JP7656826B2 - Mounting board and method for manufacturing the same - Google Patents

Description

This disclosure relates to a mounting substrate and a method for manufacturing the mounting substrate.

Conventionally, mounting boards that are substrates on which chip-type electronic components are surface-mounted are known (for example, Patent Document 1). The mounting board of Patent Document 1 includes a wiring layer including lands to which terminals of the chip-type electronic components are connected, and a solder resist layer that selectively covers the wiring layer, and the solder resist layer includes a resist pattern that partially covers the lands. A structure in which the lands are partially covered with the solder resist layer in this manner is widely known as an over resist structure. On the other hand, a structure in which the lands are not covered with the solder resist layer is called a normal resist structure.

JP 2014-110303 A

Boards on which chip-type electronic components are mounted can have either an over resist structure or a normal resist structure, with the normal resist structure being more suitable for increasing the mounting density of components on the board. However, in recent years, as chip-type electronic components have become smaller, the dimensions of the lands that connect the terminals of the chip-type electronic components via the soldering have also become smaller. As the area of the lands becomes smaller, the adhesive strength between the board and the lands becomes insufficient, which can result in the lands being judged to have insufficient strength during inspection after soldering.

To solve this problem, an over-resist structure can be adopted. In other words, the problem of insufficient strength can be solved by increasing the area of the land to improve adhesive strength, and by covering the periphery of the land with a solder resist layer to provide a reinforcing effect.

However, the over-resist structure has the disadvantage that it is more difficult to shorten the distance between adjacent chip-type electronic components than the normal resist structure. This is because the dimensions of the land must be larger than those of the normal resist structure by the area covered by the solder resist layer. Therefore, even if miniaturized electronic components are used, there is a problem that a mounting density commensurate with the miniaturization of the electronic components cannot be achieved because of the unavoidable circumstances of having to use the over-resist. This problem is particularly evident when using electronic components with long sides of 1.0 mm or less and short sides of 0.5 mm or less. In this situation, one of the objectives of the present disclosure is to achieve high-density mounting commensurate with the miniaturization of electronic components.

One aspect of the present disclosure relates to a mounting board. The mounting board includes a first electronic component, a second electronic component adjacent to the first electronic component at an adjacent distance of 100 μm or less, a board on which the first electronic component and the second electronic component are surface-mounted, a first solder part for soldering the first electronic component to the board, a second solder part for soldering the second electronic component to the board, and a resin part for bonding the first electronic component and the second electronic component to the board, and the first electronic component and the second electronic component are each a chuck with a long side of 1.0 mm or less and a short side of 0.5 mm or less and terminals on both ends. The surface of the substrate has a first region covered with solder resist and a second region not covered with the solder resist, the second region has a first land that connects to a terminal of the first electronic component via the first solder part and a second land that connects to a terminal of the second electronic component via the second solder part, and the resin part bonds the periphery of the first electronic component and the second electronic component to the second region and is continuously bonded to the region of the second region sandwiched between the first land and the second land.

Another aspect of the present disclosure relates to a method for manufacturing a mounting substrate. The method is a method for manufacturing a mounting substrate in which a first electronic component and a second electronic component are surface-mounted and adjacent to each other with a distance of 100 μm or less, and the first electronic component and the second electronic component are chip-type electronic components each having a long side of 1.0 mm or less and a short side of 0.5 mm or less and terminals at both ends, and includes a substrate preparation step of preparing a substrate having a first region covered with solder resist and a second region not covered with the solder resist on its surface, and having a first land and a second land adjacent to each other with a distance of 100 μm or less in the second region, a solder precoat formation step of forming a solder precoat on the first land and the second land, and applying a thermosetting flux to the solder precoat. The method includes a flux application process, a component mounting process in which the first electronic component and the second electronic component are mounted on the solder precoat via the flux, and a reflow process in which the substrate on which the first electronic component and the second electronic component are mounted is heated. In the reflow process, the solder precoat is melted and then solidified to form a first solder portion that connects the terminal of the first electronic component to the first land and a second solder portion that connects the terminal of the second electronic component to the second land, and the flux is softened and then hardened to form a resin portion that bonds the periphery of the first electronic component and the second electronic component to the second region and that is continuously bonded to the region of the second region between the first land and the second land.

This disclosure makes it possible to achieve high-density mounting that matches the miniaturization of electronic components.

FIG. 1 is a front view illustrating an example of a mounting board according to the present disclosure. 1A to 1E are diagrams for explaining an example of a manufacturing method for a mounting board according to the present disclosure, in which (a) shows a board preparation process, (b) shows a solder precoat formation process, (c) shows a flux application process, (d) shows a component mounting process, and (e) shows a reflow process.

Embodiments of a mounting substrate and a method for manufacturing a mounting substrate according to the present disclosure are described below using examples. However, the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be given as examples, but other numerical values and materials may be applied as long as the effects of the present disclosure are obtained.

(Mounting board)
A mounting board according to the present disclosure includes a first electronic component, a second electronic component, a substrate, a first solder portion, a second solder portion, and a resin portion.

The first electronic component is a chip-type electronic component having a long side of 1.0 mm or less, a short side of 0.5 mm or less, and terminals on both ends. The external size of the first electronic component may be, for example, 1005 (1.0 mm x 0.5 mm), 0603 (0.6 mm x 0.3 mm), or 0402 (0.4 mm x 0.2 mm). The first electronic component may be, for example, a chip-type capacitor or a chip-type resistor, but is not limited to these.

The second electronic component is adjacent to the first electronic component with a distance of 100 μm or less. The second electronic component is a chip-type electronic component with a long side of 1.0 mm or less, a short side of 0.5 mm or less, and terminals on both ends. The external size of the second electronic component may be, for example, 1005 (1.0 mm x 0.5 mm), 0603 (0.6 mm x 0.3 mm), or 0402 (0.4 mm x 0.2 mm). The second electronic component may be, for example, a chip-type capacitor or a chip-type resistor, but is not limited to these.

The first electronic component and the second electronic component are surface-mounted on the substrate. The substrate may include a base material and a wiring layer, and the wiring layer typically includes a plurality of electrodes such as lands and pads. The base material is made of, for example, a semiconductor, glass, or resin. The substrate may be, for example, a glass epoxy resin substrate having a wiring layer, a bismaleimide triazine substrate, a polyimide substrate, a fluororesin substrate, a glass substrate, or a semiconductor wafer.

In this embodiment, the surface of the substrate has a first region covered with solder resist and a second region not covered with solder resist. The second region has a first land that connects to a terminal of a first electronic component via a first solder part, and a second land that connects to a terminal of a second electronic component via a second solder part. In this way, the substrate of this embodiment has a normal resist structure and is suitable for closely spaced mounting of chip-type electronic components. Each of the first and second lands may be made of, for example, copper or a copper alloy.

The first solder section solders the first electronic component to the substrate. The first solder section may be formed, for example, by melting and then solidifying cream solder, or by melting and then solidifying a solder precoat.

The second solder section solders the second electronic component to the substrate. The second solder section may be formed, for example, by melting and then solidifying cream solder, or by melting and then solidifying a solder precoat.

The resin portion bonds the first electronic component and the second electronic component to the substrate. The resin portion may include a thermosetting resin (e.g., an epoxy resin). The resin portion bonds the periphery of the first and second electronic components to the second region, and is continuously bonded to the region between the first land and the second land in the second region. Such a resin portion firmly fixes the first electronic component and the second electronic component to the substrate having a normal resist structure. Therefore, each land located between the terminal of each electronic component and the substrate surface is prevented from peeling off from the substrate. In this specification, the resin portion being continuously bonded to the predetermined region means that the resin portion and the predetermined region are in close contact with each other over 95% or more of the area of the predetermined region.

The first land and the second land do not have to overlap with the first region or the solder resist.

The resin portion may be bonded to the first land and the second land. With this configuration, the first and second lands are more firmly fixed to the substrate via the resin portion. This further prevents the first and second lands from peeling off from the substrate.

The resin part may be bonded to the bottom and side surfaces of the first electronic component and the bottom and side surfaces of the second electronic component. With this configuration, the adhesive strength between the resin part and each electronic component can be improved compared to when the resin part is bonded to only one of the bottom and side surfaces of each electronic component. Thus, each electronic component can be more firmly fixed to the substrate.

When viewed from the top surface side of the first electronic component, the area of the first land may be equal to or smaller than the area of the terminal of the first electronic component. Specifically, the area of the first land may be equal to or smaller than the area of the terminal of the first electronic component. With this configuration, the first land can be arranged closer to the second land. In other words, the first electronic component can be arranged closer to the second electronic component, shortening the adjacent distance between the two.

When viewed from the top surface side of the second electronic component, the area of the second land may be equal to or smaller than the area of the terminal of the second electronic component. Specifically, the area of the second land may be equal to or smaller than the area of the terminal of the second electronic component. With this configuration, the second land can be arranged closer to the first land. In other words, the second electronic component can be arranged closer to the first electronic component, shortening the adjacent distance between the two.

(Manufacturing method of mounting board)
A method for manufacturing a mounting substrate according to the present disclosure includes surface-mounting a first electronic component and a second electronic component adjacent to each other with a distance of 100 μm or less, the first electronic component and the second electronic component being chip-type electronic components each having a long side of 1.0 mm or less and a short side of 0.5 mm or less and having terminals on both ends, the method comprising: a substrate preparation step; a solder precoat formation step; a flux application step; a component mounting step; and a reflow step.

In the substrate preparation process, a substrate is prepared that has a first region on its surface that is covered with solder resist and a second region that is not covered with solder resist, and that has a first land and a second land in the second region that are adjacent to each other with a distance of 100 μm or less.

In the solder precoat forming process, a solder precoat is formed on the first land and the second land. The solder precoat may be formed by melting and then solidifying cream solder that has been applied to each land.

In the flux application process, a thermosetting flux is applied to the solder precoat. The thermosetting flux may include a thermosetting resin such as an epoxy resin, a flux component such as rosin, and an activator. The thermosetting flux may be applied to the solder precoat by, for example, a screen printing method or using a dispenser.

In the component mounting process, the first electronic component and the second electronic component are mounted on the solder precoat via flux. A known component mounting device (e.g., a device equipped with a nozzle that sucks and holds the electronic components) can be used to mount each electronic component.

In the reflow process, the substrate on which the first electronic component and the second electronic component are mounted is heated. In this reflow process, the solder precoat is melted and then solidified to form a first solder portion that connects the terminal of the first electronic component to the first land and a second solder portion that connects the terminal of the second electronic component to the second land. By forming such first and second solder portions, the first and second electronic components are surface-mounted on the substrate. In addition, in the reflow process, the flux is softened and then hardened to form a resin portion that bonds the periphery of the first electronic component and the second electronic component to the second region and that continuously bonds to the region sandwiched between the first land and the second land in the second region. By forming such a resin portion, the first electronic component and the second electronic component are firmly fixed to the substrate having a normal resist structure. Therefore, each land located between the terminal of each electronic component and the substrate surface is prevented from peeling off from the substrate.

As described above, according to the present disclosure, by improving the fixing strength of electronic components in a normal resist structure, it is possible to achieve high-density mounting that is commensurate with the miniaturization of electronic components.

Below, an example of a mounting board and a method for manufacturing a mounting board according to the present disclosure will be specifically described with reference to the drawings. The above-mentioned components and steps can be applied to the components and steps of the mounting board and the method for manufacturing a mounting board of the example described below. The components and steps of the mounting board and the method for manufacturing a mounting board of the example described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiment. Among the components and steps of the mounting board and the method for manufacturing a mounting board of the example described below, components and steps that are not essential to the mounting board and the method for manufacturing a mounting board according to the present disclosure may be omitted. Note that the figures shown below are schematic and do not accurately reflect the shape and number of actual members.

As shown in FIG. 1, the mounting board 10 of this embodiment includes a first electronic component 11, a second electronic component 12, a substrate 13, a first solder portion 21, a second solder portion 22, and a resin portion 23.

The first electronic component 11 is a chip-type electronic component with long sides of 1.0 mm or less, short sides of 0.5 mm or less, and terminals 11a at both ends. The long and short sides refer to the long and short sides of a rectangle when the rectangular first electronic component 11 is viewed from the top side (top side in FIG. 1). In this embodiment, the first electronic component 11 is a 0402 size chip-type capacitor, but is not limited to this.

The second electronic component 12 is a chip-type electronic component with long sides of 1.0 mm or less, short sides of 0.5 mm or less, and terminals 12a at both ends. The long and short sides refer to the long and short sides of a rectangle when the rectangular second electronic component 12 is viewed from the top side (top side in FIG. 1). In this embodiment, the second electronic component 12 is a 0402 size chip-type capacitor, but is not limited to this.

The adjacent distance L1 between the first electronic component 11 and the second electronic component 12 is 100 μm or less. The adjacent distance L1 may be, for example, 90 μm or less, 80 μm or less, 70 μm or less, or 50 μm or less, or may be, for example, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more.

The first electronic component 11 and the second electronic component 12 are surface-mounted on the substrate 13. The substrate 13 has a base material made of glass epoxy resin. The surface of the substrate 13 has a first region 14 covered with a solder resist 15 and a second region 16 not covered with the solder resist 15. The second region 16 has a first land 17 that connects to the terminal 11a of the first electronic component 11 via a first solder section 21, and a second land 18 that connects to the terminal 12a of the second electronic component 12 via a second solder section 22. Each of the first land 17 and the second land 18 is made of copper or a copper alloy and has a rectangular shape when viewed from above. The first land 17 and the second land 18 do not overlap the first region 14 or the solder resist 15 when viewed from above.

The adjacent distance L2 between the first land 17 and the second land 18 may be equal to or smaller than the adjacent distance L1 between the first electronic component 11 and the second electronic component 12, or may be greater than the adjacent distance L1 between the first electronic component 11 and the second electronic component 12. If the areas of the first and second lands 17 and 18 are smaller than the areas of the terminals 11a and 12a of the first and second electronic components 11 and 12, the adjacent distance L1 between the first electronic component 11 and the second electronic component 12 can be smaller than the adjacent distance L2 between the first land 17 and the second land 18. In this embodiment, the areas of the first and second lands 17 and 18 are substantially equal to the areas of the terminals of the first and second electronic components 11 and 12. "Substantially equal" means that the ratio of the difference between the areas of the first and second lands 17 and 18 to the areas of the first and second lands 17 and 18 is 5% or less.

The first solder section 21 solders the first electronic component 11 to the substrate 13. In this embodiment, the first solder section 21 is formed by melting and then solidifying the solder precoat 24 (see FIG. 2(b)).

The second solder section 22 solders the second electronic component 12 to the substrate 13. In this embodiment, the second solder section 22 is formed by melting and then solidifying the solder precoat 24 (see FIG. 2(b)).

The resin part 23 bonds the first electronic component 11 and the second electronic component 12 to the substrate 13. The resin part 23 contains epoxy resin, which is a thermosetting resin. The resin part 23 bonds the peripheries of the first and second electronic components 11, 12 to the second region 16, and also continuously bonds the region sandwiched between the first land 17 and the second land 18 in the second region 16 (the region sandwiched between the first land 17 and the second land 18 on the sides adjacent to each other).

The resin part 23 is continuously bonded in the second region 16 to the region sandwiched between the two first lands 17 and the region sandwiched between the two second lands 18. The resin part 23 is continuously bonded in the second region 16 to the region sandwiched between the first land 17 and the solder resist 15 and the region sandwiched between the second land 18 and the solder resist 15. The resin part 23 is bonded to the first land 17 and the second land 18. The resin part 23 is bonded to the first solder part 21 and the second solder part 22. The resin part 23 is bonded to the bottom and side surfaces of the first electronic component 11 and the bottom and side surfaces of the second electronic component 12. The resin part 23 is bonded to the solder resist 15.

- Manufacturing method of mounting board -
Next, a method for manufacturing the above-mentioned mounting board 10 will be described with reference to Fig. 2. As shown in Fig. 2, the manufacturing method for the mounting board includes a substrate preparation process, a solder precoat formation process, a flux application process, a component mounting process, and a reflow process.

In the substrate preparation process, as shown in FIG. 2(a), a substrate 13 is prepared that has a first region 14 covered with solder resist 15 and a second region 16 not covered with solder resist 15 on its surface, and has a first land 17 and a second land 18 in the second region 16 that are adjacent to each other with an adjacent distance L2 of 100 μm or less. Here, the adjacent distance L2 between the first land 17 and the second land 18 is the adjacent distance between the first land 17 and the second land 18 on the sides that are close to each other.

In the solder precoat formation process, as shown in FIG. 2(b), a solder precoat 24 is formed on the first land 17 and the second land 18. The solder precoat 24 is formed by applying cream solder (not shown) onto the first and second lands 17 and 18, for example, by using a screen printing method, and then melting and solidifying the cream solder.

In the flux application process, as shown in FIG. 2(c), a thermosetting flux 25 is applied to the solder precoat 24. The thermosetting flux 25 contains epoxy resin, which is a thermosetting resin, a flux component, and an activator. The thermosetting flux 25 is applied to the solder precoat 24 by a screen printing method.

In the component mounting process, as shown in FIG. 2(d), the first electronic component 11 and the second electronic component 12 are mounted on the solder precoat 24 via the flux 25. At this time, the first and second electronic components 11, 12 are mounted so that the terminal 11a of the first electronic component 11 is placed on the first land 17, and the terminal 12a of the second electronic component 12 is placed on the second land 18.

In the reflow process, as shown in FIG. 2(e), the substrate 13 on which the first electronic component 11 and the second electronic component 12 are mounted is heated. In this reflow process, the solder precoat 24 is melted and then solidified to form the first solder portion 21 connecting the terminal 11a of the first electronic component 11 to the first land 17 and the second solder portion 22 connecting the terminal 12a of the second electronic component 12 to the second land 18. In addition, in the reflow process, the thermosetting flux 25 is softened and then hardened to form the resin portion 23 that bonds the periphery of the first electronic component 11 and the second electronic component 12 to the second region 16 and continuously bonds to the region sandwiched between the first land 17 and the second land 18 of the second region 16. The above-mentioned mounting substrate 10 can be manufactured by each of the above processes.

This disclosure can be used for mounting substrates and methods for manufacturing mounting substrates.

10: Mounting board 11: First electronic component 11a: Terminal 12: Second electronic component 12a: Terminal 13: Board 14: First region 15: Solder resist 16: Second region 17: First land 18: Second land 21: First solder portion 22: Second solder portion 23: Resin portion 24: Solder precoat 25: Flux L1: Adjacent distance between electronic components L2: Adjacent distance between lands

Claims (6)

A first electronic component;
a second electronic component adjacent to the first electronic component at a distance of 100 μm or less;
a substrate on which the first electronic component and the second electronic component are surface-mounted;
a first solder portion for soldering the first electronic component to the substrate;
a second solder portion for soldering the second electronic component to the substrate;
a resin portion that bonds the first electronic component and the second electronic component to the substrate;
Equipped with
the first electronic component and the second electronic component are chip-type electronic components each having a long side of 1.0 mm or less, a short side of 0.5 mm or less, and terminals on both ends;
the surface of the substrate has a first region covered with a solder resist and a second region not covered with the solder resist;
the second region has a first land connected to a terminal of the first electronic component via the first solder portion and a second land connected to a terminal of the second electronic component via the second solder portion;
A mounting board, wherein the resin portion adheres the peripheries of the first electronic component and the second electronic component to the second region, and is continuously adhered to a region of the second region sandwiched between the first land and the second land. The mounting board according to claim 1, wherein the first land and the second land do not overlap the first region or the solder resist. The mounting board according to claim 1 or 2, wherein the resin part is bonded to the first land and the second land. The mounting board according to any one of claims 1 to 3, wherein the resin part is bonded to the bottom and side surfaces of the first electronic component and the bottom and side surfaces of the second electronic component. an area of the first land is equal to or smaller than an area of a terminal of the first electronic component when viewed from a top surface side of the first electronic component;
5. The mounting board according to claim 1, wherein an area of the second land is equal to or smaller than an area of a terminal of the second electronic component when viewed from the top surface side of the second electronic component. A method for manufacturing a mounting substrate, comprising: surface-mounting a first electronic component and a second electronic component adjacent to each other with a distance of 100 μm or less; the first electronic component and the second electronic component are chip-type electronic components each having a long side of 1.0 mm or less, a short side of 0.5 mm or less, and terminals on both ends, the method comprising:
a substrate preparation step of preparing a substrate having a first region covered with a solder resist and a second region not covered with the solder resist on a surface thereof, the first land and the second land being adjacent to each other at a distance of 100 μm or less in the second region;
a solder precoat forming step of forming a solder precoat on the first land and the second land;
a flux application step of applying a thermosetting flux to the solder precoat;
a component mounting step of mounting the first electronic component and the second electronic component on the solder precoat via the flux;
a reflow process of heating the substrate on which the first electronic component and the second electronic component are mounted;
Equipped with
a first solder portion connecting a terminal of the first electronic component to the first land and a second solder portion connecting a terminal of the second electronic component to the second land, and a second solder portion connecting a terminal of the second electronic component to the second land, the second land being connected to the first land by melting the solder precoat and then hardening the flux to form a resin portion that bonds the peripheries of the first electronic component and the second electronic component to the second region and that continuously bonds to a region of the second region between the first land and the second land.

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