductive material has a thermal conductivity of about 1 W/m-K or more as determined in accordance with ISO 22007-2:2014 and a volume resistivity of about 1×10 12 ohm-cm or more as determined in accordance with ASTM D257-14;
wherein the thermally conductive material contains a thermally conductive filler that is dispersed within a polymer matrix;
wherein the polymer matrix constitutes from about 5 vol. % to about 75 vol. % of the thermally conductive material; and
wherein thermally conductive fillers constitute from about 25 vol. % to about 95 vol. % of the thermally conductive material.
2. The capacitor assembly of claim 1 , wherein the thermally conductive material exhibits a degree of moisture absorption of about 1% or less as determined in accordance with ASTM D570-98(2010)e-1.
3. The capacitor assembly of claim 1 , wherein the thermally conductive filler includes a metallic filler, metal oxide filler, nitride filler, carbon filler, or a combination thereof.
4. The capacitor assembly of claim 3 , wherein the thermally conductive filler includes aluminum, silver, copper, nickel, iron, cobalt, aluminum oxide, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, silicon nitride, silicon carbide, carbon black, carbon fullerene, graphite flakes, carbon nanotubes, carbon nanofibers, or a combination thereof.
5. The capacitor assembly of claim 1 , wherein the thermally conductive filler includes filler particles having an average size of from about 10 to about 500 nanometers.
6. The capacitor assembly of claim 1 , wherein the thermally conductive filler includes particles having an average size of from about 1 to about 50 micrometers.
7. The capacitor assembly of claim 1 , wherein the thermally conductive filler contains nano-scale particles and micro-scale particles, wherein the ratio of the average size of the micron-scale filler particles to the average size of the nano-scale filler particles is about 50:1 or more.
8. The capacitor assembly of claim 1 , wherein the polymer matrix includes a organopolysiloxane.
9. The capacitor assembly of claim 8 , wherein the organopolysiloxane is polydimethylsiloxane.
10. The capacitor assembly of claim 8 , wherein the organopolysiloxane has a molecular weight of from about 5,000 to about 30,000 g/mol.
11. The capacitor assembly of claim 1 , wherein thermally conductive fillers constitute from about 40 vol. % to about 90 vol. % of the thermally conductive material.
12. The capacitor assembly of claim 1 , wherein the polymer matrix constitutes from about 10 vol. % to about 50 vol. % of the thermally conductive material.
13. The capacitor assembly of claim 1 , wherein the anode body includes tantalum and the dielectric includes tantalum pentoxide.
14. The capacitor assembly of claim 1 , wherein the solid electrolyte includes a conductive polymer layer.
15. The capacitor assembly of claim 14 , wherein the conductive polymer layer includes a substituted polythiophene.
16. The capacitor assembly of claim 1 , wherein the housing defines a gaseous atmosphere, and wherein inert gases constitute from about 50 wt. % to 100 wt. % of the gaseous atmosphere.
17. The capacitor assembly of claim 1 , wherein the housing is formed from a metal, ceramic, or a combination thereof.
18. The capacitor assembly of claim 1 , wherein the thermally conductive material is in direct contact with the capacitor element.
19. The capacitor assembly of claim 1 , wherein the housing defines sidewalls having an upper surface and a lid that is positioned on the upper surface of the sidewalls.
20. The capacitor assembly of claim 19 , wherein the thermally conductive material is disposed on the lid.