Thyristor Semiconductor Products Page 39 Thyristor

2014 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 12/14/14 Teccor brand Thyristors AN1004 Heat Sinking Use of the largest, most efficient heat sink as is practical and cost effective extends device life and increases reliability. In the illustration shown in Figure AN1004.3, each device is electrically isolated. Heat Sink Figure AN1004.3 Several Isolated TO-220 Devices Mounted to a Common Heat Sink Many power device failures are a direct result of improper heat dissipation. Heat sinks with a mating area smaller than the metal tab of the device are unacceptable. effective and efficient. Note that in all applications the maximum case temperature (T C ) rating of the device must not be exceeded. Refer to the individual device data sheet rating curves (T C versus I T ) as well as the individual device outline drawings for correct T C measurement point. Figure AN1004.4 through Figure AN1004.6 show additional examples of acceptable heat sinks. Figure AN1004.4 Examples of PC Board Mounts Heat Sink Printed Circuit Board B A Figure AN1004.5 Vertical Mount Heat Sink Several types of vertical mount heat sinks are available. Keep heat sink vertical for maximum convection. Figure AN1004.6 Examples of Extruded Aluminum When coupled with fans, extruded aluminum mounts have the highest efficiency. Heat Sinking Notes Care should be taken not to mount heat sinks near other heat-producing elements such as power resistors, because black anodized heat sinks may absorb more heat than they dissipate. Some heat sinks can hold several power devices. Make sure that if they are in electrical contact to the heat sink, the devices do not short-circuit the desired functions. Isolate the devices electrically or move to another location. Recall that the mounting tab of Littelfuse isolated TO-220 devices is electrically isolated so that several devices may be mounted on the same heat sink without extra insulating components. If using an external insulator such as mica, added to the R JC device rating. Allow for adequate ventilation. If possible, route heat sinks to outside of assembly for maximum airflow. Mounting Surface Selection Proper mounting surface selection is essential to efficient transfer of heat from the semiconductor device to the heat sink and from the heat sink to the ambient. The most popular heat sinks are flat aluminum plates or finned extruded aluminum heat sinks. The mounting surface should be clean and free from burrs or scratches. It should be flat within 0.002 inch per inch, and a surface finish of 30 to 60 microinches is acceptable. Surfaces with a higher degree of polish do not produce better thermal conductivity. Many aluminum heat sinks are black anodized to improve thermal emissivity and prevent corrosion. Anodizing results in high electrical but negligible thermal insulation. This is an excellent choice for isolated TO-220 devices. For applications of non-isolated TO-220 devices where electrical connection to the common anode tab is required, the anodization Mounting and Handling of Semiconductor Devices (continued)

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