Package Mounting Methods
2) Mounting heat sink of package
When attaching the heat sink of power packages to the chassis, etc., attention should be paid to the tightening torque of the
attaching bolts and to the flatness of the attachment surface.
Do not bend, cut deform, or bend the mounting pins of the heat sink. Also, avoid applying solder directly to the heat sink.
When attaching the heat sink, since if the mounting brackets or positioning tabs (projections) are in contact with the plastic
areas of the product, cracks may occur and mechanical stress may be applied internally, resulting in element breakage or
disconnection faults, care must be taken with the attachment methods.
Regarding the hole diameter of the attachment surface, it should be determined taking into consideration the screw head
diameter and the overlapping of insulation tubes, insulation plates, etc.
[ Tightening torque ]
If the tightening torque is too low, the heat resistance will be high, and the heat emission effectiveness will be poor. On the
other hand, if the torque is too high, it may cause warpage of elements or apply stress to the semiconductor chips inside the
package, causing element breakage or disconnection.
Since the recommended tightening torque, mounting hardware etc. are different for each package, refer to the product
specifications or contact our company's sales division.
Further, when tightening at two or more points, be careful to tighten all points equally so that no warpage is applied to the
[ Flatness ]
The purpose of attaching power transistors to the chassis, etc. is to enable the efficient transfer of the heat generated by the
elements to the heat sink. In order to achieve this, the attachment surface of the transistor must be sufficiently smooth. If
the surface roughness is high, or if there are burrs or metal chips, dirt, or other foreign materials stuck to the surface, not
only will the heat sink be damaged, but the elements may also be damaged. Therefore, be sure to keep the surface flatness
to 0.05 mm or less and the surface twist to 20
or less.
When the mounting plate such as a chassis is a pressed plate, be sure that there is no press burrs or bending, and be sure to
smooth the surface of the screw holes. In addition, since if gaps occur between the product and the attachment surface,
heat emission efficiency may be poor, when attaching the heat sink, be sure to check that the mounting plate or the product
are not deformed.
3) Attaching to the printed circuit board
Do not attach heat sinks to the elements after soldering lead wires to the printed circuit board. Attaching heat sinks to the
elements after soldering the leads to the printed circuit board will cause excessive stress due to variations in the lead wire
length, heat sink, printed circuit board, etc. to be concentrated in the lead wires, causing damage to the lead wires such as
pulling them out, disconnecting them, etc.
Processes should be carried out in the following order:
Attachment of heat sink to power transistor
Attachment of heat sink to printed circuit board
Soldering of power
transistor to printed circuit board.
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