CA1152586A

CA1152586A - Electronic component comprising at least one piezoelectric resonator and method of manufacture thereof

Info

Publication number: CA1152586A
Application number: CA000355524A
Authority: CA
Inventors: Raymond Huguenin; Gottfried Kuechli
Original assignee: DRYAN-FORDAHL TECHNOLOGIES SA
Current assignee: DRYAN-FORDAHL TECHNOLOGIES SA
Priority date: 1979-07-05
Filing date: 1980-07-04
Publication date: 1983-08-23
Also published as: IT8023198A1; US4445256A; GB2056764B; JPS5610723A; CH626479A5; FR2460565B1; IT1150027B; GB2056764A; FR2460565A1; IT8023198A0; DE3025477A1

Abstract

ELECTRONIC COMPONENT COMPRISING AT LEAST ONE PIEZOELECTRIC
RESONATOR AND METHOD OF MANUFACTURE THERF~F

ABSTRACT OF THE DISCLOSURE

An electronic component comprising at least one piezo-electric resonator and a process for mass production there-of include the superpositioning of n (n ~ 1) layers having one or several cut outs defining m (m ~1) resonating ele-ments. Such layers are separated by n - 1 intermediate la-yers in which are provided openings forming frames for the resonating elements. Two terminal layers providing covers in which are arranged blind cavities corresponding to the frames cover the assembly. The resonating elements are pro-vided with electrodes and the layers are fixed to one ano-ther by welding together of metaIlization layers. The com-ponent may be used as an individual resonator or as a multi-ple channel filter.

Description

~LS25~

BACKGROUND OF THE INVENTION
The invention concerns piezoelectric resonators and gen-erally electronic components comprising at least one such resonator.
The search for further improved manufacturing methods in order to permit mass production and resulting lowering of costs thereof has led to the conception of quartz resonators referred to as monolithic, that is to say such as described for instance in French patent applications Nos. 244 1959 and 244 1960 published on June 13, 1980, wherein the resonating element and its support are formed of and from a single piece of material. In such resonators the resonating ele-ment is cut out from a piezoelectric layer without being been detached therefrom: in the region of the non active zones the resonating element remains attached to the layer which thus forms a frame support. The resonant element is there-after provided with electrodes by metal deposits, and in the same manner its frame receives metallized tracks intended for electrical connection of the electrodes with the exterior as well as final assembly by welding of covers on each of the faces of the frame, this resulting in a high quality package.
This technique has led to the possibility of mass produc-tion of resonant elements associated with supports having an excellent mechanical resistance. However such individual elements must thereafter be separated from one another in order to realize the packaging and thus the methods of mass production must then be replaced by individual treatment.
Moreover it is to be noted that mass production processes have not, up to the present time, been applied except for simple units and never for more complex components which might for instance comprise several resonators and eventu-ally further electronic components which might possibly be in-` ~5;~5~6 tegrated therewith.

These limitations, and notably the fact that individual handling of the resonators for the operations of assembly and termination do not appear rational and are a source of time loss have led to efforts for developing new components utilising monolithic resonators to which may be applied ma-nufacturing processes permitting mass production, even for the more complex components comprising several resonators and eventually further elements which may be integrated on the same layer from which the resonators are obtained, thus permitting the realisation of hybride circuits.

SUMMARY OF THE INVENTION

The invention comprises an electronic component and method of manufacture thereof comprising m piezoelectric resonators (where m is an integer~l) being formed by the superpositioning of n layers of piezoelectric material (where n is an integer and m~n~l), each layer having at least one open cut out portion so as to define a zone which constitutes aresonant element and a zone which forms a fra-me support to which the resonant element remains attached, n - 1 intermediate layers of insulating material separating said layers of piezoelectric material from one another and in each of which is formed at least one opening forming fra-me of the same dimensions as corresponding frame supports in contiguous piezoelectric layers, two terminal layers of in-sulating material forming cover members in the thickness of each of which is arranged at least one blind cavity forming a frame of the same dimensions as corresponding frame sup-ports inthe contiguous piezoelectric layers, the resonant elements bearing electrodes connected to metallized tracks applied to their respective frame supports to effect elec-trical connections, the surface of each frame being coated with metal or metallic alloy and the several layers being 1~5~5~36 fixed to one another by a weld formed by the alloy.

More particularly, there is provided:
A manufacturing process for electric components which include at least one p;`ezoelectric resonant element wherein - n layers of piezoelectric material are blanked so as to form m resonant elements and surrounding zones which con-st~tute frame supports to ~hich said elements remain attached (where m and n are integers and m ~n ~1), - electrodes are deposited on the resonant elements and metalli~zed tracks electrically coupled to the electrodes on each surface of the surrounding zones, said tracks being of a metal or alloy of low melt;~ng point in the form of frames, - n - 1 intermediate layers are formed frcm piezoelectric material so as to have openings constituting frames of the same dimensions as the frame supports in an arrangement ~mitting placing said frames in registry with said frame supports, - metal tracks are deposited on each surface of said inter-mediate layers, - two termi`nal layers are formed from piezoelectric materi`al so as to have blind cavities in each which provide frames of th`e same dimensions as`the frame supports in an ar-rangement permitting placing said frames in registry with said frame supports, - metal tracks are deposited on that surface of the -termi~nal layers hav~ng the b-lind cavities, ~ openings are provided permitting access from the ex-teri~or to tfie metallized tracks so as to define areas of con-tact clearance, - the several layers are assembled under vacuum or partial vacuum in the presence of a noble or inert gas by bringing them into contact after correct positioning thereof~ and - the assembly is brought to a temperature above the melting point of the metal or alloy and then cooled until solidifica-tion of said metal or alloy, - only thereafter the various individual components are separated among the assembled layers, and finally tfie connection wires are attached.
~' 115~5~5 -4a-BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an exploded perspective view of a compo-nent comprising a tuning fork type resonator in accordance with the invention, before assembly, Figure ~ shows the same component following assembly and, Figure 3 snows the finished component following fixing of the connecting wires, Figure 4 illustrates a process *or mass production of a component such as that of figure 3, Figures 5and 6 represent an exploded view of the fini-shed product of a component according to the invention com-prising two resonators, Figures 7 and 8 illustrate the case of a number of reso-nators used as a multichannel filter, Figure 9 represents a component according to the inven-tion comprising a resonator as well as further discrete ele-ctronic components, Figure 10 illustrates a process for obtaining components comprising two superposed resonators of different types, Figure 11 is an exploded view of a component as obtained from the process of figure 10 while figures 12 and 13 show the finished component before and after fixing of the connec-ting wires, Fi~ure 14 and 15, appearing with ~igures 5 and 6, il-lustrate, i~n the framework of the invention, a component which.ena~les f~l fre~uency aju~ment through the addition of material.

DETAILED DESCRIPTION OF THE INVENTION

A first example, especially simple, of the component in accordance with the invention and comprising only a single resonator is shown in figure 1. Resonant element 1 shown he-re as a tuning fork, but in any case capable of taking anyother planar form for example a bar, and of utilising any vibration mode compatible with such planar form, is ob-tained from a single piece of material along with its support 2 by blanking from a layer 3 of piezoelectric material, for ins-tance monocrystalline quartz for which the cut, defined re-lative to a privileged direction, has been chosen in accor-dance with the desired application. Layer 3 thus forms a-round the resonant element 1 a frame support 2. ~he resonant element 1 bears the usual electrodes (not shown) obtained by metallization according to any appropriate known techni-que. The frame support 2 receives on each of the surface a metallized track to which is conrecte~ the corresponding electrode, and a layer of metallic alloy having a low mel-ting point which will serve for the ~inal assembly.

The resonator is completed by two cover members above and below. In accordance with the invention these are for-med by two layers of electrically insulating material ha-ving the same dimensicns as layer 3 and shown respectively as 4 and 5. Preferably the insulating material will be op-tically transparent,permitting thus the transmission of a laser beam or heat ray. Glass is well adapted to this utili-sation but in view of thermal expansion a cristallyne quartz having the same cut as layer 3 appears to have greater advan-tages. In order to provide clearance for the resonant ele -ment 1, blind cavities 6 are arranged in the terminal layers 4 and 5 having the same contour as the frame support 2 for the resonant element. A metallic film of alloy as in the ca-se ~f frame support 2 is deposited around the cavities in a manner so as to form an analagous frame 7. In order to leave clear a portion of the metallized surface of each of the faces of layer 3, a notch 8 is provided in each of layers 4 and 5, preferably on opposite edges relative to the median axis of the finished component.

Assembly of the component is effectea thereafter under vacuum or a partial vacuum in the presence of a noble or i-nert gas by bringing together the three layers ormed by individual parts 3, 4 and 5 aliyned in a manner such that the frames are facing one another. The layers in contact are heated above the melting temperature of the metallic alloy and then cooled until solidification of the alloy.
Preferably however this operation is effected in two stages.
In the first stage a single terminal layer or cover 4 or 5 is fixed to the support layer 3 of the resonant element 1.
Then by utilising the contact area left free by notch 8 and the metallic track on the still open face of layer 3, the resonant element may be excited and maintained in oscilla-tion by electrical means, thus permitting the adjustment of the frequency by removal of material from the open face for example through use of a laser beam. This operation terminated, one proceeds in the same manner as previously described for the fixation of the second terminal layer 5.
The final fre~uency adjustment and the usual tests may then be effected through utilisation of the contact areas which the notches 8 leave free. To the assembled product as shown in perspective in figure 2 are then fixed electrical conductors 9 thereby to result in the finished component as shown in figure 3.

In order to explain the conception of theresonator which has just been described -the layer forming the support for the resonant element 1 or the terminal layers 4 and 5 have been considered as having already been cut to the final dimension and prepared before their assembly. Such conception even in the case of a multilayer structure is particularly adapted to mass or series rather than piece by piece. Such mass pro-duction of the resonator previously described is illustrated by figure 4 wherein the individual elements bear the same reference number as in the preceding.

On layer 3 of piezoelectric material are blanked reso-nant elements 1 as previously but in series, the electrodes 51~6 are deposited with the desired connections with the metallic tracks forming a frame support 2 and this on both faces of layer 3. In the terminal layers 4 and 5 on their single internal face are arrange~blind cavities 6 with position and aimensions corresponding to frame support 2 of layer 3. A
metallized track forms a frame 7 of the metallic alloy ha-ving a low melting point around cavity 6. Perforations 8 are thereafter provided in the edge of each frame 7 of the terminal layers 4 and 5. Such perforations are intended to give access to the metallized tracks associated with the resonant elements 1 of layer 3. The perforations 8 at each terminal layer 4 and 5 are preferably arranged in a manner so as not to be face to face with those of the other layer just as in the case of the notches 8 mentioned above.

This being accomplished, assembly of the layers 3, 4 and 5 carrying in their turn the individual elements is ef-fected in the same manner as in the case of the resonator of figures 1 to 3. It is only after the final frequency a-justment through utilisation of the areas of layer 3 left free by the perforations 8 for electrical supply that the indi-vidual resonators are separated fromone another by sawing through the assembled layers, thereby to give components identical to those of figure 2. One may thereafter proceed to an individual piece-by-piece treatment in order to ob-tain finished products with the connected wires 9 such as that shown in figure 3.

In what has preceded the final product is a simple re- y sonator but the same multilayer technology may be equally well be applied to the realisation of electronic components comprising two associated resonators having the same frequen-cy, or several (m) resonators of different frequencies for utilisation as multichannel filters, or again of components comprising at least one resonator associated with other dis-crete electronic components within the same packaging. Exam-ples of such individual realisations which can be obtained ~ .

- ~lS;~5~36 by the process of mass production described above are illus-trated in figures5, 6, 7, 8, and 9.

For these general examples with several resonators or individual components within the same component assembly, what has previously been said for the elementary case is applicable by analogy, thus it seems unnecessary and useless to recite every detail.

In figure 5 the resonant element 1 with its frame sup-port 2 is associated within the same product, thus on the same layer 3, with a second resonant element 1' with its frame support 2'. The two frames supports 2 and 2' are se-parated by a non-metallized, thus insulating zone. In the corresponding terminal layeLs 4 and 5 the cavities 6 are doubled as shown at 6' at well as their frames 7, 7' and serarated by an insolating track. The same goes for the no-tches 8, 8' freeing the metallized areas of the frame sup-ports 2, 2' on the layer 3.

Assembly is carried out as in the preceding instance to obtain the finished product shown in figure 6. It is obvious that the mass production method described for the simple resonators may be applied to the present case without any fundamental modification. ~uch application is particularly interesting for components comprising two resonators having the same frequency but with different dimensional relation-ships, thereby providing staggered inversion temperatures, such staggering being employed in cases where thermal com-pensation is desired.

The case of components having two resonators may equally be generallised without difficulty to any desired number of resonators disposed side by side as shown in figures 7 and 8. In this case however for the realisation of the external connections (internal cross connections may be easily obtai-ned by well known processes of insulation by evaporation of 5~51!36 g SiO2 ~sputtering~ of SiO2, A1203, or TA205 , or again de-position in gaseous phase of appropriate compositions on layer 3), the upper terminal layer 4 will be slightly less wide than the two other layers 3 and 5 in a fashion to free the extremities of the metallizecl tracks of layer 3, this being equivalent to notches 8 of the preceding cases. A fi-nished product may then have the aspect as shown in figure 8. Such a component may be utilised as a multichannel fil-ter.

On figure 9 is shown in plan the layer 3 concerning another type of component in accordance with the invention.
This comprises at least one resonator 1 but on the surface of layer3which remains free are attached, according to any appropriate method, other individual discrete components, as for instance an integrated circuit J and condensers Cl and C2. The layer 3 is thus employed as a substrate provi-ded with electrical conductors formed as a thin film with their areas of connection.

It is evident that the process of mass manufacture des-cribed previously in a connection with isolated resonators is equally applicable without major changes to the other examples which have just been described and illustrated by figures 5 to 9.

In all that has previously been described, it is to be noted that by the ~tilisation of the same layer 3 of piezo-electric material, for instance monocristallyne quartz, the monolithic resonators thus obtained and enclosed in the sa-me final electronic component are necessarily of the same cut, for instance the cut X,Z,AT, etc., as the layer 3 it-self. The same technique can, without particular technolo-gical difficulties, be generalised to components which may include resonators having different cuts. For this one may employ several piezoelectric layers cut as desired and su-perposed in a manner to be insulated from one another by in-, termediate layers, the stack been completed on either handby a terminal layer. Thus with n ~ n an integer~fl) piezo-electric layers in each of which is blanked at least one resonant element, one may have in the same final component m monolithic resonators (m~n ~/1), the piezoelectric layers being separated by n - 1 intermediate insulating layers, and the entire assembly being enclosed between two terminal in-sulating layers.

Figure 10 illustrates such an assembly having five la-yers obtained by the mass production process already des-cribed in connection with the simple resonators. The indi-vidual component appears in an exploded view in figure 11, and following sawing apart of the assembled stack of layers in figure 12 Figure 13 represents the finished product following attachment of the connecting wires. In the exam-ple shown, in order to clear an access area above and be-low to a metallized area on each piezoelectric layer 3, 3' thereby to electrically excite the resonators and subse-quently for definite fixing ofthe conductor wires (figure 13) the intermediate layer 10 and terminal layers 4,5 each bear two perforations on the edge of their frames, for exam-ple as shown at the extremities of a diagonal for the inter-mediate layer 10 and at the extremities of a principal edge which is not the same in both cases for the terminal layers 4 and 5. The piezoelectric layers each bear a single perfo-ration in a corner of the frame, the perforation of one being in the opposite corner to that of the other. Each of the piezoelectric layers is thus accessible from above and be-low.

Assembly and adiustment of the frequency do not pose any particular problem beyond that described for the simple case. The utilisation of components thus obtained is of in-terest in thermal compensation techniques.

The technology of the multilayer conception oE the com-~5;251~36 ponent in accordance with the invention enables, beyondwhat has already been described, the application of a pro-cess for the application of material for final adjustment of the frequency as an alternative to the process by which material is removed. An example of such an application is shown in figure 14 and 15 for an individual component this being evidently valid for mass production. As previously, the piezoelectric layer with its resonant element is placed between two terminal layers 4 and 5. The latter are opti-cally transparent and their cavities are coated with a film 11, 11' of evaporable metal having a high vapour pres-sure. Between the two terminal layers 4 and 5 and the piezo-electric layer 3 are interposed insulating layers 12 and 12' each provided with a blind cavity 13 on the side facing the resonant element in order to provide clearance for the lat-ter, and a frame of the metallic alloy, as in the previous case, on both surfaces. In these cavities are provided ca-librated openings 14 facing at least one portion of the active zone of the resonant element. Such openings 14 thus provide communication between the housing of the resonant element and the cavities of the terminal layers 4 and 5.

The component is assembled as in the preceding cases and its coarse frequency adjustment is obtained according to the process already described. A final frequency adjust-ment is effected thereafter by submitting one or the other of the covers which comprise the terminal layers 4 and 5 to a heat ray represented schematically at 15 in figure 15.
This ray causes melting and evaporation of the charges 11, 11' of evaporable metal within the terminal layers 4 and 5.
The vapour, for which the pressure is elevated, thereafter is deposited via openings 14, which play the role of dia-phragms, onto the active zones of the resonant element. The procedure of evaporation-deposition is evidently controlled in accordance with the measurement of the frequency accor-ding to an appropriate control technology.

~Ls~s~

As has been shown there are a certain number of advan-tages which the technology of monolithic resonators and the multilayer conception thereof may bring about, notably the effecting of mass production processes. The described exam-ples concern certain specific applications but it is evident that many other combinations are possible without departing from the basis of the invention through varying the num-ber of resonant elements per layer and per component, em-ploying different cuts of the piezoelectric material and by use of basic electronic components which may be associa-ted with the resonant elements.

Claims

1. A manufacturing process for electric components which include at least one piezoelectric resonant element whêrein - n layers of piezoelectric material are blanked so as to form m resonant elements and surrounding zones which constitute frame supports to which said elements remain attached (where m and n are integers and m ~ n a 1), - electrodes are deposited on the resonant elements and metallized tracks electrically coupled to the electro-des on each surface of the surrounding zones, said tracks being of a metal or alloy of low melting point in the form of frames, - n - 1 intermediate layers are formed from piezo-electric material so as to have openings constituting frames of the same dimensions as the frame supports in an arrangement permitting placing said frames in registry with said frame supports, - metal tracks are deposited on each surface of said intermediate layers, - two terminal layers are formed from piezoelectric material so as to have blind cavities in each which pro-vide frames of the same dimensions as the frame supports in an arrangement permitting placing said frames in regis-try with said frame supports, - metal tracks are deposited on that surface of the terminal layers having the blind cavities, - openings are provided permitting access from the exterior to the metallized tracks so as to define areas of contact clearance, - the several layers are assembled under vacuum or partial vacuum in the presence of a noble or inert gas by bringing them into contact after correct positioning thereof, and _ th~ ~.c.s~mhl v i .s br~ught to a temperature above ~3 the melting point of the metal or alloy and then cooled until solidification of said metal or alloy, - only thereafter the various individual components are separated among(~the assembled layers~ and finally ~ - the connection wires are attached.

2. A manufacturing process as set forth in claim 1 wherein, when n = 1, only the edges of each frame other thar those containing the resonant elements are provided with openings.

3. A manufacturing process as set forth in claim 1 wherein, when n ~ 1, the edges of each frame are provided with openings.

4. A manufacturing process as set forth in claim 1 including the steps of initially assembling the layers utilising oneterminal layer only toform asubassembly and adjusting the frequency of the exposed resonant elements by removal of material therefrom while exciting said elements via the track access openings.

5. A manufacturing process as set forth in claim 4 including the steps of applying a laser beam to the expos-ed faces of the resonant elements so as to remove material therefrom, assembling the remaining terminal layer with the subassembly and completing the process by heat seal-ing of the full assembly.

6. A manufacturing process as set forth in claim 1 including the steps of aepositing a metallinc evaporable film in the cavities of the terminal layers, forming mask-ing layers with openings corresponding to the electrode positions on the resonant elements, interposing said mask-ing layers between the terminal layers and the other layers forming the assembly, and adjusting the frequency of the resonant element after assembly by applying suffi-cient heat to the terminal layers to effect evaporation of metal deposited in the cavities thereof and subsequent condensation of said evaporated metal on the surfaces of the resonant elements exposed by the openings in the mask-ing layers.

7. A manufacturing process as set forth in claim 1 wherein two resonant elements are formed onto one layer of piezoelectric material in order to obtain after separation~two electronic components)which include only one resonant element.

8. A manufacturing process as set forth in claim 1 wherein four resonant elements are formed onto one layer having the same frequency but alternatively being of different dimensions in order to obtain after separation two electronic components which include two resonant elements so that their respective inversion temperatures are staggered thereby to enable thermocompensation.

9. A manufacturing process as set forth in claim 1 wherein four resonant elementsare formed ontotwo layersof piezoelectricmaterialhaving(differentcutslin order to obtain after separation two electronic components which include two resonant elements.

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