EP3146536B1 - Electronic component and method for manufacturing it - Google Patents

Description

Electronic component and method for producing the same The present invention relates to an electronic component, for example a varistor component, and a method for producing the same. US 4,157,527 A. describes an electronic component with a varistor functional body, the varistor having a smaller thickness in a central region than in an edge region. One problem to be solved is to provide means for an improved electronic component, in particular a more flexible and / or more robust electronic component.
This object is solved by the features of the independent claims. Advantageous refinements and developments are the subject of the dependent claims.
A proposed electronic component comprises a functional body. The functional body expediently represents the functional element of the electronic component. Furthermore, the electronic component comprises a contact which is electrically connected to or contacts a first surface of the functional body. The contact can be an electrical contact layer and / or a metallization or another contact. Via the contact, the functional body is expediently contacted and / or electrically connected to further connections, for example an outer electrode of the electronic component. The surface is preferably a first surface, for example a first main surface of the functional body. The contact has an edge area and a central area. Furthermore, the functional body is designed in such a way that the electrical resistance of the functional body between the first surface and a second surface or main surface of the functional body facing away from the first surface is viewed in a first functional body section, which is viewed from above in view of the electronic component, in particular the first surface overlaps with the edge area is larger than in a second functional body section that overlaps with the central area of the contact. The first and the second functional body section are preferably radial sections of the functional body.

The central region of the contact preferably denotes an inner and / or middle region of the contact, while the edge region preferably denotes or defines an outer edge of the contact.

The contact is preferably electrically connected to both the first and the second functional body section. The first functional body section preferably designates an outer or edge section of the functional body. The second functional body section, on the other hand, preferably designates an inner or central section of the functional body. The second functional body section and the central area are — when viewed from the top of the electronic component — preferably congruent.

The said contact is preferably a first contact. The electronic component also expediently comprises a second contact, which is electrically connected to the second surface of the functional body or contacts it. The second contact is preferably configured analogously to the first contact and is arranged in relation to the second surface in the same way as the first contact in relation to the first surface. The first and the second contact can, for example, be arranged symmetrically with respect to a longitudinal axis of the electronic component. The electronic component and / or the functional body is preferably disk-shaped and at least largely rotationally symmetrical with respect to the longitudinal axis.

In the case of a disk varistor as an electronic component, a contact is preferably provided or arranged on an upper side and on a lower side of the disk for the electrical connection or contacting.

The first and the second contact are preferably arranged congruently, for example when viewed from the top of the electronic component.

For example, when viewed in a section along the longitudinal axis, the functional body is preferably arranged directly or immediately between the contacts.

In a preferred embodiment, the electronic component is a varistor component. Varistor components are preferably used as overvoltage protection. According to this configuration, the functional body is expediently designed such that it represents the functional element of the varistor component. In this regard, the Functional body comprise a polycrystalline, sintered, material.

In a preferred embodiment, the electronic component is a disk or block varistor.

In one embodiment, the first functional body section, at least partially, runs around the second functional body section when viewed from the top of the electronic component. The first functional body section preferably completely surrounds or surrounds the second functional body section.

In one configuration, the functional body is designed such that the electrical current density in the first functional body section, in particular at a contact point of the first functional body section and the edge region of the contact or between the first functional body section and the edge region, during operation of the electronic component and / or in the case of a Current flow in the functional body reduced or reduced. The electrical current density is preferably reduced or reduced in comparison to a conventional electronic component or a component of the prior art.

In particular at the contact point mentioned, the electrical current density and the associated temperature load can be particularly high, for example during operation of the electronic component. The cause of this can be an edge effect that occurs during the operation of the electronic component.

By means of the electronic component presented, the heat development in the first functional body section can advantageously be reduced or reduced during operation, for example because of increased electrical resistance and thus reduced electrical current density, as less heat is generated as a rule. This makes the electronic component more temperature-resistant and versatile at the same time. Furthermore, the lifespan of the electronic component can advantageously be increased.

High temperatures in the functional element can considerably limit the service life and / or the area of use of the electronic component, in particular in the case of a varistor component. The thermal loads described, in particular for varistor components, can even lead to the destruction of the component in the event of prolonged overvoltage. This can be counteracted by the above-described configuration of the functional body, in that the first functional body section has a greater electrical resistance than the second functional body section, since this weakens the edge effect described.

In a preferred embodiment, the surface area of the second functional body section, when viewed from the top of the electronic component, is larger than the surface area of the first functional body section. This configuration can in particular ensure that the electrical resistance of the functional body of the electronic component between the first and the second surface is or remains defined overall by the second functional body section. Thereby in turn, the electrical properties, in the case of a varistor component, for example the varistor voltage, remain essentially unchanged. For example, the area of the second functional body section is twice as large, three times as large or ten times as large as the area of the first functional body section.

In a preferred embodiment, the functional body has a contact-free area in the first functional body section. The contact-free area is preferably an outer radial section of the functional body. Accordingly, the contact-free area is preferably arranged on the edge with respect to the functional body. There is preferably no contact in the non-contact area. With this configuration, improved contacting of the functional body can advantageously be achieved. In particular, electrical flashovers on the edge, edge area or on an edge of the functional body can be prevented or restricted. The contact-free area or an edge thereof preferably runs without kinks when viewed from above on the electronic component. Due to the kink-free design, in particular an edge length or edge area of the contact can be reduced or minimized and thus the formation of "hot spots" (English for "hot spots") in which particularly high electrical fields, thermomechanical voltages and / or thermal, mechanical or electrical Stresses occur, are prevented or restricted.

In a preferred embodiment, the thickness of the functional body in the first functional body section is greater than the thickness of the functional body in the second functional body section. Preferably the thickness of the first functional body section and the thickness of the second functional body section are at least predominantly constant or approximately constant. This configuration advantageously allows a means for increasing the electrical resistance in the first functional body section to be specified, as a result of which the electrical current density and thus the temperature load in the first functional body section can be reduced during the operation of the electronic component. In other words, the electrical resistance of the first functional body section is increased by the greater distance of the contacts or surfaces in the first functional body section, or by the greater path length along the thickness, in contrast to the second functional body section, with, for example, the same electrical applied to the electronic component Voltage, the current load and thus the overheating or temperature load can be reduced in the first functional body section.

The thickness described here preferably extends along the above-mentioned longitudinal axis of the electronic component.

The thickness of the functional body is preferably increased only on one side or main surface of the electronic component and / or the functional body, whereas on the other side of the electronic component the surfaces of the first functional body section and the second functional body section of the functional body are flat and / or lie in one plane , Alternatively, the functional body can be designed such that, for example, an upper and a lower side of the first Functional body section is not arranged in one plane with respect to an upper or an underside of the second functional body section.

In a preferred embodiment, the thickness of the functional body in the first functional body section is 5% to 15% greater than the thickness of the functional body in the second functional body section. The thickness of the functional body in the first functional body section is particularly preferably at least 10% greater than the thickness of the second functional body section. Alternatively, the thickness mentioned can also be increased by more than 15%, for example. The effect of increasing the thickness with regard to the electrical resistance is qualitatively the same.
In a preferred embodiment, the radial extent of the first functional body section is between the single and double the thickness of the functional body in the first functional body section.
In a preferred embodiment, the material properties of the functional body in the first functional body section are different from those in the second functional body section. This configuration can expediently achieve that the electrical resistance in the first functional body section is increased in comparison to the second functional body section.

According to the invention, the functional body is designed such that the first functional body section is one in comparison to the second functional body section has greater specific electrical resistance. As a result, the current density in the first functional body section can be reduced or reduced during operation of the electronic component. Corresponding differences in the material properties can preferably be generated or formed during the manufacturing process of the electronic component and / or during sintering of the functional body (see below). As already indicated above, the greater specific electrical resistance advantageously allows the current densities and thus the temperature loads in the first functional body section to be reduced in the first functional body section given the current pulses.
In a preferred embodiment, the functional body has a sintered material.

In a preferred embodiment, the contact is a first contact, the electronic component additionally having a second contact which is electrically connected to the second surface of the functional body, and the functional body being designed such that the electrical current or current density distribution when a current flows is homogenized in the functional body between the contacts in the first and the second functional body section. This can mean that discrepancies or the scatter of the electrical current densities, which are present, for example, during operation of the electronic component and / or when there is a current flow in the functional body, are reduced. Preferably analogously to the first contact, the second contact has an edge area and a central area.

In a preferred embodiment, the functional body is, preferably largely, polycrystalline. In this sense, the functional body can have a polycrystalline material, for example, as the main component.

In a preferred embodiment, the functional body has a ceramic, for example as the main component. The ceramic is preferably a sintered ceramic.

In a preferred embodiment, the functional body is designed in such a way that, after the application of an electrical voltage above a characteristic threshold, in the case of a varistor component, for example the varistor voltage, it conducts electrically between the first and the second surface without the functional body having electrically insulating regions ,

A method for producing the functional body for the electronic component described above is also specified. The functional body and / or the electronic component can preferably be produced or produced using the method described here. In particular, all the features disclosed for the method can also relate to the functional body and / or the electronic component, and vice versa.

The method comprises providing a basic material for the functional body for the electronic component and forming the functional body using the Base material such that the electrical resistance of the functional body, measured between two opposite surfaces, that is to say the above-mentioned first and second surfaces, is greater in the first functional body section than in the second functional body section.

In a preferred embodiment of the method, this comprises providing the functional body with a contact on the opposite surfaces, each contact, for example the above-mentioned first and second contact, being electrically connected to the first and second functional body sections.

In a preferred embodiment of the method, the base material has a more homogeneous material composition than the functional body. The material composition of the base material is preferably largely homogeneous, whereas the material composition of the functional body, in particular when comparing the material compositions of the first and second functional body sections with one another and with respect to individual material components, is inhomogeneous.

In a preferred embodiment of the method, the base material is formed in the first functional body section with a greater thickness than the second functional body section. This configuration advantageously enables the electrical resistance of the first functional body section to be increased in comparison to the second functional body section.

In a preferred embodiment of the method, the base material is sintered to form the functional body in such a way that the specific electrical resistance of the functional body is greater in the first functional body section than in the second functional body section. For example, the base material is sintered in such a way that crystal grains or corresponding grain sizes in the first functional body section of the functional body are smaller or are formed than in the second functional body section. Due to the smaller grain sizes or greater density of grain boundaries of the first functional body section in comparison to the second functional body section, the specific electrical resistance of the functional body in the first functional body section is advantageously made larger than in the second functional body section.

In a preferred embodiment of the method, the material composition of the base material is changed in a first section thereof during the sintering in order to form the first functional body section. The first functional body section is preferably formed from the first section of the base material by sintering.

In a preferred embodiment of the method, the base material is exposed to a temperature gradient during the sintering, the base material not being provided with material additives during the sintering and preferably likewise before the sintering. Preferably, no further material is added to the base material from outside, for example from outside the sintering furnace, during sintering. The material composition of the base material in the first functional body section preferably changes instead by migration and / or diffusion processes of material components originally contained in the base material.

In a preferred embodiment, the base material is provided with a dopant before sintering, which diffuses into the base material during sintering in order to form the first functional body section. The dopant or the additional material is preferably applied to the base material or the base material is dipped into the dopant or a solution containing it before sintering. The dopant can be yttrium oxide, for example Y ₂ O ₃ , or other rare earth metals or their oxides.

In a preferred embodiment of the method, the first functional body section is designed such that the maximum temperature which occurs in the first functional body section under an electrical test pulse with a current strength of 30 A of pulse shape 8/20, for example in comparison to a conventional electronic component, is reduced by at least 500 ° C.

A method for producing an electronic component is furthermore specified which comprises the method steps of the above-mentioned method for producing the functional body.

• Figur 1 zeigt eine schematische perspektivische Ansicht eines elektronischen Bauelements.
• Figur 2 zeigt eine schematische Schnittansicht eines erfindungsgemäßen elektronischen Bauelements.
• Figur 3 zeigt eine schematische Schnittansicht eines erfindungsgemäßen elektronischen Bauelements gemäß einer alternativen Ausführungsform.
• Figur 4 zeigt eine beispielhafte Spannungs-Stromkennlinie des elektronischen Bauelements ausgeführt als Varistorbauelement.

Further advantages, advantageous configurations and expediencies of the invention result from the following description of the exemplary embodiments in connection with the figures.

• Figure 1 shows a schematic perspective view of an electronic component.
• Figure 2 shows a schematic sectional view of an electronic component according to the invention.
• Figure 3 shows a schematic sectional view of an electronic component according to the invention according to an alternative embodiment.
• Figure 4 shows an exemplary voltage-current characteristic of the electronic component designed as a varistor component.

The Figures 5A to 5D show simulation results of the operation of the electronic component.

Figure 6 shows a table with values for the simulation of the operation of the electronic component.

Identical, similar and identically acting elements are provided with the same reference symbols in the figures. The figures and the proportions of the elements shown in the figures among one another are not to be considered to scale. Rather, individual elements can be exaggerated in size for better representation and / or for better understanding.

Figure 1 shows a schematic perspective view of an electronic component 100. The electronic component 100 is preferably a varistor component, in particular a disk or block varistor. The electronic component 100 is particularly preferably a disk varistor.

The electronic component 100 is in accordance with Figure 1 designed disc-shaped and has a longitudinal axis or axis of symmetry X, which runs through the center of the disc. With regard to the longitudinal axis X, the electronic component is preferably at least approximately rotationally symmetrical. The electronic component points in accordance with Figure 1 furthermore a disc-shaped functional body 1.

In the case of a varistor component, the functional body 1 preferably comprises a semiconductor material and / or a sintered ceramic, for example. Accordingly, the functional body 1 preferably further comprises polycrystalline material, or material which comprises grain boundaries and or grains of different electrical conductivity. As a functional component of a varistor component, the functional body 1 is preferably designed such that it can be switched from the electrically insulating to the electrically conductive state after the application of an electrical voltage above the varistor voltage. The functional body 1 comprises a first functional body section 3 and a second functional body section 2. The first functional body section 3 rotates or surrounds the second functional body section 2, as viewed from the top, preferably viewed at its outer edge, and is preferably cohesive and / or in one piece with it connected to form the functional body 1. The boundary of the sections mentioned is indicated by the dashed line.

The electronic component, or the disk or block varistor, for example, has a diameter of about 30 mm and a thickness of about 3 mm. The thickness mentioned preferably relates to the thickness of the second functional body section 2 along the longitudinal axis.

In an alternative, not explicitly illustrated embodiment of the electronic component, this or a corresponding functional body has a rectangular shape. Accordingly, according to the invention, the electronic component can be, for example, an angular block varistor.

Figure 2 shows a schematic sectional view of an embodiment of the electronic component 100 according to the invention. Figure 2 preferably shows a section through the electronic component 100 according to FIG Figure 1 along the longitudinal axis X. It can also be seen that the functional body 1 has a thickness D1 in its first functional body section 3. In the second functional body section 2, the functional body 1 has a thickness D2. The thickness D2 is smaller than the thickness D1. The thickness D1 can for example be 5%, 10% or 15% larger or even larger than the second thickness.

The functional body 1 also has a first surface 5 and a second surface 6 facing away from the first surface 5. The second surface 6 is in accordance with Figure 1 flat, while the first surface 5 is not flat due to the increase in the thickness D1 in the first functional body section 3 compared to D2. Alternatively, the greater thickness D1 of the first functional body section 3 compared to the second functional body section 2 can also be realized in such a way that both surfaces 5, 6 in the first functional body section 3 compared to the second Functional body section 2 raised, that is, are not flat overall.

As in Figure 2 shown, the thickness of the functional body 1 can increase, for example, from the first to the second functional body section (from the inside to the outside) over an oblique course (cf. also FIG Figures 5A to 5D further down). Alternatively, an abrupt change in the thickness over a step in the course of the thickness of the functional body 1 is also conceivable (not explicitly shown in the figures).

Due to the greater thickness D1 of the first functional body section 3 compared to the second functional body section 2 (cf. D2 in Figure 2 ) According to the invention, the electrical resistance of the functional body 1 between the first surface 5 and the second surface 6 can be made larger than in the second functional body section 2, in particular due to the increased distance in the first functional body section 3.

The electronic component 100 also has a first contact 4a, which is electrically connected to the first surface 5. The first contact 4a is preferably connected both to the first functional body section 3 and to the second functional body section 2. The contact 4a in turn has an edge area 7 and a central area 8. The edge region 7 preferably encloses the central region 8.

Analogously, the electronic component has a second contact 4b, which on the second surface 6 to the first functional body section 3 and the second functional body section 2 is connected. Corresponding to the first contact, the second contact 4b preferably has an edge region 7 and a central region 8. The first and the second contacts 4a, 4b are preferably congruently arranged when viewed from the top of the electronic component 100.

The contacts 4a, 4b preferably contact the functional body 1. The contacts can, for example, be electrodes metallized, in particular metallic contact layers. Furthermore, the contacts 4a, 4b can be provided for an electrical connection or contacting of an outer electrode (not explicitly shown) on the functional body 1.

If - in the case of a varistor component - an electrical voltage is applied between the contacts 4a, 4b, preferably only a small leakage current flows as long as the voltage is less than the characteristic varistor voltage between the contacts 4a, 4b. When an overvoltage is applied to or between the contacts 4a, 4b, the functional body 1 expediently becomes electrically conductive in order, for example, to protect a further electrical component from an overvoltage or an electrical voltage damaging the component.

When viewed from above, the first functional body section 3 overlaps the electronic component 100, that is to say, for example, in the view of the surface 5, preferably with the edge region 7. The second functional body section 2 overlaps when viewed from the top, preferably with the central region 8.

By designing the greater resistance of the first functional body section 3 compared to the second functional body section 2, the electrical current occurring in the operation of the electronic component 100 in the second functional body section 3 or in particular the electrical current density can advantageously be reduced or reduced. Due to the reduced current load, the generation of heat and thus the temperature load in the first functional body section can be reduced at the same time.

The electronic component 100 according to the invention preferably has dimensions comparable to the thickness D1 of the first functional body section 3 compared to a conventional electronic component or an electronic component of the prior art. In particular, the contact areas, that is to say the areas in which the contacts 4a, 4b are connected to the functional body 1, are dimensioned or configured similarly or comparably in this respect.

In particular at the border or contact point of the above-mentioned edge region 7 or the edge of the contacts 4a, 4b to the first functional body section 3, the electrical current density and the associated temperature load, for example during operation of the electronic component, can be particularly high due to an "edge effect". The edge effect can be caused by electrical fields which are larger in operation of the component 100 on or in the edge region 7 than, for example, in the central region 8.

Although the electrical current density is reduced by the greater distance between the contacts in the first functional body section 3, further electrical properties of the electronic component 100 preferably remain unchanged and / or are determined by the second functional body section 2.

The area of the second functional body section 2 is preferably larger than that of the first functional body section 3. For example, the area of the second functional body section 3 is twice as large, three times as large or ten times as large as the area of the first functional body section 3. As a result, the electrical properties, im In the case of a varistor component, for example the varistor voltage, the electronic component is preferably independent of the configuration of the first functional body section 3.

A radial expansion of the first functional body section 3 is shown in FIG Figure 2 marked with R1. Furthermore, a radial extension, in particular the diameter of the second functional body section 2, is identified by R2. The radial extent R1 is preferably between the single and double the thickness D1 of the functional body 1 in the first functional body section 3.

In Figure 2 a non-contact edge 9 of the functional body 1 is further shown in the first functional body section 3, in which the contacts 4a, 4b are not electrically connected to the functional body 1. The contact-free area 9 preferably designates a radial outer section of the functional body 1. In other words, the contacts 4a, 4b close at the outer edge of the Electronic component 100 is not flush with the functional body 1, but the edge region 7 of the contacts 4a, 4b is offset inwards in comparison to the outer edge of the component. The contacts 4a, 4b are preferably arranged and designed such that they completely contact the functional body 1 except for the contact-free edge.

Figure 3 shows a schematic sectional view of the electronic component 100 according to a further embodiment of the invention. It is in Figure 3 It can be seen that the functional area 2 has a constant thickness over its entire extent, which for example corresponds to the thickness D2 in Figure 2 corresponds. For the configuration according to the invention of the greater resistance of the first functional body section 3 compared to the second functional body section 2, the material properties of the first and the second functional body section are preferably selected differently here.

In order to reduce the electric current and / or current density - with the same corresponding area - in the first functional body section 3 during the operation of the electronic component 100, the first functional body section 3 has a greater specific electrical resistance than the second functional body section 2 analogous to the above embodiment with the increased thickness, by the greater resistance, a current density and thus the heat development in the first functional body section 3, in particular in or at the contact point with the edge region 7.

The functional body 1 preferably has a sintered, polycrystalline material. In the case of a varistor component, the material is preferably silicon carbide, zinc oxide or another metal oxide, such as bismuth oxide, chromium oxide or manganese oxide. According to the configuration described here, the first functional body section 3 is preferably produced or obtained by sintering a starting material for the functional body 1, for example, or by selecting the composition of the starting material for the functional body before the sintering such that the first functional body section 3 is compared to the second functional body section 2 has a greater specific electrical resistance. In the present case, this can be achieved by the formulation of the starting material and the sintering conditions, in particular the process conditions during the sintering. A manufacturing method of the functional body 1 for the electronic component 100 and / or the electronic component itself preferably comprises the provision of a green compact or base material 1 for the functional body 1, the formation of the functional body 1 using the base material 1 such that the electrical resistance of the functional body 1 is larger in the first functional body section 3 than in the second functional body section 2.

As described above, the thickness D1 of the first functional body section 3 is made larger than the thickness D2 of the second functional body section 2.

Alternatively or additionally, the base material 1 can be sintered into the functional body 1 in such a way that the specific electrical resistance of the functional body 1 in the first functional body section 3 is larger than in the second functional body section 2. For this purpose, the base material 1 can be exposed to a temperature gradient during the sintering, for example, without further material being added to the base material 1 during the sintering. Instead, the properties of the functional body 1 with respect to the specific electrical resistance are preferably formed solely by the formulation or composition, for example on the basis of migration and / or diffusion processes of material components originally contained in the base material 1.

According to this embodiment, the composition can comprise, for example, materials which, during the sintering, preferably migrate, diffuse or accumulate in the first functional body section 3 due to the temperature gradient described.

Alternatively or additionally, certain original materials of the base material 1 can be removed from the stoichiometry of the base material 1 by evaporation from the base material 1 or evaporation from a surface of the base material 1, so as to produce a more inhomogeneous material composition in the functional body 1 in contrast to the base body.

The effects or processes described can expediently lead to crystal grains or their grain sizes in the first functional body section 3 of the functional body 1 being smaller or being formed than in the second functional body section 2 and thus the specific electrical resistance in the first functional body section 3 is enlarged in contrast to the second functional body section 2.

Alternatively, the base material 1 can be provided with a dopant before sintering, which diffuses into the base material 1, for example during the sintering, in order to form the first functional body section 3. The dopant can comprise or consist of, for example, yttrium oxide, in particular Y ₂ O ₃ , or other rare earth metals or their oxides. The dopant or the additional material is preferably applied to the base material or the base material is immersed in the dopant or, for example, a solution or compound contained therein before sintering.

The configurations of the Figures 2 and 3 can also be combined according to the invention, for example by means of the described production method, in such a way that both a greater thickness of the first functional body section 3 compared to the second functional body section, as well as a changed material formulation or composition are present, as a result of which the effects described for reducing or reducing the electrical current density / Add or increase heat development in the first functional body section 3.

Figure 4 shows an exemplary voltage-current characteristic of an electronic component according to the invention (dashed line) and an exemplary voltage-current characteristic of a conventional corresponding electronic component (solid line). The electric field strength is plotted as a function of the electric current density in logarithmic scales. The

Characteristic curves preferably describe a working range of the components in question (cf. in particular the range above 10 A / mm ² ).

The dashed voltage-current characteristic curve describes in particular the electrical behavior of a varistor component according to the invention, in which the thickness of the above-mentioned first functional body section 3 (cf. for example Figure 2 ) is enlarged by 10% compared to the second functional body section. The conventional varistor component here is preferably identical or similar to the component according to the invention, except for the greater thickness described.

For example, it is in Figure 4 to recognize that, given the logarithmic scale on the X-axis, the electrical current density of the component according to the invention is significantly lower than at the conventional varistor component at a given electrical field strength, at least in the middle.

The Figures 5A to 5D show simulation results of the operation of varistor components according to the invention and conventional varistor components according to the characteristic curve (s) Figure 4 , The simulations preferably relate to "finite element (FEM) simulations. In particular, the electrical current density and the temperature of the components or the temperature distribution in the components were each under an electrical load with a standard test pulse of pulse shape 8/20 (µs) with a current of 30 amps simulated at 25 ° C.

The Figures 5A to 5D each describe four different geometries or partial figures of disk varistors (cf. numbering (1) to (4)), at least in the Figures 5A and 5B each about the right half or an upper right quarter of a sectional view similar or corresponding to that Figures 2 and 3 is shown. The results relate to disk varistors with a diameter of 30 mm and a thickness of a corresponding second functional body section (cf. reference number 2 above) of 3 mm. The vertical dashed lines in the Figures 5A to 5D define the first functional body section of the respective components described above and visually delimit this from the second functional body section. At least the thickness of the first contact is 10 µm. In the circled areas, the edge area 7 of the contacts can be seen (see reference number 4a above).

The numbers (2) to (4) each correspond to configurations according to the invention, whereas number (1) denotes the simulation of the conventional component, as described above.

In the Figures 5A and 5C results for the electrical current density are shown in A / mm ² . The Figures 5B and 5D each show results for the temperature in ° C (cf. the corresponding color scales in the lower area of the respective figure).

According to the present invention, the partial figures (2) each show the thickness (cf. D1 in Figure 2 ) of the first functional body section compared to the second functional body section enlarged by 10% (see right edge of the partial figures (2) of the Figures 5A to 5D ).

The partial figures (3) each show corresponding simulation results for the configuration of the component according to the invention, in which the functional body sections are of the same thickness, but the first functional body section has a greater specific electrical resistance than the second functional body section due to the material composition ( Figure 3 including description).

The sub-figures (4) combine the configurations of the sub-figures (2) and (3), each showing and simulating both a greater thickness of the first functional body section and an increased specific electrical resistance due to the material composition.

It is at least partially in the Figures 5A to 5D It can be seen that the temperatures and also the electrical current densities are distributed more unevenly in the first functional body sections 3 than in the second functional body sections 2 in accordance with the color scales shown below. This is shown in FIGS Figures 5C and 5D by the enlarged representation in contrast to the Figures 5A and 5B clarified.

In particular, at the edge areas 7 of the contacts or the contact points of the edge areas 7 mentioned on or to the functional bodies or first functional body sections (see circled areas), both the temperature and the electrical current density are considerably higher at points than in the corresponding other functional body.

Under the abovementioned conditions, the temperature of the varistor component, which arises in response to the test pulse described in the first functional body section, in particular in the vicinity of the edge region 7 of the contact, can be reduced by up to 750 ° C. according to the invention. Corresponding results of the electrical current densities at the pulse maximum of the test pulse and the maximum temperature at the end of the pulse on the basis of numerical values are in the table of Figure 5 shown for all sub-figures (1) to (4). The electrical voltage of the varistor is also shown. While the voltage values differ only slightly for all simulated situations (partial figures), temperature and electrical current density, for example, are sufficient for the partial figures (4), ie for the combination of the configurations according to the invention Figures 2 and 3 in contrast to the partial figures (1) significantly reduced (see also the numerical values on the right in Figure 6D ).

The invention is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses every new feature and every combination of features, which in particular includes every combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

LIST OF REFERENCE NUMBERS

1

Functional body / basic material

2

Second functional body section

3

First functional body section / section of the base material

4a

First contact

4b

Second top

5

First surface

6

Second surface

7

border area

8th

Central area

9

Non-contact area

100

Electronic component

D1, D2

thickness

R1, R2

Radial expansion

Claims (15)

1. Electronic device (100) with a functional body (1) and a contact (4a), which is electrically connected to a first surface (5) of the functional body (1), the contact (4a) having a peripheral zone (7) and a central zone (8), and the functional body (1) being configured in such a way that the electrical resistance of the functional body (1) between the first surface (5) and a second surface (6) of the functional body (1) remote from the first surface (5) is greater in a first functional body portion (3), which, when viewed in plan view onto the electronic device (100), overlaps with the peripheral zone (7), than in a second functional body portion (2), which, when viewed in plan view onto the electronic device (100), overlaps with the central zone (8) of the contact (4a), characterized in that the functional body (1) is configured in such a way that the first functional body portion (3) has a greater resistivity compared with the second functional body portion (2).
2. Electronic device (100) according to Claim 1, wherein the first functional body portion (3) surrounds the second functional body portion (2) at least in part when viewed in plan view onto the electronic device (100).
3. Electronic device (100) according to Claim 1 or 2, wherein the area of the second functional body portion (2), when viewed in plan view onto the electronic device (100), is greater than the area of the first functional body portion (3).
4. Electronic device (100) according to one of the preceding claims, wherein the functional body (1) has a contact-free zone (9) in the first functional body portion (3), in which zone the contact (4a) is not connected electrically to the functional body (1).
5. Electronic device (100) according to one of the preceding claims, wherein the thickness (D1) of the functional body (1) is greater in the first functional body portion (3) than the thickness (D2) of the functional body (1) in the second functional body portion (2).
6. Electronic device (100) according to Claim 5, wherein the thickness (D1) of the functional body (1) is 5 % to 15 % greater in the first functional body portion (3) than the thickness (D2) of the functional body (1) in the second functional body portion (2).
7. Electronic device (100) according to one of the preceding claims, wherein the contact is a first contact (4a), wherein the electronic device (100) has a second contact (4b), which is electrically connected to the second surface (6) of the functional body (1), and wherein the functional body (1) is configured in such a way that the current density distribution is homogenized in the first and second functional body portions (3, 2), when current flows in the functional body (1) between the contacts (4a, 4b).
8. Electronic device (100) according to one of the preceding claims, which is a varistor device, for example a disc varistor or block varistor.
9. Electronic device (100) according to one of the preceding claims, wherein the functional body (1) is polycrystalline.
10. Method for producing a functional body (1) for an electronic device (100), comprising the following steps:

    - providing a base material for the functional body (1) for the electronic device (100),

    - forming the functional body (1) using the base material in such a way that the electrical resistance of the functional body (1), measured between two opposing surfaces (5, 6), is greater in a first functional body portion (3) than in a second functional body portion (2), characterized in that the base material is sintered to yield the functional body (1), in such a way that the resistivity of the functional body (1) is greater in the first functional body portion (3) than in the second functional body portion (2).
11. Method according to claim 10, wherein the base material has a more uniform material composition than the functional body (1).
12. Method according to claim 10 or 11, wherein the base material is formed with a greater thickness in the first functional body portion (3) in comparison with the second functional body portion (2).
13. Method according to one of claims 10 to 12, wherein the material composition of the base material is modified in a first portion (3) thereof during sintering in order to form the first functional body portion (3).
14. Method according to one of claims 10 to 13, wherein the base material is exposed to a temperature gradient during sintering and wherein the base material is not provided with material additives during sintering.
15. Method according to one of claims 10 to 14, wherein the base material is provided with a dopant prior to sintering, which dopant diffuses into the base material during sintering in order to form the first functional body portion (3).

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