RU2275763C1 - Method and device for thermal protection of electronic modules - Google Patents

Abstract

FIELD: technology for protection in emergency situations of electronic modules like flight information registers, used on planes or in any other means of transportation.

SUBSTANCE: method includes draining heat from electronic modules by means of thermo-protective mixtures during their melting and dehydration, while device for realization of method contains body, thermo-reflective cover, separating internal portion, formed by internal surface of body, on two portions, filled with thermo-protective mixtures, and means for removing water steams from the body. A portion of hollow between internal surface of body and external surface of heat-reflective cover contains mixture, consisting of barium citrate or calcium citrate crystals, while portion of hollow between internal surface of thermo-reflective cover and electronic modules is filled with mixture, consisting of barium citrate or sodium-two citrate crystals, while crystals of thermo-protective mixtures have cover of silicic acid.

EFFECT: increased reliability of thermal protection for electronic modules due to increased operation resource of heat-protective mixtures, to allow electronic modules to operate for longer time spans.

2 cl, 1 dwg

Description

Method and device for thermal protection of electronic modules belong to a special field of electronic technology and can be used for protection in emergency situations of electronic modules such as flight information recorders used on airplanes and any other vehicles.

A known method of thermal protection of electronic modules by removing heat from the device using a heat-shielding mixture consisting of a bicarbonate mixture and a binder (US patent No. 5932839, IPC N 05 K 5/02).

A device is known for implementing this method, comprising an outer case, the inner surfaces of which form an inner cavity filled with a heat-shielding mixture, in which electronic modules are placed, an insulating thermal pad located between the inner surfaces and the heat-shielding mixture, and means for removing carbon dioxide from the case (patent USA No. 5932839, IPC N 05 K 5/02).

Known inventions are characterized by low reliability of protection, due to a short period of time, up to 160 seconds, during which the modules are protected from high ambient temperatures.

A known method of thermal protection of electronic modules by removing heat from the device using two layers of heat-shielding mixtures, consisting of a mixture of crystalline sodium hydrate and sodium pentaerythritol in a weight ratio of 80:20 to 20:80 and a mixture of crystalline hydrates of sodium carbonate and sodium hydrogen phosphate in a weight ratio of 20:80 to 80:20 (RF application No. 2002118812, publ. March 20, 2004).

A device is known comprising a housing, the inner surfaces of which form an internal cavity for accommodating electronic modules, a heat-reflecting casing dividing the internal cavity of the housing into two parts filled with heat-shielding mixtures: a part of the cavity between the internal surfaces of the housing and the external surfaces of the heat-reflecting casing is filled with a mixture consisting of carbonate crystalline hydrates sodium and sodium hydrogen phosphate, and part of the cavity between the inner surfaces of the heat-reflecting casing and electronic modules E is filled with a mixture consisting of sodium carbonate and crystalline sodium pentaeritritborata, and means for removing from the housing gaseous decomposition products (patent of RF №2002118812, publ. 20.03.2004).

The described method and device for thermal protection in combination of essential features are the closest to the claimed invention and are selected as the closest analogues.

A disadvantage of the closest analogs is also the low reliability due to the small life of the heat-shielding mixtures in a given volume, i.e. their low heat dissipation capacity, as a result of which the modules are protected from high ambient temperatures for a short period of time - up to 30 minutes.

The technical result achieved by the implementation of the proposed invention is to increase the reliability of thermal protection of electronic modules by increasing the life of heat-shielding mixtures, which ensures the operation of electronic modules for a longer time.

The technical result is achieved due to the fact that in the method of thermal protection of electronic modules by removing heat from the device using two layers of heat-shielding mixtures, a mixture of crystals of barium citrate and calcium citrate in a weight ratio of from 20:80 to 80:20 and a mixture are used as heat-shielding mixtures crystals of barium citrate and sodium citrate two (double salt) in a weight ratio of from 20:80 to 80:20.

To increase the dehydration time, to ensure uniform density of the mixtures and to increase its shelf life, two crystals of barium, calcium and sodium citrates are coated with a porous shell of silicic acid.

A device for implementing the method of thermal protection of electronic modules comprises a housing, the inner surfaces of which form an internal cavity for accommodating electronic modules, a heat-reflecting casing dividing the internal cavity of the housing into two parts filled with heat-shielding mixtures, and means for removing gaseous decomposition products from the housing, and part of the cavity between the inner surfaces of the housing and the outer surfaces of the heat-reflecting casing is filled with a mixture consisting of crystals of barium citrate and calcium citrate, a part of the cavity between the inner surfaces of the heat-reflecting casing and the electronic modules is filled with a mixture consisting of crystals of barium citrate and two sodium citrate (double salt).

Between the inner surface of the housing and the heat-shielding mixture, a thermal gasket is placed.

The heat-reflecting casing is made of layers of aluminum foil, separated by epoxy or silicone resin.

The drawing shows the design of a thermal protection device for electronic modules.

The device for thermal protection includes a housing 1, usually made of metal having high strength and resistant to crushing and penetration of the tip. The housing 1 may have any desired shape. A thermal pad 2 is adjacent to the inner surface of the housing 1, which is, for example, a material based on quartz fibers, lined on both sides with a silica fabric, and having low thermal conductivity. The heat-reflecting casing 3 divides the internal cavity into two parts, between the gasket 2 and the outer surfaces of the heat-reflecting casing 3 there is a heat-shielding mixture 4, consisting of crystals of barium citrate and calcium citrate in a weight ratio of 20:80 to 80:20. The inner surfaces of the casing 3 form a cavity in the center of which one or more protected electronic modules 5 are located. The heat-shielding mixture 6 occupies a part of the cavity between the inner surfaces of the casing 3 and the electronic modules 5 and consists of crystals of barium citrate and two sodium citrate (double salt) in weight ratio from 20:80 to 80:20. The crystals of heat-shielding mixtures 4 and 6 are coated with a silicic acid shell.

The housing 1 and the casing 3 are closed, respectively, with covers 7 and 8.

When exposed to high temperature on the housing 1, the energy of the incoming heat goes to the melting of mixtures 4 and 6, and since the melting temperature of the salts that make up the mixtures 4 and 6 is different, from 130 to 185 ° C, the salt melting reaction occurs sequentially, with the transition to dehydration. These reactions with uniform heat flow occur in layers, in the "shell" with a thickness of 0.5 ... 0.8 mm, repeating the shape of the inner surface of the housing 1, moving from the periphery to the center. The high dehydration energy of the mixtures used is due to the presence of molecules of only constitutional water of primary hydration in barium, calcium and sodium citrates, an odd number of water molecules in barium citrates and two.

The melting and dehydration reactions of mixtures are accompanied by the evaporation of water. When water vapor passes through mixtures 4 and 6, the case 1 is forcedly cooled and heat is absorbed from the high-temperature environment. This process allows you to keep the maximum temperature inside the housing 1 at an acceptable level, 98 ... 105 ° C, that is, at a level at which the electronic modules 5 located in the housing 1 are not substantially damaged. However, the accumulation of a large amount of steam inside the sealed enclosure 1 can lead to crushing of the electronic modules 5 located there under the action of excessive pressure. To exit the steam in the housing 1, casing 3, covers 7 and 8, there are special tools. Moreover, the output of H ₂ O contributes to the extinction of the flame. The porous coating material (silicic acid) of salt crystals also contributes to the release of steam, therefore the density of the mixtures is not limited and is determined by the efforts when packing the mixtures into the body of the product.

The thickness of the layers of mixtures 4 and 6 depends on the weight ratios of salts in these mixtures and on the time of their dehydration.

The roughness, hardness and smooth shape of the coating of salt crystals contribute to the dissipation of part of the energy of impacts on the body of the product on the friction energy between the grains of salts.

The use in the proposed device of two heat-protective layers of a mixture of crystals of barium citrate with calcium citrate and a mixture of crystals of barium citrate with sodium citrate two (double salt), coated and separated by a heat-reflecting casing, the presence of an insulating pad made it possible to protect the electronic modules for at least 60 minutes at a temperature of 1100 ° C and 10 hours at a temperature of 260 ° C.

Claims (3)

1. The method of thermal protection of electronic modules by removing heat using two layers of heat-shielding mixtures, characterized in that as heat-shielding mixtures using a mixture of crystals of barium citrate and calcium citrate in a weight ratio of from 20:80 to 80:20 and a mixture of crystals of barium citrate and a double salt of sodium citrate in a weight ratio of 20:80 to 80:20, and the crystals of barium citrate and calcium and a double salt of sodium citrate are coated with a porous shell of silicic acid. 2. A device for implementing the method of thermal protection of electronic modules comprises, a housing, the inner surfaces of which form an internal cavity for accommodating electronic modules, a heat-reflecting casing dividing the internal cavity of the housing into two parts filled with heat-shielding mixtures, and means for removing gaseous decomposition products from the housing, characterized in that a thermal pad is adjacent to the inner surface of the housing, a part of the cavity between the thermal pad and the external surfaces of the heat the pressing casing is filled with a mixture consisting of crystals of barium citrate and calcium citrate, and part of the cavity between the inner surfaces of the heat-reflecting casing and electronic modules is filled with a mixture consisting of crystals of barium citrate and a double salt of sodium citrate, with crystals of barium citrate and a double salt of sodium citrate covered with a porous shell of silicic acid. 3. The device according to claim 2, characterized in that the heat-reflecting casing is made of layers of aluminum foil separated by epoxy or silicone resin.