JP2013140874A - Electronic device, ceramic substrate, manufacturing method, and piezoelectric oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of cracks in a ceramic portion and peeling of a metalization layer due to a difference in temperature drop rates of a metal lid and a ceramic substrate during cooling when the metal lid and the ceramic substrate are welded by using a brazing material and radiating a laser beam etc. thereto.SOLUTION: An electronic device includes: a ceramic substrate 10; an electronic component 20 joined to one surface of the ceramic substrate; and a metal lid 19 which is joined onto the ceramic substrate at its periphery thereby sealing the electronic component; and a metalization layer 13 fixed to the one surface of the ceramic substrate or the periphery of the metal lid. In the electronic device, the ceramic substrate and the periphery of the metal lid are joined by using a brazing material layer 19B with the metalization layer sandwiched therebetween. Young's modulus of the metalization layer is equal to or less than 200 GPa.

Description

  The present invention relates to an electronic device, a ceramic substrate, and an electronic device manufacturing method, in which a metal lid is bonded by locally heating the ceramic substrate to which the electronic component is bonded using laser light or the like, and the electronic component is sealed. And a piezoelectric oscillator.

  Conventionally, an electronic device for surface mounting in which an electronic component bonded to a ceramic substrate is sealed with a metal lid has been widely used. For example, as a clock source for electronic circuits of various electronic devices such as OA equipment such as information communication equipment and computers, consumer equipment, etc., a piezoelectric vibrating piece as an electronic component is joined to a ceramic substrate and the piezoelectric vibrating piece is covered A piezoelectric device is widely used as an electronic device in which a piezoelectric vibrating piece is hermetically sealed in a space formed by a ceramic substrate and a metal lid by bonding a concave metal lid on the ceramic substrate.

In general, when joining a metal lid and a ceramic (alumina) substrate by laser light or electron beam irradiation, the peripheral portion of the metal lid is placed on a metallized layer formed in advance on the ceramic substrate side via a brazing material. In the overlapped state, laser beam or the like is irradiated from the peripheral part of the metal lid, and welding is performed by melting and solidifying the brazing material. In this case, the temperature of the metal lid and the brazing material is about 800 to 1000 ° C., for example. Since welding with laser light is local welding, the temperature of the ceramic portion corresponding to the lid portion irradiated with the laser light rises locally to about 100 to 200 ° C., but the metal lid It does not rise to 800-1000 ° C like the body. Thus, during welding, a temperature difference of about 700 to 900 ° C. occurs between the metal lid and the ceramic. For this reason, when the welded part cools, strain stress is generated between the members, and cracks are generated on the ceramic substrate side, which is a material that is overwhelmingly brittle than metal, due to the strain stress during contraction. The upper wiring is easy to peel off.
If the ceramic substrate is heated so as to approach the temperature of the metal lid during laser light irradiation in order to eliminate the temperature difference during welding, the wiring and brazing material of the ceramic substrate may be deteriorated by oxidation.

  In the electronic device described in Patent Document 1, in the hermetic sealing of electronic parts to be joined by heating and melting silver brazing by electron beam irradiation, cracks are generated in the package (ceramic) due to local thermal shrinkage due to a rapid temperature gradient. The problem of loss of hermeticity that is formed is solved by increasing the thickness of the metallized metal film disposed at the joint to 25 μm or more.

Japanese Patent Laid-Open No. 11-126839

However, if the thickness of the metallized metal film is excessively increased to 25 μm or more in an ultra-compact piezoelectric device having vertical, horizontal, and height dimensions of about several millimeters, it will hinder the reduction of the height of the electronic component. In addition, it is clear that the amount of metallized material used increases, leading to an increase in cost.
Alternatively, by arranging a thick metal film such as Kovar between the metallized layer on the ceramic substrate and the metal lid, it is used as a stress relaxation layer to prevent cracking during welding. However, not only the increase in man-hours and cost increase due to the increase in the number of members, but also a result against the low profile, improvement has been demanded.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 An electronic device according to this application example includes a ceramic substrate provided with wiring on the surface, an electronic component bonded to the wiring, and a metallized layer having a Young's modulus of 200 GPa or less. And a metal lid that is joined to the ceramic substrate at a peripheral portion and covers the electronic component in a plan view.

  According to the piezoelectric device of this application example, by interposing a metallized layer having a Young's modulus of 200 GPa or less between the ceramic substrate and the metal lid, the difference in the temperature decrease rate of both members is reduced by the metallized layer. It is possible to effectively prevent cracks from being formed in the ceramic substrate and the wiring material from being peeled off.

  Application Example 2 The metal lid is bonded to the ceramic substrate at the peripheral edge via a brazing material together with the metallized layer. The effect of Application Example 1 can be further enhanced.

  Application Example 3 The metallization layer is made of copper.

  According to this configuration, by selecting copper as the material of the metallized layer having a Young's modulus of 200 GPa or less, an excellent buffering effect is exhibited, cracks are formed in the ceramic substrate, and the wiring material is peeled off. It can be effectively prevented.

  Application Example 4 The thickness of the metallized layer is 15 to 25 μm.

  According to this configuration, when the thickness of the metallized layer is 15 μm or more, the buffering effect against shrinkage at the time of cooling after welding is reduced, thereby effectively preventing the ceramic substrate from cracking or peeling of the wiring material. it can. In addition, since the film thickness does not exceed 25 μm, the time required for temperature rise during welding can be shortened, and cost reduction and productivity improvement can be achieved.

  Application Example 5 The ceramic substrate is provided with wiring on the surface for joining electronic components and a metallized layer having a Young's modulus of 200 GPa or less for joining to the peripheral portion of the metal lid. The brazing material is made of silver brazing.

  According to this configuration, the electronic device as described above can be realized.

  Application Example 6 In the ceramic substrate according to this application example, the metallized layer is made of copper and has a thickness of 15 to 25 μm.

  Application Example 7 This electronic device manufacturing method is the electronic device manufacturing method according to any one of Application Examples 2 to 4, wherein each of the electronic component, the ceramic substrate, and the metal lid is provided. A step of preparing, a step of bonding the electronic component on the wiring, and a step of bonding the metal lid to the ceramic substrate to form an internal space for accommodating the electronic component. In the step of forming, the metal lid is disposed on the metallized layer, and then the brazing material is melted by irradiating a laser beam or an electron beam from the metal lid side.

  According to this configuration, by interposing a metallized layer that functions as a buffer layer and has a Young's modulus of 200 GPa or less between the ceramic substrate and the metal lid, the rate of temperature decrease between the ceramic substrate and the metal lid is reduced. The difference can be mitigated by the metallization layer. For this reason, it can prevent effectively that a crack is formed in a ceramic base material or a wiring material peels.

  Application Example 8 A piezoelectric oscillator according to this application example is characterized in that the electronic device according to any one of Application Examples 1 to 4 is a piezoelectric vibrator and includes a semiconductor element.

  According to this, by interposing a metallized layer having a Young's modulus of 200 GPa or less that functions as a buffer layer between the ceramic base and the metal lid, the difference in temperature decrease rate between the ceramic base and the metal lid. Can be relaxed by the metallized layer. For this reason, it can prevent effectively that a crack is formed in a ceramic base material or a wiring material peels.

It is a top view of one embodiment of a piezoelectric device as an example of an electronic device of the present invention. (A) is the partial cross section top view which looked at the piezoelectric device from the upper side, (b) is the longitudinal cross-sectional view along the AA line of (a). It is a fragmentary sectional view which expands and demonstrates in detail a part (joining part) of FIG.2 (b). (A) And (b) is the longitudinal cross-sectional view of the piezoelectric device as an example of the electronic device which concerns on other embodiment of this invention, and the principal part enlarged view. It is a flowchart which shows an example of the manufacturing method of the piezoelectric device which concerns on this invention. It is a top view which shows the process in which a ceramic substrate is manufactured with a green sheet. It is sectional drawing which shows the piezoelectric oscillator as another structural example of the electronic device of this invention. It is a schematic block diagram which shows the structure of the electronic device which concerns on this invention.

Preferred embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a plan view of an embodiment of a piezoelectric device as an example of an electronic device of the present invention, FIG. 2 (a) is a partial sectional plan view of the piezoelectric device as viewed from above, and FIG. It is a longitudinal cross-sectional view along the AA line. In FIG. 2A, for convenience of explanation of the internal structure of the piezoelectric device, a part of the metal lid (19) provided above the piezoelectric device is cut out. FIG. 3 is a partial cross-sectional view illustrating a part (joint portion) of FIG.

1 and 2, the piezoelectric device 1 includes a ceramic substrate 10 as a substrate, a piezoelectric vibrating piece 20 as an electronic component bonded on one main surface (upper surface) of the ceramic substrate 10, and a piezoelectric vibrating piece 20. A concave metal lid 19 joined on the ceramic substrate 10 so as to cover the piezoelectric substrate 20, and the piezoelectric vibrating reed 20 is hermetically sealed in a cavity T formed by the ceramic substrate 10 and the metal lid 19. Has been.
The ceramic substrate 10 and the metal lid 19 constitute a package.
The ceramic substrate 10 has a resonator element connecting terminal 18 to which the piezoelectric resonator element 20 is bonded to one main surface (upper surface) of a plate-shaped ceramic base material (alumina) 11, and a plurality of elements are formed on the other main surface (lower surface). The external mounting terminal 16 is provided. The resonator element joining terminal 18 and other terminals (not shown) are formed by burying a conductive paste containing a refractory metal in a through hole (via hole) provided in the ceramic substrate 11. To the corresponding external mounting terminal 16. The ceramic substrate is provided with wiring on the surface for joining electronic components and a metallized layer (described later) having a Young's modulus of 200 GPa or less for joining to the peripheral portion of the metal lid. .

One main surface of the ceramic substrate 10 provided with the external mounting terminals 16 serves as an outer bottom surface of the piezoelectric device 1, and the external mounting terminals 16 provided on the outer bottom surface make the piezoelectric device 1 an external mounting substrate such as an electronic device. Can be implemented. The ceramic substrate 11 constituting the ceramic substrate 10 of the present embodiment is formed by forming and processing a green sheet and firing it.
The piezoelectric vibrating piece 20 has a configuration in which excitation electrodes 25 as counter electrodes are provided on both main surfaces of a flat plate-like piezoelectric substrate made of a piezoelectric material such as quartz. Further, an external connection electrode 26 is provided on one end side of each main surface of the piezoelectric vibrating piece 20, and each is electrically connected by an inter-electrode wiring drawn from the corresponding excitation electrode 25. In addition, as a material of the piezoelectric vibrating piece 20, examples of the piezoelectric material other than quartz include lithium tantalate and lithium niobate, and examples of materials other than the piezoelectric material include silicon. On the ceramic substrate 10 (the other main surface side), the piezoelectric vibrating piece 20 is in a state where the external connection electrode 26 provided on one end side thereof is aligned with the corresponding vibrating piece joining terminal 18 of the ceramic substrate 10, for example. They are joined together while being electrically connected by a joining member 30 such as silver paste, and are cantilevered with the other end as a free end.

The metal lid 19 hermetically seals the mounting area of the piezoelectric vibrating piece 20 by accommodating the piezoelectric vibrating piece 20 in the cavity T surrounded by the recess and the bonding surface of the piezoelectric vibrating piece 20 of the ceramic substrate 10. Is for. The metal lid is bonded to the ceramic substrate at the peripheral edge via a brazing material together with the metallized layer.
The concave metal lid 19 is formed by forming a plate material made of a metal such as Kovar, 42 alloy, or phosphor bronze by a conventionally well-known sheet metal working, and has a concave portion formed in the lower surface of the central portion, and a bowl-shaped outer peripheral portion. The contact leg portion 19c is formed in an annular shape.
That is, the metal lid 19 has a horizontal portion 19a at the center, a side wall portion 19b extending downward from the outer peripheral side of the horizontal portion 19a is formed, and the lower edge portion of the side wall portion 19b is bent to the outer peripheral side. Thus, an annular contact leg portion 19c substantially parallel to the horizontal portion 19a is formed on the outer peripheral portion of the metal lid body 19. The side wall portion 19b may be inclined obliquely outward as illustrated, or may be a vertical wall.

As shown in FIG. 3, a metallized layer 13 made of the same material as that of the resonator element joining terminal 18 is formed in an annular shape on the outer peripheral upper surface 12 of the ceramic substrate 10 to which the lower surface of the contact leg 19 c is bonded.
The metal lid 19 has the contact leg 19c facing the metallized layer 13 of the ceramic substrate 10 with the opening side of the recess formed by the horizontal portion 19a and the side wall portion 19b facing the ceramic substrate 10 side. Are joined.
In the present embodiment, as shown in FIG. 3, the annular metallized layer 13 on the outer peripheral upper surface of the ceramic substrate 10 and the lower surface of the annular contact leg 19 c of the metal lid 19 have a relatively low melting point, for example. It joins via the brazing material layer 19B as a joining member which consists of alloys.

The metal lid 19 is preferably electrically connected to a ground terminal (not shown) of the ceramic substrate 10 through the metallized layer 13. In this way, when the piezoelectric device 1 is used, the metal lid body 19 made of metal is held at the ground potential, so that the piezoelectric vibrating piece 20 can be electrically connected to the outside due to the shielding effect of the metal lid body 19. It is possible to protect from effects such as noise.
Thus, the piezoelectric device 1 described above applies a variable voltage from the outside between the excitation electrodes 25 provided on both main surfaces of the piezoelectric vibrating piece 20 via the external mounting terminals 16 provided on the bottom surface of the ceramic substrate 10. It functions as the piezoelectric device 1 by causing vibration at a predetermined frequency according to the characteristics of the piezoelectric vibrating piece 20, and oscillates and outputs a reference signal having a predetermined frequency by an external oscillation circuit based on the resonance frequency of the piezoelectric device 1. can do. Such a reference signal can be used as a clock signal in an electronic device such as a portable communication device.

The characteristic configuration of the piezoelectric device 1 according to the present invention includes a ceramic substrate 10 provided with wiring on the surface, an electronic component 20 bonded to the wiring, and a metallized layer 13 having a Young's modulus of 200 GPa or less. And a metal lid 19 that is bonded to the ceramic substrate at the peripheral portion and covers the electronic component in a plan view.
In other words, a ceramic substrate 10 having a metallization layer 13 for bonding on one surface, an electronic component (piezoelectric vibrating piece 20) bonded on one surface of the ceramic substrate, and silver brazing or the like on the metallized layer. In an electronic device including a metal lid 19 that seals an electronic component by bonding the periphery using a brazing material layer 19B, a metal having a Young's modulus of 200 GPa or less is selected as the metallization layer.

Since the metallized layer 13 is formed at the same time when the resonator element joining terminal 18 is formed on the ceramic material constituting the ceramic substrate, it is made of the same material as the resonator element joining terminal 18. In the present invention, copper is selected as an example of a metal having a Young's modulus of 200 GPa or less constituting the metallized layer 13. The Young's modulus of copper is 110 to 130 GPa. In addition, as long as Young's modulus is a metal of 200 GPa or less, you may be other than copper.
The reason why the constituent materials of the metallized layer 13 and the resonator element joining terminal 18 are the same is in the manufacturing process of the ceramic substrate. That is, the ceramic substrate 11 having a wiring pattern is formed by firing a printed material of a wiring material (conductor paste) on a green sheet before firing, and is formed on the same surface of the green sheet. The resonator element joining terminal 18 and the metallized layer 13 are simultaneously applied and fired in the wiring material printing step to be integrated with the ceramic substrate 11.

However, since it is necessary to print, bake, and heat and bond the wiring material to the green sheet in this way, a metal material that can withstand high temperatures such as tungsten is used, and the surface is heated by high temperature heating such as copper. However, it was not possible to use a material that was oxidized and reduced in conductivity.
Conventionally, tungsten (Young's modulus: 400-410 GPa), which has a very high Young's modulus, has been mainly used as the wiring material constituting the wiring pattern formed on one surface of the ceramic substrate 11 (= alumina, Young's modulus: 310 GPa). For this reason, when a metal lid was joined on the metallized layer made of tungsten, it was not possible to prevent cracks in the ceramic substrate (ceramic base material) during welding.
In the present invention, for example, copper is used as the flexible metal having a Young's modulus of 200 GPa or less, and therefore, it is possible to prevent cracking of the ceramic substrate and peeling of the wiring material during welding due to the buffering effect of copper.
However, in the manufacturing method in which the wiring material is integrated with the surface of the ceramic substrate 11 by firing the green sheet at a high temperature as described above, it is difficult to use copper as the wiring material.

By the way, in recent years, a method of forming a copper wiring on a ceramic substrate surface by using a semi-additive method without high temperature heating has been developed. This method does not print the wiring material paste on the green sheet and then fires it, but performs plating, sputtering, and etching on the fired green sheet in order using photolithography technology, thereby forming an arbitrary copper wiring. It is formed without being oxidized.
In the present invention, by using this semi-additive method, a copper wiring including the metallized layer 13 and the resonator element joining terminal 18 is formed later on the fired green sheet, so that the copper wiring is formed without being oxidized. can do.

Next, the structure of the joint between the metallized layer 13 and the metal lid 19 will be described in detail with reference to FIG.
In the case where the metallized layer and the contact leg 19c of the metal lid are welded by laser light, the laser light irradiation position is such that the center portion C of the laser beam spot diameter is the width of the contact leg 19c as shown in FIG. It is set so as to coincide with the center of the dimension W1.
When local welding is performed by irradiating laser light, cracks are generated in the ceramic substrate due to the difference between the temperature decrease rate of the ceramic base 11 and the temperature decrease rate of the metal lid 19. ing. That is, when the contact leg portion 19c is irradiated with laser light, the temperature of the contact leg portion and the silver braze increases locally to about 800 to 1000 ° C. On the other hand, the temperature of the ceramic portion in contact with the contact leg portion instantaneously rises to about 100 to 200 ° C., but does not rise to 800 to 1000 ° C. like a metal lid. For this reason, when the welded part cools, strain stress due to shrinkage occurs between the members, and cracks are generated on the ceramic side, which is a material that is overwhelmingly brittle than metal, due to strain stress during shrinkage, The upper wiring is easy to peel off.

In the present invention, the metallized layer 13 that relaxes the difference in the temperature decrease rate by interposing the metallized layer 13 having a Young's modulus of 200 GPa or less functioning as a buffer layer between the ceramic base and the metal lid. It is.
On the surface of the metallization layer 13 made of copper (linear expansion coefficient: 16.8 ppm / ° C.) as a metal having a Young's modulus of 200 GPa or less, an extremely thin nickel thin film 14 and an anti-oxidation gold thin film 15 are sequentially plated. Are stacked.

On the other hand, the metal lid 19 includes a base material 19A made of Kovar (linear expansion coefficient: 5.5 ppm / ° C.), which is a metal material having a linear expansion coefficient close to the linear expansion coefficient (7 ppm / ° C.) of the ceramic substrate, Silver brazing 19B as a brazing material laminated on the lower surface of the base material including the contact leg 19c by the cladding method, and a nickel film 19C as an antioxidant film laminated on the upper surface of the base material 19A by the cladding method. It is configured.
As the material of the base material 19A, 42 nickel and SUS can be used except for Kovar.
Since silver solder is made of silver and copper as well known and has a melting point of about 700 to 800 ° C., the silver solder is similar to the temperature difference between the metal lid and the ceramic substrate when melted by welding. A large temperature difference also occurs between the ceramic substrate and the ceramic substrate. For this reason, the buffer effect by the metallized layer 13 is exhibited in welding using silver solder.
As the brazing material, gold-tin brazing material can be used in addition to silver brazing.
In this example, the thickness of the base 19A of the metal lid is 40 μm, the thickness of the silver solder 19B is 10 to 15 μm, and the thickness of the nickel film 19C is 5 μm. The width W1 of the contact leg 19c of the metal lid was 40 μm.

Moreover, the thickness of the insulating base material 11 which concerns on this example is 200 micrometers.
The width W2 of the metallized layer 13 is 120 μm, and the thickness of the copper portion of the metallized layer 13 is t15 μm to 25 μm. When the thickness of the copper portion of the metallized layer 13 is less than 15 μm, the buffering effect against shrinkage at the time of cooling after welding is reduced, cracks are generated in the ceramic substrate, and the wiring material is peeled off. Also, the greater the thickness of the metallized layer, the greater the stress relaxation effect because the distance between the insulating substrate and the lid can be separated, but when the thickness of the metallized layer exceeds 25 μm Increases the energy required to raise the temperature of the metallized layer during welding and increases the time required for the rise, which raises the problem of increased costs and reduced productivity.

In the above embodiment, the metallized layer 13 is formed on the ceramic substrate side. However, the metallized layer 13 made of copper or the like is previously integrated on the lower surface of the contact leg 19c of the metal lid. Also good. When the metallized layer 13 is formed on the contact leg side, the copper annular body is integrated with the bottom surface of the contact leg by the cladding method. As is well known, the clad method is a method in which metal foils are laminated and pressure-bonded.
In the piezoelectric device 1 of the present embodiment, since the metallized layer 13 and the silver braze 19B are interposed on the joint surface between the metal lid 19 and the ceramic substrate 11, when welding is performed by irradiating laser light as shown in FIG. In addition, cracks may occur in the ceramic portion due to the temperature difference between the ceramic and the metal lid during the temperature rise, and the temperature decrease rate difference between the two members during the cooling, or the metallized layer 13 may peel off. Is prevented.

Next, FIGS. 4A and 4B are a longitudinal sectional view and a main part enlarged view of a piezoelectric device as an example of an electronic device according to another embodiment of the present invention.
The piezoelectric device 40 is different from the piezoelectric device according to the above embodiment in that the ceramic substrate 10 is not flat and has a recessed portion 41 at the center of the upper surface, and an annular outer frame 42 surrounds the recessed portion 41. It is in the structure formed. The same members as those in the piezoelectric device of FIG.
The ceramic substrate 10 has a plurality of external mounting terminals 16 on the lower surface of the ceramic substrate 11, and the resonator element bonding terminal 18 to which the piezoelectric resonator element 20 is bonded to the inner bottom surface of the recessed portion 41 provided on the other main surface. Have. The resonator element joining terminal 18 and other terminals (not shown) are connected to the corresponding external mounting terminals 16 by intra-layer wiring (vias) 17.
The piezoelectric vibrating piece 20 is bonded while being electrically connected by a bonding member 30 such as a silver paste in a state where the external connection electrode provided on one end side thereof is aligned with the corresponding vibrating piece bonding terminal 18. The other end side is cantilevered as a free end.

The flat metal lid 19 is made of a metal such as Kovar, 42 alloy, or phosphor bronze.
The metal lid 19 includes a base material 19A made of Kovar (linear expansion coefficient: 5.5 ppm / ° C.), which is a metal material having a linear expansion coefficient close to that of the ceramic substrate (7 ppm / ° C.), and a base material A silver solder 19B as a brazing material laminated on the lower surface of the substrate by a clad method, and a nickel film 19C as an antioxidant film laminated on the upper surface of the base material 19A by a clad method. As the material of the base material 19A, 42 nickel and SUS can be used except for Kovar.
A metallized layer 13 is formed on the upper surface of the annular outer frame 42 of the ceramic substrate. As the metallized layer 13, a metal having a Young's modulus of 200 GP or less, such as copper, is used. In addition, as long as Young's modulus is a metal of 200 GPa or less, you may be other than copper.

In the present invention, the metallized layer 13 having a Young's modulus of 200 GPa or less that functions as a buffer layer is interposed between the ceramic base 11 and the metal lid 19, thereby reducing the temperature of the ceramic base 11 and the metal lid 19. The difference in ratio can be alleviated by the metallized layer 13.
The metal lid 19 is irradiated with a laser beam or an electron beam as shown in FIG. 4B with the outer peripheral lower surface in contact with the metallized layer 13 to melt and solidify the silver braze 19B. The upper surface of the annular outer frame 42 is joined and integrated. In addition, seam welding can also be used as a welding method.

In this embodiment, as shown in FIG. 4B, the metallized layer 13 formed on the entire upper surface of the annular outer frame 42 of the ceramic substrate 10 and the lower surface of the metal lid 19 have a relatively low melting point, for example. It joins via the silver braze 19B as a joining member which consists of alloys.
The metallized layer 13 may be formed not on the ceramic substrate 11 side but on the lower surface of the outer periphery of the metal lid 19. When the metallized layer 13 is formed on the metal lid side, the copper annular body is integrated on the lower surface of the metal lid body by the cladding method.
Also in the piezoelectric device 40 of the present embodiment, since the metallized layer 13 and the silver braze 19B are interposed on the joint surface between the metal lid and the ceramic substrate, welding is performed by irradiating laser light as shown in FIG. In this case, the ceramic portion is cracked or the metallized layer 13 is peeled off due to the temperature difference between the ceramic and the metal lid at the time of temperature rise and the temperature decrease rate difference between the two members at the time of cooling. It is prevented.

Next, FIG. 5 is a flowchart showing an example of a method for manufacturing a piezoelectric device according to the present invention. FIG. 6 is a plan view showing a process of manufacturing a ceramic substrate using a green sheet.
In this example, the manufacturing method of the electronic device shown in FIGS. 1 and 2 will be described. However, the electronic device according to FIG. 4 can be manufactured by the same procedure.
The manufacturing method of the present invention includes a step of preparing the electronic component 20, the ceramic substrate 10, and the metal lid, a step of bonding the electronic component on the wiring, and an electronic component by bonding the metal lid 19 to the ceramic substrate. Forming an internal space for housing the internal space, and in the step of forming the internal space, a metal lid is disposed on the metallized layer and then irradiated with a laser beam or an electron beam from the metal lid side. It is characterized by melting the brazing material.
The manufacturing process of the piezoelectric device 1 includes a pre-process for preparing the piezoelectric vibrating piece 20, the ceramic substrate 10, and the metal lid 19, and joining the piezoelectric vibrating piece 20 on the ceramic substrate 10 and then joining the metal lid 19. Thus, it can be roughly divided into a post-process (assembly process) for hermetically sealing the piezoelectric vibrating piece 20. First, an outline of the preparation of the piezoelectric vibrating piece 20 and the metal lid 19 in the previous process will be described.

In the preparation of the piezoelectric vibrating piece 20 shown in step S1-1, the piezoelectric vibrating piece 20 is manufactured so that the piezoelectric device 1 can be assembled. A plurality of piezoelectric vibrating reeds 20 can be collectively formed by arranging a plurality of large-size wafers obtained by cutting and polishing a piezoelectric material such as quartz into a predetermined size. The outline will be described. First, a large crystal substrate (crystal wafer) which is cut out at a predetermined cut angle with respect to the crystal axis and then polished to have a desired thickness and surface state is prepared. Then, the outer shape of the plurality of piezoelectric vibrating pieces 20 is formed on the quartz substrate by wet etching using photolithography. In addition, the outer shape of the piezoelectric vibrating piece 20 is efficiently connected to the crystal wafer (wafer) while being connected to the crystal wafer by a perforated break-off portion or the like so as not to be completely separated from the crystal substrate. It is preferable to flow. Then, by forming electrodes such as the excitation electrode 25 and the external connection electrode 26 by sputtering or vapor deposition, a plurality of piezoelectric vibrating reeds 20 are formed in a matrix on the quartz wafer.
In the preparation of the metal lid 19 shown in step S1-3, the metal lid 19 is manufactured so that the piezoelectric device 1 can be assembled. The metal lid 19 has a structure in which, for example, a nickel film 19C is laminated on the surface of a plate-like base material 19A made of a metal such as 42 alloy, Kovar, or phosphor bronze, and a silver solder 19B is laminated and integrated on the back surface by a cladding method. And forming a metal lid body 19 having a concave portion formed in the central portion and a contact leg portion 19c provided in an annular shape on the outer peripheral portion.

Next, the manufacturing process from manufacturing the ceramic substrate 10 to assembling the piezoelectric device 1 will be described.
In the present embodiment, a ceramic green sheet 51 is used as a base material of the ceramic substrate 10, and in manufacturing the ceramic substrate 10, the green sheet prepared in step S1-2 is fired in step S2. Next, in step S3, the metallized layer 13, the resonator element joining terminal 18, and the external mounting terminal 19 are respectively formed using copper on the fired green sheet using a semi-additive method. A nickel thin film 14 and a gold thin film 15 are sequentially stacked on the surface of copper constituting the metallized layer 13 to prevent oxidation.
As described above, a green sheet in which a plurality of ceramic substrates 10 are formed in a matrix is completed by the steps from the green sheet 51 preparation in steps 0000S1-2 to steps S2 and S3 (see FIG. 6).
At this stage, the green sheet 51 can be divided into individual ceramic substrates 10. For example, the green sheet 51 in which the plurality of piezoelectric device forming regions 1A are formed in a matrix is diced along vertical and horizontal dicing lines formed between the piezoelectric device forming regions 1A, and the like, for example. Can be obtained.

In the present embodiment, a method for efficiently assembling the piezoelectric device 1 in the state of the green sheet 51 on which the plurality of ceramic substrates 10 are formed will be described below.
In the piezoelectric device assembly process, first, as shown in step S4, the piezoelectric vibrating reed 20 prepared in step S1-1 is joined to each piezoelectric device forming region 1A of the green sheet 51. Specifically, first, a bonding member 39 such as a silver paste is applied to the vibrating piece bonding terminal 18 in each piezoelectric device forming region 1A by a dispenser or screen printing, and then provided on one end side of the piezoelectric vibrating piece 20. The formed external connection electrode 26 is positioned and temporarily fixed to the corresponding resonator element joining terminal 18. Then, a process according to the curing method of the joining member 39, for example, if the thermosetting joining member 39 is heated at a predetermined temperature, and if it is an ultraviolet curable joining member, the joining is performed by irradiating with ultraviolet rays. The member 39 is solidified, and the piezoelectric vibrating piece 20 is joined in a cantilevered manner.

Next, in step S5, the metal lid 19 is disposed in each piezoelectric device forming region 1A of the green sheet 51 to which the piezoelectric vibrating piece 20 is bonded. The silver solder 19B on the lower surface of the contact leg portion 19c of the metal lid 19 is positioned in a positional relationship that is aligned with the metallized layer 13 on the ceramic substrate.
Next, in the metal lid joining process of step S6, as shown in FIG. 3, the laser beam having a required spot diameter is irradiated toward the upper surface of the contact leg 19c to heat and melt the silver solder 19B. As a result, the hermetic sealing of the piezoelectric vibrating piece 20 by the metal lid 19 can be made stronger and more reliable.
Note that the above-described series of metal lid joining steps to the ceramic substrate 10 (metal lid arrangement in step S5 and metal lid joining in step S6) are performed in an inert gas atmosphere such as nitrogen gas or argon gas, for example. Or it is preferable to carry out in a decompression space. As a result, the inside of the cavity T formed by the ceramic substrate 10 in which the piezoelectric vibrating piece 20 is accommodated and the metal lid 19 is filled with an inert gas, or is sealed and sealed in a decompression space. It is possible to effectively prevent the resonator element 20 from being corroded or deteriorated by oxygen or moisture in the atmosphere.
As described above, the plurality of piezoelectric devices 1 are formed in a matrix on the green sheet 51 through the series of steps described above.

Next, in the dividing step of step S7, the green sheet 51 that has undergone the steps up to step S6 described above is divided to obtain a plurality of pieces of piezoelectric devices 1 simultaneously.
The piezoelectric device 1 obtained by the dividing step is completed by inspecting electrical characteristics and appearance quality in step S8, and a series of manufacturing processes of the piezoelectric device 1 is completed.
According to the method for manufacturing a piezoelectric device of the above-described embodiment, a laser beam is used in a state where the contact leg portion 19c of the metal lid is placed on the metallized layer 13 formed on the ceramic substrate 10 and having a Young's modulus of 200 GPa or less. Since the contact leg portion 19c is heated, the metallized layer and the contact leg portion are joined by the silver braze 19B previously disposed on the lower surface of the contact leg portion.
By interposing the metallized layer 13 having a Young's modulus of 200 GPa or less that functions as a buffer layer between the ceramic substrate 11 and the metal lid body, the difference in temperature decrease rate between the ceramic substrate 11 and the metal lid body 19 can be reduced. It can be relaxed by the metallized layer 13. For this reason, it can prevent effectively that a crack is formed in the ceramic base material 11 or the wiring material is peeled off.

The specific forms described in the above embodiments and modifications, for example, the shape of the ceramic substrate 10 or the piezoelectric vibrating piece 20 as an electronic component are not limited.
Similarly, the position and shape of each electrode, wiring, terminal, etc. are not limited to the above embodiment.
In the embodiment and the modification, the piezoelectric devices 1 and 40 on which the piezoelectric vibrating piece 20 as an electronic component is mounted have been described as an example of the electronic device. However, the configuration shown in the above embodiment and the modification is not limited to this, and various configurations of structures in which various electronic components such as a semiconductor circuit element are bonded to a substrate as an electronic component and the electronic component is hermetically sealed with a metal lid. It can be applied to a package structure of an electronic device.
Specifically, for example, the present invention is applied to a package structure of a piezoelectric oscillator in which a semiconductor circuit element constituting an oscillation circuit is incorporated inside a cavity T of a package of a piezoelectric vibrator such as a crystal vibrator or outside the package. can do.

That is, FIG. 7 is a sectional view showing a piezoelectric oscillator as another configuration example of the electronic device of the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to the same part as FIG. 1, FIG.
As shown in FIG. 7, the present invention is also applied to a package structure of a piezoelectric oscillator 60 in which a semiconductor circuit element 61 constituting an oscillation circuit is incorporated inside a cavity T of a package of a piezoelectric vibrator such as a crystal vibrator or outside the package. The invention can be applied.
Also in this piezoelectric oscillator, by interposing the metallized layer 13 functioning as a buffer layer and having a Young's modulus of 200 GPa or less between the ceramic substrate 11 and the metal lid 19, the temperature of the ceramic substrate and the metal lid is increased. The difference in reduction rate can be mitigated by the metallized layer. For this reason, it can prevent effectively that a crack is formed in a ceramic base material or a wiring material peels.

  Next, FIG. 8 is a schematic configuration diagram showing the configuration of the electronic apparatus according to the present invention. The electronic apparatus 70 includes the piezoelectric devices 1 and 40 described above. Examples of the electronic device 70 using the piezoelectric devices 1 and 40 include a transmission device. In these electronic devices 70, the piezoelectric device is used as a reference signal source, a voltage variable piezoelectric oscillator (VCXO), or the like, and can provide a small and favorable electronic device.

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric device, 10 ... Ceramic substrate, 11 ... Ceramic base material, 12 ... Outer peripheral upper surface, 13 ... Metallized layer, 14 ... Nickel thin film, 15 ... Gold thin film, 16 ... External mounting terminal, 18 ... Vibrating piece joint terminal, 19 ... Metal lid, 19A ... Base material, 19B ... Brazing material (silver brazing), 19C ... Nickel film, 19a ... Horizontal part, 19b ... Side wall part, 19c ... Contact leg part, 20 ... Piezoelectric vibrating piece, 25 ... Excitation Electrode, 26... External connection electrode, 30. Bonding member, 40... Piezoelectric device, 41.

Claims (8)

A ceramic substrate with wiring on the surface;
An electronic component joined to the wiring;
A metal lid that is bonded to the ceramic substrate at a peripheral portion through a metallized layer having a Young's modulus of 200 GPa or less and covers the electronic component in plan view;
An electronic device comprising:   2. The electronic device according to claim 1, wherein the metal lid is bonded to the ceramic substrate at the peripheral portion via a brazing material together with the metallized layer.   The electronic device according to claim 1, wherein the metallized layer is made of copper.   The electronic device according to claim 1, wherein the metallized layer has a thickness of 15 to 25 μm. Wiring for joining electronic components;
A metallized layer having a Young's modulus of 200 GPa or less for bonding to the peripheral portion of the metal lid;
Is provided on the surface of the ceramic substrate.   The ceramic substrate according to claim 5, wherein the metallized layer is made of copper and has a thickness of 15 to 25 μm. A method for manufacturing an electronic device according to any one of claims 2 to 4,
Preparing the electronic component, the ceramic substrate, and the metal lid, respectively;
Bonding the electronic component on the wiring;
Bonding the metal lid to the ceramic substrate to form an internal space for accommodating the electronic component;
With
In the step of forming the internal space, the metal lid is disposed on the metallized layer, and then the brazing material is melted by irradiating a laser beam or an electron beam from the metal lid side. A method for manufacturing an electronic device. The electronic device according to any one of claims 1 to 4 is a piezoelectric vibrator,
A piezoelectric oscillator comprising a semiconductor element.

Images