MXPA00000004A - A protective containment apparatus for potted electronic circuits - Google Patents

Abstract

A protective containment apparatus for preventing damage to expensive components of an assembly due to the failure of an electronic component in a nearby potted circuit which is known to fail catastrophically. The containment aparatus can employ a resilient material (38) placed around the at-risk electronic component (34) prior to putting the circuit. The resilient material (38) absorbs the expanding gases and fragmented parts of the at-risk component (34) which are expelled during the catastrophic failure. The cushioning effect of the resilient material (38) prevents the fragments and parts of the potting material from becoming projectiles that can damage any nearby components of the assembly. The containment apparatus can also employ a restrictive material (42) placed around the at-risk component (34) prior to potting the circuit. The restrictive material (42) prevents any expelled fragments of the at-risk component (34) and expanding gases from causing the potting material to fracture and become projectiles which can damage nearby components of the assembly. A combination of the resilient material (34) and the restrictive material (42) can also be employed and is most effective in preventing damage to nearby component of the assembly.

Description

PROTECTION EQUIPMENT FOR SEMBRATED ELECTRONIC CIRCUITS Field of the Invention The present invention relates to electronic circuits and, particularly, to a protective containment apparatus to prevent damage to nearby components due to the catastrophic failure of an electronic component in a seeding circuit. Antecedent-bes of the Invention The seeding of electronic circuits has long been a method of protecting circuit components from the effects of vibration or to make the work of potential copyists extremely difficult. To achieve these goals, the circuit is generally partially or totally surrounded by a housing of some kind. A liquid seeding material is poured or forced into the housing, such that it completely fills the housing and surrounds most or all electronic components. The seeding material then solidifies into an extremely hard material that can not be easily removed from the surrounding electrical components. The electrical components surrounded by hardened seeding material are protected against vibration damage and, to a certain degree, against reverse engineering. The seeding material carries out its intended purpose extremely well; however, major damage to other nearby components of the assembled device can occur when a catastrophic failure of one of the electronic components sown 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 electric arc formation. If enough gases are produced by the component that fails, parts of the component that fails, hot plasma and pieces of the seed material will form many large and small projectiles that are quickly ejected from the component that fails.These projectiles can cause major damage to any components The electronic circuit that is planted, which fails, which can be replaced inexpensively, can cause damage to extremely expensive nearby components, which must also be replaced due to the Therefore, it would be desirable to provide additional protection for those electronic components that tend to fail in an extremely explosive manner such that the surrounding seeding material is not ejected as projectiles Compendium of the Invention The present invention provides a simple method to prevent the one Catastrophic failure of an electronic component in a sown circuit causes damage to nearby elements of the assembly. The electronic elements that are known to fail in an explosive manner are surrounded either by a material similar to a resilient cushion or a restrictive material or a combination of both, before seeding the circuit. The resilient material provides a cushioned space for the gases that expand from the component that fails, thus preventing pieces of the component that fail and / or the hard seeding material from being ejected as projectiles. The restrictive material tends to restrict or encourage the gases that expand, thus preventing the seed material from being ejected away from the component that fails. A combination of the resilient material and the restrictive material allows limited expansion of the gases and further restricts expansion so that the seeding material is not compromised. A thin layer of the resilient material is placed such that it surrounds the electronic component at risk. For purposes of description herein, an electronic component "at risk" is one that can fail in an explosive manner. The restrictive material is wrapped around the electronic component at risk to prevent it from expanding due to the gases produced. The combination of the cushioning and the wrapping is achieved by placing the resilient material around the electronic component at risk and then wrapping the resilient material with the restrictive material, thus limiting the magnitude of the expansion that gases can produce. Both methods produce a method of prohibiting or restricting • significantly the amount of planting material that can be expelled by the catastrophic failure of the electronic component at risk. BRIEF DESCRIPTION OF THE DIBUPS Figure 1 is a top view of an electronic circuit of the state of the art before adding a sowing material. Figure 2 is a cross-sectional view of the seeded electronic circuit, taken along line 2-2 of Figure 1, with the cover installed. Figure 3 is a top view of an electronic circuit configured in accordance with the present invention before adding a seeding material such that electronic devices surrounded by a resilient material can be illustrated. Figure 4 is a cross-sectional view of the seeded electronic circuit, taken along line 4-4 of Figure 3, illustrating electronic devices surrounded by a resilient material in accordance with the present invention. Figure 5 is an illustration of an electronic device at risk, surrounded by a resilient material. Figure 6 is an illustration of an electronic device at risk, surrounded by a restrictive material. Figure 7 is an illustration of an electronic device at risk, surrounded by both a resilient material and a restrictive material. Before an embodiment of the invention is explained in detail, it should be understood that the invention is not limited in its application to the construction details described herein or illustrated in the drawings. The invention is susceptible of other embodiments and of being implemented or carried out in various other ways. Likewise, it will be understood that the phraseology and terminology used herein are for the purpose of description and should not be construed as limiting. Description of the Preferred Embodiment Form Figures 1 and 2 illustrate a seeded electronic circuit typical of the state of the art and generally indicated by the reference number 10. The circuit 10 is installed in a housing 14 which provides a shape for the material of seeded 18 and may include a cover 22, as shown in Figure 2. The circuit 10 consists of several electronic components assembled on a printed circuit board 26. The terminals 30 are electrically connected to the printed circuit board 26 and pass to through the housing 14 for connection to other electronic circuits or components in the assembled device. The circuit 10 used as an example in this application is a transient voltage shock wave suppressor (TVSS). However, any electronic circuit 10 that includes electronic devices at risk, generally indicated by reference number 34, which tend to fail catastrophically, may use the technology of the present invention to protect expensive components near the seeded circuit 10. circuit TVSS 10 includes several metal oxide varistors (MOVs) which tend to fail catastrophically and are therefore at risk electronic components 34 of exemplary circuit 10. Figures 3 and 4 illustrate an electronic circuit seeded, assembled in accordance with the present invention. The at-risk components 34 are generally spaced "or separated from the sowing material 18 by a resilient material 38, which absorbs the pressure of the gases produced by the failing components 34. The density of the resilient material 38 must be considerably less than the density of the sowing material, such that the expanding gases and the particles of the at-risk component 34 can be absorbed without causing the sowing material to fracture and be ejected.The resilient material 38 can be provided in any of several ways, such as sheet material that is wrapped around the component at risk 34molded or extruded material sized to closely receive the at-risk component 34, or a generally fluid material that is poured or otherwise placed around the component at risk 34 before seeding the circuit 10. The resilient material 38 must be of or must cured to a consistency that allows it to be compressed by the gases that expand from the component at risk that fails 34. A commercially available material, which has been found to meet this requirement, is Foamega silicone foam, manufactured by Rogers Brisco. By absorbing the pressure of the gas produced by and any fragmented parts of the component at risk of failure 34, the resilient material 38 prevents fragments of the at-risk component 34 and the surrounding seed material 18 from being dislocated and turning into projectiles that can cause greater damage to other costly components in the assembled product. Another method of providing protection for the at-risk component 34 is to wrap the component 34 with a restrictive material 42 that substantially maintains the structural integrity of the component at risk 34 during a catastrophic failure and provides limited expansion of the expanding gases. The restrictive material 42 must be sufficiently flexible so that it can easily conform to the shape of the component at risk 34, have sufficient strength to substantially maintain the structural integrity of the component at risk 34, and be sufficiently thin so that multiple wrappings of the restrictive material can be applied. 42 if required. A commercially available product, such as Scotch 69 glass ribbon, manufactured by 3M Company, satisfies these requirements. Other forms of glass reinforced materials can be used as an alternative to the above described tape product.

It has been found that the most effective is a combination of the resilient material 38 and the restrictive material 42. The at-risk component 34 is first surrounded by the resilient material 38 and then wrapped with the restrictive material 42, providing both a suitable space for expansion and restriction to substantially ensure the structural integrity of the component at risk 34. Figure 5 illustrates the placement of the resilient material 38 around and between various components at risk 34, such as the MOVs of the exemplary circuit. The circular shape of the MOVs is easily covered by a flat sheet of the resilient material 38. The components at risk 34 of irregular shapes may require extruded or molded shapes, sized to closely surround their particular shape. Figure 6 illustrates the placement of restrictive material 42 around an at-risk component 34, such as an MOV of the exemplary circuit. Restrictive material 42 is generally a tape or wrapping material incorporating filaments of glass fiber or similar materials having high strength fibers that allow limited stretching, but do not break easily. The restrictive material 42 must also be sufficiently flexible so that it can be easily wrapped around the at-risk component 34 or the resilient material 38. Figure 7 illustrates placing both the resilient material 38 and the restraining material 42 on and around a component at risk 34 such as an MOV of the exemplary circuit. When the restraining material 42 is used in combination with a resilient material 38, it should not be wrapped around the resilient material 38 so tightly that the resilient material 38 is compressed. The compression of the resilient material 38 will prevent it from absorbing the expended gases and particles. of components ejected due to the catastrophic failure of the component at risk 34.

Claims (18)

1. CLAIMS 1. A containment device for protecting nearby components of an assembly against damage by the catastrophic failure of an electronic component at risk that is known to catastrophically fail and which is located in a seeded electronic circuit, said containment device comprising: a resilient material placed around the component at risk before seeding the electronic circuit. The containment apparatus of claim 1, wherein said resilient material absorbs the pressure of the expanding gases caused by the catastrophic failure of the component at risk. 3. The containment apparatus of claim 1, wherein said resilient material absorbs particles from the at-risk component expelled by the catastrophic failure of the component at risk. The containment apparatus of claim 1, wherein said resilient material prevents fracture and ejection of projectiles comprised of particles of the component at risk and seeding material and the expulsion of hot gases that can cause major damage to nearby components of the whole. The containment apparatus of claim 1, wherein said resilient material is a material having a considerably lower density than the seeding material. 6. The containment apparatus of claim 5, wherein said resilient material is a silicone-based material. The containment apparatus of claim 1, wherein said resilient material is a sheet material. 8. The containment apparatus of claim 1, wherein said resilient material is a formed material. The containment apparatus of claim 1, wherein said resilient material is an extruded material. 10. A containment apparatus for protecting nearby components of an assembly from damage caused by the failure of an electronic component at risk that is known to catastrophically fail and which is located in a seeded electronic circuit, said containment apparatus comprising: a restrictive material placed around the component at risk before seeding the electronic circuit. The containment apparatus of claim 10, wherein said restrictive material substantially maintains the structural integrity of the component at risk during a catastrophic failure, thereby preventing the pressure of the expanding gases caused by the failure of the component at risk cause fragmentation of the sowing material. The containment apparatus of claim 10, wherein said restrictive material prevents particles of the material at risk from being ejected during the catastrophic failure of the component at risk. 13. The containment apparatus of claim 10, wherein said restrictive material prevents fracture and ejection of projectiles comprised of particles of the component at risk and seeding material and escape of hot gases that can cause major damage to nearby components of the assembly. . The containment apparatus of claim 10, wherein said restrictive material includes a fiber in filaments. 15. The containment apparatus of claim 10, wherein said restrictive material includes fiberglass filaments. 16. The containment apparatus of claim 10, wherein said restrictive material includes an adhesive backing. 17. A containment apparatus for protecting nearby components of an assembly against damage by the failure of an electronic component at risk that is known to fail catastrophically and which is located in a seeded electronic circuit, said containment apparatus comprising: a resilient material placed around the component at risk; and a restrictive material placed around the resilient material before seeding the electronic circuit. The containment apparatus of claim 17, wherein said resilient material and said restrictive material prevent fracture and ejection of projectiles comprised of particles of the component at risk and seeding material and escape from hot gases that can cause major damage to the nearby components of the set.