TMP93CS42AF datasheet(45/48 Pages) TOSHIBA

45 / 48 page

Quality and Reliability Assurance / Handling Precautions

030901

QUA-45

2002-02-20

4.5.5

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.

4.6

Protecting Devices in the Field

4.6.1

Temperature

Semiconductor devices are generally more sensitive to temperature than are

other electronic components. The various electrical characteristics of a

semiconductor device are dependent on the ambient temperature at which the

device is used. It is therefore necessary to understand the temperature

characteristics of a device and to incorporate device derating into circuit

design. Note also that if a device is used above its maximum temperature

rating, device deterioration is more rapid and it will reach the end of its usable

life sooner than expected.

4.6.2

Humidity

Resin-molded devices are sometimes improperly sealed. When these devices

are used for an extended period of time in a high-humidity environment,

moisture can penetrate into the device and cause chip degradation or

malfunction. Furthermore, when devices are mounted on a regular printed

circuit board, the impedance between wiring components can decrease under

high-humidity conditions. In systems which require a high signal-source

impedance, circuit board leakage or leakage between device lead pins can

cause malfunctions. The application of a moisture-proof treatment to the

device surface should be considered in this case. On the other hand, operation

under low-humidity conditions can damage a device due to the occurrence of

electrostatic discharge. Unless damp-proofing measures have been specifically

taken, use devices only in environments with appropriate ambient moisture

levels (i.e. within a relative humidity range of 40% to 60%).

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