WO2024117127A1

WO2024117127A1 - Wiring board and electronic component

Info

Publication number: WO2024117127A1
Application number: PCT/JP2023/042548
Authority: WO
Inventors: 勝彦尾上
Original assignee: 京セラ株式会社
Priority date: 2022-11-29
Filing date: 2023-11-28
Publication date: 2024-06-06

Abstract

This wiring board comprises: an insulating substrate; and a plurality of mounting electrodes that are positioned on a first surface of the insulating substrate, and have SAW elements mounted thereon. The insulating substrate has a protruding section within a range surrounded by the plurality of mounting electrodes of the first surface. The protruding section may have a width that is half or more the vertical and horizontal widths of the range surrounded by the mounting electrodes. The protruding section may surround at least a portion of the periphery of the mounting electrodes. The protruding section may be positioned where a plurality of portions are separated from each other within the range surrounded by the mounting electrodes. The protruding section may have a convex top surface.

Description

Wiring boards and electronic components

This disclosure relates to wiring boards and electronic components.

In electronic components with moving parts, such as vibrating parts, the moving space is secured using resin or the like and then sealed. In JP 2003-338729 A, a resin frame is formed around the piezoelectric element, and then it is sealed with a resin that has a lower elasticity than the resin.

One aspect of the present disclosure is
An insulating substrate;
a plurality of first electrodes on a first surface of the insulating substrate, on which SAW elements are mounted;
Equipped with
The insulating substrate is a wiring substrate having a protruding portion on the first surface in an area surrounded by the plurality of first electrodes.

1 is a perspective view illustrating an external configuration of an electronic component having a wiring board according to an embodiment of the present invention. FIG. 2 is a plan view of the lower surface of the wiring board. FIG. 2 is a plan view of the upper surface of the wiring board. FIG. FIG. 13 is a diagram showing a wiring board according to a first modified example. FIG. 13 is a diagram showing a wiring board according to a second modified example. FIG. 11 is a plan view showing a wiring board according to a third modified example. FIG. 11 is a cross-sectional view showing a wiring board according to a third modified example. FIG. 13 is a cross-sectional view showing a wiring board according to a fourth modified example. FIG. 13 is a cross-sectional view showing a wiring board according to a fifth modified example. FIG. 13 is a diagram showing a wiring board according to a sixth modified example.

Hereinafter, an embodiment will be described with reference to the drawings.
1A and 1B are diagrams illustrating the external configuration of an electronic component 1 having a wiring board 10 according to the present embodiment. Fig. 1A is a perspective view of the electronic component 1. Fig. 1B is a plan view of the bottom surface of the electronic component 1.

The electronic component 1 has a wiring board 10 and a resin layer 30 exposed on the outer surface. The wiring board 10 may have electrodes and signal lines (not shown) on or inside an insulating substrate 11, such as a ceramic substrate made of a material such as an aluminum oxide sintered body (alumina ceramics), an aluminum nitride sintered body, a mullite sintered body, or a glass ceramic sintered body. A SAW element 20 (see FIG. 2B), which will be described later, is mounted on the wiring board 10. The electrodes of the wiring board 10 include an external electrode 15. The external electrode 15 is located on the second surface, which is the lower surface of the insulating substrate 11, and connects the SAW element 20 to an external substrate or the like. A plurality of external electrodes 15 are arranged on the lower surface of the electronic component 1. The resin layer 30 covers the SAW element 20 on the upper surface of the wiring board 10.

FIG. 2A is a plan view of the top surface of the wiring board 10. FIG. 2B is a cross-sectional view of the electronic component 1 taken along the cross-sectional line AA shown in FIGS. 1B and 2A.

2A, in addition to the insulating substrate 11 and external electrodes 15 described above, the wiring substrate 10 has a plurality of mounting electrodes 14 located on the upper surface, which is the first surface opposite to the second surface of the insulating substrate 11. The mounting electrodes 14 correspond to the first electrodes of the present disclosure. The number of mounting electrodes 14 is at least the number necessary for connecting the SAW elements 20, and is not particularly limited. In one embodiment, the mounting electrodes 14 may be arranged point-symmetrically with respect to the center of the insulating substrate 11. However, the arrangement may not be point-symmetrical due to some of the mounting electrodes 14 being missing, or the sizes and intervals of the mounting electrodes 14 being uneven. In other words, the mounting electrodes 14 are arranged in an appropriate number and positions for connecting a predetermined SAW element 20. The predetermined SAW element 20 may be selected from different SAW elements having the same terminal arrangement. The signal lines (not shown) connected to the mounting electrodes 14 also extend in an appropriate manner for signal input/output to and from the SAW element 20.

The mounting electrode 14 and the external electrode 15 are conductive metals, and may be, for example, gold, silver, copper, tungsten, molybdenum, manganese, palladium, platinum, or an alloy of a combination of two or more of these. The mounting electrode 14 and the external electrode 15 may be formed on the insulating substrate 11 by, for example, screen printing.

The insulating substrate 11 has a protrusion 111 that protrudes upward, i.e., outward, from the other parts of the first surface at a position surrounded by the mounting electrodes 14 in a plan view. This protrusion 111 is rectangular in plan view. The lengths H1 and W1 of the two sides of the protrusion 111 may be half or more of the widths H2 and W2 of the area surrounded by the mounting electrodes 14. Here, the area is defined as an area connecting the centers of the mounting electrodes 14, but it is sufficient that the area is at least inscribed in the mounting electrodes 14. Specifically, for example, when the substrate size is 2.5 mm x 2.0 mm, the width H2 may be 2 mm and the width W2 may be 1.5 mm. Note that the rectangular shape in plan view referred to here may have some or all of its vertices rounded.

On the surface of the protruding portion 111, there are no other components such as signal lines or components. In addition, there is no coating or other treatment that is different from that of the non-protruding portion. In other words, the protruding portion 111 appears to simply protrude from the first surface of the insulating substrate 11.

As shown in the cross-sectional view of FIG. 2B, the SAW element 20 is connected and mounted on the mounting electrode 14 via a bump 40. The bump 40 is made of, for example, solder, gold, etc., but is not limited to these.

The SAW element 20 includes a piezoelectric member that deforms in response to the application of a voltage signal. The piezoelectric member is appropriately determined in accordance with the frequency, vibration mode, and the like. For example, the piezoelectric member may be a substrate of a single crystal having piezoelectricity, such as a lithium tantalate (LiTaO ₃ ) single crystal or a lithium niobate (LiNbO ₃ ) single crystal. On the lower surface of the piezoelectric member of the SAW element 20 facing the wiring board 10, a comb-shaped electrode 21 is located, which inputs a high-frequency signal from one side and selectively outputs a signal of a desired frequency band from the high-frequency signal from the other side. The comb-shaped electrode 21 is also called an interdigital electrode. The comb-shaped electrode 21 is a conductive member, and may be, for example, Al or an Al alloy (Al-Cu system, Al-Ti system). The comb-shaped electrode 21 may be formed on the piezoelectric member by a thin-film formation method such as a well-known deposition method, sputtering method, or CVD method.

In one embodiment, the comb-tooth electrode 21 may be located in a range facing the protrusion 111. For example, the comb-tooth electrode 21 may be included within the range of the protrusion 111 in a planar view, as shown by the dashed line in FIG. 2A. The upper and side sides of the SAW element 20 are covered with the resin layer 30. Therefore, the SAW element 20 is not exposed to the outside.

The resin layer 30 may be, for example, a thermosetting resin. The thermosetting resin may be, for example, an epoxy resin or a phenolic resin. The resin layer 30 is formed by, for example, potting, but is not limited to this.

There is an internal space between the comb-tooth electrode 21 and the protrusion 111. As a result, the vibration of the surface acoustic wave (SAW) generated by the comb-tooth electrode 21 is not hindered by the resin layer 30 or the like. The surface acoustic wave is also called a surface acoustic wave. The height of this internal space, that is, the distance between the comb-tooth electrode 21 and the protrusion 111 in a stationary state, may be, for example, 0.03 mm. Ideally, the resin layer 30 does not penetrate into the area surrounded by the mounting electrode 14 in a plan view, but in reality, if the viscosity of the resin is low during coating, it may penetrate slightly inside the mounting electrode 14. At this time, the resin component that penetrates spreads on the insulating substrate 11 according to gravity. However, since the protrusion 111 prevents the resin component from spreading, the resin does not spread into the area facing the comb-tooth electrode 21. This prevents the resin from adhering to the comb-tooth electrode 21. In addition, since it would be meaningless to supply so much resin that it spreads over the protrusions 111, the amount of resin supplied when forming the resin layer 30 is appropriately controlled.

The height of the protrusion 111 protruding from the first surface of the insulating substrate 11 may be lower than the height of the mounting electrode 14. That is, the protrusion 111 may be thinner than the mounting electrode 14. The height of the protrusion 111 may be, for example, 0.01 mm. This height may be determined according to the viscosity of the resin before hardening, etc. By not making the protrusion 111 higher than necessary, it is possible to appropriately secure the space between the comb-tooth electrode 21 and the protrusion 111.

The total planar area of the mounting electrodes 14 is smaller than the total planar area of the external electrodes 15. The difference between the total planar area of the mounting electrodes 14 and the protrusions 111 and the total planar area of the external electrodes 15 is smaller than the difference between the total planar area of the mounting electrodes 14 and the total planar area of the external electrodes 15. In this way, the protrusions 111 provide better balance between the top and bottom, making the wiring board 10, and in particular the insulating board 11, less likely to warp.

Fig. 3A is a diagram showing a first modified example of the wiring board 10 of the present embodiment. Fig. 3B is a diagram showing a second modified example of the wiring board 10 of the present embodiment.
As shown in FIG. 3A, in the wiring board 10a of the first modification, the protrusion 111a may extend between the multiple mounting electrodes 14. In other words, the protrusion 111a may each have a recess at a position that avoids the planar view range of the mounting electrodes 14. As a result, the mounting electrodes 14 that are circular in plan view are in a positional relationship in which at least a part of the angular range is partially surrounded by the protrusion 111a. Although not particularly limited, for example, the mounting electrodes 14 that are located at an angle in the arrangement of the mounting electrodes 14 may be surrounded by the protrusion 111a by 45 degrees or more. Also, the mounting electrodes 14 that are located on a line connecting the mounting electrodes 14 on both sides may be surrounded by the protrusion 111a by 90 degrees or more. Such a protrusion 111a can prevent low-viscosity resin from flowing into the area surrounded by the multiple mounting electrodes 14 when the resin layer 30 is formed.

As shown in FIG. 3B, in the wiring board 10b of the second modification, the protrusion may be divided into three parts, protrusions 111b-113b, which are multiple parts spaced apart from one another. In this electronic component 1, the comb-shaped electrodes 211-213 are also divided into three parts and positioned on the SAW element 20, as shown by the dashed lines. The protrusions 111b-113b may each encompass the range of the comb-shaped electrodes 211-213 in a plan view.

Due to the positional relationship between the multiple comb-shaped electrodes 211-213 and the protrusions 111b-113b, the flow of resin and adhesion to the comb-shaped electrodes 211-213 are appropriately reduced to the required extent. The number, size, position, orientation, etc. of the comb-shaped electrodes 211-213 may be changed as appropriate depending on the design of the SAW element 20.

Fig. 4A is a plan view of a wiring board 10c of Modification 3. Fig. 4B is a cross-sectional view of the wiring board 10c of Modification 3 taken along the same cross section as Fig. 2B.
In the wiring board 10c, the protruding portion 111c may have a frame-like shape. That is, the protruding portion 111c may have a recessed portion 115b in the center. As shown in FIG. 4B, the bottom surface of the recessed portion 115b may be at the same height as the first surface of the other insulating substrate 11. As shown in FIG. 4A and FIG. 4B, the comb-shaped electrode 21 has a portion overlapping the protruding frame-shaped portion 115a of the protruding portion 111c in a plan view, but is not limited to this. The comb-shaped electrode 21 may overlap only the recessed portion 115b in a plan view. This ensures sufficient space below the comb-shaped electrode 21. The width of the frame-shaped portion 115a may be appropriately set according to the outer circumferential size of the protruding portion 111c and the planar size of the comb-shaped electrode 21. In addition, this width may not be uniform.

The height of the bottom surface of the recess 115b does not have to be the same as the other upper surface portions of the wiring board 10c, so long as it is lower than the height of the frame-shaped portion 115a. Furthermore, the inner edge and outer edge of the frame-shaped portion 115a do not have to be rectangular in plan view. They may be rectangular with rounded corners, or elliptical. Furthermore, the inner edge and outer edge of the frame-shaped portion 115a may have different shapes in plan view.

Fig. 5A is a cross-sectional view of a wiring board 10d according to a modification 4. Fig. 5B is a cross-sectional view of a wiring board 10e according to a modification 5. These cross sections are taken at the same position as Fig. 2B.
As shown in FIG. 5A, in the wiring board 10d of the fourth modification, the protrusion 111d may have a convex upper surface. That is, the protrusion 111d may be higher toward the center and lower toward the periphery in a plan view. The upper surface of the protrusion 111d may be a curved surface in a cross section, such as a hyperbolic surface. Alternatively, the upper surface of the protrusion 111d may be a triangle in a cross section, such as a cone. Alternatively, the protrusion 111d may not have a structure that is point-symmetric with respect to the center position in a plan view.

Even in this case, the periphery of the protruding portion 111d may have a step between it and the upper surface of the wiring board 10d. This makes it difficult for the resin to continuously creep up onto the protruding portion 111d.

As shown in FIG. 5B, in the wiring board 10e of the fifth modification, the protrusion 111e may have a concave upper surface. That is, the protrusion 111e may be highest at the periphery and lower closer to the center. The height at the center may be higher than or the same as the upper surface of the wiring board 10e. The shape of the upper surface of the protrusion 111e may be a hyperbolic surface, or may be a funnel shape, i.e., an inverted cone shape. Furthermore, the protrusion 111e does not have to have a structure that is point-symmetric with respect to the center position when viewed from above.

Furthermore, by combining the shapes of the above modified examples, for example, a protrusion having a frame-shaped portion may have a boundary with a slope like a bank. Furthermore, when the heights of

protrusions

111d, 111e, etc. are non-uniform as in modified examples 4 and 5, the planar shape of

protrusions

111d, 111e, etc. does not have to be limited to simple shapes such as a rectangle, circle, or ellipse.

6 is a cross-sectional view showing a wiring board 10f according to Modification 6. The cross section is taken at the same position as in FIG. 2B.
In one embodiment, the wiring board 10f may have the protruding portion 111f made of the same metal as the mounting electrode 14. That is, the protruding portion 111f may be made of a material different from that of the insulating board 11. Such a protruding portion 111f may have the same shape as the protruding portions 111a to 111e shown in the above-mentioned modified examples 1 to 5. In addition, like the above-mentioned protruding portions 111 to 111e, the protruding portion 111f does not contact any components other than the protruding portion 111f, such as signal lines, components, and electrodes. In terms of manufacturing, it is easy to provide the protruding portion 111f on the first surface of the insulating board 11, which is a flat surface. Furthermore, since the protruding portion 111f is made of the same material as the mounting electrode 14, both the effort and the cost are reduced.

As described above, the wiring boards 10 to 10f of this embodiment include an insulating substrate 11 and a plurality of mounting electrodes 14 located on the first surface of the insulating substrate 11 on which the SAW elements 20 are mounted. The insulating substrate 11 has protrusions 111 to 111f in an area surrounded by the plurality of mounting electrodes 14 on the first surface. The protrusions do not have to be integral with the insulating substrate 11, as in the case of protrusion 111f. This prevents the resin from flowing into the area of protrusions 111 to 111f when the resin layer 30 is formed. Therefore, the wiring substrates 10 to 10f can reduce adverse effects on the operation of the SAW elements 20 caused by the resin adhering to the SAW elements 20 near the comb-tooth electrodes 21 of the mounted SAW elements 20.

In particular, when the resin layer 30 becomes thinner in response to a reduction in height, a resin that has a low viscosity before hardening and is easy to process may be used for the resin layer 30. However, low-viscosity resins tend to get into narrow gaps that need to be secured, and may adhere to components and have adverse effects. The technology disclosed herein makes it difficult for the resin to get into gaps that need to be secured, making it easier to control the resin so that it does not flow into and adhere to components such as the comb-tooth electrode 21, simplifying the manufacturing process.

In addition, even if the height of the SAW element 20 is reduced, which is important when mounting the SAW element 20 on a module, the vibration caused by the SAW temporarily converted from the signal can be obtained stably. Therefore, by using the wiring boards 10 to 10f, the functionality of the SAW filters, duplexers, etc. mounted on the module is not reduced.

Furthermore, protrusions 111-111a, 111c-111f each have a width (H1, W1) that is more than half the vertical and horizontal widths (H2, W2) of the range. In principle, the size of protrusions 111-111a, 111c-111f only needs to be determined according to the size of the SAW element that is predetermined to be attached. As this size is sufficient for comb-shaped electrode 21 in a plan view, adhesion of resin to comb-shaped electrode 21 and its surroundings can be reduced.

The protrusion 111a may also surround at least a portion of the periphery of the mounting electrode 14. A protrusion 111a of this shape can cover a large portion of the area surrounded by the mounting electrode 14 without contacting the protrusion 111a. This can further reduce the adhesion of resin to the mounting electrode 14.

In addition, the protrusions 111b to 113b may be located in multiple parts spaced apart from each other within the area surrounded by the mounting electrode 14. In the case of a SAW filter having multiple comb-shaped electrodes 21, such as a duplexer, the insulating substrate 11 may have multiple protrusions corresponding to the positions of the multiple comb-shaped electrodes 21 in a plan view. This makes it possible to effectively reduce the adhesion of resin to each comb-shaped electrode 21.

In addition, the protrusion 111d has a convex upper surface. Even with this shape, if the resin is prevented from entering the portion facing the comb-tooth electrode 21, the adhesion of the resin to the comb-tooth electrode 21 can be reduced.

Alternatively, the protrusion 111e has a concave upper surface. If the peripheral edge of the protrusion 111e is raised to prevent the resin from penetrating inward, adhesion of the resin to the comb-tooth electrode 21 can be reduced even if the entire comb-tooth electrode 21 does not face the protrusion 111e. Also, since the distance between the comb-tooth electrode 21 and the insulating substrate 11 can be increased in many areas, the obstruction of the SAW of the SAW element 20 can be reduced.

Furthermore, the protruding portion 111c may have a frame-like shape. In other words, as long as the frame-like portion 115a, which is the outer frame of the area into which resin is not desired to flow, is protruded, the inside of the frame-like portion 115a does not need to protrude from the first surface of the insulating substrate 11. This ensures that the portion of the comb-tooth electrode 21 located inside the frame-like portion 115a is kept a sufficient distance from the insulating substrate 11 as in the past.

In addition, the protrusions 111 to 111f are thinner than the mounting electrode 14. If the protrusions 111 to 111f are made taller (thicker) than necessary, the space between them and the comb-tooth electrode 21 will become narrower. Therefore, the height of the protrusions 111 to 111f can be determined so that the space between the comb-tooth electrode 21 and the protrusions 111 to 111f can be maintained without taking into account the height of the bump 40.

The wiring board 10 also has multiple external electrodes 15 located on the bottom surface opposite the top surface. The total planar area of the external electrodes 15 is greater than the total planar area of the multiple mounting electrodes 14. In this state, the additional protrusions 111-111f located on the top surface side balance the attachments on both sides of the insulating board 11, making it less likely for bending to occur.

Moreover, the electronic component 1 of this embodiment comprises the above-mentioned wiring board 10, a SAW element 20 connected to the mounting electrode 14 and having a comb-tooth-shaped electrode 21, the comb-tooth-shaped electrode 21 facing the protrusions 111 to 111f, and a resin layer 30 covering the SAW element 20.
In this electronic component 1, when the SAW element 20 is covered and sealed with resin, the resin is prevented from flowing between the comb-shaped electrode 21 and the insulating substrate 11. Therefore, in the electronic component 1, the resin is less likely to adhere to the comb-shaped electrode 21, and the SAW element 20 can operate stably.

The above-described embodiment is merely an example, and various modifications are possible.
For example, in the above embodiment, the protrusion 111a having a portion surrounding a part of the circumference of the mounting electrode 14 having a circular shape in a plan view in an arc shape is shown, but the present invention is not limited to this. The protrusion 111a may have a notch having a rectangular or triangular shape in a plan view so that the mounting electrode 14 having a circular shape in a plan view does not overlap with the protrusion 111a.

In addition, in the above embodiment, it has been described that the mounting electrode 14 and the protruding portion 111 are not in contact with each other, but they may be in contact with each other as long as this does not affect the reduction in adhesion of resin and the like to the comb-tooth electrode 21 and the protruding portion is not a metal member like the protruding portion 111f.

Furthermore, the protrusion 111 and the comb-tooth electrode 21 may have different shapes in a plan view, so long as they face each other. Furthermore, the protrusion 111 may be located, for example, on the outer periphery of the wiring board 10 with a larger margin than the position of the comb-tooth electrode 21 in a plan view. In other words, the center position of the protrusion 111 in a plan view and the center position of the comb-tooth electrode 21 in a plan view do not have to coincide. The center position in a plan view may be the two-dimensional center of gravity of the protrusion 111 and the comb-tooth electrode 21.

The protrusions may have a shape different from the shapes exemplified as protrusions 111 to 111f. The interior of frame portion 115a may also include a partial protrusion. The protrusions may have a double structure including an outer frame inscribed in mounting electrode 14 and a protruding structure in a position range inside this outer frame that faces comb-tooth electrode 21. The protrusions may not all or partly directly face comb-tooth electrode 21. In particular, these protrusions may be located in a position that inhibits the flow of resin into the range that faces comb-tooth electrode 21.

In addition, in the above-mentioned second modification, the wiring board 10 has protrusions 111b-113b corresponding to the multiple comb-tooth electrodes 211-213, respectively, but this is not limited to this. It may have a common protrusion that faces the multiple comb-tooth electrodes. In this case, depending on the positional relationship of the comb-tooth electrodes 211-213, the protrusion may have various shapes such as an L-shape, a U-shape, or a comb-tooth shape.

In addition, the protrusion 111 may have a height equal to or greater than that of the mounting electrode 14, depending on the height of the bump 40, etc.

Also, for example, there may be cases where multiple comb-shaped electrodes 21 that are small compared to the size of the area surrounded by the mounting electrode 14 are positioned in a dispersed manner. In this case, the size of the protrusions may be small compared to the above-mentioned area, in particular less than half.

Furthermore, the signal lines (not shown) do not have to pass through the surface or inside of the insulating substrate 11. Part of the signal line may pass through a bonding wire or lead, etc.

In addition, the specific configurations, structures, materials, manufacturing method contents, etc. shown in the above embodiments can be modified as appropriate without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention described in the claims and its equivalents.

This disclosure can be used in wiring boards and electronic components.

REFERENCE SIGNS LIST 1 Electronic components 10 to 10f Wiring board 11 Insulating boards 111 to 111f, 112b, 113b Projection 115a Frame-shaped portion 115b Recess 14 Mounting electrode 15 External electrode 20

SAW element

21, 211 to 213 Comb-shaped electrode 30 Resin layer 40 Bump

Claims

An insulating substrate;
a plurality of first electrodes on a first surface of the insulating substrate, on which SAW elements are mounted;
Equipped with
the insulating substrate has a protruding portion in an area surrounded by the plurality of first electrodes on the first surface.
The wiring board according to claim 1, wherein the protrusion has a width equal to or greater than half the length and width of the range.
The wiring board according to claim 1 or 2, wherein the protrusion surrounds at least a portion of the periphery of the first electrode.
The wiring board according to claim 1, wherein the protrusions are located in multiple portions spaced apart from one another within the range.
The wiring board according to claim 1, wherein the protrusion has a convex upper surface.
The wiring board according to claim 1, wherein the protrusion has a concave upper surface.
The wiring board according to claim 1, wherein the protrusion has a frame-like shape.
The wiring board according to any one of claims 1 to 7, wherein the protrusion is thinner than the first electrode.
a plurality of second electrodes located on a second surface opposite the first surface;
9. The wiring board according to claim 1, wherein a total area of the plurality of second electrodes in a plan view is larger than a total area of the plurality of first electrodes in a plan view.
A wiring board according to any one of claims 1 to 9,
a SAW element having a comb-shaped electrode, the comb-shaped electrode being connected to the first electrode in a state in which the comb-shaped electrode faces the protruding portion;
a resin layer covering the SAW element;
An electronic component comprising: