To improve a TCT characteristic of a circuit substrate. The circuit substrate comprises a ceramic substrate including a first and second surfaces, and first and second metal plates respectively bonded to the first and second surfaces via first and second bonding layers. A three-point bending strength of the ceramic substrate is 500 MPa or more. At least one of L1/H1 of a first protruding portion of the first bonding layer and L2/H2 of a second protruding portion of the second bonding layer is 0.5 or more and 3.0 or less. At least one of an average value of first Vickers hardnesses of 10 places of the first protruding portion and an average value of second Vickers hardnesses of 10 places of the second protruding portion is 250 or less.

A microcapsule includes a shell including a conducting component, and a thermally expandable component contained in the shell and having a property of expanding by heating. The shell is deformable in accordance with expansion of the thermally expandable component when the thermally expandable component is heated.

A microcapsule includes a shell including a conducting component; and a thermally expandable component contained in the shell and having a property of expanding by heating, the shell deforming due to expansion of the thermally expandable component to come in contact with another capsule and have a conducting state with the other capsule.

Provided is a power conversion apparatus including: a plurality of power converters including a first power converter and a second power converter simultaneously operated by power supplied via a first connector; and a heat dissipation board having a first pattern formed thereon for distributing the power supplied via the first connector to the first power converter and the second power converter.

Disclosed is a circuit assembly having a novel structure capable of reducing thermal resistance in a heat-dissipating path and increasing heat dissipation while ensuring insulation between a heat-dissipating portion and a heat-dissipation target. A circuit assembly includes: heat-generating components that generate heat as a result of a current flowing therethrough; a case accommodating the heat-generating components; metal plates connected to connecting portions of the heat-generating components, and each having a heat-dissipating portion exposed to an outside of the case and configured to come into thermal contact with an external heat-dissipation target; insulating films covering a contact surface of the heat-dissipating portion, the contact surface being configured to come into contact with the heat-dissipation target; and a thermal conductive filling member that is in thermal contact with the heat-dissipating portion via the insulating films and disposed between the insulating films and the heat-dissipation target.

A thermally expandable material includes microcapsules and a binder having a conducting property, each microcapsule including a shell having an insulating property, and a thermally expandable component contained in the shell and having a property of expanding by heating, the shell deforming due to expansion of the thermally expandable component to come in contact with another capsule and have an insulating state with the other capsule.

A microcapsule includes a shell including a conducting component; and a thermally expandable component contained in the shell and having a property of expanding by heating, the shell deforming due to expansion of the thermally expandable component to come in contact with another capsule and have a conducting state with the other capsule.

To improve a TCT characteristic of a circuit substrate. The circuit substrate comprises a ceramic substrate including a first and second surfaces, and first and second metal plates respectively bonded to the first and second surfaces via first and second bonding layers. A three-point bending strength of the ceramic substrate is 500 MPa or more. At least one of L1/H1 of a first protruding portion of the first bonding layer and L2/H2 of a second protruding portion of the second bonding layer is 0.5 or more and 3.0 or less. At least one of an average value of first Vickers hardnesses of 10 places of the first protruding portion and an average value of second Vickers hardnesses of 10 places of the second protruding portion is 250 or less.

To improve a TCT characteristic of a circuit substrate. The circuit substrate comprises a ceramic substrate including a first and second surfaces, and first and second metal plates respectively bonded to the first and second surfaces via first and second bonding layers. A three-point bending strength of the ceramic substrate is 500 MPa or more. At least one of L1/H1 of a first protruding portion of the first bonding layer and L2/H2 of a second protruding portion of the second bonding layer is 0.5 or more and 3.0 or less. At least one of an average value of first Vickers hardnesses of 10 places of the first protruding portion and an average value of second Vickers hardnesses of 10 places of the second protruding portion is 250 or less.

A rigid flex circuit comprised of high thermal conductivity sections, said sections having components disposed so as to have their contacts substantially planar with the surface of the thermally conductive section and wherein the contacts are interconnected directly to the traces without the use of solder and further having the thermally conductive sections interconnected to one another by means of flexible circuit sections.