SD2943 mounting recommendations

STEVAL-TDR005V1

8/11

Doc ID 14845 Rev 2

6

SD2943 mounting recommendations

6.1

Mounting recommendations

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Ensure holes in heatsinks are free from burrs;

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Minimum depth of tapped holes in heatsinks is 6 mm;

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Use 4-40 UNC-2A cheese-head screws with a flat washer to spread the joint pressure;

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The minimum flatness of the mounting area is 0.02 mm;

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Mounting area roughness should be less than 0.5 µm (micro);

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Avoid, as much as possible, use of flux or flux solutions because flux can penetrate

even when hermetically sealed ceramic-capped transistors. Tin and wash the printed-

circuit board BEFORE mounting the power transistors, then solder the transistor leads

without using flux;

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Transistor leads may be tinned by dipping them full-length into a solder bath at a

temperature of about 230 °C. No flux should be used during tinning;

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Recommended heatsink compounds: WPSII (silicon free) from austerlitz electronics,

340 from down corning etc.

6.2

Mounting sequence

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Apply a thin layer of evenly distributed heatsink compound to the flange;

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Position the device with flat washers in place;

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Tighten the screws until finger tight (0.05 Nm);

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Further tighten the screws until the specified torque is reached;

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For M174, M177 and M244 type of packages, torque should be minimum 0.6 Nm and

0.75 Nm max.