JP7565700B2 - Mounting board, electronic device, and electronic module - Google Patents

Description

This disclosure relates to a mounting substrate on which light-emitting and receiving elements are mounted, an electronic device, and an electronic module.

Mounting boards (insulating boards) on which electronic elements (semiconductor elements) are mounted are known (see Patent Document 1). Such mounting boards have recesses (castellations) on the sides for connecting external electrodes, external boards, etc.

JP 2013-232610 A

In recent years, the contact area (bonding area) between the conductor and the insulating layer of a mounting board has become smaller.
In this way, when the contact area between the conductor and the insulating layer is reduced, the bonding strength decreases in proportion to the reduction in contact area, and there is a concern that reliability will decrease due to the conductor coming off the insulating layer during processing or handling to form a mounting board.

A mounting board according to one aspect of the present disclosure includes a substrate and an electrode. The substrate has an upper surface having a mounting area, a lower surface located in a first direction of the upper surface, a side surface connecting the upper surface and the lower surface, and a recess located on the side surface and having an opening in a second direction perpendicular to the first direction. The electrode is located within the recess. The recess has a wide portion on the inside of the substrate whose width in the second direction is wider than the width of the opening in the second direction, and the electrode is located at least in the wide portion and has a width in the second direction wider than the width of the opening.

The mounting substrate according to one aspect of the present disclosure has excellent bonding strength between the substrate and the electrodes.

FIG. 1A is a top view showing the appearance of a mounting board and an electronic device according to a first embodiment of the present disclosure, and FIG. 1B is a vertical cross-sectional view corresponding to line X1-X1 in FIG. FIG. 2A is a top view showing the appearance of a mounting board and an electronic device according to an application mode of the first embodiment of the present disclosure. FIG. 3 is a top view of a mounting board and an electronic device according to an application mode of another embodiment of the present disclosure. FIG. 4 is a top view of a mounting board and an electronic device according to another embodiment of the present disclosure. FIG. 5 is a mounting board and a top view according to an application mode of another embodiment of the present disclosure. FIG. 6 is a bottom view of a mounting board and an electronic device according to an application aspect of the first embodiment of the present disclosure, and FIG. 6(b) is a vertical cross-sectional view corresponding to line X6-X6 in FIG. 6(a). FIG. 7 is a top view of a mounting board and an electronic device according to another embodiment of the present disclosure, and FIG. 7(b) is a vertical cross-sectional view taken along line X7-X7 in FIG. 7(a). FIG. 8 is a top view of a mounting board and an electronic device according to an application aspect of another embodiment of the present disclosure. FIG. 9 is a cross-sectional view of an electronic module according to an embodiment of the present disclosure.

<Configuration of mounting board and electronic device>
Hereinafter, some exemplary embodiments of the present disclosure will be described with reference to the drawings. In the following description, an electronic device or an electronic module is defined as a configuration in which an electronic element is mounted on a mounting board and the mounting board is covered with a housing. Either direction of the mounting board and the electronic device may be considered to be upward or downward, but for convenience, a Cartesian coordinate system xyz is defined, and the positive side of the z direction is considered to be upward.

(First embodiment)
A mounting substrate 1 according to a first embodiment of the present disclosure and an electronic device 21 including the same will be described with reference to Figures 1 and 2. Figure 1 shows the electronic device 21. Note that a housing 12 is omitted in Figure 1. The mounting substrate 1 has a base 2 and electrodes 3. In this case, the base 2 may be only a substrate 2a described later, or may be composed of the substrate 2a and a frame 2b.

As shown in FIG. 1, the mounting board 1 has a substrate 2a and an electrode 3. The substrate 2a has an upper surface 4b including a mounting area 4a, a lower surface 4c located in a first direction of the upper surface 4b, for example, the z direction, and a side surface 4d connecting the upper surface 4b and the lower surface 4c. The substrate 2a also has a recess 5 located on the side surface 4d and having an opening in a second direction perpendicular to the first direction. The electrode 3 is located within the recess 5.

As shown in FIG. 6, the mounting board 1 may have a frame 2b surrounding the mounting area 4a on the upper surface 4b of the board 2a. The frame 2b may be integral with the board 2a, or may be separate and joined with a bonding material or the like. Here, the board 2a and the frame 2b are referred to as the base 2.

In the mounting substrate 1 shown in FIG. 6, the substrate 2a and the frame 2b are composed of multiple layers. These multiple layers are multiple insulating layers, and may be, for example, formed by molding, formed by pressing with a metal mold or the like, or may be composed of only one layer. The material of the insulating layer that constitutes the base 2 includes, for example, electrically insulating ceramics or resin.

Examples of electrically insulating ceramics used as the material for the insulating layer forming the base 2 include aluminum oxide sintered body, mullite sintered body, silicon carbide sintered body, aluminum nitride sintered body, silicon nitride sintered body, glass ceramic sintered body, etc. Examples of resins used as the material for the insulating layer forming the base 2 include thermoplastic resin, epoxy resin, polyimide resin, acrylic resin, phenolic resin, fluorine resin, etc. Examples of fluorine resins include tetrafluoroethylene resin.

The base 2 may be formed of four layers as shown in FIG. 1, or may be formed of three or less layers or five or more layers. When the number of layers is three or less, the mounting board 1 can be made thinner. When the number of layers is five or more, the rigidity of the mounting board 1 can be increased. In addition, openings may be provided in each layer, and a step may be formed on the upper surface with openings of different sizes, and electrode pads and other electrodes connected to the electronic element 10 may be provided in the step.

For example, the size of one side of the outermost periphery of the mounting substrate 1 is 0.3 mm to 10 cm, and when the mounting substrate 1 has a quadrangular shape in a plan view, it may be a square or a rectangle. Also, for example, the thickness of the mounting substrate 1 is 0.2 mm or more.

An electrode 3 for connecting to an external circuit is located in a recess 5 located on the side surface 4d of the substrate 2a. The electrode 3 may electrically connect the mounting substrate 1 to an external circuit board, or the electronic device 21 to an external circuit board.

Furthermore, the upper surface 4b or the lower surface 4c of the base 2 may be provided with electrode pads, internal wiring conductors formed between insulating layers, and internal through conductors that vertically connect the internal wiring conductors to each other. These electrodes 3, internal wiring conductors, or internal through conductors may be exposed on the surface of the base 2. The electrodes 3 in the base 2 may be electrically connected to each other by these electrodes 3, internal wiring conductors, or internal through conductors.

When the base 2 is made of an electrically insulating ceramic, the electrode pad, the electrode 3, the internal wiring conductor and/or the internal through conductor include tungsten (W), molybdenum (Mo), manganese (Mn), palladium (Pd), silver (Ag) or copper (Cu), or an alloy containing at least one or more metal materials selected from these. They may also be made of copper (Cu) alone. When the base 2 is made of a resin, the electrode pad, the electrode 3, the internal wiring conductor and/or the internal through conductor include copper (Cu), gold (Au), aluminum (Al), nickel (Ni), molybdenum (Mo), palladium (Pd) or titanium (Ti), or an alloy containing at least one or more metal materials selected from these.

The exposed surfaces of the electrode pad, electrode 3, internal wiring conductor and/or through conductor may further have a plating layer. With this configuration, the exposed surfaces of the electrode 3 for connecting to an external circuit, the electrode pad, the internal wiring conductor and the through conductor can be protected to reduce oxidation. Also, with this configuration, the electrode pad and the electronic element 10 can be satisfactorily electrically connected via a connection member 13 such as wire bonding. The plating layer may be, for example, a Ni plating layer having a thickness of 0.5 μm to 10 μm, or the Ni plating layer and a gold (Au) plating layer having a thickness of 0.5 μm to 3 μm may be sequentially deposited.

The frame 2b shown in FIG. 6 is located on the upper surface 4b of the substrate 2a, surrounding the mounting area 4a. In other words, the base 2 has a recess 5 between the frame 2b and the substrate 2a, and the electronic element 10 to be mounted in the mounting area 4a is mounted inside the recess 5.

The recess 5 has a wide portion 6 on the inside of the substrate 2a, the width of which in the second direction is wider than the width of the opening in the second direction. The recess 5 may be, for example, a trapezoid in the top view shape as shown in FIG. 6, or may be a shape in which rectangles of different sizes are combined. Here, a rectangular shape includes a shape in which the shape including the imaginary line connecting the opening ends is a rectangle when viewed from above or seen through from the top. In addition, the recess 5 may be a shape in which a rectangle and a semicircle, a rectangle and a semiellipse, etc. are combined. When the recess 5 is a trapezoid, if the opening is the upper base, it is sufficient that the lower base is larger than the upper base. The recess 5 may be located from the upper surface 4b to the lower surface 4c, or may not reach the middle of the side surface 4d from the upper surface 4b, that is, the lower surface 4c. It may also be a shape in which the lower surface 4c does not reach the middle of the side surface 4d from the lower surface 4c, that is, the upper surface 4b. It may also be a shape in which the upper surface 4b and the lower surface 4c do not reach either. The recess 5 can be confirmed by viewing the side surface 4d from the front, top, or top see-through. The longest side, diameter, or major axis of the recess 5 is, for example, 0.15 mm to 5.00 mm. The direction toward the inside of the substrate 2a (depth) is, for example, 0.05 mm to 0.50 mm.

The electrode 3 is located at least in the wide portion 6, and its width in the second direction is wider than the width of the opening. The electrode 3 may be located along the inner surface 4d of the wide portion 6, or may be located so as to fill a part of the wide portion 6. The electrode 3 may be exposed in a part of the wide portion 6, and the other part may be located inside the substrate 2a. The longest length of the wide portion 6 is, for example, 0.20 mm to 6.00 mm, similar to the recess 5. The width of the opening is, for example, 0.10 mm to 2.00 mm. In this case, the electrode 3 may be located on the entire surface of the wide portion 6, or may be located only on a part of it. The electrode 3 may be located on the entire surface of the wide portion 6, and a part of the inside may be recessed. The electrode 3 may have a surface electrode and a via conductor. In other words, the via conductor is located so as to fill the wide portion 6, and the surface electrode is located on the surface of the via conductor.

As described above, the mounting substrate 1 according to the embodiment of the present disclosure has a recess 5 with a wide portion 6, and the electrode 3 is located in the wide portion 6. This ensures a sufficient contact area between the substrate 2a and the electrode 3, even if the mounting substrate 1 is made smaller. This reduces the risk of the substrate 2a and the electrode 3 coming apart. As a result, mounting reliability is improved in connection with the outside.

<Configuration of Electronic Device>
1 and another embodiment, which will be described later, in Fig. 4 show an example of an electronic device 21. The electronic device 21 includes a mounting substrate 1, an electronic element 10 mounted in a mounting region 4a of the mounting substrate 1, and a housing 12 located on the upper surface of the mounting substrate 1.

The electronic device 21 has a mounting substrate 1 and an electronic element 10 mounted in the mounting region 4a. Examples of the electronic element 10 include a reflective CMOS sensor, a light emitting element such as an LED (Light emitting diode) and an LD (Laser diode), a capacitor or a PD (Photo diode) sensor. The electronic element 10 and the mounting substrate 1 may be electrically connected by, for example, a connection member 13. The electronic device 21 has a lid that covers the mounting substrate 1. The lid may have a shape in which a housing made of metal or resin and a plate-shaped transparent member made of resin or glass are combined, or may be flat like a glass plate. The lid has a shape in which a housing and a plate material are combined, thereby making it possible to improve airtightness or reduce the direct application of external stress to the electronic device 21. The lid is made of, for example, a resin or metal material. The lid may also have a transparent lid made of resin, liquid, glass, quartz, or the like located on the upper surface. The lid may also be electrically connected to a pad or the like located on the surface of the mounting substrate 1 via a bonding material such as solder.

The lid may have an opening in at least one of the four directions or on the bottom surface 4c side when viewed from above. An external circuit board may be inserted through the opening in the lid and electrically connected to the mounting board 1. After the external circuit board is electrically connected to the mounting board 1, the opening in the lid may be sealed with a sealing material such as resin to make the inside of the electronic device 21 airtight.

<Electronic module configuration>
9, the electronic module 31 has an electronic device 21 and a housing 12 located on the upper surface of the electronic device 21. For the sake of explanation, an imaging module will be taken as an example in the following example.

The electronic module 31 may have a housing 12 (lens holder). By having the housing 12, it is possible to improve airtightness or reduce the application of external stress directly to the electronic device 21. The housing 12 is made of, for example, a resin or metal material. When the housing 12 is a lens holder, the housing 12 may incorporate one or more lenses made of resin, liquid, glass, crystal, or the like. The housing 12 may also be equipped with a drive device or the like for driving the housing 12 up, down, left, and right, and may be electrically connected to pads or the like located on the surface of the electronic element mounting substrate 1 via a bonding material such as solder.

The housing 12 may have an opening on at least one of the four sides when viewed from above. An external circuit board may be inserted through the opening of the housing 12 and electrically connected to the electronic device mounting board 1. After the external circuit board is electrically connected to the electronic device mounting board 1, the opening of the housing 12 may be sealed with a sealing material such as resin to make the inside of the electronic module 31 airtight. The electronic module 31 may further have a lid that covers the electronic device 10.

<Method of manufacturing mounting board and electronic device>
Next, a description will be given of an example of a method for manufacturing the mounting substrate 1 and the electronic device 21 of this embodiment. Note that the example of the manufacturing method described below is a method for manufacturing the substrate 2 using a multi-piece wiring substrate.

(1) First, a ceramic green sheet is formed to form the base 2 (substrate 2a and frame _2b ). For example, when obtaining the base 2 which is an aluminum oxide ( _Al2O3 ) sintered body, _a powder of silica ( _SiO2 ), magnesia (MgO), calcia (CaO), or the like is added as a sintering aid to _Al2O3 powder, and further a suitable binder, solvent, and plasticizer are added, and then the mixture is kneaded to form a slurry. After that, a ceramic green sheet for multiple pieces is obtained by molding using a doctor blade method, a calendar roll method, or the like.

When the base 2 is made of, for example, resin, it can be formed by using a mold capable of forming it into a desired shape and molding it by transfer molding, injection molding, or pressing with a mold or the like. The base 2 may also be a base material made of glass fiber impregnated with resin, such as glass epoxy resin. In this case, the base material made of glass fiber is impregnated with a precursor of the epoxy resin, and the epoxy resin precursor is thermally cured at a predetermined temperature to form the base material 2.

(2) Next, a metal paste is applied or filled by screen printing or the like to the ceramic green sheet obtained in step (1) above in the areas that will become the electrode pads, electrodes 3, internal wiring conductors and/or internal through conductors. This metal paste is prepared by adding an appropriate solvent and binder to metal powder made of the metal material described above and kneading it to adjust the viscosity to an appropriate level. The metal paste may contain glass or ceramics to increase the bonding strength with the base 2.

When the base 2 is made of resin, the electrode pads, electrodes 3, internal wiring conductors and/or internal through conductors can be fabricated by sputtering, vapor deposition, or the like. They may also be fabricated by plating after a metal film is provided on the surface.

(3) Next, the green sheet is processed using a mold or the like. If the base 2 has an opening or a notch, the opening or notch may be formed in a predetermined location of the green sheet that will become the base 2.

(4) Next, the ceramic green sheets that will become the insulating layers of the base 2 are stacked and pressed. In this way, the green sheets that will become the insulating layers may be stacked to produce a ceramic green sheet laminate that will become the base 2. At this time, openings in the frame 2b may be provided at predetermined positions of the ceramic green sheets that have been stacked together using a die, punching, a laser, or the like.

(5) Next, this ceramic green sheet laminate is fired at a temperature of approximately 1500°C to 1800°C to obtain a multi-piece wiring board in which multiple mounting substrates 1 are arranged. Note that, in this process, the metal paste described above is fired simultaneously with the ceramic green sheets that will become the mounting substrates 1, and becomes the electrode pads, electrodes 3, internal wiring conductors and/or internal through conductors.

(6) Next, the multi-cavity wiring board obtained by firing is divided into a plurality of mounting boards 1. In this division, a division groove is formed in the multi-cavity wiring board along the outer edge of the mounting board 1, and the board is broken along the division groove to divide the board, or a method of cutting the board along the outer edge of the mounting board 1 by a slicing method or the like can be used. The division groove can be formed by cutting the board smaller than the thickness of the multi-cavity wiring board using a slicing device after firing, but it may also be formed by pressing a cutter blade against the ceramic green sheet laminate for the multi-cavity wiring board, or by cutting the board smaller than the thickness of the ceramic green sheet laminate using a slicing device. Before or after dividing the multi-cavity wiring board described above into a plurality of mounting boards 1, plating may be applied to the electrodes 3, electrode pads, internal wiring conductors, and internal through conductors using electrolytic or electroless plating.

(7) Next, the electronic element 10 is mounted in the mounting area 4a of the mounting substrate 1. The electronic element 10 is electrically connected to the mounting substrate 1 by a connection member 13 such as wire bonding. At this time, an adhesive or the like may be provided on the electronic element 10 or the mounting substrate 1 to fix it to the mounting substrate 1. Also, after the electronic element 10 is mounted on the mounting substrate 1, a lid may be joined.

By producing the mounting substrate 1 according to the above steps (1) to (7) and mounting the electronic element 10, the electronic device 21 can be produced. The order of the steps (1) to (7) above is not specified as long as it is an order that allows processing.

Other Embodiments
The mounting board 1 of this embodiment differs from the mounting board 1 of the first embodiment in that a board 2a has a step 7 between a wide portion 6 and the opening, the width of which narrows toward the opening.

In the example shown in Figure 4, the substrate 2a has a step 7 between the wide portion 6 and the opening, which narrows toward the opening. For example, in the case of a combination of rectangles of different sizes as described above, this refers to the step 7 that occurs at the boundary between the rectangles. This step 7 may be symmetrical or asymmetrical when viewed from above or from a perspective view from above.

In this case, as shown in FIG. 7, the side of the substrate 2a extending from the wide portion 6 toward the corner of the step 7 may be concavely curved. By making the corner concavely curved, it is possible to reduce the stress load on the corner due to the difference in thermal expansion coefficient between the electrode 3 and the substrate 2a. In this case, the concave curved shape is a convex shape when viewed from the recess 5.

As shown in FIG. 8, the step 7 may have a protrusion 8 extending toward the wide portion 6. The protrusion 8 may extend slightly into the wide portion 6. The protrusion 8 may be, for example, symmetrical or asymmetrical in top view or top see-through view. The tip may be pointed or rounded. The presence of the protrusion 8 makes the electrode 3 less likely to peel off than if the protrusion 8 were not present.

As shown in FIG. 5, the substrate 2a may further have a recessed portion 9 on the inside of the substrate 2a relative to the wide portion 6. The recessed portion 9 is connected to the wide portion 6 and has a narrower width in the second direction than the wide portion 6. In this case, the electrode 3 is preferably also located in the recessed portion 9. This ensures a sufficient contact area between the electrode 3 and the substrate 2a, thereby reducing the risk of the electrode 3 peeling off from the substrate 2a. The recessed portion 9 has, for example, a long side, a long axis, or a diameter of 0.20 mm to 1.00 mm. The depth of the recessed portion 9 may be different from the depth of the recessed portion 5, that is, the recessed portion 9 may be connected to only a part of the recessed portion 5.

The recess 9 may have an arc-shaped cross section perpendicular to the first direction. In other words, it may have a shape similar to that of a part of a typical via conductor. The arc-shaped cross section increases the contact area with the substrate 2a while making it easier to reduce the stress load caused by the difference in thermal expansion coefficient between the substrate 2a and the electrode.

As shown in FIG. 3, the substrate 2a may have a plurality of recesses 5. When the substrate 2a has a plurality of recesses 5, the recesses 5 may be located adjacent to each other or may be spaced apart. The height positions and the height ranges in which the recesses 5 are formed may also be different. In particular, when the shape of the substrate 2a viewed from above is rectangular, the opposing side surfaces 4d may each have a recess 5. In this case, the opposing side surfaces 4d may have the same number of recesses 5 or different numbers of recesses 5. The opposing recesses 5 may also have different sizes or the same size.

In addition, if the recess 5 is located up to the lower surface 4c of the substrate 2a and an external electrode pad is present on the lower surface 2c of the substrate 2a, the external electrode pad and the recess 5 may be connected.

Note that the present disclosure is not limited to the above-mentioned embodiment examples, and various modifications such as numerical values are possible. Also, for example, in the examples shown in each figure, the shape of the electrode 3 may be other polygonal shapes when viewed from above. Also, the arrangement, number, shape, and mounting method of the electronic elements of the electrodes 3 in this embodiment are not specified. Note that the various combinations of the characteristic parts in this embodiment are not limited to the above-mentioned embodiment examples. Also, combinations of each embodiment are possible.

Reference Signs List 1 Mounting board 2 Base body 2a Substrate 2b Frame body 3 Electrode 4a Mounting area 4b Upper surface 4c Lower surface 4d Side surface 5 Recess 6 Wide portion 7 Step 8 Protrusion 9 Depression 10 Electronic element 12 Housing 13 Connection member 21 Electronic device 31 Electronic module

Claims (11)

a substrate having an upper surface having a mounting area, a lower surface located in a first direction of the upper surface, a side surface connecting the upper surface and the lower surface, and a recess located on the side surface and having an opening in a second direction perpendicular to the first direction;
an electrode located within the recess,
the recess has a wide portion on an inner side of the substrate, the wide portion having a width in the second direction greater than a width of the opening in the second direction,
the electrode is located at least in the wide portion, and has a width in the second direction that is wider than a width of the opening;
the electrode includes a via conductor located so as to fill at least a portion of the wide portion, and a surface electrode located on a surface of the via conductor;
the substrate has a step between the wide portion and the opening, the step narrowing toward the opening;
The step has a protrusion extending toward the wide portion . The mounting substrate according to claim 1, wherein the recess is located from the upper surface to the lower surface. The mounting board according to claim 1 , wherein the side of the board extending from the wide portion toward the corner of the step is concavely curved. a substrate having an upper surface having a mounting area, a lower surface located in a first direction of the upper surface, a side surface connecting the upper surface and the lower surface, and a recess located on the side surface and having an opening in a second direction perpendicular to the first direction;
an electrode located within the recess,
the recess has a wide portion on an inner side of the substrate, the wide portion having a width in the second direction greater than a width of the opening in the second direction,
the electrode is located at least in the wide portion, and has a width in the second direction that is wider than a width of the opening;
the substrate has a step between the wide portion and the opening, the step narrowing toward the opening;
The step has a protrusion extending toward the wide portion. The mounting board according to claim 1 , wherein the wide portion has a rectangular shape in a cross section perpendicular to the first direction. the substrate has a recessed portion that is connected to the wide portion and has a narrower width in the second direction than the wide portion, the recessed portion being located on the inner side of the substrate than the wide portion;
The mounting board according to claim 1 , wherein the electrode is also located in the recess. The mounting board according to claim 6 , wherein the recessed portion has an arc-shaped cross section perpendicular to the first direction. The mounting board according to claim 1 , wherein the board has a rectangular shape when viewed from above, and the recess is provided on each of the opposing side surfaces. The mounting board according to claim 1 , further comprising a frame on the upper surface of the board, the frame surrounding the mounting area. A mounting board according to any one of claims 1 to 9 ;
an electronic element mounted in the mounting area of the mounting board. An electronic device according to claim 10 ;
and a housing positioned above the electronic device.

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