TMPR4955AF datasheet(36/168 Pages) TOSHIBA

36 / 168 page

General Safety Precautions and Usage Considerations

3-16

3.5.8

Circuit board coating

When devices are to be used in equipment requiring a high degree of reliability or in extreme

environments (where moisture, corrosive gas or dust is present), circuit boards may be coated for

protection. However, before doing so, you must carefully consider the possible stress and

contamination effects that may result and then choose the coating resin which results in the

minimum level of stress to the device.

3.5.9

Heat sinks

(1) When attaching a heat sink to a device, be careful not to apply excessive force to the device in

the process.

(2) When attaching a device to a heat sink by fixing it at two or more locations, evenly tighten all

the screws in stages (i.e. do not fully tighten one screw while the rest are still only loosely

tightened). Finally, fully tighten all the screws up to the specified torque.

(3) Drill holes for screws in the heat sink exactly as specified. Smooth the

surface by removing burrs and protrusions or indentations which might

interfere with the installation of any part of the device.

(4) A coating of silicone compound can be applied between the heat sink and

the device to improve heat conductivity. Be sure to apply the coating

thinly and evenly; do not use too much. Also, be sure to use a non-volatile

compound, as volatile compounds can crack after a time, causing the heat

radiation properties of the heat sink to deteriorate.

(5) If the device is housed in a plastic package, use caution when selecting the type of silicone

compound to be applied between the heat sink and the device. With some types, the base oil

separates and penetrates the plastic package, significantly reducing the useful life of the

device.

Two recommended silicone compounds in which base oil separation is not a problem are

YG6260 from Toshiba Silicone.

(6) Heat-sink-equipped devices can become very hot during operation. Do not touch them, or you

may sustain a burn.

3.5.10

Tightening torque

(1) Make sure the screws are tightened with fastening torques not exceeding the torque values

stipulated in individual datasheets and databooks for the devices used.

(2) Do not allow a power screwdriver (electrical or air-driven) to touch devices.

3.5.11

Repeated device mounting and usage

Do not remount or re-use devices which fall into the categories listed below; these devices may

cause significant problems relating to performance and reliability.

(1) Devices which have been removed from the board after soldering

(2) Devices which have been inserted in the wrong orientation or which have had reverse current

applied

(3) Devices which have undergone lead forming more than once

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