Through-hole packages

AN533

12/22

With rivets: Pop rivets should never be used for the following reasons:

●

A too rigorous expansion of the metal can lead to a distortion of the heatsink hole and

induce mechanical stresses on the die.

●

High crimping shock can damage the die.

Press rivets can be used with caution provided they are of a soft metal like aluminium. The

crimping force must be applied slowly and carefully in order to avoid shock and deformation

of the heatsink.

Figure 10.

Assembly with rivet

With clips: Care should be taken with the contact area between the plastic case and the

clip: the maximum pressure allowed on plastic is 150 N/mm2. Over this value, cracks may

be induced in the package. Therefore, the clips have to be round or smooth in the contact

area to avoid concentrated loads on the plastic body. The force applied on the component

depends on the heatsink and the component thickness, so they must be specially designed

to take this value into account. Screw assembly is preferred to clip assembly for insulated

packages.

Figure 11.

Clip assembly

Rivet

Contact

grease

Component

Heatsink

Contact grease

d

Component

Clip

Heatsink