SERVO AMPLIFIER

PROBLEM TO BE SOLVED: To provide a servo amplifier whose assembly structure is improved so as to improve the size reduction, compactification, and assembly of a product while ensuring the thermal reliability of mounted circuit components without using a fan.SOLUTION: A servo amplifier is composed by fitting a main circuit board 30, control circuit board 40, a relay circuit board 50, and a case cover 20 together on a heat sink 10 provided with a fin serving as a mounting base as well. The servo amplifier is assembled by superposing a power semiconductor device 31, mounted on the main circuit board 30, on the heat sink 10. The front of the heat sink 10 is covered with a heat shield plate 70 and the space between a board accommodation space in front of the heat shield plate 70 and the heat sink is heat shielded. In this state, the relay circuit board 50 is mounted in a predetermined position by being snap fitted to the front of the heat shield plate 70. In this mounting position, the relay circuit board 50 is relay-connected to the main circuit board 30 and control circuit board 40 via a plug-in type connector.