EP2929575A1

EP2929575A1 - Method for producing an electronic component

Info

Publication number: EP2929575A1
Application number: EP13801498.0A
Authority: EP
Inventors: Alexander Glazunov
Original assignee: Epcos AG
Current assignee: TDK Electronics AG
Priority date: 2012-12-07
Filing date: 2013-11-25
Publication date: 2015-10-14
Also published as: US20150318464A1; DE102012111972A1; JP2015536580A; US9755138B2; WO2014086611A1

Abstract

The invention relates to a method for producing an electronic component (100). The method comprises the providing of a piezoelectric base body (1) having electrodes (2), the creating of a first electrical polarization field (E1) having a first polarity direction on the piezoelectric base body (1) between the two electrodes (2), the creating of a second electrical polarization field (E2) after the creating of the first electrical polarization field (E1), in a second polarity direction opposite to the first polarity direction, on the piezoelectric base body (1) between the electrodes (2). The value of the second electrical polarization field (E2) differs from that of the first electrical polarization field (E1).

Description

description

Method for producing an electronic component The present invention relates to a method for

Production of an electronic component.

An object to be solved is to provide an improved method for producing an electronic component.

This object is achieved by the method having the features of patent claim 1. Advantageous embodiments and developments are the subject of the dependent

Claims.

A proposed method comprises providing a piezoelectric body provided with electrodes and applying a first electrical

Polarizing field with a first Polungsrichtung to the piezoelectric body between the electrodes.

Furthermore, the proposed method according to the

Applying the first polarizing field, the application of a second electric polarizing field in a second polarity direction to the piezoelectric body between the electrodes. The first polarity direction is polarized opposite to the second polarity direction, wherein the magnitude of the second polarization electric field is different from that of the first polarization electric field. Furthermore, the method comprises completing the

electronic component.

The piezoelectric body is preferably electrically conductively connected to the electrodes. Preferably comprises the piezoelectric body two electrodes, for example, on two opposite sides of the

piezoelectric body in each case one electrode.

Preferably, the electrodes are external electrodes. Advantageously, an electrical operating field can be applied to the piezoelectric main body via the electrodes. With the electrical operating field is that electric field meant, which is when creating an electrical

Operating voltage between the electrodes during operation

formed. During operation, the electrical operating field can likewise be present between inner electrode layers of the electronic component, which are each connected to one of the outer electrodes. With the method described, a, preferably piezoelectric, electronic component can be produced, which advantageously has a very large in operation

Deflection has. The deflection of such

piezoelectric body in the operation of the electronic component is substantially determined by a contribution of the piezoelectric effect, i. the deformation of the

Crystal lattice upon application of an electric field

on the one hand, and on the other, by a contribution by the

Reversal of ferroelectric domains in the piezoelectric body when the electrical field of operation is applied. The piezoelectric body can be a piezoelectric

Be ceramic or contain such. Each individual grain of the piezoelectric ceramic may have one or more

having ferroelectric domains each having a uniform dielectric polarization.

Under the flip of a ferroelectric domain, the change in polarization direction of the ferroelectric Domain understood when creating an electrical operating field. There are still two types of

Domain flip, namely a 180 degree domain flip and a 180 degree domain flip. A

Domain flip-flop by 180 ° means a change in the

Polarization direction of the respective ferroelectric domain by 180 ° when applying an electric field. A

Domain flip around "not 180 °" means a change in the polarization direction of the respective ferroelectric domain by an angle other than 180 ° when the electric field is applied.

The domain flip around "not 180 °" contributes at least in piezoelectric ceramics based on lead zirconate titanate (PZT) at room temperature over 80% to the total deflection.

Accordingly, the deflection of a piezoelectric ceramic can be improved by preferentially promoting the domain flip around "not 180 °." The domain flip around "not 180 °" is influenced, for example, by the

Material composition of the piezoelectric ceramic, the Curie temperature of the piezoelectric ceramic, the

Polungszustand or the grain size of the piezoelectric

Ceramics. Furthermore, a domain flip around "not 180 °" by applying a mechanical force or

Counterforce, especially during polarization, are promoted to the piezoelectric body.

By the present manufacturing method can be achieved with advantage a polarization state of the piezoelectric body, in which the contribution of the Domainumklappung of ferroelectric domains by "not 180 °" when creating a electric operating field in operation between the

Is significantly increased, since the application of the first and the second electric polarization field, which are preferably anti-parallel and have different contributions, the Domainumklappung by "not 180 °"

can be promoted. Consequently, an electronic component can be manufactured that has a greater deflection in operation compared to a component of the prior art or easier with comparable deflection

can be produced.

The proposed application of the first and second electric polarization field, the piezoelectric body can be further polarized with advantage in such a way that the application of a mechanical force during polarization, can be dispensed with, without that in

Operation achievable deflection is reduced. This is particularly advantageous since a mechanical device for applying the described mechanical force high

Requirements for the precision of the mechanical components involved and therefore is very expensive.

Advantageously, therefore, for the described

Manufacturing process or the polarization of the

piezoelectric body requires only an electrical voltage generator.

In a preferred embodiment of the method, the first and the second electric polarization field are selected such that the achievable deflection of the electronic component in operation compared with an electronic

Component, which according to a manufacturing or

Polarization method of the prior art and / or without Applying a mechanical force has been polarized by up to 75%.

Before applying the first electric polarizing field, the piezoelectric body is preferably

unpolarized. For example, the piezoelectric body in this case may be in a state immediately after sintering. The piezoelectric body can insofar no or approximately no spontaneous

have dielectric polarization.

The application of an electric field, e.g. one

electric polarization field can change the domain structure of the ferroelectric domains. The polarization of a ferroelectric domain then aligns along the applied electric field with the predominant domain flip around "not 180 °"

Turning off the electric field, the piezoelectric ceramic is polarized, i. there is a spontaneous one

dielectric polarization. Not all ferroelectric

Domains can fold back to their original position after switching off the electric field because of the distribution of electrical charges and elastic

Voltages has changed due to polarization.

In a preferred embodiment of the method is relative to a predetermined electrical operating field of the

electronic component, which is applied for operation between the electrodes, the first polarity positive and the second polarity negative. The deflection of a piezoelectric component is usually proportional to the applied to the component electric field strength. By this configuration is advantageously the electrical Field direction or a polarity of the electrical operating field of the electronic component, in which this is to be operated and in which the electronic component is to have an increased deflection, in terms of

Connection or the assignment of the electrodes specified. The first electric polarization field can be aligned parallel to the electrical operating field. The second electric polarizing field may be anti-parallel to

be aligned electric drive field.

In a preferred embodiment of the method, the amount of the first electric polarizing field is less than 4 kV / mm. In a preferred embodiment of the method, the amount of the first electric polarizing field is greater than 1 kV / mm.

In a preferred embodiment of the method, the amount of the first electric polarizing field is between 1 and 4 kV / mm.

Advantageously, these embodiments in the operation of the electronic component, an electrical flashover

be prevented and still the largest possible

Deflection of the electronic component can be achieved.

In a preferred embodiment of the method, the amount of the first electric polarizing field is greater than the amount of the second electric polarizing field.

In a preferred embodiment of the method follows at the end of the polarization process with the first electrical Polarization field the deflection of the piezoelectric

Main body in response to the applied electric field of a hysteresis curve, which is an electrical

Coercive field strength determined, wherein the amount of the second electric polarization field is chosen smaller than the amount of the electric Koerzitivfeidstärke. The electric coercive field strength here preferably relates to that electric field strength in which a deflection of the first electric polarization field but not yet with the second electric polarization field

polarized piezoelectric body is zero. This configuration can advantageously a large

Deflection can be achieved in the positive direction of the electronic component, when the electric field during operation or the electrical operating voltage is applied in the positive direction. This is based on the hysteresis curve (so-called.

In one preferred embodiment of the method, the first and / or the second electric polarization field has a temporal field profile with one or more

electric field pulses. Through this pulsation of

electric polarization fields during polarization gives rise to Joule heat by the charge movement, which causes the

Advantageously, polarization effect can improve by up to 20% over static or unpulsed polarization. The amount of an electric polarization field may be the magnitude of the maximum of a field pulse.

In a preferred embodiment of the method, the field pulses of the first and / or the second electrical Polarizing each of at least one of the pulse shapes rectangular, triangular, trapezoidal and sinusoidal form.

In a preferred embodiment of the method, the piezoelectric body has a plurality of

piezoelectric layers and is provided with a plurality of internal electrode layers, wherein the electrodes form external electrodes, which are arranged outside the piezoelectric main body, and wherein each

Inner electrode layer with one of the outer electrodes

electrically conductive is connected. Due to the large number of piezoelectric layers and inner electrode layers, among other things an increased deflection of the electronic component can be achieved, since the electric field strength applied to a single piezoelectric layer, which is generally proportional to the

Deflection of a piezoelectric layer can be significantly increased in this way. In a preferred embodiment of the method, the piezoelectric body has a ceramic, for example, containing lead zirconate titanate.

The present application further comprises a

Operating method for an electronic component manufactured according to the method described above. The method of operation includes applying a mechanical force to the electronic component. By this configuration, the advantage of increased deflection of the electronic component can be exploited during operation or the deflection with

Advantage further increased. The reason is that by applying the mechanical force with advantage of the desired by the manufacturing process polarization state for the operation of the electronic component can be at least partially maintained, since a mechanical force on the piezoelectric body can counteract depolarization of the piezoelectric body. For this purpose, the electronic component before applying the

mechanical force are incorporated into a device for the application of the electronic component. This device may, for example, a valve, in particular a

Injection valve of a motor vehicle, his.

In a preferred embodiment of the operating method, after the application of the mechanical force to the electronic component, an electrical operating field is applied between the electrodes to the electronic component, wherein the electrical operating voltage is polarized according to the first polarity direction. This configuration can advantageously a large

Deflection can be exploited in the operation of the electronic component. In the context of the present invention, an electronic component is further specified after the above

described method was prepared.

Advantageously, in the case of the electronic component, the number of ferroelectric domains whose direction of polarization changes by an angle different from 180 ° when an electric field is applied, compared with an electronic component of the prior art, which usually polarizes and / or without applying a mechanical force has been raised. In particular, all features disclosed for the method are also disclosed for the electronic component and / or the operating method and vice versa. Further advantages, advantageous embodiments and

Expediencies of the invention will become apparent from the following description of the embodiments in conjunction with the figures. FIG. 1 shows a first side view on the basis of a schematic side view

Process steps of the described method or shows an electronic component produced by the described method. FIG. 2 shows a simplified temporal field profile

comprising a first and a second electric polarization field.

FIG. 3 shows a schematic view of ferroelectric

Domains. In Fig. 3a, a domain flip is reversed

180 ° and in Figure 3b a Umäumumappappung by "not 180 °" indicated.

FIG. 4 shows a hysteresis curve (butterfly curve) of a polarized piezoelectric ceramic.

FIG. 5 shows simplified alternative embodiments of FIG

time field courses of electric polarization fields, each comprising a first and a second electric polarization field.

The same, similar and equally acting elements are provided in the figures with the same reference numerals. The figures and the proportions of the elements shown in the figures with each other are not to scale

consider. Rather, individual elements may be exaggerated in size for better representability and / or better understanding.

FIG. 1 shows the provision of a piezoelectric

Basic body 1. The piezoelectric basic body 1 is provided with two outer electrodes 2 and inner electrode layers 3. The two outer electrodes 2 are preferably mechanically connected to the piezoelectric main body 1 on opposite sides of the piezoelectric main body 1

connected or mechanically connected to this. Of the

piezoelectric body preferably comprises a piezoelectric ceramic, for example of lead zirconate titanate (PZT) or barium titanate. The

Inner electrode layers 3 may, for example, the

Materials silver, palladium, copper, platinum and / or

Alloys or combinations of these materials.

FIG. 2 shows a schematic representation of the time sequence of electrical polarization fields. In the course of a manufacturing or polarization process, a first electric polarization field E1 and then a second electric polarization field E2 between the electrodes 2 are first of all timed to the piezoelectric one

Base body 1 (see Figure 1) applied. The first and the second electric polarization field El and E2 are, as long as they each lie between the electrodes 2, respectively constant or represented as a rectangular pulse. The first

electric polarization field El is positive and the second electric polarization field E2 is negative. Furthermore, the amount of the first electric polarization field El greater than the amount of the second electrical

Polarization field E2. The amount of the first electric polarizing field El is preferably between 1 and 4 kV / mm. With even greater electric field strengths, there is a risk of an electrical flashover, in particular in the production of electronic components having a multiplicity of piezoelectric layers. For smaller electric Feistärken the piezoelectric body 1, however, would be insufficiently polarized. Conveniently, a corresponding electronic component is also operated with an electrical operating field which is smaller than the first electric polarizing field, that is, for example, less than 4 kV / mm. Ferroelectric domains are formed in a piezoelectric ceramic, for example, upon cooling from the sintering temperature to below the Curie temperature. After cooling, the ferroelectric domains in the piezoelectric ceramic are randomly oriented so that the total polarization is low or zero.

Figure 3 shows a schematic representation of

3a) and by "not 180 °" (FIG. 3b) In the polarization by the first and the second polarizing field which can be carried out according to the manufacturing method, a polarization state of the piezoelectric main body 1 can preferably be achieved, in which the domain flip can be promoted by "not 180 °" to operate in the electronic

Component 100 to achieve the highest possible deflection. In

FIG. 3 shows the rectangles ferroelectric domains 4 whose polarization direction P is indicated on the left with the arrow respectively drawn in the ferroelectric domains 4 is. The direction of an applied electric field E is shown by the arrows shown on the right outside the ferroelectric domains 4. The arrows shown between each of the upper and lower ferroelectric domains 4 indicate an electric field E caused

Change in polarization P on. In Figure 3a is a

Domain flip represented by 180 °, with the

Polarization directions of the upper ferroelectric domains are exactly opposite to each other. FIG. 3b shows a domain flip around "not 180 °", wherein the

Polarization directions of the lower ferroelectric domains differ by an angle other than 180 °.

FIG. 4 a shows a hysteresis curve of a piezoelectric ceramic or of the piezoelectric basic body 1. The curve K originating in the origin of coordinates indicates a curve K

New curve of the piezoelectric body 1, from which after polarization with the first electrical

Polarization field El gives the hysteresis curve shown. FIG. 4b shows a hysteresis curve, whose origin 0 for better clarity in the origin of

Coordinate system has been relocated. The hysteresis curve

describes the hysteresis of the deflection (in μτ) of the

piezoelectric body 1 in response to an applied external electric field (in kV / mm) after completion of the polarization process with the first

electric polarization field El. The hysteresis of

Deflection of the piezoelectric body 1 in this case has an electric Koerzitivfeidstärke Ek.

An ordinary initial state of polarization or

Polarization state, for example, the one

electronic component of the prior art, which is polarized usually and without applying a mechanical counterforce corresponds to the point 0 (origin) in Figure 4b. Accordingly, the maximum, under one

positive electric field achievable deflection XI. The electric coercive field strength Ek corresponds

that electric field strength at which outside the origin the deflection is zero. The electrical coercive field intensity corresponds approximately to 1.2 to 1.3 kV / mm, that is approximately approximately the electric field strength at the point B. Here a domain flip-over by 180 ° takes place between points B and C, for example. The deflection between the points 0 and B or C and D, however, includes contributions from the actual, so not by Domainumklappung

caused piezoelectric effect and one

Domain flip around "not 180 °".

By the manufacturing method, in particular by the second, opposite to the first polarizing field El

aligned second polarization field E2 can now

Preferably, the initial state of the polarization from the point 0 to the point N are laid. The closer the

Initial state is at point B, the greater is the achievable deflection of the electronic component 100, when a positive electrical operating field is applied during operation. Accordingly, the maximum achievable

Deflection for an electronic component according to this

Invention X2 or approximately X2. Thus, the achievable deflection of the electronic component 100 during operation

compared with an electronic component which

according to a manufacturing or polarizing method of the prior art and / or without applying a

mechanical force was polarized to be increased by up to 75%. An increase in the deflection of piezoelectric ceramics can also be achieved by a change in the ceramic formulation

targeted addition of dopants or a reduction of the Curie temperature of the piezoelectric ceramic can be achieved, which also by changing the

Ceramic recipe is achievable. Other possibilities include the promotion of grain growth in the piezoelectric

Ceramics, also by an influence of the

Ceramic formulation or ceramic composition or the

corresponding sintering process. Also, an increase in the deflection of piezoelectric ceramics is possible by a polarization of the piezoelectric ceramic under a strong mechanical force or counterforce, especially at elevated temperatures. The proposed method can increase the maximum deflection that is possible with the measures mentioned.

It is also provided in the context of the present application that the first electric polarization field is negative and the second electric polarization field is positive. This embodiment is particularly useful in the case of a negative electrical operating field. The described embodiments apply analogously if a symmetrical butterfly curve is present.

FIG. 5 shows in simplified form alternative embodiments of time sequences of the first and second electric polarization fields E1 and E2. FIG. 5a shows a

Field course of the first and second electrical

Polarization field El and E2 according to the figure 2. The first and the second electric polarization field El and E2 are each formed by a single rectangular pulse 5. FIG. 5b shows a first and a second electrical

Polarization field El and E2 each formed by a single triangular pulse 6. In this case, as in FIGS. 2 and 5a, the second electric polarization field E2 was applied after the first electric polarization field E1 and, furthermore, the magnitude of the first electric polarization field E1 is greater than the magnitude of the second electrical field

Polarization field E2. The first electric

Polarization field El is also positive and the second polarization electric field E2 is negative.

The ratio of the duration in which the first electric polarization field El is applied to the duration in which the second electric polarizing field E2 is applied may be between 10: 1 and 1:10. Preferably, said ratio is between 2: 1 and 1: 2.

FIG. 5c shows in each case a chronological sequence of the first electric polarization field E1 and of the second one

electric polarization field E2, in contrast to the representation of Figure 5b both electrical

Polarization fields El and E2 or their courses one

Include a plurality of triangular coils. In other words, both electric polarization fields El and E2 are respectively pulsed, so that the piezoelectric base body 1 upon application of the first and second electrical

Polarization field El and E2 is polarized time-varying in each case.

In FIG. 5d, in contrast to FIG. 5c, where likewise the second electric polarization field E2 with triangular pulses is pulsed, the second electric polarization field E2 formed from a constant electric polarization field E2.

The pulse durations of the first and second electrical

Polarization field El and E2 are preferably greater than a millisecond, for example 10 milliseconds or greater. Furthermore, the pulse durations of the first and second electric polarization fields are El and E2

preferably less than 10 minutes, for example less than or equal to one minute.

Although not explicitly shown in part, the electric polarization fields and the field pulses of the first and second electric polarization fields may have one or more of the pulse shapes of a rectangular, triangular, trapezoidal and sinusoidal shape.

The pulsation of the electric polarization fields El and E2 during polarization produces waste heat, which can advantageously enhance the effect of polarization by as much as 20% over static or pulsed polarization, i. the orientation of the polarization of each ferroelectric domain 4 along the respective

applied electric polarization field is promoted with advantage.

Although not explicitly illustrated in the figures, in the context of the present application, a device for applying the mechanical force to the piezoelectric main body and to the electronic component can be provided. The invention is not limited by the description with reference to the embodiments. Rather, the includes

Invention every new feature as well as every combination of Features which in particular includes any combination of features in the claims, even if this feature or this combination itself is not explicitly in the

Claims or embodiments is given.

Reference sign list

1 Piezoelectric basic body

2 electrode

3 inner electrode

4 ferroelectric domain

5 square pulse

6 triangle pulse

100 electronic component

XI, X2 deflections

E Electric field

El First electric polarization field

E2 Second electric polarization field

Claims

claims

A method of manufacturing an electronic component (100) comprising the following steps:

- Providing a piezoelectric body (1) which is provided with electrodes (2);

- Applying a first electric polarization field (El) with a first polarity direction to the piezoelectric body (1) between the electrodes (2);

- Applying a second electric polarization field (E2) after the application of the first electrical

Polarizing field (El) in a second polarity direction opposite to the first polarity direction to the

piezoelectric body (1) between the electrodes (2), wherein the amount of the second electrical

Polarization field (E2) of that of the first

electric polarization field (El) is different;

- Completing the electronic component (100).

2. The method of claim 1, wherein relative to a predetermined electrical operating field of the electronic component (100), which is applied for operation between the electrodes (2), the first polarity direction is positive and the second polarity direction is negative.

3. The method according to claim 1 or 2, wherein the amount of the first electric polarizing field (El) is between 1 and 4 kV / mm.

4. Method according to at least one of the preceding

Claims, wherein the amount of the first electrical

Polarization field (El) is greater than the amount of the second electric polarization field (E2).

5. The method according to at least one of the preceding

Claims, wherein at the end of the polarization process with the first electric polarization field, the deflection of the piezoelectric body in response to the applied electric field of a hysteresis follows, which determines a Koerzitivfeidstärke (Ek), and wherein the magnitude of the second electric polarization field (E2) is smaller as the amount of electrical

Coercive field strength (Ek).

6. Method according to at least one of the preceding

Claims, wherein the first and / or the second electric polarization field (El, E2) have a temporal field profile with one or more electric field pulses.

7. The method of claim 6, wherein the field pulses of the first and / or the second electric polarization field (El, E2) each have at least one of the pulse shapes rectangular, triangular, trapezoidal and sinusoidal.

8. The method according to at least one of the preceding

Claims wherein the piezoelectric body (1) comprises a plurality of piezoelectric layers and is provided with a plurality of internal electrode layers (3), the electrodes (2) forming external electrodes

are arranged outside of the piezoelectric base body (1), and wherein each inner electrode layer (3) is electrically conductively connected to one of the outer electrodes.

9. The method according to at least one of the preceding

Claims, wherein the first and the second electrical

Polarizing field (El, E2) are selected such that the achievable deflection of the electronic component in operation compared with an electronic component, which

has been polarized by up to 60% according to a prior art manufacturing or polarizing process and polarized without application of mechanical force.

10. A method of operating an electronic component (100) made by the method of any one of claims 1 to 9, wherein the method of operation comprises applying a mechanical force to the electronic component (100).

11. A method of operation according to claim 10, wherein after

Applying the mechanical force to the electronic component (100) an electric operating field between the electrodes (2) is applied to the electronic component (100), wherein the electrical operating field is poled according to the first polarity direction.

12. An electronic component (100), which was prepared by the method according to at least one of claims 1 to 9.