A power electronics assembly for an electric motor controller comprising: an insulated metal substrate carrying controllable impedances of the power electronics assembly wherein the insulated metal substrate is thermally coupled to the controllable impedances; a composite material substrate carrying elements of a power provider for providing power to be supplied to an electric motor via the controllable impedances; a bolt comprising a bolt head and a bolt shaft for mechanically coupling the composite material substrate to the insulated metal substrate; an electrically conductive sleeve configured to be held between a first electrical contact carried by the insulated metal substrate and a second electrical contact carried by the composite material substrate and to at least partially surround and be held in place by the bolt; wherein the bolt is configured to clamp the composite material substrate to the insulated metal substrate to force the electrically conductive sleeve against the first electrical contact and the second electrical contact for electrical coupling with the controllable impedances; and characterised by an electrically insulating sleeve interposed between the bolt shaft and the electrically conductive sleeve, said electrically insulating sleeve comprising an electrically insulating wall arranged to stand proud of the composite material substrate, on a side of the composite substrate that is opposite to the second electrical contact, and to at least partially surround the bolt head, wherein the electrically conductive sleeve comprises a power terminal for coupling to a source of power input or a power output for providing power to be supplied to an electric motor, for example wherein the terminal is adapted to extend through the composite material substrate, and the composite material substrate comprises a hole for the terminal to pass therethrough. an insulated metal substrate carrying controllable impedances of the power electronics assembly wherein the insulated metal substrate is thermally coupled to the controllable impedances; a composite material substrate carrying elements of a power provider for providing power to be supplied to an electric motor via the controllable impedances; a bolt comprising a bolt head and a bolt shaft for mechanically coupling the composite material substrate to the insulated metal substrate; an electrically conductive sleeve configured to be held between a first electrical contact carried by the insulated metal substrate and a second electrical contact carried by the composite material substrate and to at least partially surround and be held in place by the bolt; wherein the bolt is configured to clamp the composite material substrate to the insulated metal substrate to force the electrically conductive sleeve against the first electrical contact and the second electrical contact for electrical coupling with the controllable impedances; and characterised by an electrically insulating sleeve interposed between the bolt shaft and the electrically conductive sleeve, said electrically insulating sleeve comprising an electrically insulating wall arranged to stand proud of the composite material substrate, on a side of the composite substrate that is opposite to the second electrical contact, and to at least partially surround the bolt head, wherein the electrically conductive sleeve comprises a power terminal for coupling to a source of power input or a power output for providing power to be supplied to an electric motor, for example wherein the terminal is adapted to extend through the composite material substrate, and the composite material substrate comprises a hole for the terminal to pass therethrough.