Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
1998-04-27
2001-02-06
Kincaid, Kristine (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C257S683000, C257S790000, C257S729000
Reexamination Certificate
active
06184464
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electronic circuits and particularly to a protective containment apparatus for preventing the damage of nearby components due to the catastrophic failure of an electronic component in potted circuit.
BACKGROUND OF THE INVENTION
The potting of electronic circuits has long been a method of protecting circuit components from the effects of vibration or to make the work of potential copiers very difficult. To accomplish these goals the circuit is generally partially or completely surrounded by an enclosure of some type. A liquid potting material is poured or forced into the enclosure such that it completely fills the enclosure and surrounds most or all of the electronic components. The potting material then solidifies into a very hard material that can not easily be removed from the electrical components it surrounds. The electronic components surrounded by the hardened potting material are protected from damage by vibration and, to some degree, from being reverse engineered. The potting material performs its intended purpose very well; however, major damage to other nearby components of the assembled device can occur when a catastrophic failure of one of the potted electronic components occurs. Some electronic devices fail in an explosive manner as a result of rapidly expanding gases produced by the deterioration of the electrical component material due to heat and electrical arcing. If sufficient gases are produced by the failing component, parts of the failing component, hot plasma and pieces of potting material will form a number of large and small projectiles rapidly expelled from the failing component. These projectiles can cause major damage to any mechanical or electrical components that are near the potted electronic circuit. Thus, the failed potted electronic circuit, which may be inexpensive to replace, can cause damage to very expensive nearby components, which then must also be replaced due to the failure of the potted circuit. It would therefore be desirable to provide additional protection for those electronic components that tend to fail in an extremely explosive manner such that the surrounding potting material is not expelled as projectiles.
SUMMARY OF THE INVENTION
The present invention provides a simple method of preventing the catastrophic failure of an electronic component in a potted circuit from causing damage to nearby elements of the assembly. Electronic elements known to fail in an explosive manner are surrounded by either a resilient cushion like material or a restrictive material or a combination of both prior to potting the circuit. The resilient material provides a cushioned space for the expanding gases of the failing component, thus preventing pieces of the failing component and/or the hard potting material from being expelled as projectiles. The restrictive material tends to restrict or slow the expanding gases thus preventing the potting material from being expelled away from the failing component. A combination of the resilient material and restrictive material permits limited expansion of the gases and further restricts the expansion such that the potting material is not compromised. A thin layer of the resilient material is positioned such that it surrounds the at-risk electronic component. For purposes of description herein, an at-risk electronic component is one that can fail in an explosive manner. The restrictive material is wrapped around the at-risk electronic component to prevent it from expanding due to the produced gases. The combination of cushion and wrap is accomplished by positioning the resilient material around the at-risk electronic component and then wrapping the resilient material with the restrictive material, thus limiting the amount of expansion that the gases can produce. Both methods provide a method of prohibiting or significantly restricting the amount of potting material which can expelled by the catastrophic failure of the at-risk electronic component.
REFERENCES:
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patent: 5726386 (1998-03-01), Calhoun
patent: 5977621 (1999-11-01), Stuck
Gerlach Michael Joseph
Liptak Julius M.
Golden Larry I.
Kincaid Kristine
Shrout Larry T.
Square D Company
Stacey David R.
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