JP2002261579A - Acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic wave device in which adhesive material is prevented from flowing into the casing or the acoustic wave propagating section of an acoustic wave element, vibration is prevented from being suppressed by resin adhering to the acoustic wave propagating section, and the electrical characteristics are prevented from fluctuating. SOLUTION: A piezoelectric substrate 1, provided with an exciting electrode 5 generating an acoustic wave, is contained in a casing 2 having an opening, and the open upper surface of the casing 2 is sealed hermetically by a cover 3 via an adhesive material 4. An annular recess 12 is formed in the open upper surface of the casing 2 and an outer protrusion 9, having an outer upper surface located on the outside of the recess 12, is formed lower than an inner protrusion 10 having an inner upper surface located on the inside of the recess 12. The adhesive material 4 is interposed between the outer upper surface and the cover 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elastic wave device such as a resonator and a frequency band filter incorporated in a mobile radio device such as a cellular phone and a car phone.

[0002]

2. Description of the Related Art FIG. 5 is a schematic sectional view of a conventional surface acoustic wave device. In the elastic wave element J1 shown in FIG. 5, 51 is a piezoelectric substrate, 52 is a housing (package),
Reference numeral 3 denotes a lid, 54 denotes a sealant for fixing and sealing the lid 53 to an opening of the housing 52, and 55 denotes an excitation electrode for generating an elastic wave, for example, on a piezoelectric substrate for a surface acoustic wave element. And a comb-shaped IDT (Inter Digital Transducer) electrode. Reference numeral 58 denotes a conductive pattern 56 on the housing 52.
And the input / output electrode 57 of the excitation electrode 55. Further, in the configuration shown in the figure, the housing 52 and the lid 53 are sealed by thermocompression bonding with a sealant 54 to maintain airtightness.

In general, an epoxy resin is used as the sealant 54, and the epoxy resin is softened by the high temperature heat at the time of thermocompression sealing, and the resin flows into the bonding surface to form an adhesive layer uniformly. The body and the lid can be adhered and hermetically sealed.

However, when the applied amount of the resin is large due to a change in the applied amount of the resin during the sealing step, the sealing agent 54 softened by heating flows into the housing 53 and the sealed acoustic wave element 31 There has been a problem that vibrations are suppressed due to the resin flowing into the elastic wave propagating portion and adhered to the elastic wave propagating portion, and the electric characteristics fluctuate.

Conventionally, the bonding surface in resin sealing is a flat surface or a surface having the same height. When mounting an electronic component on a mounting board by soldering, a temperature difference or an environmental change due to a time difference occurs. The housing and the lid are repeatedly expanded and contracted by the temperature difference. Due to the temperature fluctuation, a difference in linear expansion coefficient between the surfaces where the housing and the lid are bonded causes a strain stress in the bonding layer, and finally the sealant of the bonding layer and the housing or the lid due to the stress. There is a problem in that a gap is formed between the gaps, making airtightness impossible.

Furthermore, when the lid is a flat foil, the effective bonding area varies depending on the placement accuracy of the lid during the sealing step, so that the sealing performance may be poor. Therefore, when the width of the bonded portion is smaller than the designed value, there is a problem that the moisture permeability is reduced and airtight breakage is likely to occur at the time of heat curing.

The present invention has been proposed in view of the above-mentioned problems, and has as its object to prevent the sealing agent 54 softened by heating during sealing from flowing into the housing 53. To prevent the sealing agent 54 from flowing into the elastic wave propagating portion of the accommodated elastic wave element 51, to prevent vibration suppression by a resin attached to the elastic wave propagating portion, and to improve the electrical characteristics of the elastic wave device. The acoustic wave device has high environmental reliability by preventing fluctuations, and has a hermetic sealing structure that withstands temperature fluctuations due to the mounting of the acoustic wave device on the circuit board and environmental fluctuations. Is to provide.

[0008]

In order to achieve the above object, an elastic wave device according to the present invention accommodates a piezoelectric substrate provided with an excitation electrode for generating an elastic wave in a housing having an opening. The upper surface of the opening of the housing is hermetically sealed with a lid via an adhesive, and an annular concave portion is formed on the upper surface of the opening of the housing, and the outer upper surface located outside the concave portion is positioned on the inner side. It is formed lower than the located inner upper surface, and the adhesive is interposed between the outer upper surface and the lid.

A piezoelectric substrate provided with excitation electrodes for generating elastic waves is accommodated in a housing having an opening, and the upper surface of the opening of the housing is hermetically sealed with a lid via an adhesive. An elastic wave device comprising: an annular upper surface provided on the opening upper surface of the housing; and a slanted concave portion having an inner side lower than the outer side, and an adhesive interposed between the concave portion and the lid. And

Further, in particular, an annular convex portion is provided on the lower surface of the lid so as to enter the concave portion provided on the upper surface of the opening of the housing.

Specifically, for example, the piezoelectric substrate provided with an excitation electrode for generating an elastic wave on the piezoelectric substrate is mounted on an insulating casing having a conductive pattern formed to be connected to the input / output electrodes of the excitation electrode. An acoustic wave device, comprising: an input / output electrode of the excitation electrode and a conductive pattern connected to each other, wherein the insulating substrate has an outer convex portion, and the inside of the outer convex portion is higher than the outer convex portion. An inner convex portion is provided, and hermetically sealed with an adhesive provided between the outer convex portion and the inner convex portion.

[0012]

Embodiments of a surface acoustic wave device according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view (an end view taken along the line AA ′ in FIG. 2) of an elastic wave device equipped with an elastic wave element according to one embodiment.
Shows a top view of the acoustic wave device on which the acoustic wave element is mounted before the lid is bonded. 3 and 4
FIG. 7 is an end view of another embodiment.

In the elastic wave device S1 shown in FIG. 1, 1 is a piezoelectric substrate, 2 is a casing made of ceramic or the like, and 3 is a metal lid made of Kovar or the like. Reference numeral 4 denotes an adhesive (sealant) for connecting the housing 2 and the lid 3. Reference numeral 5 denotes an excitation electrode for generating an elastic wave, for example, a comb-shaped IDT (Inter DigitalTra) formed on a piezoelectric substrate for a surface acoustic wave element.
nsducer) electrode. 8 is a conductive pattern 6 on the housing 2
And a bump for electrically connecting the input / output electrode 7 of the excitation electrode 5 to the input / output electrode 7.

In the elastic wave device S1, 1 is a piezoelectric substrate,
Reference numeral 2 denotes a housing made of ceramic or the like, and reference numeral 3 denotes a metal lid made of Kovar or the like. Reference numeral 4 denotes an adhesive (sealant) for connecting the housing 2 and the lid 3. Reference numeral 5 denotes an excitation electrode for generating an elastic wave, for example, a comb-shaped IDT (Inter Digital Transducer) formed on a piezoelectric substrate for a surface acoustic wave element.
Electrodes. Reference numeral 8 denotes a bump for electrically connecting the conductive pattern 6 on the housing 2 to the input / output electrode 7 of the excitation electrode 5. Further, an outer convex portion 9 is provided on an outer peripheral portion of the housing 2 and the outer convex portion 9 is provided.
An inner convex portion 10 higher than the outer convex portion 9 is provided on the inside, and the lid 3 is hermetically sealed with the adhesive 4 provided between the outer convex portion 9 and the inner convex portion 10.

As shown in FIG. 2, the outer convex portion 9 provided on the housing 2 is formed in an annular shape on the outermost periphery of the housing 2. Also,
An inner projection 10 higher than the outer projection 9 is provided inside the outer projection 9.

As described above, the elastic wave device S1 accommodates the piezoelectric substrate 1 provided with the excitation electrode 5 for generating an elastic wave in the housing 2 having the opening, and also attaches the upper surface of the opening of the housing 2 to the adhesive material. 4 and hermetically sealed with a lid 3 through a housing 2
An annular concave portion 12 is formed on the upper surface of the opening, and the outer convex portion 9 having the outer upper surface located outside the concave portion 12 is formed lower than the inner convex portion 10 having the inner upper surface located inside. An adhesive 4 is interposed between the cover 3 and the cover 3.

As described above, in the present invention, the inner convex portion 10 is provided inside the outer convex portion 9 and higher than the outer convex portion 9. In order to hermetically seal the housing 2 and the lid 3 by bonding, the adhesive 4 is generally made of an epoxy resin, and is thermocompression-bonded. The structure is such that an adhesive surface flows between the outer convex portion 9 and the inner convex portion 10, an adhesive layer is formed at the portion, and sealing is performed.

The presence of the inner protruding portion 10 higher than the outer protruding portion 9 prevents the flow of the softened adhesive material 4 into the housing 2 due to heating at the time of sealing when the lid 3 is thermocompression-bonded. It can be prevented as much as possible. Further, it is possible to prevent the accommodated elastic wave element from flowing into the elastic wave propagation portion. Further, due to the stress due to volume reduction generated when the heated adhesive 4 is fixed,
The inner protruding portion 10 and the lid 3 are caulked and the sealing performance can be improved.

Next, another embodiment will be described with reference to FIG. In the elastic wave device S2 shown in FIG. 3, the annular projection shape (convex portion) 11 is provided between the outer convex portion 9 and the inner convex portion 10 on the lid 3 so that the inner convex portion 10 and the lid 3 The caulking is further strengthened, the sealing property is improved, and the projection shape of the lid is matched with the concave shape between the outer convex portion 9 and the inner convex portion 10, so that compared to a flat lid, Because the placement accuracy of the lid becomes good, the bonding area becomes uniform,
Further, the sealing performance is improved.

Next, the elastic wave device S3 shown in FIG. 4 will be described. By providing the protruding shape 11 in which the shape of the lid 3 and the outer convex portion 9 is adjusted to the same shape, the caulking between the inner convex portion 9 and the lid 3 is further strengthened, and the sealing property is improved. In addition, since the projection shape 11 of the lid 3 is matched with the concave shape between the outer convex portion 9 and the inner convex portion 10, the placement accuracy of the lid becomes better than that of a flat lid, As the area becomes uniform and the bonding area increases, the sealing property is further improved.

As described above, the elastic wave device S3 accommodates the piezoelectric substrate 1 provided with the excitation electrode 5 for generating an elastic wave in the housing 2 having the opening, and also attaches the upper surface of the opening of the housing 2 to the adhesive material. 4 and hermetically sealed with a lid 3 through a housing 2
The upper surface of the opening is provided with a concave portion 12 having an annular shape and an inner side lower than the outer side, and an adhesive 4 is interposed between the concave portion 12 and the lid 3.

Although the shape of the inner convex portion 10 is rectangular in the figure, it goes without saying that the same effect can be obtained even if the shape is a convex shape having an R shape including an arc.

A suitable range of the height difference h (see FIG. 1) between the outer convex portion 9 and the inner convex portion 10 is determined by the thickness of the adhesive layer of the adhesive (generally, the adhesive layer thickness is 30 μm to 200 μm). ), The range of 1/10 to 2 is a range in which good adhesion and hermetic sealing can be performed. The reason for this is that, when the lower limit value is 1/10 or less, the inner convex portion 10 and the cover 3
The crimping is insufficient, which makes it impossible to improve the sealing performance, resulting in poor sealing performance.
If the upper limit is 2 or more, the sealant cannot uniformly wrap around the bonding surface of the outer convex portion 9 and is not well bonded.
This is because hermetic sealing cannot be performed.

The material of the housing 2 is preferably ceramic, glass or plastic. Among them, ceramics such as alumina, steatite, forsterite, mullite and cordierite are excellent in cost, workability, electrical insulation, heat resistance, etc. It can be suitably used.

As the material of the lid 3, any metal can be used as long as it can form a foil having some flexibility and can be processed into the projection shape 11, and not only a single metal but also an alloy can be used. Examples of these include a single metal such as copper, iron, aluminum, zinc, tin, gold, and silver, and alloys include a copper alloy, an aluminum alloy, stainless steel, and Kovar.

Some of these metal foils may be corroded by moisture or oxygen in the air for a long period of time. In such a case, a surface protection treatment such as plating, painting, or oxidation treatment is required. By doing so, the disadvantages can be solved. In order to improve the adhesiveness, it is also effective to roughen the adhesive surface of the metal foil.

Similarly, even when the cover 3 is made of a ceramic or plastic coated with metal, the cover 3 has flexibility, workability, and corrosion resistance, so that it can be effectively used as an electronic element package.

As the adhesive 4, of course, a material having high moisture resistance should be selected. Examples of the resin adhesive 4 that satisfies these requirements include polysulfone, polyethersulfone, and phenoxy resin as the heat-resistant thermoplastic resin adhesive.

In order to use these resins as the adhesive 4, a solution of an organic solvent is used. Adhesion is performed by applying a solution to the adhesion surface and evaporating the solvent to such an extent that the adhesiveness is not lost, and then bonding the housing 2 and the lid 3 together and completely evaporating the solvent, or after applying the solution, Once the solvent is completely volatilized, the bonding surfaces of the housing 2 and the lid 3 are brought together, and the temperature is raised to the softening temperature of the resin and bonded.

If the solvent vapor is liable to damage the element or the main part of the package, the latter method must be adopted.

As the thermosetting resin adhesive which can be suitably used in the present invention, an epoxy adhesive can be used. Epoxy resins have high adhesive strength to various materials including metals, good moisture resistance, and high heat resistance because they are thermosetting.
Furthermore, various epoxy-based adhesives are sold, and the range of options is wide. Therefore, an epoxy adhesive is one of the most suitable as the adhesive of the present invention.

Auxiliary agents and fillers may be added to these adhesives as needed. In particular, the addition of a moisture-inactive mineral substance, for example, a fine powder such as glass, titanium oxide, alumina, and silica is effective in increasing the moisture resistance of the bonded portion.

Further, it is necessary to add a conductive material (for example, an alloy of Au, Ag, Sn, etc.) and use a conductive adhesive to connect the cover to the ground potential. Most essential. That is, the component that functions as a high-frequency electric signal is set to the ground potential so as to provide an electromagnetic shielding effect on the lid or the main body so as to prevent electromagnetic coupling with the component or other components. It is necessary to apply a metal pattern. Therefore, although the cover 3 is made of a metal foil and has a good shielding effect, a plastic coated with a metal also has a good shielding effect and it is desirable to use a conductive adhesive when obtaining the shielding effect.

Further, the composite component, that is, the package body has a laminated structure in which electrodes generating inductance and capacitance are built, and an electronic element (for example, an elastic wave element, a semiconductor element, etc.) is mounted in a cavity of the body. Also in the parts for electrically connecting them, the above-mentioned good hermetic sealing structure and a package structure having a high electromagnetic shielding effect are particularly useful.

The sealing method may be performed according to a usual method. First, a resin adhesive is applied to at least one of the housing and the lid. As a coating method, a screen printing method is preferable because it can be applied to a necessary portion with a relatively uniform thickness, but in addition, a method of applying with a roll, a brush coating method, and the like can also be used.

When the lid and the bonding portion of the housing are made of metal, they can be hermetically sealed with solder (Au-Sn alloy solder).

The appropriate material thickness of the lid 3 is 0.0
It is 2 mm to 0.3 mm. The lower limit of this range is lid 3
The upper limit is determined by considering the flexibility and workability of the lid at the time of sealing, and the appropriate size of electronic components. I have.

As described above, according to the present invention, it is possible to package an acoustic wave device having an alloy electrode which is corroded by moisture at low cost while avoiding damage to the device due to sealing heat. Useful for

In the above embodiment, an example in which the acoustic wave device is mounted face down in the housing has been described. However, the present invention is not limited to this. For example, the housing and the acoustic wave device are connected by wire bonding. Various modifications may be made without departing from the scope of the present invention.

[0040]

EXAMPLE A 96% by weight alumina ceramic package having the structure shown in FIG. 1 was used for a package of a surface acoustic wave filter as a piezoelectric element. In FIG. 1, 2 is a ceramic package, and 3 is a Kovar lid. The surface acoustic wave filter is flip-chip mounted on the housing 2 via ball bumps. The adhesive 4 used epoxy resin as a resin adhesive. The surface acoustic wave filter may be mounted on the housing 2 using silver paste or conductive silicon resin or the like, and bonded to the input / output pads of the housing 2 using gold wires or the like.

The size of the housing 2 was 3 mm in length, 3 mm in width, and 1.2 mm in height. The size of the lid 3 is 3mm long and 3mm wide.
mm and a thickness of 0.10 mm. The thickness of the adhesive layer of the adhesive is 0.10 mm, and the outer convex portion 9 and the inner convex portion 10 are provided.
Was 0.10 mm. The size of the surface acoustic wave filter is 1.35 mm in height, 0.8 mm in width, and 0.35 m in height
m, and the height of the ball bump was 0.08 mm. The width of the bonded portion was 0.20 mm, but the inner corners were chamfered, and the effective bonded width was 0.25 mm.

The adhesive 4 was applied as an epoxy resin adhesive by screen printing. Subsequently, the lid 2 is placed,
Pressure was applied and heat curing was performed in a dry nitrogen atmosphere at 190 ° C.

300 sealed by the method as described above
An airtight test was performed on 0 parts. First, reflow was performed at a temperature of 260 ° C. to induce airtight breakage at the solder temperature. Then, the solution was placed in 6.4 kgf / cm ² helium for 1 hour.
Helium was sealed inside the package of the part that was airtightly broken by applying pressure for a long time. Then 5.0 × 10
As a result of performing a leak check at a leak rate of ^-8 atmcc / sec, helium was detected from one part and airtight breakage was confirmed. Usually, the sealing failure due to metal welding is about 0.1%, and it has been proved that the sealing strength is almost the same.

[0044]

As described above in detail, according to the surface acoustic wave device of the present invention, since the outer upper surface of the housing having the opening is lower than the inner upper surface, the housing is hermetically sealed with the lid. At the same time, it is possible to prevent the adhesive from flowing into the housing due to heating or the like at the time of sealing as much as possible, to prevent the elastic wave device housed in the housing from flowing into the elastic wave propagation portion, and to provide a highly reliable elastic wave device. Can be provided.

Further, due to the stress due to volume reduction generated when the adhesive to which heat or the like is applied is fixed, the inner upper surface of the housing and the lid are caulked, and the sealing performance can be further improved.

Further, by appropriately forming the upper surface of the opening of the housing and the lower surface of the lid, the caulking of both can be strengthened, whereby the hermetic sealing property is further improved, and A high elastic wave device can be provided.

[Brief description of the drawings]

FIG. 1 is an end view schematically showing an embodiment of an elastic wave device according to the present invention.

FIG. 2 is a plan view (top view) schematically showing an embodiment of the elastic wave device according to the present invention.

FIG. 3 is an end view schematically showing an embodiment of another elastic wave device according to the present invention.

FIG. 4 is an end view schematically showing an embodiment of another elastic wave device according to the present invention.

FIG. 5 is an end view showing an example of a conventional elastic wave device.

[Explanation of symbols]

 1, 51: piezoelectric substrate 2, 52: housing 2a: upper surface of opening 3, 53: lid 4, 54: adhesive (sealant) 5, 55: excitation electrode 6, 56: conductive pattern on housing 7 , 57: input / output electrode of elastic wave element 8, 58: bump 9: outer convex portion (outer upper surface) 10: inner convex portion (inner upper surface) 11: projection-shaped portion (convex portion) of lid 12: concave portion S1 S3: elastic wave device

Claims (3)

[Claims] A piezoelectric substrate provided with an excitation electrode for generating an elastic wave is accommodated in a housing having an opening, and the upper surface of the opening of the housing is hermetically sealed with a lid via an adhesive. An elastic wave device comprising: an annular concave portion formed on an upper surface of an opening of the housing; an outer upper surface located outside the concave portion is formed lower than an inner upper surface located inside; An elastic wave device, wherein the adhesive is interposed between the lid and the lid. 2. A housing having an opening, a piezoelectric substrate provided with excitation electrodes for generating elastic waves is accommodated, and the upper surface of the opening of the housing is hermetically sealed with a lid via an adhesive. An elastic wave device comprising: an upper surface of an opening of the housing, wherein an annular recessed portion having an inner side lower than the outer side is provided, and an adhesive is interposed between the recessed portion and the lid. A characteristic acoustic wave device. 3. The elastic wave device according to claim 1, wherein an annular convex portion is provided on a lower surface of the lid so as to enter a concave portion provided on an upper surface of the opening of the housing.