Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Patent
1994-10-07
1996-06-18
Kincaid, Kristine L.
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
361818, H05K 900
Patent
active
055279899
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for encapsulating electronic components or circuitry such as to protect the electric circuit against substances which may act deleteriously thereon, wherein the device also attenuates radiofrequency electromagnetic radiation so as to protect the circuit against such radiation that can enter from the surroundings and disturb the function of the circuit through induction, said device also being active to protect the surroundings when the circuit concerned constitutes a disturbance or interference source. The device includes throughlet conductors which allow circuit-functional current and signals to be applied when required.
TECHNICAL FIELD
It is often necessary to protect electronic circuits against different influences emanating from the surroundings. Factors which influence electronic circuitry include water and other corrosive and electrically conductive materia. It is also often important to protect the circuitry against electromagnetic radiation. In this regard, there is traditionally used different types of capsules which can be roughly divided into two main groups, hermetic capsules and plastic capsules. In the case of hermetic capsules, the electronic circuitry is surrounded by a clean and dry volume of gas enclosed in a diffusion-impervious casing, normally a metal, glass or ceramic casing. When the casing is made of metal, glass throughlets are fused in the metal casing for leading electrical conductors between the encapsulated circuitry and the ambient surroundings. When a plastic capsule is used, the circuitry is surrounded by plastic material instead of clean or pure gas. Although the plastic material is permeable to water and gases, it will nevertheless often provide satisfactory protection, because coherent films are unable to form on the surfaces of the circuit components. Furthermore, plastic material has a more or less pronounced ability to bind chemically with the polar groups present in the surface of the circuit components. These groups are thus blocked so as to be unable to form corrosion attack sites. The differences in the coefficient of thermal expansion between the different materials present constitutes a problem in both types of capsule. Another problem is that the circuitry is often so sensitive as to react against compounds which are split or cleaved from the actual encapsulating materials. A third problem is that polymeric material is often unable to withstand the working temperatures concerned, particularly as rises in temperature are often local, spotwise temperature increases, wherewith the plastic encapsulating materials connect directly on to these points. This can result in degradation of properties and spalling of the corrosive substances. In the case of plastic capsules, it is often difficult to conduct heat away from the electronic circuitry to the surroundings and they have no electrically shielding ability. In addition to these technical problems, there is often a low price interest.
The levels of these various requirements vary, although they are particularly stringent in the case of electronic circuitry for use in cars and radio communication systems for instance. Several attempts have been made to glue hermetic metal and ceramic capsules, although it has been found difficult to obtain glue joints which are age-resistant and impervious. For the purpose of packaging electronic circuitry which is sensitive to electric discharge caused by static electricity, encapsulating bags have been developed which include a casing comprised of plastic sheets on which thin metal layers have been applied by vapour deposition. These principles cannot be applied, however, in advanced encapsulation, since the metal layers obtained by vapour deposition or sputtering do not have a thickness which renders the encapsulation impervious to diffusion. Furthermore, with regard to radio frequency radiation, the depth of current penetration is many times greater than the depth of penetration in the case of a metal layer and consequen
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Horgan Christopher
Kincaid Kristine L.
Telefonaktiebolaget LM Ericsson
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