DE102007003281A1 - Piezoelectric transformer and transformer arrangement - Google Patents

Abstract

A piezoelectric transformer is provided with a body (1) which has contact surfaces (3 ', 4', 6 ') arranged on its main surface. The linear cross-sectional size of the respective contact surface is a maximum of 200 microns.

Description

A piezoelectric transformer is from the documents JP 2002-299711 A . JP 2003-008098 A . US 6,172,447 B1 and US 6,346,764 B1 known.

A to be solved task is a piezoelectric Specify transformer, which is characterized by low parasitic Capacity and integration into electrical Components is suitable.

According to one First preferred embodiment is a piezoelectric Transformer with a body indicated on his Main surface arranged electrical contact surfaces has, which are provided as flip-chip contacts.

The linear cross-sectional size of at least one of Contact surfaces is a maximum of 200 microns.

Preferably applies to any contact surface that is linear Cross-sectional size, d. H. Diameter or width, maximum 200 microns.

The is the main surface provided with the contact surfaces preferably the lowest surface of the body. The remaining areas, d. H. the top and the Side surfaces of the body are preferably free of contact surfaces.

Of the piezoelectric transformer is hereafter piezotransformer called.

Of the specified piezoelectric transformer is as one for flip-chip mounting suitable chip implemented and thus for integration into highly integrated suitable for electrical modules. The piezotransformer can be a have very small size.

By particularly small contact surfaces manage to parasitic To keep capacities low. With a little parasitic Capacity can be especially high voltage applications a high transformation ratio of the transformer be achieved.

little one electrical contact surfaces are also advantageous in terms of low attenuation of the body excited mechanical vibrations, since in this case too Area of mechanical coupling between the body and a carrier connected thereto is very small.

According to one second preferred embodiment is a piezoelectric Transformer indicated with a body, on the underside of contact surfaces are arranged. The contact surfaces point to the outer edge of the body at a distance that is at least as large like an eighth-wavelength of the body to be excited mechanical vibrations.

According to one third preferred embodiment is a transformer assembly which is a piezoelectric transformer and a carrier includes. The piezoelectric transformer is on the carrier attached by flip-chip mounting.

According to one fourth preferred embodiment is a piezoelectric Transformer with a body specified, a first Function part and a second functional part as input part and Output part of the transformer comprises. In the body are Arranged electrodes of the transformer. The electrodes are preferably arranged inside the body. At least one of the electrodes may also be on the surface of the body, preferably on a main surface of the body, arranged be.

The Electrodes have superimposed common electrodes on, which extend over both functional parts and connected to a common potential. The respective common electrode is arranged between two electrodes of the first functional part. The respective common electrode is between two electrodes of the second Function part arranged. The functional parts are mechanical with each other connected and preferably arranged by a between the functional parts, essentially field-free isolation area of the body spaced apart. In the isolation area are only parts of Common electrodes present, d. H. the isolation area is free from the electrodes of the first and second functional part. The isolation area is perpendicular to the planes in which electrodes are arranged, aligned.

The Embodiments can be combined with one another as desired.

Of the Body comprises a first functional part and a second Functional part of the transformer, which mechanically coupled with each other are. The first functional part is for example an output part and the second functional part is an input part of the transformer, or the other way around.

Everyone Functional part comprises at least one a first electrical Potential associated first electrode and at least one second electrical potential associated second electrode.

To the electrodes of the input part is an electrical alternating voltage is applied, which causes there mechanical oscillations of the body due to an inverse piezoelectric effect. The mechanical vibrations of the body cause a potential difference between the electrodes of the output part. From the output part, an output voltage is tapped, which may differ from the input voltage by a transformation factor dependent on the structure of the transformer.

Of the Body comprises at least one piezoelectric layer, the preferably ceramic such. B. lead zirconate titanate (PZT) contains. Lead-free piezoelectric materials, preferably ceramics, come also into consideration. The body preferably comprises several piezoelectric layers.

Between two consecutive piezoelectric layers is one Plated metallization. Other metallization levels are provided on the top and bottom of the body. Each metallization level comprises at least one electrode of the respective functional part. The in the respective metallization level arranged electrode of the first functional part is in a variant surrounded annularly by an electrode of the second functional part.

The Contact surfaces are preferably in the lowest metallization level arranged. On a main surface called the bottom of the body are associated with two different potentials Contact surfaces of the first functional part and at least arranged a contact surface of the second functional part.

to Contacting the first functional part is a first contact surface and a second contact surface is provided. For contacting of the second functional part is a third contact surface intended. The second contact surface is in a variant for contacting both the first functional part and the second functional part provided. For contacting the second Function part is in a further variant in addition to the third Contact surface additionally a fourth contact surface intended.

in the Input part are caused by an AC voltage due to the inverse piezoelectric effect preferably mechanical vibrations in a lateral plane, d. H. parallel to the electrodes, excited. These vibrations cause a potential difference between the Electrodes of the output part.

The In one embodiment, electrodes comprise at least an external electrode attached to the surface of the body and therefore as an outer electrode is designated. The outer electrodes can open the top as well as on the bottom of the body arranged be. A arranged on the bottom, relatively large area Outer electrode is in an advantageous variant of Formation of a relatively small contact area down to the area passivated this contact surface. On this outer electrode can, with the exception of that provided as a contact surface Area of the outer electrode, a passivation layer be applied. The passivation layer may be an organic or contain inorganic material. For example, silicon dioxide, Glass or composite materials. The outer electrode may alternatively have a partially oxidized surface.

In An advantageous variant is on the bottom of the body a first outer electrode and a second outer electrode arranged. The first outer electrode belongs to the first functional part and the second outer electrode the second functional part of the transformer. The outer electrodes are from each other z. B. galvanically isolated by a gap. The first outer electrode is up to an area that as the first contact surface is provided, preferably passivated. The second outer electrode is up to an area that as the third contact surface is provided, preferably passivated.

The first outer electrode has in a variant at least a recess in which the from this outer electrode electrically insulated second contact surface is arranged. The fourth contact surface may be in the recess of the first Outer electrode and / or in a recess of the second Be arranged outside electrode.

In a variant is the second outer electrode with the third Contact surface, the second contact surface and the fourth contact surface in a recess of the first outer electrode arranged, which is annular. The first outer electrode has preferably indentations in which the second, third and fourth Contact surface protrudes. The second outer electrode preferably has recesses into which the first, third and fourth contact surface protrudes.

The Electrodes of the respective functional part comprise in an advantageous manner Variant also at least one internal electrode, but preferably a plurality of internal electrodes, hereinafter be referred to as internal electrodes. The internal electrodes are inside the body in each case between two piezoelectric Layers arranged.

First electrodes of the respective functional part are conductively connected to a first contact surface and second electrodes of this functional part are connected to a second contact surface. In different chen Metallisierungbenbenen arranged electrodes of a functional part, which are assigned to one and the same potential, are conductively connected by means of plated-through holes with each other and with one of the contact surfaces. A first through-connection is provided for connecting first electrodes and a first contact surface of the first functional part. A second through-connection is provided for connecting second electrodes and a second contact surface of the first functional part. Also, for connecting first or second electrodes of the second functional part with a contact surface assigned to them, a respective through-connection is provided in each case.

In a variant are those with different electrical potentials to be connected electrodes of the respective functional part of each other arranged. An electrode of the first functional part is in one Level arranged adjacent to an electrode of the second functional part. For example, the electrode of the second functional part the arranged in the same plane electrodes of the first functional part surround. The second functional part surrounds the first functional part.

First Electrodes, the superimposed first internal electrodes and a contact surface conductively connected thereto, have in a variant in each case at least ei ne recess. In the recess of a first electrode preferably protrudes a projection a second electrode arranged in the same plane. In the each recess is a via in a variant arranged, the second internal electrodes connects. The Through-connection preferably occurs in the respective plane the projection of the second electrode. The respective recess can the Have the shape of an opening or indentation.

Both Functional parts are in a variant to a common potential connected. At least one common electrode extends in this variant over both functional parts. Also several, underneath, conductive via a via interconnected electrodes may be the two functional parts belong.

Of the Piezotransformator is preferably on a carrier substrate attached in a flip-chip design. They are on the bottom the body arranged contact surfaces of the transformer arranged with those on the top of the carrier substrate Contact surfaces z. By means of bumps, BGA (Ball Grid Array) or LGA (Land Grid Array).

The Carrier substrate is in a variant as a circuit board executed. The carrier substrate is in another Variant on the basis of a ceramic, such. As an LTCC substrate, executed. LTCC stands for Low Temperature Co-Fired Ceramics.

A through bumps realized electrical connection between the body and the carrier substrate also provides a mechanical connection through which transmit the vibrations of the body to the carrier substrate which can lead to undesired damping from mechanical vibrations of the body can. This effect can be explained by a below Design of the bumps and an advantageous arrangement of the contact surfaces be reduced.

The Bumps can also be designed in the form of a ball grid array be. A Landgrid array is also possible.

The Contact surfaces point to the outer edge of the body a distance that is at least as large as one 8th wavelength of the mechanical stimulated in the body Vibration.

Preferably are all contact surfaces in an area of the body surface arranged in a wave node area or nearby a wave node region of the body is arranged, in which the oscillation amplitude or the material deflection least is. Thus, it succeeds, the electrical connections between the Relieve the body and the carrier substrate mechanically and such a possible cracking of the body in the area prevent the contact surfaces. This increases the Reliability of the arrangement, the piezotransformer and the carrier.

to Reduction of vibration damping are bumps that one Core with elastic properties include, especially advantageous. The elastic core may be an elastic material such. B. thermoplastics or duromers. As thermoplastics, for example Polyamides or polyesters into consideration. As thermos come, for example Epoxy resins into consideration. Silicone may also be suitable. The elastic Core has an electrically conductive, preferably metallized surface. The elastic core may also be electrically conductive, being, for example, electrically insulating base material z. B. is filled with conductive particles.

Of the Body can be a square, rectangular or too have any polygonal cross-section. The body with a round, oval or elliptical cross section, so a largely cylindrical body, however, is particularly advantageous.

The contact surfaces are preferably in equidistant from the center of the underside of the body. The contact surfaces are preferably arranged on an imaginary circle at regular intervals of 360 ° / n, where n is the number of contact surfaces. The piezotransformer with such an arrangement of contact surfaces is characterized by a very high mechanical stability.

In an advantageous embodiment, three contact surfaces provided that determine a plane. The offset of 120 ° between These contact surfaces will be special in this case considered advantageous.

Of the Piezotransformator will now be based on schematic and not to scale Figures explained. Show it:

1A in cross-section a piezo transformer, which is mounted in a flip-chip construction on a carrier substrate;

1B View of the underside of the piezotransformer according to the 1A ;

1C another embodiment of the in the 1A shown piezotransformer;

2A in cross-section a piezo transformer in a multi-layer construction, which has suitable contact surfaces for a flip-chip connection;

2 B View of a first inner metallization of the piezoelectric transformer according to the 2A ;

2C View of a second internal metallization of the piezoelectric transformer according to the 2A ;

2D View of the lowest level of metallization of the piezotransformer according to the 2A ;

3A . 4A in cross section in each case a further piezotransformer;

3B . 4B the view of the bottom of the piezotransformer according to the 3A respectively. 4A ;

3C . 4C the view of the top of the piezotransformer according to the 3A respectively. 4A ,

In the 1A and 1B is a first piezotransformer with a body 1 explained. The body 1 in this variant comprises a single piezoelectric layer 95 which is arranged between two metallization levels.

In the lowest metallization level is a substantially round first electrode 4 and a substantially annular second electrode 3 arranged. The electrodes 3 . 4 are through a substantially annular gap 11 electrically isolated from each other. The electrodes 3 . 4 are preferably provided as signal electrodes.

In the uppermost metallization level, a third electrode, preferably provided as a ground electrode, is provided 6 arranged, which represents a common electrode for both functional parts of the transformer. The third electrode 6 is from the first and second electrodes 4 . 3 galvanically isolated.

The first electrode 4 has a projection that acts as a first contact surface 4 ' is provided. The second electrode 3 has a projection that acts as a second contact surface 3 ' is provided. The first electrode 4 has a recess in which the second contact surface 3 ' is arranged. The second electrode 3 has a recess in which the first contact surface 4 ' is arranged.

The first electrode 4 can be down to the area of the contact area 4 ' be passivated. The second electrode 3 can be down to the area of the contact area 3 ' be passivated.

In the lowest metallization level is a third contact surface 6 ' arranged by the electrodes 3 . 4 electrically isolated and with the third electrode 6 by means of a via 7 is conductively connected. The electrodes 3 . 4 each have a recess in which the third contact surface 6 ' is arranged.

The first electrode 4 and a region of the third electrode opposite it 6 is assigned to a first functional part, preferably the output part, of the transformer. The second electrode 3 and an opposing annular portion of the third electrode 6 is assigned to a second functional part, preferably the input part, of the transformer. The centrally located first electrode 4 can in a further variant of the input part and arranged in the edge region of the bottom surface of the second electrode 3 be assigned to the output part of the transformer.

The piezotransformer is soldered using bumps 8th . 9 . 10 - With contact surfaces of a carrier substrate 2 conductively connected. The bump 10 connects the contact surface 4 ' with a first contact surface of the carrier substrate 2 , The bump 8th connects the contact surface 3 ' with a second contact surface surface of the carrier substrate 2 , The bump 9 connects the contact surface 6 ' with a third contact surface of the carrier substrate 2 ,

In a variant it is possible to use the third electrode 6 in the lowest metallization level and the electrodes 3 . 4 to arrange in the top metallization. In this case, the third electrode includes 6 the third contact area 6 ' , which can be realized in the form of a projection of this electrode. The third electrode 6 can in this case down to the area of the contact surface 6 ' be passivated. The electrode 3 is by means of a first via contact with the contact surface 3 ' and the electrode 4 by means of a second through-connection with the contact surface 4 ' conductively connected. The contact surface 3 ' is in a first recess and the contact surface 4 ' in a second recess of the third electrode 6 arranged. The contact surfaces 3 ' . 4 ' in this case are in the same metallization plane as the third electrode 6 arranged.

The above-described embodiment of the contact surfaces 3 ' . 4 ' . 6 ' also applies to embodiments described below.

In the 1C is an embodiment of the transformer with a further dielectric, preferably piezoelectric layer 96 shown. The layer 96 covers the electrodes 3 . 4 with contact surfaces lying on the underside of the body 3 ' and 4 ' are conductively connected by means of a respective via. The layer 96 preferably has the properties of a passivation layer. The dielectric constant of this layer is preferably smaller than that of the piezoelectric layer 95 ,

In a variant, as in the 1C indicated a dielectric layer 97 provided the upper electrode 6 covered. It preferably has the same properties as the layer 96 ,

In the 2A to 2D a further embodiment of a piezoelectric transformer is shown.

The body 1 here comprises a plurality of electrodes arranged one above the other 3 , a plurality of superimposed electrodes 4 and a plurality of electrodes arranged one above the other 6 ,

The electrodes 3 are by means of a via 13 with each other and with a contact surface 3 ' conductively connected. The electrodes 4 are by means of a via 12 with each other and with a contact surface 4 ' conductively connected. The electrodes preferably provided as ground electrodes 6 are by means of the via 7 with each other and with the contact surface 6 ' conductively connected. The contact surface 6 ' is in 2D bounded by a dashed line. The lowest electrode 6 is passivated to this contact surface.

The contact surface 3 ' is in the recess 11a ' the lowest electrode 6 and the contact area 4 ' in the recess 11b ' the electrode 6 arranged.

The via 12 is electrical from the electrodes 3 . 6 isolated. The via 12 is through the recesses 11b . 11b ' electrically from the electrodes 6 isolated. The via 13 is electrical from the electrodes 4 . 6 isolated. The via 13 is through the recesses 11a . 11a ' electrically from the electrodes 6 isolated. The via 7 is electrical from the electrodes 3 and 4 isolated. The via 7 is in the recess 11 ' the electrode 3 arranged. The electrical insulation is realized by a recess in the respective electrode from which the via is to be isolated.

The electrodes 6 extend over both functional parts of the transformer. The internal electrodes 6 each have a first recess 11b on, in which the via 12 is arranged. They also have a second recess 11a on, in which the via 13 is arranged. The electrode located on the underside 6 has a first recess in which the contact surface 4 ' is arranged, as well as a second recess in which the contact surface 3 ' is arranged. The electrode located on the underside 6 includes the contact surface 6 ' ,

The electrodes 3 . 4 are in the respective metallization plane through a gap 11 electrically isolated from each other. The electrodes 3 each have a recess 11 ' on, in which the via 7 is arranged.

The electrodes 4 and first areas of the electrode 6 are alternately stacked to form the first functional part. The electrodes 3 and second regions of the electrode 6 are alternately stacked to form the second functional part.

The arrangement of a ground electrode 6 on the bottom as well as on top of the body 1 is particularly advantageous, since thus an electromagnetic shielding of internal signal electrodes 3 . 4 can be achieved. As a result, electromagnetic interference that can affect the electrical properties of the transformer can be reduced.

In the 3A . 3B and 3C is a further piezotransformer presented. In contrast to the above-described piezotransformer the functional parts of the transformer are galvanically separated from each other. The electrodes 3 . 6 are the first functional part and the electrodes 4 . 5 assigned to the second functional part.

The body 1 is by means of bumps 32 . 42 . 52 . 62 with the carrier substrate 2 connected. The bumps are here, as well as in the variant according to the figures 1A . 1B equidistant from the center of the bottom surface of the body, evenly spaced along an imaginary circle. The imaginary circle is indicated by a dashed line.

The electrodes arranged on the top of the body 5 . 6 are each by means of a via 52 ' respectively. 62 ' with a contact surface arranged on the underside 51 respectively. 61 conductively connected. The contact surface 51 is in a recess 11 the electrode 4 and the contact area 61 in a recess 11 the electrode 3 arranged.

The electrodes 5 . 6 are through a gap 11b electrically isolated from each other. The electrodes 3 . 4 are also through a gap 11a electrically isolated from each other.

In the 4A . 4B and 4C another piezotransformer is presented. Also in this case, the functional parts of the transformer are galvanically separated from each other. In contrast to the variant according to the 3A - 3C the first functional part is surrounded by the second functional part. The electrodes 3 . 6 of the second functional part are largely annular and the electrodes 4 . 5 largely circular or disc-shaped.

The electrodes arranged on the underside 3 . 4 each have a projection to form a contact surface. The electrodes 3 . 4 also have recesses in which the electrically isolated from these electrodes contact surfaces 51 . 61 are arranged.

The design of the piezotransformer is not limited to the examples presented in the figures, in particular the shape and number of elements shown. For example, the in 1A . 1B . 3A - 3C . 4A - 4C presented piezotransformer be formed with a body in multilayer technology, wherein external electrodes are connected to internal electrodes by means of vias.

1

body

2

carrier substrate

3, 4, 5, 6

Conductor surface / electrode

3 ', 4 ', 5', 6 '

contact area

7

via

8th, 9, 10

bumps

11 11 '

gap

11a, 11b

Gap / recess

11a ', 11b '

Gap / recess

12

via

13

via

32 42

bumps

51 61

contact area

52 62

bumps

52 ', 62 '

via

95

piezoelectric layer

96 97

dielectric layer

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 2002-299711A [0001]
• JP 2003-008098 A [0001]
• - US 6172447 B1 [0001]
• - US 6346764 B1 [0001]

Claims (17)

Piezoelectric transformer - with one body ( 1 ), the contact surfaces arranged on its main surface ( 3 ' . 4 ' . 6 ' ), wherein the linear cross-sectional size of at least one of the contact surfaces 200 Micrometer does not exceed. Transformer according to claim 1, - with at least one electrode arranged on the surface of the body ( 3 ), which has a first contact surface ( 3 ' ), wherein this electrode in the from the first contact surface ( 3 ' ) is passivated in different areas. Transformer according to claim 2, - wherein the electrode arranged on the surface ( 3 ) at least one recess ( 11 ), in which at least one of said electrode electrically isolated second contact surface ( 4 ' . 51 . 61 ) is arranged. Transformer according to one of claims 1 to 3, - with internal electrodes which are in the body ( 1 ) are arranged, - wherein each of an electrical potential associated with internal electrodes by means of plated-through holes ( 7 . 12 . 13 ) conductive with each other and with the contact surfaces ( 3 ' . 4 ' . 6 ' ) are connected. Transformer according to one of claims 1 to 4, - wherein the body ( 1 ) comprises a first functional part and a second functional part as an input part and output part of the transformer, - wherein electrodes of the respective functional part are arranged one above the other. Transformer according to claim 5, - wherein the body ( 1 ) - wherein at least one Metallisierungsebene a first electrode and a second electrode is arranged, - wherein the first electrode is associated with the first functional part and the second electrode associated with the second functional part. Transformer according to claim 6, - wherein the at least one metallization plane with the first and the second electrode inside the body ( 1 ) is arranged. Transformer according to claim 6 or 7, - in which the second electrode surrounds the first electrode. Transformer according to one of claims 6 to 8, - wherein inner second electrodes ( 3 ) Recesses ( 11 . 11 ' ), in which the plated-through holes ( 7 . 12 ), the inner first or third electrodes ( 4 . 6 ), and / or - wherein inner first electrodes ( 4 ) Have recesses in which the plated-through holes are arranged, the inner second or third electrodes ( 3 . 6 ) connect. Transformer according to one of the claims 5 to 9, - At least one inside Electrode extends over both functional parts. Transformer according to one of claims 1 to 10, - wherein the contact surfaces ( 3 ' . 4 ' . 6 ' ) to the outer edge of the body ( 1 ) have a distance which is at least as large as an eighth-wavelength of the mechanical vibration to be excited in the body. Transformer according to one of the claims 1 to 11, on a carrier substrate in a flip-chip design is attached. Piezoelectric transformer - with one body ( 1 ), on the underside of which contact surfaces ( 3 ' . 4 ' . 6 ' ), wherein the contact surfaces to the outer edge of the body have a distance which is at least as large as an eighth wavelength of the mechanical vibration to be excited in the body. transformer assembly - with a piezoelectric transformer and a carrier, wherein the piezoelectric transformer on the carrier in one Flip-chip assembly is attached. Trans formator arrangement - with a Piezoelectric transformer according to one of the claims 1 to 13 and a carrier, wherein the piezoelectric transformer is mounted on the carrier in a flip-chip arrangement. Piezoelectric transformer - with one body ( 1 ) comprising a first functional part and a second functional part as an input part and an output part of the transformer, - with electrodes which are in the body ( 1 ) are arranged one above the other, - wherein the electrodes have stacked common electrodes extending over both functional parts and connected to a common potential. are, - where between the functional parts of an isolation is arranged, which is aligned perpendicular to the planes in which electrodes are arranged. Transformer according to claim 16, - in which the respective common electrode between two electrodes of the first Function part is arranged, and - where the respective Common electrode between two electrodes of the second functional part is arranged.