Appeal No. 2002-1919 Page 2
Application No. 09/266,376
According to the appellants, however, such cycling of power can lead to continual
thermal stress as the device is turned on, dissipates considerable power, and is then
turned off. (Spec. at 3.) In the confined space of a personal communication device
such as a portable telephone, they add, temperature swings due to the rapid cycling of
power can lead to significant, continuous mechanical stress on the telephone's
semiconductor devices, circuit connections, wire bonds, and other mechanical
connections. (Id.)
Accordingly, the object of the invention is to reduce peak temperatures and
thermal excursions of a semiconductor device operating in a pulsed power mode.
Specifically, a Phase Change Material ("PCM") is thermally coupled to the
semiconductor device. A PCM is a material that absorbs heat and stays at a constant
temperature during its phase change from solid to liquid. For the invention, a PCM
having a melting point just below the temperature the device would otherwise achieve is
used. When the device approaches the maximum temperature, the PCM melts,
absorbing heat released from the device and lowering the device's peak temperature.
When the device's power is pulsed off, the PCM solidifies, releasing the absorbed heat.
This release of heat keeps the device from cooling off as much as it would absent the
PCM. By lowering the peak temperature the device achieves, and increasing the
temperature of the device when it is powered off, the appellants assert that
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