EP0855722A1 - High energy and/or power dissipation resistor - Google Patents

Abstract

A high power and/or energy dissipation resistor has one or more screen printed insulating layers (21-23) of dielectric material provided between a steel base plate (20) and a multilayer structure which includes a resistive material layer (24) and a conductive material layer (6). Preferably, the base plate (20) is a ≥ 1 mm thick plate of ferritic stainless steel containing ≥ 17 wt.% Ti and the insulating layer (21), in contact with the base plate (20), has a thermal expansion coefficient similar to that of the steel of the base plate (20).

Description

The present invention relates to resistance to strong dissipation of power and / or energy with integrated radiator.

Generally, this type of resistance has a substrate and a multilayer structure applied to the substrate and comprising a layer of resistive material and a layer of conductive material.

Such resistance is illustrated in section transverse to Figure 1.

The substrate 12 receives a multilayer structure comprising a layer of resistive material 24 and a layer of conductive material 6.

In known resistances, the structure includes an aluminum sole 10 on which is deposited a layer of glue 11 to fix a substrate in alumina 12 intended to receive the multilayer structure.

The use of an aluminum soleplate on which is stuck an alumina substrate present the downside of not being ideal for transfer heat. Such a structure is described in the U.S. Patent 4,689,270A.

In addition, the mounting of the resistor is tedious, requiring the bonding of a plate in alumina on the sole.

The object of the present invention is to provide a high power resistance simplified manufacturing and having improved thermal performance.

High power dissipation resistance targeted by the invention comprises a substrate comprising a steel sole and a multilayer structure applied to said substrate and comprising a layer of resistive material and a layer of conductive material.

According to the invention, this resistance is characterized in that at least one insulating layer in dielectric material is applied by screen printing on the steel soleplate and is disposed between said soleplate and said multilayer structure.

Thanks to the steel sole, the resistance thermal performance are including the thermal resistance between the resistive layer and a possible auxiliary radiator, on which the resistance is fixed, is reduced.

The steel sole increases the heat dissipation and improve mechanical strength resistance.

In addition, the resistance assembly is simplified due to the continuous use of the screen printing to apply one or more coats insulating materials made of dielectric material as well as the layers in resistive and conductive material.

Preferably, the insulating layer in contact with the sole of the substrate made of a material dielectric having a coefficient of expansion thermal substantially equal to the coefficient of expansion thermal of the steel of the sole.

During the different thermal cycles at which the high dissipation resistance conforms to the invention, the adequacy of the expansion coefficients steel constituting the sole and the layer insulation in contact with the sole prevents cracks or separation of the insulating layers screen printed on the sole.

According to a preferred version of the invention the steel of the sole comprises at least 17% by weight of titanium.

The titanium content of the steel allows improve the adhesion of the dielectric material screen printed on the sole.

Other features and advantages of the invention will appear further in the description below.

• la figure 1 est une vue en coupe transversale d'une résistance à forte dissipation de l'état de la technique antérieure; et
• la figure 2 est une vue en coupe transversale de la résistance à forte dissipation conforme à l'invention.

In the appended drawings, given by way of nonlimiting examples:

• Figure 1 is a cross-sectional view of a high dissipation resistance of the prior art; and
• Figure 2 is a cross-sectional view of the high dissipation resistance according to the invention.

Referring to the figures, a high resistance dissipation comprises an insulating housing 1, fixed on a sole 10, 20, fixing lugs not shown being provided for fixing the resistance, by example by screwing, on an auxiliary radiator.

Connection pads 2, two in number allow the resistance to be linked to a source of Electric power.

Electric current is transmitted by a rod conductive 4, fixed for example by means of solder 5, on a conductive element 6, generally made of an alloy silver and palladium.

This conductive element 6 is in contact with the layer of resistive material 24 and makes it possible to supply the latter in electric current.

The multilayer structure of the resistance successively comprises this layer of material resistive 24, in contact with the substrate, a layer of glue 25, an alumina plate 26, a second layer glue 27 and a block of conductive material 28 such as copper.

The alumina plate 26 on which is stuck the block of thermal conductive material 28, with high heat capacity constitutes a whole forming thermal tank.

As illustrated in Figure 2, and in accordance with the present invention, the substrate comprises a sole made of steel 20 and at least one insulating layer 21, 22, 23 dielectric material applied by screen printing on the steel sole 20 and disposed between the sole 20 and the previously described multilayer structure.

Preferably, the substrate comprises at least two insulating layers 21, 22, 23 superimposed in dielectric material.

In this exemplary embodiment, the substrate comprises three insulating layers 21, 22, 23.

The insulating layer 21 in contact with the sole 20 of the substrate is made of a dielectric material having a coefficient of thermal expansion substantially equal to the coefficient of thermal expansion steel of sole 20 in order to avoid any detachment or crack of this insulating layer 21.

The characteristics of the dielectric material used to make this first layer 21 are mainly determined to allow hanging of this insulating layer 21 on the steel of the sole 20.

The second and third layers 22 and 23 allow to realize strictly speaking a layer insulating between the steel sole 20 and the layer in resistive material 24.

The different superimposed insulating layers 21, 22, 23 are applied by screen printing and baked separately, before each new application screen printing.

A continuous insulating coating is thus obtained on one face of the sole 20.

When the layers of resistive material 24 and conductor 6 are also applied by screen printing, resistance to high dissipation can thus be easily assembled, by continuous screen printing of different layers 21, 22, 23, 24, 6.

All layers of dielectric material 21, 22, 23, arranged between the sole 20 and the multilayer structure of the resistance, have a total thickness of up to around 80 µm so ensure good electrical insulation.

The different layers 21, 22, 23 can be made of an identical dielectric material, such as that marketed by the company ESL ® under the ESL reference D - 4914, having a coefficient of expansion accorded to ferritic stainless steel.

The last layer 23 can also be made of a dielectric material different from previous, such as that marketed under the reference ESL D - 4913.

A high resistance is thus obtained dissipation, able to hold in tension until about 7000 Volt, and having an ohmic value which does not vary practically not throughout the life of the resistance.

Preferably, the sole is made of steel ferritic stainless, comprising at least 17% by weight titanium.

The presence of titanium improves the attachment of the dielectric coating applied by screen printing.

This steel sole has an equal or greater than about 1 mm, so as to present a sufficient mechanical rigidity and good dissipation heat.

For example, a steel suitable for realize the sole is marketed by the company UGINE ® under the reference UGINOX F 17 T, corresponding to the European designation X 3 Cr Ti 17.

Standard steels X 2 Cr Ti 12, X 2 Cr Ti Nb 18 or X 2 Cr Mo Ti 18 - 2 may also be suitable.

Of course, many modifications can be made to the example described above without depart from the scope of the invention.

Thus, the number of insulating layers in dielectric material can be adjusted according to the thickness of each of the screen-printed layers and the insulating power of the material used.

Claims (8)

Resistance to high power dissipation, and / or energy, comprising a substrate comprising a steel base (20) and a multilayer structure applied to said substrate and comprising a layer of resistive material (24) and a layer of conductive material (6), characterized in that at least one layer insulator (21, 22, 23) of dielectric material is applied by screen printing on the steel soleplate (20) and is arranged between the sole (20) and said multilayer structure. Resistor according to claim 1, characterized in that the multilayer structure further comprises a first layer of glue (25), an alumina plate (26), a second adhesive layer (27) and a block of conductive material (28). Resistance according to either of Claims 1 or 2, characterized in that the insulating layer (21) in contact with the sole (20) of the substrate consists of a dielectric material having a coefficient of thermal expansion substantially equal to coefficient of thermal expansion of the steel of the sole (20). Resistance according to one of claims 1 to 3, characterized in that said insulating layers (21, 22, 23) are cooked separately. Resistance according to one of Claims 1 to 4, characterized in that the layer or layers of dielectric material (21, 22, 23), arranged between the sole (20) and the structure multilayer, have a total thickness of up to 80 µm about. Resistance according to one of claims 1 to 5, characterized in that the sole (20) is made of stainless steel ferritic. Resistance according to one of Claims 1 to 6, characterized in that the steel of the sole (20) comprises at minus 17% by weight of titanium. Resistance according to one of claims 1 to 7, characterized in that the steel base (20) has a thickness equal to or greater than about 1 mm.

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