Electronic control unit having connector positioned between two circuit substrates

An electronic control unit comprising:

• a casing including a heat dissipation plate;
• a driving circuit substrate having driving elements mounted thereon for supplying electric power in a controlled manner to actuators connected to the electronic control unit, the driving circuit substrate being mounted on the heat dissipation plate;
• a control circuit substrate having control elements mounted thereon for controlling operation of the driving elements based on signals fed from sensors connected to the electronic control unit, the control circuit substrate being contained in the casing apart from the driving circuit substrate with a separating space;
• a flexible printed-circuit-sheet for electrically connecting the driving circuit substrate and the control circuit substrate, the flexible printed-circuit-sheet comprising a hard printed-board and a pair of flexible printed-sheets, each connected to one of the sides of the hard printed-board;
• a connector for electrically connecting the actuators and sensors to the electronic control unit, the connector being mounted on and electrically connected to the hard printed-board;
• and
• a noise-absorbing element for absorbing external noises entering into the electronic control unit, and that is mounted on and electrically connected to the hard printed-board in a vicinity of the connector.

A method of manufacturing an electronic control unit comprising:

• providing a casing with a heat dissipation plate;
• mounting a driving circuit substrate on which heat generating driving elements are mounted on the heat dissipation plate;
• providing a control circuit substrate on which heat sensitive elements are mounted in the casing so that the control circuit substrate is spaced apart from the driving circuit substrate with a separating space;
• providing a flexible printed-circuit-sheet in the casing, the flexible printed-circuit-sheet including a hard printed-board and a pair of flexible printed-sheets, each connected to different sides of the hard printed-board;
• mounting a connector on the casing and electrically connecting the connector to the hard printed-board;
• and
• electrically connecting a first of the pair of flexible printed-sheets to the driving circuit substrate and a second of the pair of flexible printed-sheets to the control circuit substrate.