Refrigeration – Structural installation – With electrical component cooling
Reexamination Certificate
2002-03-26
2004-05-18
Jones, Melvin (Department: 3744)
Refrigeration
Structural installation
With electrical component cooling
C062S003700
Reexamination Certificate
active
06735972
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electronic devices, and more particularly to an apparatus and method to substantially minimize breakage or low-cycle fatigue of electrical connections between components.
BACKGROUND OF THE INVENTION
Electronic devices and integrated circuits are being required to perform more functions at ever increasing speeds. Component densities are also increasing while packaging size requirements are decreasing. The higher component densities, higher operating frequencies and tighter packaging requirements are resulting in the generation of more heat that must be managed for proper operation and longevity of current and future high performance electronic devices and circuits.
Components in an electronic device can be electrically connected to one another by solder connections. For example, a microelectronic die, chip or other component may be electrically connected to a printed wiring board (PWB) or the like by a plurality of solder ball connections or a ball-grid array (BGA). Because of possible size variations and differences in composition between the electrically connected components, they can expand and contract at different rates of thermal expansion during thermal cycling as the components build up heat under operating conditions and cool down during low duty cycles or non-operating conditions. Additionally, variations in ambient temperature under both operating and non-operating conditions can also cause the components to expand and contract at different rates. The repeated thermal expansion and contraction of the components can result in low-cycle fatigue and breakage of the solder connections or BGA connecting the components. Low-cycle fatigue can be an especially significant problem with ceramic components that have low expansion relative to typical PWB materials.
Thermal expansion mismatches can be managed to some extent by mechanical arrangements, such as aramid-reinforced printed wiring boards, heat sinks and by attachment of leads or columns to the components to increase mechanical compliance during thermal cycling. Solder fatigue can still occur using these mechanical arrangements because a contributing factor is the need to thermally control the actual solder connections or BGAs by transferring heat away from the connections. Additionally, these mechanical arrangements are passive and cannot react or adapt to changing conditions during the operational cycles of an electronic device.
Accordingly, for the reason stated above, and for other reasons that will become apparent upon reading and understanding the present specification, there is a need for an apparatus and method to substantially minimize the low-cycle fatigue or breakage of electrical connections between components caused by the thermal expansion mismatch between the components. There is also a need for an apparatus or method to substantially control low-cycle fatigue that is adaptive to changing conditions during the different operational cycles of the components and that can thermally control the actual electrical connections by actively transferring heat away from the connections.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus to prevent low-cycle fatigue or breakage of at least one electrical connection between a first component and a second component includes at least one thermoelectric device to thermally contact at least the first component and includes at least one sensor to couple to at least one of the first component and the second component. A controller is coupled to the at least one thermoelectric device and to the at least one sensor. The controller controls operation of the thermoelectric device to prevent low-cycle fatigue of the at least one electrical connection by transferring heat from at least the first component in response to signals from the at least one sensor.
In accordance with an embodiment of the present invention, an electronic device with thermal expansion control includes a first component and a second component electrically coupled to the first component. A thermoelectric device thermally contacts at least the first component and at least one sensor is coupled to one of the first component or the second component. A controller is coupled to the at least one sensor and to the thermoelectric device to transfer heat from at least the first component in response to signals from the at least one sensor.
In accordance with another embodiment of the present invention, a method to prevent low-cycle fatigue of at least one electrical connection between a first component and a second component includes sensing at least one of temperature, strain or deflection of at least one of the first component or the second component and transferring heat from at least one of the first component and the second component in response to the sensing of at least one of temperature, strain or deflection.
REFERENCES:
patent: 4963414 (1990-10-01), LeVasseur et al.
patent: 5188286 (1993-02-01), Pence, IV
patent: 5584183 (1996-12-01), Wright et al.
BAE Systems Controls Inc.
Jones Melvin
Krauss Geoffrey H.
Moore Charles L.
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