This invention provides a structure for holding cards having electronic and/or micromachined components. A chassis comprises a plurality of bays for receiving cards such that the cards are oriented parallel to one another. Each bay comprises a fin front-plate fabricated from thermally-conductive material(s). Each fin front-plate is coupled to or integrally formed with a base in a manner which permits thermal conductivity therebetween. For each bay holding a card, a backplane comprises an electrical connector for coupling to the card. When held in their respective bays, cards are thermally coupled to the fin front-plates. The base of the chassis preferably comprises an ingress port, an egress port and a network of conduits for conducting fluid which cools and/or redistributes heat created by the cards and their components. The network of conduits may extend from the base and into the fin front-plates.