CA1071751A - Piezoelectric tuning device and method for making the same - Google Patents
Piezoelectric tuning device and method for making the sameInfo
- Publication number
- CA1071751A CA1071751A CA217,054A CA217054A CA1071751A CA 1071751 A CA1071751 A CA 1071751A CA 217054 A CA217054 A CA 217054A CA 1071751 A CA1071751 A CA 1071751A
- Authority
- CA
- Canada
- Prior art keywords
- electrodes
- thin films
- piezoelectric
- conductive means
- tuning device
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims description 15
- 239000010409 thin film Substances 0.000 claims abstract description 42
- 239000004033 plastic Substances 0.000 claims abstract description 29
- 229920003023 plastic Polymers 0.000 claims abstract description 29
- 239000010408 film Substances 0.000 claims description 14
- 239000002390 adhesive tape Substances 0.000 claims description 13
- 239000000843 powder Substances 0.000 claims description 7
- 229920005989 resin Polymers 0.000 claims description 7
- 239000011347 resin Substances 0.000 claims description 7
- 239000003822 epoxy resin Substances 0.000 claims description 5
- 229920000647 polyepoxide Polymers 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 4
- 238000000151 deposition Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 1
- 230000001902 propagating effect Effects 0.000 claims 1
- 229910003781 PbTiO3 Inorganic materials 0.000 description 3
- 238000007792 addition Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 241000182988 Assa Species 0.000 description 1
- 229920000298 Cellophane Polymers 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000007772 electroless plating Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000001883 metal evaporation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000001259 photo etching Methods 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/05—Holders; Supports
- H03H9/10—Mounting in enclosures
- H03H9/1007—Mounting in enclosures for bulk acoustic wave [BAW] devices
- H03H9/1042—Mounting in enclosures for bulk acoustic wave [BAW] devices the enclosure being defined by a housing formed by a cavity in a resin
Landscapes
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE A piezoelectric tuning device having a thin piezoelectric plate which has a pair of elec-trodes thereon and conductive means extending there-from. The surface of the electrodes are covered with thin films and electrical load terminals are connected to the conductive means. The thin piezo-electric thin plate covered with the thin films embedded in a plastic body without an air space between the plastic body and the thin plate and the ends of the electrical terminals extend through and out of the plastic body. This tuning device has excellent electrical and mechanical properties.
Description
BACKGROUND OF THE INVENTION
This invention relates to a piezoelectric tuning device and a method for making the same.
Piezoelectric resonators vibrating in the thickness mode of vibration are usually housed in a plastic casing and are used for tuning devices such as filters, oscillators, and the like. They are housed in a manner such that the plastic case and at least the surfaces of vibrating area of a resonator element have a free space therebetween.
Usually, no effort is made to eliminate the free spaGe because this deteriorates the vibration re-sponse characteristics of the resonator element.
SUMMARY OF THE INVENTION
.
It is an object of this invention to pro-vide a piezoelectric turning device and a method for making the same in which a plastic casing dir-ectly contacts a piezoelectric (resonator) element, i.e. there is no air space therebetween, and which device has excellent electrical and mechanical properties.
This object is achieved according to this invention mainly by utilizing a thin film between the piezoelectric element and the plastic casing.
The piezoelectric tuning device according to this invention comprises a plastic casing having ~107~751 no air space therein, and an assembly of a piezoelectric element having at least one pair of electrodes, thereon, electrically condu¢tive means connected to said elec-trodes, electrical lead terminals connected to said con-ductive means and thin films covering at least the entire surfaces of said electrodes, said films being of a ma-terial for substantially preventing vibrations from the piezoelectric element from being transferred to the plastic casing, said assembly being embedded in the plastic of said casing with said plastic being in direct contact with said thin films, said piezoelectric element having a first region on which said electrically con-ductive means is deposited, said piezoelectric element having a thickness for vibrating in a thickness mode of vibration at a pre-selected frequency when an electric signal is applied between said pair of electrodes through said electrical lead terminals and said 7175~ :
conductive means, the maximum length of the elec-trodes being less than twenty times the thickness of the piezoelectric element so as to prevent a thickness vibration wave induced at the first re-gion from propogating to the second region, the thin film covering at least the entire surfaces of the electrodés, and one end of the electrical lead terminals protruding out of the plastic casing. The thin film can be a paper film or an organic resin film. Adhesive tape can be adhered over the thin fi~ms for holding the thin films on the electrodPs.
The method for making the piezoelectric tuning device, comprises the steps of: attaching at least one pair of electrodes to a piezoelectric element; attaching at least one pair of electrically conductive means to said piezoelectric element, ea~h of said electrically conductive means being in con-tact, at one end thereof, with a corresponding one of said electrodes; attaching an electrical lead terminal to the other end of each of said electri-cally conductive means; depositing a thin film at least on the whole surface of each of said elec-trodes so as to form a unitary body comprising said piezoelectric element, said conductive means, said electrical lead terminals and said thin films;
and embedding said unitary body in an organic epoxy ~ 1071751 ,.'`
resin as a plastic casing with said electrical lead terminals partially protruding out of said plastic casing. The thin films can be prelimin- -arily deposited on an adhesive tape and the ad-hesive tape applied over the piezoelectric element and the electrodes so as to sandwich said thin fi~ between said electrode and said adhesive tape.
The embedding step can comprise pre- ~ ;
heating said unitary body, embedding said unitary body in an organic epoxy resin powder, and ther-mally hardening the powder attached to said unitary body.
BRIEF DESCRIPTION OF THE DRAWINGS
The above mentioned and other objects and features of this invention will become appar-ent from the following description taken together with the accompanying drawings in which:
Fig. 1 is a schematic perspective view, partly in section, of one example of a piezoelec-tric tuning device according to this invention;
Fig.,2 and Fig. 3 are schematic perspec-tive views showing piezoelectric resonator elements which vibrate in the thickness-mode and which are used in this invention;
Fig. 4 schematically shows a method for making a piezoelectric tuning device according to this invention; and ~7~75~ ::
Fig. 5 is a graph showing the frequency response curve of a typical piezoelectric tuning device according to this invention and the frequency response curve of a piezoelectric tuning device similar to that of this invention but not using a thin film between the plastic casing and the piezo-electric element.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Fig. 1, a piezoelectric tun-ing device comprises a plastic casing 40 in which a piezoelectric element 1 in a plate form having a pair of electrodes 10 and 12, on opposite sides thereof, electrically conductive means 14 and 16 connected to the respective electrbdes 10 and 12 and extending to the edge of said plate 1, and electrical lead terminals 18 and 2~ connected to the conductive means 14 and 16 are housed with thin films 30 and 32 between the plastic casing 40 and the piezoelectric element 1. There is no air space between the piezoelectric element 1 and each of the thin films 30 and 32 nor between the plastic casing 40 and each of the thin films 30 and 32. Therefore, the piezoelectric tuning de-vice of this invention can be easily made, and is mechanically stronger than a tuning device which has such spaces. The number of the pairs of elec-trodes is not necessarily one. It can be plural. -.
1~71751 If the number of the electrode pairs increases, the num~er of the conductive means and the number of the electrical lead terminals should also in-crease accordingly. The plastic casing 40 can be formed by any available and suitable method such as casting, molding, coating and dipping e.g.
of an organic resin. The size of the casing 40 is not critical. The casing 40 is only required to have embedded therein the unitary body compris-ing the piezoelectric element, electrodes, conduc-tive means, thin films and parts of the electrical lead terminals. The function of the thin films 30 and 32 is to substantially prevent the vibration induced in the piezoelectric element 1 from being transferred to the plastic casing 40. For this function of the films 30 and 32, the material of the thin films 30 and 32 can be selected e.g. from among such films as paper films and organic resin or plastic films such as Teflon (trademark) films, Cellophane (tradsmark) films, and the like. The thickness of the thin films can be chosen fairly freely.
In view of the frequency response of the resultant device, the upper limit thereof is not critical.
Too small thickness of the thin films will not contribute to the prevention of the vi~ration transfer, of course, but the lower limit of the thickness of the thin ~o7~75~
films which can be applied to any device cannot be defined ~umerically. The lower limit thereof de-pends mainly on the vibration frequency of the pie-zoelectric resonator element. For example, when the vibration frequency is lMHz, a preferable thick-ness of the thin films is about 10 ~ to about 100 ~ .
Details of the pieæoelectric element 1 will be illustrated with reference to Fig. ~ and Fig 3. In Fig. 2 and Fig. 3, the piezoelectric element 1 is a plate of piezoelectric material such -~
as a piezoelectric ceramic material and/or a pie-zoelectric crystal. The thickness of the piezo-electric element 1 is such that it will vibrate in the thickness mode of vibration at a pre-selected frequency, when an electrical signal is applied be-tween the pair of electrodes 10 and 12 through the lead terminals 18 and 20. The piezoelectric element 1 has a first region 2 and a second region 3 on which the electrodes 10 and 12 and the electrically conductive means 14 and 16 are deposited, respect-ively. The electrodes and the electrically conduc-tive means can be deposited by any available and suitable method such as a metal evaporation and and electroless plating together with, for example, a photo etching technique which is usually used e.g. for an electrode coating process of a semi-conductor device. The electrodes 10 and 12 can .
: : . . .
~c~7~75~
. .
have any shape such as a circular form, a rectang~
ular form, an elliptic form or other irregular form.
The Figures here show the case when it is a rec-tangular form. A maximum dimension of the electrodes, that is e.g. a diameter for the circular electrodes -;
or a diagonal length for the rectangular electrodes or a longest straight line length of an electrode of irregular form, is less than twenty times than the thickness of the piezoelectric element. The electrode length is important to confine the thick-ness vibration energy induced by the electrical signal in the first region of the piezoelectric element. The conductive means 14 and 16 are provided to electrically connect the electrical terminal 18 to the electrode 10, and connect the electrical ter-mînal 20 to the electrode 12, respectively. If the conductive means 14 and 16 are deposited on the second region so as to face each other through the second region (i.e. if these conductive means over-lap each other in such a `to~ plan view as Fig. 4), undesired vibration responses will be produced.
Therefore, the conductive means 14 and 16 should be deposited on the second region so as not to face each other through the second region. The electri-cal terminals 1$ and 20 are conductive metal wires and/or conductive metal sheets. One end of each of the terminals 18 and 20 is connected to ~he ~ 1~717Sl other end of the respective conductive means 14 and 16. This connection can be made e.g. by solder- ;
ing or ultrasonic bonding of a conductive material and/or applying a conductive adhesive. The material for the terminals 18 and 20 should be deposited on the surfaces of the second region (on which the vibration energy of the thickness mode does not pro-pagate~3 not on the surfaces of the first region, i.e. the terminals 18 and 20 should not directly con-tact the electrodes 10 and 12.
A method for making the piezoelectric tuning device according to this invention will be described hereinbelow. Referring to Fig. 4 (Fig. 4 shows one piezoelectric tuning device of a plurality of piezoelectric tuning devices which are made at the same time), the piezoelectric device according to this invention can be made e.g. by connecting the pieæoelectric element 1 having thereon electrodes 10 and 12 and the conductive means 14 and 16 to the electrical terminals 18 and 20, depositing the thin films 30 and 32 which thin films cover at least the entire surfaces of the electrodes 10 and covering both sides of the assembly with layers of adhesive tapes 34 and 36, cutting the ~nds of the adhesive tapes 34 and 36 along the lines 42 and 43, pre-heating the entire tape covered assa~ly, dipping it into an epoxy resin powder with the ends of the 1C~7i751 electrical terminals 18 and 20 extending out of the powder, thermosetting the e~oxy resin powder, and cutting the ends of the electrical terminals. Each of the thin films is, in the resulting structure, sandwiched between one of the electrodes and the corresponding achesive tape. The effect of using the adhesive tapes 34 and 36 is that the thin films can be easily deposited on the desired positions by pr~liminarily attaching the thin films to the adhesive tapes and the films do not slip out of position during the holding process. of course, it is not always necessary to use such adhesive tapes. One of the good methods which does not use an adhesive tape is to use thin films of large area size, and cut off unnecessary portions of the thin , films protruding out of the resultant plastic casing.
The influence of the thin films can be ex-plained with reference to Fig. 5. In Fig. 5, the curve ~) shows the frequency response curve of a typical piezoelectric tuning device of this inven-tion, and the curve (B) shows the frequency response curve of a piezoelectric tuning device which is similar to that of this invention but which does not include the thin films during the assembly process. In the devices used for obtaining the curves (A) and ~B). piezoelectric PbTiO3 ceramic ~7~751 plates were used for the resonator elements and were vibrating, during the measurements, in the third harmonic overtone of the thickness-extensional mode at a frequency of 40 MHz. There was no dif-ference between the cur~e ~A) and a curve obtained by measuring the response of the resonator before the addition of a housing. On the contrary, the curve lB) was clearly different from the curve ob-tained by measuring the resonator before the addi-tion of a housing, as is apparent from Fig. 5.
This clearly indicates that the vibration damping is very large for the piezoelectric tuning device having no thin film.
Equivalent circuit constants of the pie-zcelectric tuning device according to this invention (corresponding to the curve (A) in Fig. 5) are shown in Tahle. 1. In this case, a piezoelectric PbTiO3 ceramic plate having dimensions 4mm long, 3mm wide, and 0.2mm thick was used. Each electrode was a rectangular electrode 0.5x0.5 mm, and the vibration mode used was the third harmonic overtone of the thickness-extensional mode.
1~7~751 Table 1 ,:
resonance frequency 40.000 MHz anti-resonance frequency 40.235 MHz electro-static capacity 3.6 pF
motional capacity 0.04 pF
motional inductance 3`~0 ~Mz motional resistance ~80 capacitance ratio ~85 tuning quality factor , 1200 As shown in Table 1, the tuning quality factor Q was 1200 and the value is almost the same as the quality factor of the PbTiO3 ceramic material.
These experimental results clearly show that the piezoelectric plate vibrating in the thick-ness mode can be embedded in a casing of an organic resin ~without any air space between the piezoelec-tric plate and the casing) without changing the vibration response characteristics, by using a thin film. In other words, the thin film can stop the vibration energy flow from the first region to the epoxy resin (plastic) casing.
From the above description and the draw-ings of the embodiments chosen as examples of the principles of both the method and article aspects , . ~, - ~ , .
1~7175~
of this invention, it will be clear to those skilled in the art that certain minor modifications and var-iations may be employed without departing from the essence and true spirit of this invention. Accord-ingly, it is to be understood that this invention should be deemed limited only by the fair scope of claims that follow and equivalents thereto.
: -13-
This invention relates to a piezoelectric tuning device and a method for making the same.
Piezoelectric resonators vibrating in the thickness mode of vibration are usually housed in a plastic casing and are used for tuning devices such as filters, oscillators, and the like. They are housed in a manner such that the plastic case and at least the surfaces of vibrating area of a resonator element have a free space therebetween.
Usually, no effort is made to eliminate the free spaGe because this deteriorates the vibration re-sponse characteristics of the resonator element.
SUMMARY OF THE INVENTION
.
It is an object of this invention to pro-vide a piezoelectric turning device and a method for making the same in which a plastic casing dir-ectly contacts a piezoelectric (resonator) element, i.e. there is no air space therebetween, and which device has excellent electrical and mechanical properties.
This object is achieved according to this invention mainly by utilizing a thin film between the piezoelectric element and the plastic casing.
The piezoelectric tuning device according to this invention comprises a plastic casing having ~107~751 no air space therein, and an assembly of a piezoelectric element having at least one pair of electrodes, thereon, electrically condu¢tive means connected to said elec-trodes, electrical lead terminals connected to said con-ductive means and thin films covering at least the entire surfaces of said electrodes, said films being of a ma-terial for substantially preventing vibrations from the piezoelectric element from being transferred to the plastic casing, said assembly being embedded in the plastic of said casing with said plastic being in direct contact with said thin films, said piezoelectric element having a first region on which said electrically con-ductive means is deposited, said piezoelectric element having a thickness for vibrating in a thickness mode of vibration at a pre-selected frequency when an electric signal is applied between said pair of electrodes through said electrical lead terminals and said 7175~ :
conductive means, the maximum length of the elec-trodes being less than twenty times the thickness of the piezoelectric element so as to prevent a thickness vibration wave induced at the first re-gion from propogating to the second region, the thin film covering at least the entire surfaces of the electrodés, and one end of the electrical lead terminals protruding out of the plastic casing. The thin film can be a paper film or an organic resin film. Adhesive tape can be adhered over the thin fi~ms for holding the thin films on the electrodPs.
The method for making the piezoelectric tuning device, comprises the steps of: attaching at least one pair of electrodes to a piezoelectric element; attaching at least one pair of electrically conductive means to said piezoelectric element, ea~h of said electrically conductive means being in con-tact, at one end thereof, with a corresponding one of said electrodes; attaching an electrical lead terminal to the other end of each of said electri-cally conductive means; depositing a thin film at least on the whole surface of each of said elec-trodes so as to form a unitary body comprising said piezoelectric element, said conductive means, said electrical lead terminals and said thin films;
and embedding said unitary body in an organic epoxy ~ 1071751 ,.'`
resin as a plastic casing with said electrical lead terminals partially protruding out of said plastic casing. The thin films can be prelimin- -arily deposited on an adhesive tape and the ad-hesive tape applied over the piezoelectric element and the electrodes so as to sandwich said thin fi~ between said electrode and said adhesive tape.
The embedding step can comprise pre- ~ ;
heating said unitary body, embedding said unitary body in an organic epoxy resin powder, and ther-mally hardening the powder attached to said unitary body.
BRIEF DESCRIPTION OF THE DRAWINGS
The above mentioned and other objects and features of this invention will become appar-ent from the following description taken together with the accompanying drawings in which:
Fig. 1 is a schematic perspective view, partly in section, of one example of a piezoelec-tric tuning device according to this invention;
Fig.,2 and Fig. 3 are schematic perspec-tive views showing piezoelectric resonator elements which vibrate in the thickness-mode and which are used in this invention;
Fig. 4 schematically shows a method for making a piezoelectric tuning device according to this invention; and ~7~75~ ::
Fig. 5 is a graph showing the frequency response curve of a typical piezoelectric tuning device according to this invention and the frequency response curve of a piezoelectric tuning device similar to that of this invention but not using a thin film between the plastic casing and the piezo-electric element.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Fig. 1, a piezoelectric tun-ing device comprises a plastic casing 40 in which a piezoelectric element 1 in a plate form having a pair of electrodes 10 and 12, on opposite sides thereof, electrically conductive means 14 and 16 connected to the respective electrbdes 10 and 12 and extending to the edge of said plate 1, and electrical lead terminals 18 and 2~ connected to the conductive means 14 and 16 are housed with thin films 30 and 32 between the plastic casing 40 and the piezoelectric element 1. There is no air space between the piezoelectric element 1 and each of the thin films 30 and 32 nor between the plastic casing 40 and each of the thin films 30 and 32. Therefore, the piezoelectric tuning de-vice of this invention can be easily made, and is mechanically stronger than a tuning device which has such spaces. The number of the pairs of elec-trodes is not necessarily one. It can be plural. -.
1~71751 If the number of the electrode pairs increases, the num~er of the conductive means and the number of the electrical lead terminals should also in-crease accordingly. The plastic casing 40 can be formed by any available and suitable method such as casting, molding, coating and dipping e.g.
of an organic resin. The size of the casing 40 is not critical. The casing 40 is only required to have embedded therein the unitary body compris-ing the piezoelectric element, electrodes, conduc-tive means, thin films and parts of the electrical lead terminals. The function of the thin films 30 and 32 is to substantially prevent the vibration induced in the piezoelectric element 1 from being transferred to the plastic casing 40. For this function of the films 30 and 32, the material of the thin films 30 and 32 can be selected e.g. from among such films as paper films and organic resin or plastic films such as Teflon (trademark) films, Cellophane (tradsmark) films, and the like. The thickness of the thin films can be chosen fairly freely.
In view of the frequency response of the resultant device, the upper limit thereof is not critical.
Too small thickness of the thin films will not contribute to the prevention of the vi~ration transfer, of course, but the lower limit of the thickness of the thin ~o7~75~
films which can be applied to any device cannot be defined ~umerically. The lower limit thereof de-pends mainly on the vibration frequency of the pie-zoelectric resonator element. For example, when the vibration frequency is lMHz, a preferable thick-ness of the thin films is about 10 ~ to about 100 ~ .
Details of the pieæoelectric element 1 will be illustrated with reference to Fig. ~ and Fig 3. In Fig. 2 and Fig. 3, the piezoelectric element 1 is a plate of piezoelectric material such -~
as a piezoelectric ceramic material and/or a pie-zoelectric crystal. The thickness of the piezo-electric element 1 is such that it will vibrate in the thickness mode of vibration at a pre-selected frequency, when an electrical signal is applied be-tween the pair of electrodes 10 and 12 through the lead terminals 18 and 20. The piezoelectric element 1 has a first region 2 and a second region 3 on which the electrodes 10 and 12 and the electrically conductive means 14 and 16 are deposited, respect-ively. The electrodes and the electrically conduc-tive means can be deposited by any available and suitable method such as a metal evaporation and and electroless plating together with, for example, a photo etching technique which is usually used e.g. for an electrode coating process of a semi-conductor device. The electrodes 10 and 12 can .
: : . . .
~c~7~75~
. .
have any shape such as a circular form, a rectang~
ular form, an elliptic form or other irregular form.
The Figures here show the case when it is a rec-tangular form. A maximum dimension of the electrodes, that is e.g. a diameter for the circular electrodes -;
or a diagonal length for the rectangular electrodes or a longest straight line length of an electrode of irregular form, is less than twenty times than the thickness of the piezoelectric element. The electrode length is important to confine the thick-ness vibration energy induced by the electrical signal in the first region of the piezoelectric element. The conductive means 14 and 16 are provided to electrically connect the electrical terminal 18 to the electrode 10, and connect the electrical ter-mînal 20 to the electrode 12, respectively. If the conductive means 14 and 16 are deposited on the second region so as to face each other through the second region (i.e. if these conductive means over-lap each other in such a `to~ plan view as Fig. 4), undesired vibration responses will be produced.
Therefore, the conductive means 14 and 16 should be deposited on the second region so as not to face each other through the second region. The electri-cal terminals 1$ and 20 are conductive metal wires and/or conductive metal sheets. One end of each of the terminals 18 and 20 is connected to ~he ~ 1~717Sl other end of the respective conductive means 14 and 16. This connection can be made e.g. by solder- ;
ing or ultrasonic bonding of a conductive material and/or applying a conductive adhesive. The material for the terminals 18 and 20 should be deposited on the surfaces of the second region (on which the vibration energy of the thickness mode does not pro-pagate~3 not on the surfaces of the first region, i.e. the terminals 18 and 20 should not directly con-tact the electrodes 10 and 12.
A method for making the piezoelectric tuning device according to this invention will be described hereinbelow. Referring to Fig. 4 (Fig. 4 shows one piezoelectric tuning device of a plurality of piezoelectric tuning devices which are made at the same time), the piezoelectric device according to this invention can be made e.g. by connecting the pieæoelectric element 1 having thereon electrodes 10 and 12 and the conductive means 14 and 16 to the electrical terminals 18 and 20, depositing the thin films 30 and 32 which thin films cover at least the entire surfaces of the electrodes 10 and covering both sides of the assembly with layers of adhesive tapes 34 and 36, cutting the ~nds of the adhesive tapes 34 and 36 along the lines 42 and 43, pre-heating the entire tape covered assa~ly, dipping it into an epoxy resin powder with the ends of the 1C~7i751 electrical terminals 18 and 20 extending out of the powder, thermosetting the e~oxy resin powder, and cutting the ends of the electrical terminals. Each of the thin films is, in the resulting structure, sandwiched between one of the electrodes and the corresponding achesive tape. The effect of using the adhesive tapes 34 and 36 is that the thin films can be easily deposited on the desired positions by pr~liminarily attaching the thin films to the adhesive tapes and the films do not slip out of position during the holding process. of course, it is not always necessary to use such adhesive tapes. One of the good methods which does not use an adhesive tape is to use thin films of large area size, and cut off unnecessary portions of the thin , films protruding out of the resultant plastic casing.
The influence of the thin films can be ex-plained with reference to Fig. 5. In Fig. 5, the curve ~) shows the frequency response curve of a typical piezoelectric tuning device of this inven-tion, and the curve (B) shows the frequency response curve of a piezoelectric tuning device which is similar to that of this invention but which does not include the thin films during the assembly process. In the devices used for obtaining the curves (A) and ~B). piezoelectric PbTiO3 ceramic ~7~751 plates were used for the resonator elements and were vibrating, during the measurements, in the third harmonic overtone of the thickness-extensional mode at a frequency of 40 MHz. There was no dif-ference between the cur~e ~A) and a curve obtained by measuring the response of the resonator before the addition of a housing. On the contrary, the curve lB) was clearly different from the curve ob-tained by measuring the resonator before the addi-tion of a housing, as is apparent from Fig. 5.
This clearly indicates that the vibration damping is very large for the piezoelectric tuning device having no thin film.
Equivalent circuit constants of the pie-zcelectric tuning device according to this invention (corresponding to the curve (A) in Fig. 5) are shown in Tahle. 1. In this case, a piezoelectric PbTiO3 ceramic plate having dimensions 4mm long, 3mm wide, and 0.2mm thick was used. Each electrode was a rectangular electrode 0.5x0.5 mm, and the vibration mode used was the third harmonic overtone of the thickness-extensional mode.
1~7~751 Table 1 ,:
resonance frequency 40.000 MHz anti-resonance frequency 40.235 MHz electro-static capacity 3.6 pF
motional capacity 0.04 pF
motional inductance 3`~0 ~Mz motional resistance ~80 capacitance ratio ~85 tuning quality factor , 1200 As shown in Table 1, the tuning quality factor Q was 1200 and the value is almost the same as the quality factor of the PbTiO3 ceramic material.
These experimental results clearly show that the piezoelectric plate vibrating in the thick-ness mode can be embedded in a casing of an organic resin ~without any air space between the piezoelec-tric plate and the casing) without changing the vibration response characteristics, by using a thin film. In other words, the thin film can stop the vibration energy flow from the first region to the epoxy resin (plastic) casing.
From the above description and the draw-ings of the embodiments chosen as examples of the principles of both the method and article aspects , . ~, - ~ , .
1~7175~
of this invention, it will be clear to those skilled in the art that certain minor modifications and var-iations may be employed without departing from the essence and true spirit of this invention. Accord-ingly, it is to be understood that this invention should be deemed limited only by the fair scope of claims that follow and equivalents thereto.
: -13-
Claims (7)
1. A piezoelectric tuning device comprising a plastic casing having no air space therein, and an assembly of a piezoelectric element having at least one pair of elec-trodes, thereon, electrically conductive means connected to said electrodes, electrical lead terminals connected to said conductive means and thin films covering at least the entire surfaces of said electrodes, said films being of a material for substantially preventing vibrations from the piezoelectric element from being transferred to the plastic casing, said assembly being embedded in the plastic of said casing with said plastic being in direct contact with said thin films, said piezoelectric element having a first region on which said electrodes are positioned, and a second region on which said electrically conductive means is deposited, said piezo-electric element having a thickness for vibrating in a thick-ness mode of vibration at a pre-selected frequency when an electric signal is applied between said pair of electrodes through said electrical lead terminals and said conductive means, the maximum length of said electrode being less than twenty times the thickness of said piezoelectric element so as to prevent the thickness vibration wave induced in said first region from propagating to said second region and one end of each of said electrical lead terminals protruding out of said plastic casing.
2. A piezoelectric tuning device as claimed in claim 1 wherein each of said thin films is a paper film.
3. A piezoelectric tuning device as claimed in claim 1 wherein each of said thin films is an organic resin film.
4. A piezoelectric tuning device as claimed in claim 1, wherein adhesive tape is adhered over thin films for holding said thin films on said electrodes.
5. A method of making a piezoelectric tuning device, comprising the steps of: attaching at least one pair of electrodes to a piezoelectric element; attaching at least one pair of electrically conductive means to said piezo-electric element, each of said electrically conductive means being in contact, at one end thereof, with a corresponding one of said electrodes; attaching an electrical lead terminal to the other end of each of said electrically conductive means;
depositing a thin film at least on the whole surface of each of said electrodes so as to form a unitary body comprising said piezoelectric element, said conductive means, said electrical lead terminals and said thin films; and embedding said unitary body in an organic epoxy resin as a plastic casing with said electrical lead terminals partially protruding out of said plastic casing.
depositing a thin film at least on the whole surface of each of said electrodes so as to form a unitary body comprising said piezoelectric element, said conductive means, said electrical lead terminals and said thin films; and embedding said unitary body in an organic epoxy resin as a plastic casing with said electrical lead terminals partially protruding out of said plastic casing.
6. A method for making a piezoelectric tuning device as claimed in claim 5, wherein each of said thin films is preliminarily deposited on an adhesive tape and said adhesive tape is applied over the piezoelectrical element and said electrodes so as to sandwich said thin films between said electrodes and said adhesive tape.
7. A method for making a piezoelectric tuning device as claimed in claim 5, wherein said embedding step comprises a pre-heating said unitary body, embedding said unitary body in an organic epoxy resin powder, and thermally hardening the powder attached to said unitary body.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9529174A JPS5122388A (en) | 1974-08-19 | 1974-08-19 | Atsudenshindosochi oyobi sonoseiho |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1071751A true CA1071751A (en) | 1980-02-12 |
Family
ID=14133658
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA217,054A Expired CA1071751A (en) | 1974-08-19 | 1974-12-30 | Piezoelectric tuning device and method for making the same |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5122388A (en) |
| CA (1) | CA1071751A (en) |
| FR (1) | FR2282747A1 (en) |
| GB (1) | GB1507333A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS587701Y2 (en) * | 1975-05-28 | 1983-02-10 | 日本特殊陶業株式会社 | Atsuden Rohaki |
| JPS58184919U (en) * | 1982-06-03 | 1983-12-08 | 株式会社村田製作所 | Electrode structure of piezoelectric vibrating parts |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2512878A (en) * | 1945-12-28 | 1950-06-27 | Brush Dev Co | Piezoelectric crystal |
-
1974
- 1974-08-19 JP JP9529174A patent/JPS5122388A/en active Granted
- 1974-12-30 CA CA217,054A patent/CA1071751A/en not_active Expired
-
1975
- 1975-01-16 FR FR7501306A patent/FR2282747A1/en active Granted
- 1975-05-21 GB GB2196875A patent/GB1507333A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5744048B2 (en) | 1982-09-18 |
| DE2504550B2 (en) | 1976-10-14 |
| FR2282747B1 (en) | 1978-02-03 |
| DE2504550A1 (en) | 1976-03-04 |
| JPS5122388A (en) | 1976-02-23 |
| GB1507333A (en) | 1978-04-12 |
| FR2282747A1 (en) | 1976-03-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 19970212 |
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| MKEX | Expiry |
Effective date: 19970212 |