Electronic components, filters and multiplexers

Abstract

To provide an electronic component capable of suppressing stress applied to the bonding layer.SOLUTION: An electronic component has a substrate 10, a functional element on the substrate 10, an annular metal layer 30 provided on the substrate 10 to surround the functional element in plan view, a lid 20 provided on the annular metal layer 30 to seal the functional element in a void 26 with the annular metal layer 30, and a metal bonding layer 24 bonded to the lid 20 and the lid 20 side surface in the annular metal layer 30 and the lid 20 side portion in the annular metal layer 30.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to electronic components, filters, and multiplexers.

Background Art

[0002] An electronic component is known in which a functional element such as an elastic wave element is provided on a substrate, an annular metal layer is provided on the substrate so as to surround the functional element, and a lid is joined on the annular metal layer, and the functional element is sealed in a void by the lid and the annular metal layer (for example, Patent Documents 1 to 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the lid and the annular metal layer are joined using a joining layer such as solder, stress is applied to the joining layer due to the thermal stress between the lid and the substrate, and cracks or the like may occur in the joining layer. As a result, the airtightness of the voids in the lid and the annular metal layer decreases.

[0005] The present invention has been made in view of the above problems, and an object thereof is to suppress the stress applied to the joining layer.

Means for Solving the Problems

[0006] <00The present invention relates to an electronic component comprising: a substrate; a functional element provided on the substrate; an annular metal layer provided on the substrate so as to surround the functional element in a plan view; a lid provided on the annular metal layer and sealing the functional element in a gap with the annular metal layer; and a metal bonding layer bonded to the lid, the lid-side surface of the annular metal layer, and the lid-side portion of the side surface of the annular metal layer.

[0007] In the above configuration, the annular metal layer comprises a first metal layer and a second metal layer which is mainly composed of a second metal element having a higher resistivity than the first metal element which is the main component of the first metal layer, is thinner than the first metal layer, is in contact with the metal bonding layer, and is provided on the first metal layer, and the metal bonding layer can be bonded to the side surface of the second metal layer.

[0008] In the above configuration, the content of the first metal element in the first metal layer is 50 atomic percent or more, and the content of the second metal element in the second metal layer is 50 atomic percent or more.

[0009] In the above configuration, the metal bonding layer may be bonded to a part of the side surface of the first metal layer.

[0010] In the above configuration, at the surface where the first metal layer and the second metal layer are in contact, the width of the first metal layer in the direction perpendicular to the direction in which the annular metal layer extends can be smaller than the width of the second metal layer in the same perpendicular direction.

[0011] In the above configuration, the first metal layer may be mainly composed of copper, the second metal layer may be mainly composed of nickel, and the metal bonding layer may be mainly composed of gold and tin.

[0012] In the above structure, the copper content in the first metal layer is 50 atomic% or more, the nickel content in the second metal layer is 50 atomic% or more, and the total of the gold content and the tin content in the metal bonding layer is 50 atomic% or more.

[0013] In the above structure, the metal bonding layer can be configured to be solder.

[0014] In the above structure, the metal bonding layer can be configured to contact the surface on the lid side in the annular metal layer and the portion on the lid side in the side surface of the annular metal layer.

[0015] In the above structure, the linear expansion coefficients of the substrate and the lid can be different.

[0016] In the above structure, the functional element can be configured to be an elastic wave element.

[0017] In the above structure, the substrate includes a support substrate and a piezoelectric layer provided on the support substrate, the elastic wave element is provided on the surface of the piezoelectric layer, and the annular metal layer is provided on the support substrate in a region where the piezoelectric layer is removed.

[0018] The present invention is a filter including the above electronic component.

[0019] The present invention is a multiplexer including the above filter.

Effects of the Invention

[0020] According to the present invention, the stress applied to the bonding layer can be suppressed.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1(a) and FIG. 1(b) are a cross-sectional view and a plan view of an elastic wave device according to Example 1. [Figure 2] Figure 2 is a plan view of the elastic wave element in Example 1. [Figure 3] Figure 3 is an enlarged cross-sectional view of the vicinity of the annular metal layer in Example 1. [Figure 4] Figures 4(a) to 4(d) are enlarged cross-sectional views showing the method for forming the annular metal layer of the elastic wave device in Example 1. [Figure 5] Figure 5 is an enlarged cross-sectional view of the vicinity of the annular metal layer in Comparative Example 1. [Figure 6] Figures 6(a) and 6(b) are enlarged cross-sectional views of the vicinity of the annular metal layer in modified examples 1 and 2 of Example 1. [Figure 7] Figure 7 is an enlarged cross-sectional view of the vicinity of the annular metal layer in Modification 3 of Example 1. [Figure 8] Figure 8(a) is a cross-sectional view of the elastic wave device according to Modification 4 of Example 1, and Figure 8(b) is a cross-sectional view of the elastic wave element in Modification 4 of Example 1. [Figure 9] Figure 9(a) is a circuit diagram of the filter according to Example 2, and Figure 9(b) is a circuit diagram of the duplexer according to Modification 1 of Example 2. [Modes for carrying out the invention]

[0022] The embodiments of the present invention will be described below with reference to the drawings. [Examples]

[0023] Example 1 is an example of an elastic wave device having an elastic wave element as an electronic component. Figures 1(a) and 1(b) are a cross-sectional view and a plan view of the elastic wave device according to Example 1. Figure 1(b) mainly shows the substrate 10 and the annular metal layer 30. The thickness direction of the substrate 10 is the Z direction, and the planar directions of the substrate 10 are the X and Y directions.

[0024] As shown in Figures 1(a) and 1(b), the substrate 10 comprises a support substrate 10a, a piezoelectric layer 10c provided on the support substrate 10a, and an insulating layer 10b provided between the support substrate 10a and the piezoelectric layer 10c. An elastic wave element 12 and a metal layer 14 are provided on the piezoelectric layer 10c. The elastic wave element 12 is, for example, a surface acoustic wave element. The metal layer 14 functions as wiring and pads electrically connected to the elastic wave element 12. The piezoelectric layer 10c and the insulating layer 10b are removed from the peripheral edge of the substrate 10 and the region on the substrate 10 where the via wiring 16 is provided, and the upper surface of the substrate 10 is the upper surface of the support substrate 10a. The via wiring 16 penetrates the support substrate 10a. A terminal 18 is provided on the lower surface of the substrate 10. The via wiring 16 electrically connects the metal layer 14 and the terminal 18. An annular metal layer 30 is provided on a support substrate 10a at the periphery of the substrate 10, surrounding the elastic wave element 12. The annular metal layer 30 comprises an annular metal layer 30a provided on the substrate 10 and an annular metal layer 30b provided on the annular metal layer 30a. A lid 20 is provided above the substrate 10. A metal layer 22 is provided on the lower surface of the lid 20. The annular metal layer 30 and the metal layer 22 are joined by a bonding layer 24. The lid 20 and the annular metal layer 30 seal the elastic wave element 12 in the gap 26.

[0025] The support substrate 10a is, for example, a sapphire substrate, alumina substrate, quartz substrate, crystal substrate, spinel substrate, SiC substrate, or silicon substrate. The insulating layer 10b is, for example, a single layer or a stack of silicon oxide layer, aluminum oxide layer, silicon nitride layer, or aluminum nitride layer. The piezoelectric layer 10c is, for example, a piezoelectric substrate such as a single-crystal lithium tantalate substrate, a single-crystal lithium niobate substrate, or a single-crystal crystal substrate. The single-crystal lithium tantalate substrate and single-crystal lithium niobate substrate are, for example, rotational Y-cut X-propagation substrates. The metal layer 14, via wiring 16, and terminals 18 are, for example, a single layer or a stack of metal layers such as a copper layer, gold layer, silver layer, titanium layer, nickel layer, or tungsten layer. The lid 20 is, for example, a metal layer such as Kovar, or an insulating layer such as a sapphire substrate, alumina substrate, quartz substrate, crystal substrate, spinel substrate, SiC substrate, or silicon substrate. Another functional element may be provided on the lower surface of the lid 20. In this case, another functional element is sealed in the gap 26.

[0026] The metal layer 22 is provided when the bonding layer 24 and the lid 20 cannot be directly joined, and is a layer that provides good wettability to the bonding layer 24. If the bonding layer 24 is gold-tin, the metal layer 22 is, for example, a gold layer. If the bonding layer 24 and the lid 20 can be directly joined, the metal layer 22 may not be provided. The bonding layer 24 is, for example, gold-tin solder, tin-silver solder, or tin-silver-copper solder. The annular metal layer 30a functions as a shield, so it is preferable to use a material with low resistivity, such as a copper layer, gold layer, aluminum layer, or silver layer. The annular metal layer 30b functions as a diffusion prevention layer to prevent diffusion between the bonding layer 24 and the annular metal layer 30a, and is, for example, a nickel layer, chromium layer, or titanium layer. If diffusion between the bonding layer 24 and the annular metal layer 30a is not a problem, the annular metal layer 30b may not be provided. The annular metal layer 30 may have another annular metal layer between the substrate 10 and the annular metal layer 30a.

[0027] Figure 2 is a plan view of the elastic wave element in Embodiment 1. As shown in Figure 2, the elastic wave element 12 is a surface acoustic wave resonator or a Lamb wave resonator. An IDT (Interdigital Transducer) 40 and a reflector 42 are formed on the piezoelectric layer 10c. The IDT 40 has a pair of comb-shaped electrodes 40a facing each other. The comb-shaped electrodes 40a have a plurality of electrode fingers 40b and a busbar 40c connecting the plurality of electrode fingers 40b. The reflector 42 is provided on both sides of the IDT 40. The IDT 40 excites surface acoustic waves in the piezoelectric layer 10c. The wavelength of the elastic wave is approximately equal to the pitch of the electrode fingers 40b of one of the pair of comb-shaped electrodes 40a. That is, the wavelength of the elastic wave is approximately equal to twice the pitch of the electrode fingers 40b of the pair of comb-shaped electrodes 40a. The IDT 40 and the reflector 42 are formed from, for example, an aluminum film, a copper film, or a molybdenum film. A protective film or temperature compensation film may be provided on the piezoelectric layer 10c so as to cover the IDT 40 and the reflector 42. The elastic wave element 12 includes electrodes that excite elastic waves. For this reason, the elastic wave element 12 is covered with an air gap 26 so as not to restrict the elastic waves.

[0028] Figure 3 is an enlarged cross-sectional view of the vicinity of the annular metal layer in Example 1. As shown in Figure 3, the bonding layer 24 covers the upper surface of the annular metal layer 30, and the annular metal layer 30 covers the side surfaces corresponding to the YZ plane. That is, the bonding layer 24 covers the edge 50 at the interface between the upper surface of the annular metal layer 30 and the bonding layer 24. The upper surfaces of the annular metal layers 30a and 30b are curved surfaces with the central part protruding upward. This is because the annular metal layers 30a and 30b were formed using the electroplating method. The upper surfaces of the annular metal layers 30a and 30b may be flat. Both sides of the annular metal layer 30 are parallel. The width of both sides of the annular metal layer 30 on the substrate 10 side may be narrower or wider than the width on the lid 20 side. The sides of the annular metal layer 30 may be curved or uneven.

[0029] Let T1 and T2 be the thicknesses of the annular metal layers 30a and 30b in the Z direction, respectively. Let T3a and T3b be the maximum and minimum thicknesses of the bonding layer 24 between the annular metal layer 30 and the lid 20 in the Z direction, respectively. Let W1 be the width of the annular metal layer 30 in the X direction. Let W3 be the width of the bonding layer 24 in the X direction at the interface between the annular metal layer 30 and the bonding layer 24. Let W4 be the width of the bonding layer 24 in the X direction at the interface between the lid 20 and the metal layer 22 and the bonding layer 24. Let H be the height in the Z direction at which the bonding layer 24 is in contact with the side surface of the annular metal layer 30. The thickness T1 is, for example, 10 μm to 20 μm, the thickness T2 is, for example, 1 μm to 5 μm, the thicknesses T3a and T3b are, for example, 1 μm to 5 μm and 2 μm to 6 μm, respectively, the width W1 is, for example, 10 μm to 30 μm, the width W3 is, for example, 0.5 μm to 10 μm, the width W4 is, for example, 10 μm to 50 μm, and the height H is, for example, 1 μm to 10 μm. The thickness of the support substrate 10a of the substrate 10 is, for example, 50 μm to 200 μm, and the thickness of the lid 20 is, for example, 10 μm to 50 μm.

[0030] Figures 4(a) to 4(d) are enlarged cross-sectional views showing the method for forming the annular metal layer of an elastic wave device in Example 1. As shown in Figure 4(a), a mask layer 52 having an opening 53 is formed on the substrate 10. The mask layer 52 is, for example, a photoresist and is formed, for example, using a photolithography method.

[0031] As shown in Figure 4(b), an annular metal layer 30 and a bonding layer 24 are formed in the opening 53 using electroplating. If the side surface of the mask layer 52 is inclined, the side surface of the annular metal layer 30 may also be inclined. Depending on the conditions of the electroplating method, the central part of the upper surface of the annular metal layer 30 and the upper surface of the bonding layer 24 may become curved and protrude upward.

[0032] As shown in Figure 4(c), the mask layer 52 is removed. The substrate 10 is heated so that the bonding layer 24 reaches a temperature above its melting point. The lid 20 is pressed against the bonding layer 24 from above, as indicated by arrow 54. As shown in Figure 4(d), the bonding layer 24 is bonded to the metal layer 22. The lid 20 is pressed against the bonding layer 24 again, as indicated by arrow 55. As a result, as indicated by arrow 56, the molten bonding layer 24 wraps around the side of the annular metal layer 30. Subsequently, as the substrate 10 returns to room temperature, the bonding layer 24 solidifies, and the lid 20 is bonded to the annular metal layer 30 via the bonding layer 24.

[0033] [Comparative Example 1] Figure 5 is an enlarged cross-sectional view of the vicinity of the annular metal layer in Comparative Example 1. As shown in Figure 5, in Comparative Example 1, the bonding layer 24 covers the upper surface of the annular metal layer 30 but not the sides. The other configurations are the same as in Example 1. In Comparative Example 1, there is a difference in the coefficient of linear expansion between the substrate 10 and the lid 20. Therefore, when the temperature is raised to melt the bonding layer 24 and bond the annular metal layer 30 and the lid 20, and then the temperature is returned to room temperature, the stress at the edge 50 at the interface between the upper surface of the annular metal layer 30 and the bonding layer 24 increases. Furthermore, the stress at the edge 50 increases with temperature cycling. This may cause the bonding layer 24 and the annular metal layer 30 to peel off, or cracks to form in the bonding layer 24. If peeling or cracking occurs, the airtightness of the void 26 may decrease.

[0034] [simulation] The stress applied to the bonding layer 24 for Comparative Example 1 and Example 1 was simulated using the two-dimensional finite element method. In the simulation, a straight line passing through the midpoints of the substrate 10 and lid 20 in the X direction was used as a mirror surface condition, and the simulation was performed in half of the region in the X direction. The dimensions and materials of each component in the simulation are as follows: Support substrate 10a: Sapphire substrate with a thickness of 75 μm Insulating layer 10b, piezoelectric layer 10c: Not provided Annular metal layer 30a: A copper layer with a thickness T1 of 21 μm and a width W1 of 25 μm. Upper surface of the annular metal layer 30a: part of the arc Annular metal layer 30b: Nickel layer with a thickness T2 of 2.5 μm and a width W1 of 25 μm. Upper surface of the annular metal layer 30b: part of the arc Bonding layer 24: Gold-tin (20% tin by mass) with thickness T3a of 7 μm and thickness T3b of 5 μm. Width W4 of the upper surface of bonding layer 24: 31 μm Metal layer 22: A gold layer with a thickness of 1 μm and a nickel layer with a thickness of 1 μm, from the substrate 10 side. Lid 20: Kovar with a thickness of 30 μm Width W3: 2μm Height H: 2.5 μm The bonding layer 24 is not bonded to the side surface of the annular metal layer 30a (structure of modified example 2 of Example 1, described later). The width of half of the support substrate 10a and lid 20 in the X direction was set to 550 μm.

[0035] The conditions for the process of joining the lid 20 to the annular metal layer 30 are as follows. As shown in Figure 4(c), the temperature is linearly increased over time from 25°C to 320°C with respect to time, while the lid 20 is not in contact with the bonding layer 24. Then, at 320°C, the lid 20 is brought into contact with the bonding layer 24. The lid 20 and the bonding layer 24 are fixed in place, and the temperature is linearly decreased over time from 320°C to 25°C.

[0036] After cooling to 25°C, the stress at the -X end 50 at the interface between the upper surface of the annular metal layer 30 and the bonding layer 24 in Figure 3 of Example 1 and Figure 5 of Comparative Example 1 is as follows: Comparative example 1: 204MPa Example 1: 137 MPa Thus, in Example 1, the stress at end 50 is approximately 67% of that in Comparative Example 1.

[0037] Thus, in Example 1, the bonding layer 24 covers not only the upper surface of the annular metal layer 30 but also a portion of the upper part of the annular metal layer 30. This suppresses stress near the interface between the bonding layer 24 and the upper surface of the annular metal layer 30. This prevents delamination between the bonding layer 24 and the annular metal layer 30 and prevents cracking of the bonding layer 24, thereby improving the airtightness of the void 26.

[0038] [Example 1 Modification 1] Figure 6(a) is an enlarged cross-sectional view of the vicinity of the annular metal layer in Modification 1 of Example 1. As shown in Figure 6(a), the annular metal layer 30b is not provided, and the annular metal layer 30 is the annular metal layer 30a. The annular metal layer 30b may not be provided if the diffusion of elements between the annular metal layer 30a and the bonding layer 24 is not a problem. For example, if the annular metal layer 30a is a gold layer and the bonding layer 24 is gold-tin, the annular metal layer 30b may not be necessary. The other configurations are the same as in Example 1, and their explanation is omitted.

[0039] [Modification 2 of Example 1] Figure 6(b) is an enlarged cross-sectional view of the vicinity of the annular metal layer in Modification 2 of Example 1. As shown in Figure 6(b), the bonding layer 24 covers the side surface of the annular metal layer 30b but not the side surface of the annular metal layer 30a. As in Example 1, by having the bonding layer 24 cover a portion of the side surface of the annular metal layer 30a, the stress applied to the bonding layer 24 can be further suppressed. However, when the bonding layer 24 and the annular metal layer 30a come into contact, elements of the bonding layer 24 and the annular metal layer 30a diffuse. In Modification 2 of Example 1, since the bonding layer 24 and the annular metal layer 30a do not come into contact, the diffusion of elements of the bonding layer 24 and the annular metal layer 30a can be suppressed. The other configurations are the same as in Example 1 and will not be described further.

[0040] [Modification 3 of Example 1] Figure 7 is an enlarged cross-sectional view of the vicinity of the annular metal layer in Modification 3 of Example 1. As shown in Figure 7, the width W1 of the annular metal layer 30a at the interface where the annular metal layers 30a and 30b meet is smaller than the width W2 of the annular metal layer 30b. The bonding layer 24 covers the step difference on the sides of the annular metal layers 30a and 30b. This improves the adhesion between the bonding layer 24 and the annular metal layer 30, and prevents the bonding layer 24 and the annular metal layer 30 from peeling off. The other configurations are the same as in Example 1 and will not be described further.

[0041] [Modification 4 of Example 1] Figure 8(a) is a cross-sectional view of an elastic wave device according to a modified example 4 of Example 1. As shown in Figure 8(a), an elastic wave element 12a is provided on a substrate 10. The substrate 10 is, for example, a sapphire substrate, an alumina substrate, a quartz substrate, a crystal substrate, a spinel substrate, a SiC substrate, or a silicon substrate. The other configurations are the same as in Figure 1(a) of Example 1.

[0042] Figure 8(b) is a cross-sectional view of the elastic wave element in Modification 4 of Example 1. As shown in Figure 8(b), in the elastic wave element 12a, which is a piezoelectric thin-film resonator, a piezoelectric film 46 is provided on the substrate 10. A lower electrode 44 and an upper electrode 48 are provided so as to sandwich the piezoelectric film 46. A gap 45 is formed between the lower electrode 44 and the substrate 10. The region where the lower electrode 44 and the upper electrode 48 face each other with at least a portion of the piezoelectric film 46 in between is the resonance region 47. In the resonance region 47, the lower electrode 44 and the upper electrode 48 excite elastic waves in thickness longitudinal vibration mode or thickness sliding vibration mode within the piezoelectric film 46. The lower electrode 44 and the upper electrode 48 are metal films such as ruthenium films. The piezoelectric film 46 is, for example, an aluminum nitride film, a lithium tantalate film, or a lithium niobate film. Instead of the gap 45, an acoustic reflective film that reflects elastic waves may be provided. The other configurations are the same as in Example 1 and will not be described.

[0043] In Example 1 and its modified form, the elastic wave element 12 or 12a (functional element) and the annular metal layer 30 are provided on the substrate 10, and in a plan view, the annular metal layer 30 is provided so as to surround the elastic wave element 12 or 12a. The lid 20 is provided on the annular metal layer 30 and together with the annular metal layer 30 seals the elastic wave element 12 or 12a within the gap 26. The bonding layer 24 (metal bonding layer) is bonded to the lid 20 and the lid 20 side surface of the annular metal layer 30 and the lid 20 side portion of the side surface of the annular metal layer 30. As a result, as shown in the simulation, the stress applied to the bonding layer 24 near the interface between the annular metal layer 30 and the bonding layer 24 can be suppressed.

[0044] The bonding layer 24 is, for example, solder. The melting point of the bonding layer 24 is lower than that of the annular metal layer 30. For example, the melting point of gold-tin (tin concentration is 20% by mass) is approximately 270°C. Thus, the melting point of solder is 300°C or lower. In contrast, the melting points of copper, nickel, gold, aluminum, and silver used in the annular metal layer 30 are 1085°C, 1455°C, 1064°C, 660°C, and 962°C, respectively, which are more than 300°C higher than the melting point of the bonding layer 24.

[0045] To suppress stress at the interface between the annular metal layer 30 and the bonding layer 24, it is preferable that the width W3 of the bonding layer 24 at the interface between the annular metal layer 30 and the bonding layer 24 be large. Comparing the width W3 with the width W1 of the annular metal layer 30, the width W3 is preferably 1 / 50 or more, more preferably 1 / 20 or more, even more preferably 1 / 10 or more, and preferably 2 μm or more. A larger width W3 results in a larger size. From this viewpoint, the width W3 is preferably 1 / 2 or less of the width W1, and more preferably 1 / 5 or less. Comparing the width W3 with the thickness T3b of the bonding layer 24, the width W3 is preferably 1 / 5 or more of the thickness T3b, and more preferably 1 / 2 or more. The width W3 is preferably 2 times or less of the thickness T3b.

[0046] To suppress stress at the interface between the annular metal layer 30 and the bonding layer 24, it is preferable that the height H at which the bonding layer 24 contacts the side surface of the annular metal layer 30 is large. When comparing the height H with the thickness (T1 + T2) of the annular metal layer 30, the height H is preferably 1 / 20 times or more of the thickness T1 + T2, more preferably 1 / 10 times or more, and even more preferably 1 / 5 times or more. If the thickness H is large, the bonding layer 24 may come into contact with the substrate 10. From this viewpoint, it is preferable that the height H is 1 / 2 times or less of the thickness T1 + T2.

[0047] As shown in Figure 6(a) of Modification 1 of Example 1, if the diffusion of elements between the bonding layer 24 and the annular metal layer 30a is not a problem, the annular metal layer 30b may not be provided.

[0048] As shown in Figures 3, 6(b), and 7 of Example 1 and its modified examples 2-4, the annular metal layer 30 comprises an annular metal layer 30a (first metal layer) and an annular metal layer 30b (second metal layer). The annular metal layer 30b is provided on the annular metal layer 30a and is in contact with the bonding layer 24. The bonding layer 24 is bonded to the side surface of the annular metal layer 30b. If the diffusion of elements from the bonding layer 24 into the annular metal layer 30a is a problem, the annular metal layer 30b can be provided as a diffusion prevention layer. Since the annular metal layer 30a functions as a shield, its resistivity is low and its thickness T1 is preferably thick. On the other hand, the main function of the annular metal layer 30b is diffusion prevention. For this reason, the resistivity of the annular metal layer 30b is higher than that of the annular metal layer 30a. The resistivity of the first metal element, which is the main component of the annular metal layer 30b, is higher than that of the second metal element, which is the main component of the annular metal layer 30a. The resistivity of the first and second metal elements refers to the resistivity of the bulk material containing 100% of the first and second metal elements, respectively. The content of the first metal element in the cyclic metal layer 30b is, for example, 50 atomic percent or more (or 80 atomic percent or more, or 90 atomic percent or more), and the content of the second metal element in the cyclic metal layer 30a is, for example, 50 atomic percent or more (or 80 atomic percent or more, or 90 atomic percent or more). Furthermore, the thickness T2 of the cyclic metal layer 30b is smaller than the thickness T1 of the cyclic metal layer 30a.

[0049] The resistivity of copper, gold, aluminum, and silver used in the annular metal layer 30a is 1.68 × 10⁻⁶, respectively. -8 Ω·m, 2.44 × 10 -8 Ω·m, 2.65 × 10 -8 Ω·m and 1.59 × 10 -8 The resistivity is Ω·m. The resistivity of nickel, titanium, and chromium used in the annular metal layer 30b is 7.0 × 10⁻⁶, respectively. -8 Ω·m, 4.2 × 10 -7 Ω·m and 1.3 × 10 -7 The resistivity is Ω·m. Thus, the resistivity of the annular metal layer 30b is more than twice and more than three times the resistivity of the annular metal layer 30a. Also, the thickness T2 of the annular metal layer 30b is less than or equal to half and less than or equal to one-fifth the thickness T1 of the annular metal layer 30a.

[0050] The annular metal layer 30a is mainly composed of copper, the annular metal layer 30b is mainly composed of nickel, and the bonding layer 24 is mainly composed of gold and tin. This allows the stress applied to the bonding layer 24 to be suppressed, as shown in the simulation. When a layer is said to be mainly composed of a certain element, it means that the content of that element in that layer is 50 atomic percent or more, although the content of that element in a layer may be 80 atomic percent or 90 atomic percent or more. When the bonding layer 24 is said to be mainly composed of gold and tin, it means that the total content of gold and tin in the bonding layer 24 is 50 atomic percent or more, although it may be 80 atomic percent or 90 atomic percent or more. The ratio of gold to tin in the gold and tin is such that a eutectic of gold and tin is formed, and the tin content is between 10 mass% and 30 mass%.

[0051] The bonding layer 24 covers the side surface of the annular metal layer 30b. This suppresses stress at the interface between the annular metal layer 30 and the bonding layer 24. Preferably, the bonding layer 24 is in contact with the entire surface of the side surface of the annular metal layer 30b.

[0052] If elemental diffusion between the bonding layer 24 and the annular metal layer 30a does not pose a significant problem even when the bonding layer 24 is in contact with a portion of the side surface of the annular metal layer 30a, the bonding layer 24 may be bonded to a portion of the side surface of the annular metal layer 30a, as shown in Figures 3 and 7 of Example 1 and Modification 3. This further suppresses stress at the interface between the annular metal layer 30 and the bonding layer 24.

[0053] If the bonding layer 24 comes into contact with a portion of the side surface of the annular metal layer 30a, and elemental diffusion between the bonding layer 24 and the annular metal layer 30a becomes a major problem, then, as shown in Figure 6(b) of Modification 2 of Example 1, the bonding layer 24 does not need to be bonded to the side surface of the annular metal layer 30a. This suppresses elemental diffusion between the bonding layer 24 and the annular metal layer 30a.

[0054] As shown in Figure 7 of Modification 3 of Example 1, at the surface where the annular metal layers 30a and 30b are in contact, the width W1 of the annular metal layer 30a is smaller than the width W2 of the annular metal layer 30b. This creates an overhang below the periphery of the annular metal layer 30b, and the bonding layer 24 is provided so as to surround the overhang. Therefore, peeling between the bonding layer 24 and the annular metal layer 30 can be suppressed. The width W1 is preferably 0.99 times or less of the width W2, more preferably 0.98 times or less, and even more preferably 0.95 times or less. If the width W1 is too small, the strength of the annular metal layer 30a will be weakened. From this viewpoint, the width W1 is preferably 0.7 times or more of the width W2. Note that the widths W1 and W2 are the widths in the direction (X direction) perpendicular to the stretching direction (Y direction) of the annular metal layer 30 in Figure 7.

[0055] If the coefficients of thermal expansion of the substrate 10 and the lid 20 are different, thermal stress will be applied to the bonding layer 24. Therefore, it is preferable that the bonding layer 24 be bonded to a part of the side surface of the annular metal layer 30. When the substrate 10 is a sapphire substrate, the coefficient of thermal expansion of the substrate 10 is approximately 7 ppm / °C. When the lid 20 is Kovar, the coefficient of thermal expansion of the lid 20 is approximately 0 ppm / °C. When the difference in the coefficients of thermal expansion between the substrate 10 and the lid 20 is 1 ppm / °C or more, 2 ppm / °C, or 5 ppm / °C, it is preferable that the bonding layer 24 be bonded to a part of the side surface of the annular metal layer 30.

[0056] As shown in Figure 1(a), the substrate 10 comprises a support substrate 10a and a piezoelectric layer 10c provided on the support substrate 10a. The elastic wave element 12 is provided on the surface of the piezoelectric layer 10c, and the annular metal layer 30 is provided on the support substrate 10a in the region where the piezoelectric layer 10c has been removed.

[0057] In Example 1 and its modifications, examples of elastic wave elements 12 and 12a (piezoelectric thin film resonators or surface acoustic wave resonators) were described as functional elements. However, the functional elements may also be passive elements such as inductors or capacitors, active elements including transistors, or MEMS (Micro Electro Mechanical Systems) elements. [Examples]

[0058] Figure 9(a) is a circuit diagram of the filter according to Embodiment 2. As shown in Figure 9(a), one or more series resonators S1 to S4 are connected in series between the input terminal Tin and the output terminal Tout. One or more parallel resonators P1 to P4 are connected in parallel between the input terminal Tin and the output terminal Tout. At least one of the series resonators S1 to S4 and the parallel resonators P1 to P4 can use the elastic wave elements 12 and 12a of Embodiment 1 and its modified versions. The number of series and parallel resonators can be set as appropriate. A ladder filter has been described as an example of a filter, but a multimode filter may also be used.

[0059] Figure 9(b) is a circuit diagram of a duplexer according to Modification 1 of Example 2. As shown in Figure 9(b), a transmit filter 60 is connected between the common terminal Ant and the transmit terminal Tx. A receive filter 62 is connected between the common terminal Ant and the receive terminal Rx. The transmit filter 60 allows the transmit band signal from the high-frequency signal input from the transmit terminal Tx to pass to the common terminal Ant as the transmit signal, and suppresses signals of other frequencies. The receive filter 62 allows the receive band signal from the high-frequency signal input from the common terminal Ant to pass to the receive terminal Rx as the receive signal, and suppresses signals of other frequencies. At least one of the transmit filter 60 and the receive filter 62 can be the filter of Example 2.

[0060] I used Duplexa as an example of a multiplexer, but Triplexa or Quadplexa would also work.

[0061] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0062] 10 circuit boards 10a support board 10b Insulating layer 10c piezoelectric layer 12, 12a Elastic wave element 14, 22 metal layer 16 via wiring 18 terminals 20 Lid 24 Bonding layer 26 void 30, 30a, 30b Annular metal layer 60 Sending Filters 62 Receiving Filter

Claims

1. circuit board and A functional element provided on the substrate, An annular metal layer is provided on the substrate so as to surround the functional element in a plan view, A lid provided on the annular metal layer, which seals the functional element in the gap with the annular metal layer, A metal bonding layer bonded to the lid and the lid-side surface of the annular metal layer and the lid-side portion of the side surface of the annular metal layer, Equipped with, The aforementioned annular metal layer is The first metal layer and The second metal layer is provided on the first metal layer, and is mainly composed of a second metal element having a higher resistivity than the first metal element which is the main component of the first metal layer, is thinner than the first metal layer, is in contact with the metal bonding layer, and is a second metal layer provided on the first metal layer. Equipped with, The metal bonding layer is bonded to the annular metal layer over an area of ​​1 / 20 to 1 / 2 times the combined thickness of the first and second metal layers, forming an electronic component.

2. The electronic component according to claim 1, wherein the content of the first metal element in the first metal layer is 50 atomic percent or more, and the content of the second metal element in the second metal layer is 50 atomic percent or more.

3. The electronic component according to claim 1, wherein, at the surface where the first metal layer and the second metal layer are in contact, the width of the first metal layer in the direction perpendicular to the direction in which the annular metal layer stretches is smaller than the width of the second metal layer in the same perpendicular direction.

4. The electronic component according to any one of claims 1 to 3, wherein the first metal layer is mainly composed of copper, the second metal layer is mainly composed of nickel, and the metal bonding layer is mainly composed of gold and tin.

5. The electronic component according to claim 4, wherein the copper content in the first metal layer is 50 atomic percent or more, the nickel content in the second metal layer is 50 atomic percent or more, and the total gold content and tin content in the metal bonding layer is 50 atomic percent or more.

6. The electronic component according to any one of claims 1 to 3, wherein the metal bonding layer is solder.

7. The electronic component according to any one of claims 1 to 3, wherein the metal bonding layer is in contact with the lid-side surface of the annular metal layer and the lid-side portion of the side surface of the annular metal layer.

8. The electronic component according to any one of claims 1 to 3, wherein the coefficients of linear expansion of the substrate and the lid are different.

9. The electronic component according to any one of claims 1 to 3, wherein the functional element is an elastic wave element.

10. The substrate comprises a support substrate and a piezoelectric layer provided on the support substrate. The electronic component according to claim 9, wherein the elastic wave element is provided on the surface of the piezoelectric layer, and the annular metal layer is provided on the support substrate in the region where the piezoelectric layer has been removed.

11. A filter comprising the electronic component described in claim 9.

12. A multiplexer comprising the filter described in claim 11.

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