EP1425762B1 - Electrical multi-layer component - Google Patents

Abstract

An electrical component includes a base body that contains dielectric layers. The dielectric layers are superimposed and contain ceramic. The component also includes outer contacts on an exterior of the base body, and a resistor in an interior of the base body located between two of the dielectric layers. The resistor is connected to the outer contacts, and is made from a layer that forms a path between the outer contacts. The path between the outer contacts has multiple bends.

Description

The invention relates to an electrical multilayer component, which contains a base body with a stack of superimposed ceramic dielectric layers. In addition, external contacts are arranged on the outside of the main body. In the interior of the base body, a resistor is arranged, which is connected to the external contacts.

Multi-layer devices of the type mentioned are usually produced in the so-called multilayer technology. For example, multilayer varistors or even ceramic capacitors can be produced with the aid of this technology. In order to give these components specific properties with regard to their application, the integration of a resistor is often necessary. By means of such a resistor, for example, properties such as the frequency response, the insertion loss or the course of the terminal voltage can be changed in a positive manner in an electrical pulse coupled into a varistor. The known ceramic components additionally contain electrically conductive electrode layers in addition to the dielectric layers and thus form a stack of superimposed electrode layers separated from one another by dielectric layers. Such stacks can form, for example, capacitors or even varistors.

From the document US 5,889,445 multilayer components of the type mentioned are known in which an external contact is arranged in each case on the two end faces and on two longitudinal sides of the base body. These components are also known to the person skilled in the art under the name "feedthrough components". In the known device resistors are integrated, in the form of a printed along a rectangular path resistance paste between two ceramic layers are integrated. They connect an external contact of the component with an electrode layer which belongs to a capacitor which is likewise integrated in the component. The resistor structure is in the same plane as the internal electrodes needed to build up a capacitance. As a result, series circuits of capacitors and resistors are integrated into a multilayer component according to the prior art.

The known resistor has the disadvantage that the material forming the resistor is printed along a wide path on a dielectric layer. This makes it difficult to realize high resistance values as they are normally desired. The realization of high resistance values is made possible according to the prior art by using special resistor pastes. However, these special resistor pastes have the disadvantage that they can not withstand the high sintering temperatures usually occurring in the production of ceramic components> 1000 ° C. Accordingly, according to the prior art, the multilayer component is limited to ceramic materials which can be sintered by means of the so-called "LTCC sintering process". These are ceramic materials that can be sintered at low temperatures <800 ° C. Naturally, according to this requirement, the choice of ceramic materials is severely limited, which means a further disadvantage of the known multilayer component.

From DE 3125281 A1 an electrical component combination is known in which the top surface of a multilayer capacitor is provided with a resistance track which can be adjusted to the desired resistance value by material balance and consists of a material whose temperature coefficient is opposite in terms of the temperature coefficient of the capacitor.

The aim of the present invention is therefore to provide a multilayer component which allows a high degree of flexibility in the integration of resistors in multilayer components.

This object is achieved by an electric multilayer component according to claim 1. Further embodiments of the invention can be found in the dependent claims.

The invention is defined by the features of claim 1 and provides a multilayer electrical component comprising a base body containing a stack of superimposed ceramic dielectric layers. Outside of the main body at least two external contacts are arranged. In the interior of the main body, a resistor is arranged between two dielectric layers, which is contacted with two of the external contacts. The resistor has the form of a structured layer, which forms at least one multiply curved path as a current path between the external contacts.

The multilayer component according to the invention has the advantage that, owing to the structuring of the layer forming the resistance, there is a greater choice in the resistance values to be realized, and in particular relatively large resistance values can be achieved.

In the case of resistors produced in the form of printed tracks in accordance with the printed conductor technology, the ratio of the length of the web to the width of the web is particularly important. The longer the train is, the greater its resistance. Conversely, with decreasing width of the track, the resistance increases. A large ratio length / width is therefore favorable for the realization of a large resistance. By carrying out the resistor in the form of a structured layer, the space which is available only to a limited extent between the two external contacts, in particular for small component sizes, can now be optimally used to form a large resistor. In contrast, a non-curved, only rectilinearly extending between the two external contacts resistance path would allow only a very small resistance. Although it would be possible to lower the resistance by changing the web width, in particular by reducing the web width. However, too small a web width would mean that the current carrying capacity of the resistor is low, so that the resistance at a would melt according to the application of the multilayer component occurring pulsed high current load or even with permanent DC load.

In a further advantageous embodiment of the invention, the resistor is arranged in a plane of the multilayer component which is free of electrically conductive electrode layers. This means that the entire area of one plane of the multilayer component is available for the formation of the resistor. Together with the multi-curved path can thus be provided an optimally large area for the realization of a particularly high resistance.

The multilayer device of the invention, because of the patterned layer for the resistor, allows the internal sintering of the dielectric layers with the resistor in a single step. Thereby, a monolithic body can be formed, as it is common for use in multilayer technology and which has the usual advantages.

With regard to the achievement of particularly large resistors, it is furthermore advantageous if the resistance between the external contacts runs in the form of a web whose length is at least ten times greater than its width.

The resistor may be formed in one embodiment of the invention of a closed resistance layer, which is subsequently provided with recesses. As a result, the rectilinear current path between the external contacts can be interrupted and the current forced to multiple curved paths. As a result, a high resistance can be achieved.

In a further embodiment of the invention, the resistor can also be designed as a meandering path. A meandering path with a plurality of turns allows the realization of a very long current path along the longitudinal direction of the meander. In particular, a large amount of resistance can be realized by a plurality of successive bends made in opposite directions.

The resistive material may include, for example, an alloy of silver and palladium, wherein palladium has a weight fraction of 15 to <100% of the alloy. Pure palladium can also be used. Such materials are known in multilayer technology in the manufacture of multilayer devices. So far, however, only electrode layers were made from these materials, where it depends on a good conductivity. These materials have the advantage that they are sintered together with a variety of ceramic materials. Although they do not have a very high resistance, but the structuring according to the invention, the resistance can be sufficiently increased.

It is particularly advantageous if the resistance material contains an alloy of silver and palladium, wherein palladium has a weight fraction of between 50 and 70% of the alloy. Due to the high palladium content, the resistance can be increased approximately by a factor of three because of the poorer conductivity of palladium compared to silver.

Furthermore, the resistance can be increased by forming the resistor from a resistive material having a sheet resistance of at least 0.1 ohms in the patterned layer.

The resistance of the resistance material can be increased, for example, by adding the resistance material in addition to an electrically conductive component nor additives in an amount of up to 70 vol .-%. Such additives may have a resistivity at least ten times greater than the resistivity of the conductive component. It is important to ensure that the conductive components are not isolated in a matrix of insulating additives, because then no conductivity at all would be available.

As additive, for example, aluminum oxide (Al ₂ O ₃ ) into consideration.

An alloy of silver and palladium having a weight ratio Ag / Pd = 70/30 has a sheet resistance of 0.04 Ω for a layer of thickness 2 μm. The sheet resistance is the specific resistance of the material divided by the thickness of a layer to be considered in the form of a rectangle. The resistance of the layer is then obtained by multiplying the sheet resistance with the layer length and then dividing by the layer width. By producing a resistive material containing 70 vol.% Al ₂ O ₃ and 30 vol.% Of said alloy, the sheet resistance can be increased from 0.04 to 0.12 Ω.

When using a suitable resistance material, it is possible to use for the ceramic material of the dielectric layers materials whose sintering temperature is between 950 and 1200 ° C. This has the advantage that a multiplicity of ceramic materials are available for the multilayer component according to the invention, which makes it possible to produce components with optimum ceramic properties.

For example, ceramic materials based on barium titanate are suitable for the dielectric layers. With the help of such ceramic materials, for example, capacitors can be realized.

Furthermore, it is possible to use a so-called "COG" ceramic for the dielectric layers. Such a material would be, for example, a (Sm, Ba) NdTiO ₃ ceramic. In addition to these class 1 dielectrics, so-called class 2 dielectrics such as X7R ceramics are also suitable.

In particular, zinc oxide is suitable for the production of a varistor, optionally with doping of praseodymium or bismuth oxide.

There is also the need to produce said ceramic components with very small external dimensions. This complicates the realization of large resistors in addition, since only very short rectilinear resistance paths are made possible thereby. Due to the inventive structure of the resistor, however, sufficiently high values can be achieved.

In a specific embodiment of the invention, the multilayer component may be designed such that two juxtaposed multilayer varistors are contained therein. By suitable arrangement of one or more resistors, a π filter can be realized by such a device. Such π filters are based on the fact that multilayer varistors naturally also have not inconsiderable capacitance in addition to their varistor characteristic which is responsible for the attenuation behavior of such a filter.

Such a π filter can be formed in the form of a component in which two stacks of superimposed electrode layers separated from one another by dielectric layers are arranged in the main body next to each other. The electrode layers of the first stack are alternately contacted with the first and second external contacts of a first pair of external contacts. By this alternating contact comb-like interdigitated electrode structures can be realized, for example, to achieve of high capacities are required. According to the first stack, the electrode layers of the second stack are also contacted alternately with the first and the second external contact of a second pair of external contacts.

The π filter corresponding connection of the two multilayer components thus formed by a resistor is realized in that belonging to different pairs and lying on opposite side surfaces of the body external contacts are connected by a resistor. The external contacts of each pair lie on opposite side surfaces of the body. Overall, in each case two external contacts are arranged on two opposite side surfaces of the base body. This corresponds to the so-called "feedthrough" embodiment of components.

By virtue of the dielectric layers at least partially containing a varistor ceramic, it can be ensured that each of the stacks of electrode layers is part of a multilayer varistor. By the two external contacts connecting resistor can be formed from the two varistors a π-filter.

Due to the increased coupling resistance, such a π filter has an improved damping behavior, whereby an entire frequency band extending between the two damping frequencies defined by the capacitances of the varistors can be attenuated.

Furthermore, it is advantageous if the component is formed symmetrically to a plane which runs parallel to a dielectric layer. For this it is necessary that, for example, a resistor is arranged above and below the stack. These resistors would then be connected in parallel. A symmetrical embodiment of the device has the advantage that it is in the assembly of the device On a printed circuit board, in particular in the case of high-frequency applications, it no longer matters whether the layer stack of the component with the lower side or with the upper side rests on the circuit board.

The component according to the invention can be produced particularly advantageously by sintering a stack of superposed ceramic green sheets. This creates a monolithic, compact component that can be produced very quickly and easily in large quantities.

The component according to the invention can be embodied in particular in a miniaturized form, the base area of the main body being less than 2.5 mm ² . Such a base could be realized for example by a design of the body, in which the length is 1.25 mm and the width is 1.0 mm. This design is also known under the name "0405".

Figur 1

zeigt den Schnitt D-D aus Figur 2.

Figur 2

zeigt einen Längsschnitt durch ein erfindungsgemäßes Bauelement.

Figur 3

zeigt den Schnitt E-E aus Figur 2.

Figur 4

zeigt eine Draufsicht des Bauelements aus Figur 2.

Figur 5

zeigt eine Seitenansicht des Bauelements aus Figur 2.

Figur 6

zeigt ein Ersatzschaltbild für das Bauelement aus Figur 2.

Figur 7

10 zeigt eine weitere mögliche Ausführungsform für den in Figur 1 dargestellten Widerstand.

Figur 8

zeigt eine weitere mögliche Ausführungsform für den in den Figuren 1 und 7 dargestellten Widerstand.

Figur 9

zeigt schematisch das Dämpfungsverhalten eines Bau-elements gemäß Figur 2.

In the following the invention will be explained in more detail by means of exemplary embodiments and the associated figures:

FIG. 1

shows the section DD of Figure 2.

FIG. 2

shows a longitudinal section through a device according to the invention.

FIG. 3

shows the section EE of Figure 2.

FIG. 4

shows a plan view of the device of Figure 2.

FIG. 5

shows a side view of the device of Figure 2.

FIG. 6

shows an equivalent circuit diagram for the device of Figure 2.

FIG. 7

10 shows another possible embodiment for the resistor shown in FIG.

FIG. 8

shows a further possible embodiment for the resistor shown in Figures 1 and 7.

FIG. 9

schematically shows the damping behavior of a building element according to Figure 2.

For all figures, the same reference numerals also designate the same elements.

FIG. 2 shows a multilayer component according to the invention in a schematic longitudinal section. It comprises a main body 1, which contains superimposed dielectric layers 2 in the form of a stack. The dielectric layers 2 contain a ceramic material. They are indicated in Figure 2 by the dotted lines. In addition, stacks 7, 8 of superimposed electrode layers 9 are contained in the main body 1. These stacks 7, 8 each form a varistor VDR1, VDR2. Above and below the varistors VDR1, VDR2, a resistor 41, 42 is arranged in each case. The resistors 41, 42 are formed from a structured layer 5 whose shape is apparent in particular from FIG. In FIG. 2, only individual sections of a meander can be seen in cross section. The component shown in FIG. 2 is formed symmetrically with respect to a plane 14 that runs parallel to the dielectric layers 2. The symmetry of the device has particular advantages for applications in the high-frequency range, where it depends on the orientation of the components on the circuit board. A symmetrical design of the component means that it is not necessary to pay attention to the position of the component with respect to the plane of symmetry.

FIG. 1 shows the section DD of the component in FIG. 2.

FIG. 1 shows the shape of the resistor 41. It has the shape of a meander. The meander is formed by a web having the width b. In the example shown in FIG. 1, the width b is 50 μm . The length of the meander shown in FIG. 1 is approximately 4000 .mu.m . The length is determined by adding the lengths of the individual rectangles from which the meander can be composed. Accordingly, the embodiment of the invention according to Figure 1 with respect to the resistance of a ratio L / B of 80. This makes it possible to produce large resistances. The resistance shown in Figure 1 is about 3 ohms. The web shown in FIG. 1 is applied in the form of a structured layer 5, the layer thickness being approximately 2 μm . The resistor shown in Figure 1 is formed of a material containing a silver-palladium alloy, wherein palladium has a weight fraction of 30% of the alloy. In addition, the starting material of the resistor contains an organic substance and a solvent. These latter additives are contained only in the resistance material in order to apply the resistance in the form of a screen printing paste by means of a screen printing process on a ceramic layer can. These ingredients are removed by burnout during sintering. These are organic components.

FIG. 1 also shows that the resistor 41 connects two external contacts 3 of the component to one another.

FIG. 1 also shows that, in the plane shown in FIG. 1, apart from the resistor 41, there are no electrode layers belonging to a capacitor or to a varistor. Accordingly, the entire surface shown in FIG. 1 is available for filling with the meander forming a resistance.

FIG. 3 shows the section EE of the component from FIG. 2. In FIG. 3, on the left side, an electrode layer 9 of FIG Stack 7 of electrode layers 9 and on the right side to see an electrode layer 9 of a stack 8 of electrode layers 9. Several similar such electrode layers 9 are stacked in the device. Due to the varistor material arranged between the electrode layers 9, they each form a varistor VDR1, VDR2, which, however, also has a high capacitive component due to the large-area electrode layers 9 facing one another. From a combination of Figure 1 and Figure 3 it can be seen that the device according to the invention according to the specific embodiment is designed as a feed-through device. Each stack 7, 8 of electrode layers 9 is associated with a pair of external contacts 10, 11 and 12, 13, respectively. Within a stack 7, 8 of electrode layers 9, the contacting of the electrode layers 9 with the external contacts 10, 11 or 12, 13 takes place alternately. A circuit-technical coupling of the varistors formed by the stacks 7, 8 takes place through the resistor 41 or 42, as can be seen from FIG. 1 and FIG. 2, respectively.

FIGS. 4 and 5 show the position of the external contacts 3. They are arranged on two opposite side surfaces of the main body 1. The plan view of Figure 4 shows that the external contacts 3 engage around on the top or corresponding to the underside of the base body 1. As a result, the component can be electrically conductively connected to a printed circuit board on the upper side or on the lower side by a surface mounting technique.

FIG. 6 shows an equivalent circuit diagram of the component according to the invention shown in FIGS. 1 to 3. It can be seen that the two varistors VDR1, VDR2 are coupled together by a circuit resistor R to form a π-filter. The circuit resistance R results from a parallel connection of the two resistors 41, 42 of Figure 2. This results from the fact that the resistance 42 in Figure 2 looks exactly the same as the resistor 41 in Figure 1. In Figure 6 are still the external contacts 3 of the device in detail denoted by reference numerals, so that the circuitry assignment of the physical external contacts of the device can take place.

Figures 7 and 8 show further embodiments of a resistor 4, as it could be used in place of the resistor 41 shown in Figure 1. Accordingly, Figure 7 shows a further meandering structure for the resistor 4. Here, the layer 4 forming the resistor 4 is structured in the form of a meander. The meander is formed by a web with the width b, which may correspond to the width b of FIG. In contrast to FIG. 1, the meander in FIG. 7 does not run in the longitudinal direction of the main body 1, but in the transverse direction.

In Figure 8, a resistor 4 is shown, which is formed of a rectangular closed layer 5 by arranging recesses 6 in the layer 5. These recesses 6 may be circular, but they may also have other shapes, such as rectangles. By a uniform distribution of a plurality of recesses 6, the resistance of the originally rectangular layer 5 can be significantly increased. As an effect of the recesses 6 results in a plurality of multiply curved current paths between the external contacts 3, which have a high resistance.

FIG. 9 shows the insertion loss of the component shown in FIG. 2 or in FIG. 6. The insertion loss S is plotted in the unit dB over the frequency f [MHz]. Resonance frequencies f ₁ , f _{2 are} formed by the two capacitors C1, C2 contained in the varistors VDR1, VDR2. At the locations of the resonant frequencies f _1, f ₂ the device exhibits an increased attenuation. Also between the resonant frequencies f ₁ , f ₂ , the device due to the π circuit realizing resistor R a very good attenuation, which is better than -20 dB in the frequency interval between 740 MHz and 2.7 GHz. As a result, the component is suitable for suppressing a frequency band which lies between the resonance frequencies f ₁ (part of C1) and the resonance frequency f ₂ (part of C2). The resonance frequencies f ₁ and f ₂ are defined by the capacitances C1 and C2 of the varistors VDR1 and VDR2, which can be determined by converting the frequencies to C1 = 40 pF and C2 = 20 pF. The resistance R is 1.8 Ω in the embodiment shown in the figures.

Claims (18)

1. Electrical multilayer component with

   - a base body (1) containing a stack of ceramic dielectric layers (2) lying one on top of the other,

   - two external contacts (3) arranged on the outside of the base body (1),

   - electrode layers (9) forming, together with the dielectric layers, at least one capacitance,

   - a resistor (4, 41, 42) arranged between two dielectric layers (3) inside the base body (1),

   characterized in that the resistor is contacted with the external contacts (3) and comprises the form of a structured layer (5) forming at least one multiply curved path as a current path between the external contacts.
2. Component according to Claim 1,
   wherein the dielectric layers (2) and the resistor (4, 41, 42) are sintered together in a single sintering step and form a monolithic body.
3. Component according to either of Claims 1 and 2,
   wherein electrode layers (9) are arranged in the base body (1) and wherein the plane of the resistor (4, 41, 42) is free of electrode layers (9).
4. Component according to one of Claims 1 to 3,
   wherein the resistor (4) runs between the external contacts (3) in the form of a path whose length is at least ten times larger than its width (b).
5. Component according to one of Claims 1 to 4,
   wherein the resistor (4, 41, 42) is formed from a closed layer (5) provided with recesses (6).
6. Component according to one of Claims 1 to 4,
   wherein the resistor (4, 41, 42) comprises the form of a meander.
7. Component according to one of Claims 1 to 6,
   wherein the resistor (4, 41, 42) is formed from a resistance material having a sheet resistance of at least 0.1 ohm in the structured layer (5).
8. Component according to one of Claims 1 to 6,
   wherein the resistor (4, 41, 42) is formed from a resistance material containing an alloy of silver and palladium, the palladium having a proportion of 15 to < 100% by weight of the alloy.
9. Component according to Claim 8,
   wherein the proportion of palladium is between 50 and 70% by weight.
10. Component according to one of Claims 1 to 8,
    wherein the resistance material additionally contains up to 70% by volume of an additive having a resistivity at least ten times larger than the resistivity of the other constituents of the resistance material.
11. Component according to Claim 10,
    wherein the additive contains Al₂O₃.
12. Component according to one of Claims 1 to 11,
    wherein the dielectric layers (2) contain a ceramic material whose sintering temperature is between 950 and 1200°C.
13. Component according to Claim 12,
    wherein the dielectric layers (2) contain a ceramic based on BaTiO₃.
14. Component according to Claim 12,
    wherein the dielectric layers (2) contain a varistor ceramic.
15. Component according to one of Claims 1 to 14,

    - wherein two stacks (7, 8) of electrode layers (9), which respectively lie one on top of the other and are separated from each other by means of dielectric layers (2), are arranged next to each other in the base body (1),

    - wherein the electrode layers (9) of the first stack (7) are alternately contacted with a first external contact (10) and with a second external contact (11) of a first pair of external contacts,

    - wherein the electrode layers (9) of the second stack (8) are alternately contacted with a first external contact (12) and with a second external contact (13) of a second pair of external contacts,

    - and wherein external contacts (10, 13; 11, 12) belonging to different pairs and lying on mutually opposite side surfaces of the base body (1) are connected by means of a resistor (4) arranged inside the base body.
16. Component according to Claim 15,
    wherein the stacks (7, 8) of electrode layers (9) are each part of a multilayer varistor (VDR1, VDR2).
17. Component according to Claim 16,
    wherein the two varistors (VDR1, VDR2) and the resistor (4) form a π filter.
18. Component according to Claim 17,
    wherein the component is formed symmetrically with respect to a plane (14) that runs parallel to a dielectric layer (2), and wherein a respective resistor (41, 42) is arranged above and below the stack (7, 8) of electrode layers (9).

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