Method for producing electronic component mounting substrate

Abstract

A method for manufacturing an electronic component mounting substrate according to an embodiment disclosed herein comprises: a first step for applying a solder flux on at least a portion of each of a plurality of first lands of a circuit board; a second step for mounting first electronic components, having a size of at most 0402 defined by JIS standards, on each of the plurality of first lands via the solder flux; and a third step for heating the circuit board, on which the first electronic components were mounted in the second step, and soldering the first electronic components to each of the first lands. The first electronic component includes: an electronic component body having a pair of end surfaces, an upper surface, a lower surface, and a pair of side surfaces; and a pair of first terminals disposed on at least the pair of end surfaces and the lower surface of the electronic component body and having solder plating on the surface. The pair of first terminals are soldered to the first lands by melting and solidifying solder included in the solder plating in the third step. None of the plurality of first lands has a solder precoat formed thereon. The distance between the first lands respectively corresponding to the first electronic components soldered to the first lands so as to be adjacent to each other is 0.02-0.10 mm inclusive.

Description

Method for manufacturing an electronic component mounting substrate

[0001] The present invention relates to a method for manufacturing an electronic component mounting substrate.

[0002] In recent years, with the miniaturization of electronic devices, miniaturization of electronic component mounting substrates has also been demanded. In order to meet such a demand for miniaturization of electronic component mounting substrates, it is necessary to densely mount minute electronic components on a circuit board at a narrow pitch. As a technique for densely mounting minute electronic components, a method using solder precoat has been studied (Patent Document 1).

[0003] International Publication No. 2022 / 195937

[0004] However, there remains room for further improvement in order to improve the production yield of electronic component mounting substrates, and in particular, it has been necessary to suppress the formation of solder bridges between adjacent electronic components.

[0005] Therefore, the present disclosure provides a method for manufacturing an electronic component mounting substrate capable of suppressing the formation of solder bridges between adjacent electronic components.

[0006] One aspect of the present invention is a first step of applying solder flux to at least a portion of each of a plurality of first lands on a circuit board; a second step of mounting a first electronic component of size 0402 or smaller as defined by JIS standards on each of the plurality of first lands via the solder flux; and a third step of heating the circuit board on which the first electronic components are mounted in the second step to solder the first electronic components to each of the first lands, wherein the first electronic component comprises an electronic component body having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and the The present invention relates to a method for manufacturing an electronic component mounting substrate, comprising: a pair of first terminals disposed on at least one of the pair of end faces and the lower surface of an electronic component body and having solder plating on their surfaces, wherein the pair of first terminals are soldered to the first land by melting and solidifying the solder contained in the solder plating in the third step, no solder precoat is formed on each of the plurality of first lands, and the distance between the first lands corresponding to each of the first electronic components soldered adjacent to each other on the first lands is 0.02 mm or more and 0.10 mm or less.

[0007] According to this disclosure, it is possible to provide a method for manufacturing an electronic component mounting substrate that can suppress the formation of solder bridges between adjacent electronic components.

[0008] This is a flowchart of a method for manufacturing an electronic component mounting substrate according to an embodiment of this disclosure. This is a side cross-sectional view showing an example of a circuit board used in the method for manufacturing an electronic component mounting substrate according to an embodiment of this disclosure. This is a side cross-sectional view illustrating an example of the first step of the method for manufacturing an electronic component mounting substrate according to an embodiment of this disclosure. This is a side cross-sectional view illustrating an example of the second step of the method for manufacturing an electronic component mounting substrate according to an embodiment of this disclosure. This is an enlarged side cross-sectional view of part A in Figure 4. This is a side cross-sectional view illustrating an example of the third step of the method for manufacturing an electronic component mounting substrate according to an embodiment of this disclosure. This is an enlarged side cross-sectional view illustrating part B in Figure 6.

[0009] The embodiments of this disclosure will be described below with examples, but this 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, materials, etc. may be applied as long as the effects of this disclosure are obtained. Notwithstanding, known components may be applied to components of parts that are characteristic of this disclosure. In this specification, when "the range of numerical values ​​A to numerical values ​​B" is used, that range includes numerical values ​​A and B.

[0010] In the following explanation, when examples are given for the lower and upper limits of numerical values ​​related to specific physical properties or conditions, any combination of either of the given lower limits and any of the given upper limits is permitted, as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, unless otherwise specified, one type may be selected and used alone, or two or more types may be used in combination.

[0011] This disclosure includes any combination of two or more claims that can be arbitrarily selected from the claims set forth in the attached claims. In other words, any combination of two or more claims that can be arbitrarily selected from the claims set forth in the attached claims is possible, as long as it does not result in a technical inconsistency.

[0012] (Method for manufacturing an electronic component mounting substrate) As shown in Figure 1, the method for manufacturing an electronic component mounting substrate comprises: a first step of applying solder flux to at least a portion of each of the plurality of first lands on the circuit board; a second step of mounting first electronic components of size 0402 or smaller as defined by JIS standards on each of the plurality of first lands via solder flux; and a third step of heating the circuit board on which the first electronic components were mounted in the second step to solder the first electronic components to each of the first lands. In the method for manufacturing an electronic component mounting substrate as shown in the embodiment of this disclosure, no solder precoat is formed on each of the plurality of first lands.

[0013] Solder precoat is formed by coating the surface of a land with solder for soldering electronic components. For example, it is formed by supplying solder paste containing solder particles to the land, melting the solder particles contained in the solder paste, wetting and spreading it on the land, and then solidifying the resulting solder. Therefore, solder precoat does not include the solder paste that was supplied to the land but before the solder particles were melted. Solder precoat may be formed with solder obtained by electrolytic plating, or with solder generated by heating a special material applied to the land.

[0014] In the method for manufacturing an electronic component mounting substrate according to the embodiment of the present disclosure, the first electronic component comprises an electronic component body having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and a pair of first terminals disposed on at least one pair of end faces and the lower surface of the electronic component body and having solder plating on their surfaces. In the method for manufacturing an electronic component mounting substrate according to the embodiment of the present disclosure, the pair of first terminals are soldered to the first land in a third step by melting and solidifying the solder contained in the solder plating.

[0015] In the method for manufacturing an electronic component mounting substrate according to the embodiment of this disclosure, the distance between first lands corresponding to each of the first electronic components soldered adjacent to each other on the first land is 0.02 mm or more and 0.10 mm or less. The aforementioned distance can also be described as the distance between opposing first lands in a pair of first lands on which the first electronic components are mounted adjacent to each other.

[0016] In the method for manufacturing an electronic component mounting substrate according to the embodiment of this disclosure, it is important that (i) the first electronic component has an electronic component body having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and a pair of first terminals disposed on at least one pair of end faces and the lower surface of the electronic component body and having solder plating on their surfaces, (ii) the pair of first terminals are soldered to the first land in the third step by melting and solidifying the solder contained in the solder plating, and (iii) no solder precoat is formed on each of the plurality of first lands. In short, it is important to solder the first electronic component to the first land, which is covered with solder flux without forming a solder precoat, using the solder contained in the solder plating of the pair of first terminals. The reasons for this will be explained below.

[0017] In conventional methods of manufacturing electronic component mounting boards using solder precoating, as described in publicly available literature, when the solder precoating melts into molten solder, the molten solder, being in a liquid state, wets and spreads across the surface of the electronic component terminals. For tiny electronic components, the volume of solder precoating tends to be excessive relative to the surface area of ​​the terminal. As a result, the excess molten solder that has risen onto the terminal surface (end face of the terminal) bulges outwards laterally due to the action of its own weight and surface tension. Consequently, when the distance between adjacent electronic components (distance between lands) becomes narrow, the molten solder that has bulged laterally can come into contact with each other and connect, forming a solder bridge.

[0018] While the self-alignment effect of molten solder's surface tension can cause electronic components to move and align with the solder pads, if adjacent components accidentally move closer together due to this self-alignment effect, the molten solder bulging laterally from the end faces of these adjacent components is particularly prone to contact. This problem is especially pronounced when the distance between opposing pads is short (for example, between 0.02 mm and 0.10 mm) in a pair of pads on which adjacent electronic components are mounted.

[0019] To solve this problem, one might consider reducing the volume of solder precoat formed on the land. However, since the land used to join tiny electronic components such as the first electronic component of size 0402 or smaller as defined by JIS standards is so small, it is technically difficult to reduce its volume using conventional solder precoat. Furthermore, while it is possible to reduce the volume by using a special solder precoat, this is disadvantageous in terms of cost.

[0020] The method for manufacturing an electronic component mounting substrate according to the embodiment of this disclosure has the configurations (i) to (iii) described above. That is, in the method for manufacturing an electronic component mounting substrate according to the embodiment of this disclosure, first electronic components are soldered to a first land covered with solder flux without forming a solder precoat, using the solder contained in the solder plating of a pair of first terminals. Since the volume of the solder plating is much smaller than that of the solder precoat, the formation of solder bridges between adjacent first electronic components can be suppressed compared to the case where a solder precoat is formed on the land as described above.

[0021] Hereinafter, a method for manufacturing an electronic component mounting substrate according to one embodiment of this disclosure will be described step by step with reference to the drawings. Before describing each step, an example of a circuit board used in the method for manufacturing an electronic component mounting substrate according to the embodiment of this disclosure will be described.

[0022] [Circuit Board] As shown in Figure 2, one example of a circuit board 1 has a substrate portion 1a and a plurality of lands 2 arranged on the main surface of the substrate portion 1a. As shown in Figure 2, the plurality of lands 2 have at least a plurality of first lands 2A and a plurality of second lands 2B. In Figure 2, an example is shown in which the circuit board 1 has four first lands 2A and two second lands 2B, with a pair of first lands 2A arranged adjacent to each other, but the number of first lands 2A and second lands 2B is not limited to this. Also, in the circuit board 1, a pair of second lands 2B may be arranged adjacent to each other.

[0023] The substrate portion 1a may be composed of various known substrates such as a laminated substrate, a resin substrate, a ceramic substrate, and a silicon substrate. An example of a circuit board 1 is a printed circuit board.

[0024] The first land 2A is a land on which a first electronic component of size 0402 or smaller as defined by the JIS standard is mounted. As shown in Figure 4, the first electronic component 5 is mounted on a pair of first lands 2A. The first electronic component 5 has an electronic component body 5a and a pair of first terminals 5b arranged on both end faces of the electronic component body 5a. In other words, the first electronic component 5 is a chip component. Examples of chip components include chip resistors, chip capacitors, and chip inductors. Details of the configuration of the first electronic component 5 will be described later. In the first electronic component 5, each of the pair of first terminals 5b is mounted on each of the pair of first lands 2A. In addition, the distance between two opposing first lands 2A (distance L shown in Figure 2) is 0.02 mm or more and 0.10 mm or less. The distance L may be 0.02 mm or more and 0.07 mm or less.

[0025] Furthermore, as shown in Figure 4, when the first electronic component 5 is mounted on the first land 2A, distance L is also the distance between the first lands 2A corresponding to each of the first electronic component 5 soldered adjacent to each other on the first land 2A. In addition, distance L is also the distance between the opposing first lands 2A in a pair of first lands 2A on which the first electronic component 5 is mounted adjacent to each other.

[0026] As shown in Figure 2, the second land 2B is a land on which a solder precoat 4 is formed on at least a portion of its surface. The solder precoat 4 can be formed by a so-called solder paste printing method, which involves supplying solder paste to the second land 2B and then melting the solder particles contained in the solder paste, as described above. The solder precoat 4 is used for soldering electronic components. Chip components are mounted on the second land 2B. As shown in Figure 4, the second electronic component 7 is soldered to the second land 2B. The second electronic component 7 is a chip component with a larger volume than the first electronic component 5. The second electronic component 7 has an electronic component body 7a and a pair of second terminals 7b arranged on both end faces of the electronic component body 7a (see Figure 4). Details of the configuration of the second electronic component 7 will be described later. In the second electronic component 7, as with the first electronic component 5, each of the pair of second terminals 7b is mounted on each of the pair of second lands 2B.

[0027] As described above, both the first land 2A and the second land 2B are used to mount chip components. On the other hand, the circuit board 1 may have a third land for mounting third electronic components other than chip components. Examples of third electronic components include flat packages, connectors, ball grid arrays, and cylindrical capacitors.

[0028] In the following section, an example of manufacturing an electronic component mounting board according to one embodiment of this disclosure will be described using a circuit board 1 shown in Figure 2.

[0029] <First Step> In the first step of the method for manufacturing an electronic component mounting substrate according to one embodiment of the present disclosure, as shown in Figure 3, solder flux 3 is applied to at least a portion of each of the plurality of first lands 2A, and solder flux 3 is also applied to the solder precoat 4 formed on each of the plurality of second lands 2B. In this case, the solder flux 3 can be applied (coated) to the plurality of first lands 2A and the plurality of second lands 2B at once by a screen printing method described later. That is, the solder flux 3 can be efficiently applied to the plurality of first lands 2A and the plurality of second lands 2B. In the method for manufacturing an electronic component mounting substrate according to one embodiment of the present disclosure, solder precoat 4 is not formed on each of the plurality of first lands 2A. Therefore, the solder flux 3 is arranged to come into direct contact with each of the plurality of first lands 2A without going through the solder precoat 4 (see Figure 3).

[0030] The method for applying the solder flux 3 is not particularly limited, and various known application methods can be used. For example, stencil printing, dispensing, and spraying methods can be used. Stencil printing is preferred because it allows for the formation of a layer of solder flux 3 of a constant thickness in one step. Stencil printing may also be a screen printing method. Screen printing may be carried out using a mask with through holes corresponding to the land positions. Screen printing may also be a contact printing method using a metal mask, for example. Contact printing is suitable for precisely controlling the amount of solder flux 3 applied. Screen printing may also be a printing method using a mesh screen (off-contact printing method). Off-contact printing can print solder flux at a higher speed than contact printing. Therefore, by adopting off-contact printing as the screen printing method, productivity can be increased compared to adopting contact printing.

[0031] The typical thickness of a mask used in screen printing is about 60 μm. On the other hand, when screen printing is performed on a circuit board 1 having a first land 2A on which a tiny electronic component such as a first electronic component is mounted, the thickness of the mask is preferably 40 μm or less, and more preferably 30 μm or less.

[0032] Solder flux 3 is used to mount electronic components on the circuit board 1. Solder flux 3 typically contains a main resin, a thixotropic agent, an activator, and a solvent. Solder flux 3 can be prepared by mixing these components. Solder flux 3 is typically tacky. Solder flux 3 exhibits tackiness, for example, by containing a main resin. This tackiness allows the first electronic component to be mounted by temporarily fixing it to the first land 2A, and the electronic component (chip component) to be mounted by temporarily fixing it to the second land 2B.

[0033] As the main resin, it is preferable to use a rosin-based resin that has reducing properties itself, but other resins may also be used. The main resin may be used alone or in combination of two or more types.

[0034] Examples of rosin-based resins include natural rosins such as gum rosin and wood rosin, and their derivatives (polymerized rosin, hydrogenated rosin, disproportionated rosin, acid-modified rosin, and rosin esters).

[0035] Other resins besides rosin-based resins include terpene resins, terpene phenol resins, styrene resins, xylene resins, acrylic resins, polyester resins, polyolefin resins, polyamides, polyamines, phenolic resins, phenoxy resins, and epoxy resins.

[0036] Examples of thixotropic agents include wax-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents. Thixotropic agents may be used individually or in combination of two or more types.

[0037] The activator used is a compound that reduces the oxide film covering the surface of solder used for soldering electronic components. An example of solder is the solder contained in the solder plating applied to a pair of first terminals of a first electronic component. Note that the main resin, such as rosin-based resin, may also have some degree of activating effect. Therefore, in this specification, the term "activator" refers to a compound other than the main resin, such as rosin-based resin, that has an activating effect.

[0038] The activator reduces the oxide film and assists in the formation of a good junction. Examples of activators with reducing properties include organic acids, amines, and halides. The activator may be used alone or in combination of two or more. It is preferable to use an organic acid as the activator.

[0039] Examples of organic acids used as activators include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, propionic acid, 2,2-bishydroxymethylpropionic acid, tartaric acid, malic acid, glycolic acid, diglycolic acid, thioglycolic acid, dithioglycolic acid, stearic acid, 12-hydroxystearic acid, palmitic acid, and oleic acid.

[0040] Examples of solvents include water, alcohol-based solvents, glycol-based solvents, ketone-based solvents, hydrocarbon-based solvents, ester-based solvents, glycol ether-based solvents, and terpionelles. A single solvent may be used, or two or more may be used in combination.

[0041] Solder flux 3 may contain other components besides those listed above. Other components include surfactants, silane coupling agents, antioxidants, and colorants.

[0042] <Second Step> In the second step of the method for manufacturing an electronic component mounting substrate according to an embodiment of the present disclosure, as shown in FIG. 4, in addition to mounting a first electronic component 5 having a size of 0402 or less defined by JIS standards on each of a plurality of first lands 2A via a solder flux 3, a second electronic component 7 is mounted on each of a plurality of second lands 2B via the solder flux 3. The mounting of these electronic components can be performed by a known component mounting apparatus. The second electronic component 7 is a chip component having a larger volume than the first electronic component 5 as described above. Note that, as described above, the electronic components mounted on the plurality of second lands 2B may be chip components, and may also be the first electronic components 5. The solder flux 3 usually contains a main resin as described above, and has adhesiveness by containing this main resin. Therefore, the first electronic component 5 is temporarily fixed and mounted on the first land 2A by the main resin contained in the solder flux 3, and the second electronic component 7 is also temporarily fixed and mounted on the second land 2B by the main resin contained in the solder flux 3.

[0043] Here, the first electronic component 5 and the second electronic component 7 will be described.

[0044] The sizes of the first electronic component 5 are 0402, 03015, 0201, 01005, etc. defined by JIS standards. Note that the 0402-size electronic component means an electronic component having a size of length 0.4 mm × width 0.2 mm, the 03015-size electronic component means an electronic component having a size of length 0.3 mm × width 0.15 mm, the 0201-size electronic component means an electronic component having a size of length 0.25 mm × width 0.125 mm, and the 01005-size electronic component means an electronic component having a size of length 0.1 mm × width 0.05 mm. The first electronic component 5 has a smaller size and is extremely lightweight compared to the second electronic component 7 described later.

[0045] The first electronic component 5 usually has a rectangular shape and includes an electronic component body 5a having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and a pair of first terminals 5b arranged on at least the pair of end faces and the lower surface of the electronic component body 5a and having solder plating 6 on the surface (see FIGS. 4 and 5). Note that the end face is a side surface in the longitudinal direction of the electronic component. The lower surface is the surface to be mounted on the circuit board 1, and the upper surface is the surface opposite to the lower surface. Further, the side surface is a surface orthogonal to all of the end face, the upper surface, and the lower surface.

[0046] The solder plating 6 is, for example, tin (Sn) plating. The melting point of the solder plating may be 200°C or higher, may be 215°C or higher, or may be 225°C or higher. The melting point of the solder plating may be 240°C or lower, or may be 235°C or lower.

[0047] The thickness of the solder plating 6 is preferably 1 μm or more and 10 μm or less. When the thickness of the solder plating 6 is 1 μm or more, the pair of first terminals 5b can be more sufficiently soldered to the first land 2A. Further, when the thickness of the solder plating 6 is 10 μm, it is possible to suppress an excessive amount of solder contained in the solder plating 6.

[0048] The second electronic component 7 is a chip component having a larger volume than the first electronic component 5. The second electronic component 7 also usually has a rectangular shape.

[0049] The size of the second electronic component 7 is, for example, 0603 and 1005 defined by the JIS standard. Note that the 0603-size electronic component means an electronic component with a size of length 0.6 mm × width 0.3 mm, and the 1005-size electronic component means an electronic component with a size of length 1.0 mm × width 0.5 mm.

[0050] As described above, the second electronic component 7 has a rectangular shape and includes an electronic component body 7a having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and a pair of second terminals 7b arranged in contact with at least the lower surface on both end face sides of the electronic component body 7a (see FIG. 4).

[0051] <Third Step> In the third step of the method for manufacturing an electronic component mounting substrate according to one embodiment of the present disclosure, as shown in Figure 6, the circuit board 1 on which the first electronic component 5 is mounted in the second step is heated and the first electronic component 5 is soldered to each of the first lands 2A, and the second electronic component 7 is soldered to each of the second lands 2B. The pair of first terminals 5b are soldered to the first lands 2A in the third step by melting and solidifying the solder contained in the solder plating 6. On the other hand, the pair of second terminals 7b are soldered to the second lands 2B in the third step by melting and solidifying the solder precoat 4. That is, the first electronic component 5 is soldered to the first lands 2A via the pair of first terminals 5b, and the second electronic component 7 is soldered to the second lands 2B via the pair of second terminals 7b. In Figures 6 and 7, the solder used to solder the first terminal 5b to the first land 2A is shown as solder portion 6a, and the solder used to solder the second terminal 7b to the second land 2B is shown as solder portion 4a.

[0052] The circuit board 1 on which the first electronic component 5 and the second electronic component 7 are mounted can be heated, for example, using a heating device such as a reflow oven. Heating the circuit board 1 softens the solder flux 3 placed on the first land 2A, increasing its fluidity. As explained above, the solder flux 3 contains an activator. Also, an oxide film is usually formed on the surface of the solder plating 6 placed on the surface of the first terminal 5b. Therefore, the activator contained in the solder flux 3, whose fluidity has been increased as described above, reduces the oxide film formed on the surface of the solder plating 6 on the surface of the first terminal 5b, exposing the solder portion on the surface of the solder plating 6. This ensures sufficient solder bonding of the first terminal 5b to the first land 2A when the solder contained in the solder plating 6 is melted by heating. In addition, on the second land 2B, increasing the fluidity of the solder flux 3 can remove the oxide film on the surface of the solder precoat 4 and the second terminal 7b.

[0053] The softening point of the main resin contained in the solder flux 3 is usually lower than the melting point of the solder contained in the solder plating 6. Therefore, when the circuit board 1 is heated, the main resin melts before the solder contained in the solder plating 6. The activator contained in the main resin that melts first reduces the oxide film formed on the surface of the solder plating 6, exposing the solder portion on the surface of the solder plating 6. Then, the molten solder can be used to solder the first terminal 5b to the first land 2A. In other words, the first electronic component 5 can be soldered to the first land 2A via the first terminal 5b. Similarly, the second electronic component 7 can be soldered to the second land 2B via the second terminal 7b.

[0054] In the third step, the solder contained in the solder plating 6 is melted by heating in a heating device such as a reflow oven, and this molten solder is spread onto the first land 2A. In addition, the solder precoat 4 is melted, and this molten solder is spread onto the second land 2B, after which the circuit board 1 is cooled. As a result, the molten solder spread onto the first land 2A solidifies, and the first terminal 5b is soldered to the first land 2A. That is, the first terminal 5b is soldered to the first land 2A via the solder portion 6a. Also, the molten solder spread onto the second land 2B solidifies, and the second terminal 7b is soldered to the second land 2B. That is, the second terminal 7b is soldered to the second land 2B via the solder portion 4a.

[0055] In the third step, the solder contained in the solder plating 6 is melted and becomes liquid, and as shown in Figure 7, although the solder (solder portion 6a) swells between the terminals of adjacent first electronic components 5, the volume of the solder plating 6 is far smaller than that of the solder precoat 4, so the swelling is extremely small. Therefore, compared to the case where the solder precoat 4 is formed on the first land 2A, the formation of solder bridges between the terminals of adjacent first electronic components 5 can be suppressed.

[0056] Some first electronic components 5, such as chip inductors, have first terminals 5b only on their end face and the adjacent lower surface (for example, Figure 4). Because the surface area of ​​the first terminals 5b is small, conventional methods for manufacturing electronic component mounting boards using solder precoating are prone to solder bridging, as described above. In contrast, the method for manufacturing electronic component mounting boards according to the embodiment of this disclosure can reduce the occurrence of solder bridging to a level that does not pose a practical problem. Therefore, the method for manufacturing electronic component mounting boards according to the embodiment of this disclosure is particularly useful when soldering a first electronic component 5 that has first terminals 5b only on its end face and the adjacent lower surface to a circuit board 1.

[0057] The present invention may be modified in any way that does not depart from the spirit of the invention. For example, although the first electronic component 5 is mounted on a first land 2A that does not have a solder precoat 4, it is not prohibited to solder it to a second land 2B that has a solder precoat 4. For example, in the circuit board 1, the first electronic component 5 soldered to the first land 2A and the second electronic component 7 soldered to the second land 2B may be mixed together. In this case, it is desirable that the first electronic component 5 soldered to the second land 2B be separated from adjacent first electronic components 5 by a sufficient distance so that no solder bridges occur.

[0058] (Note) The following technologies are disclosed in accordance with the above description. (Technology 1) A first step of applying solder flux to at least a portion of each of a plurality of first lands on a circuit board; a second step of mounting a first electronic component of size 0402 or smaller as defined by JIS standards on each of the plurality of first lands via the solder flux; a third step of heating the circuit board on which the first electronic component is mounted in the second step to solder the first electronic component to each of the first lands, wherein the first electronic component comprises an electronic component body having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and a pair of first terminals disposed on at least the pair of end faces and the lower surface of the electronic component body and having solder plating on their surfaces, wherein the pair of first terminals are soldered to the first lands in the third step by melting and solidifying the solder contained in the solder plating, and no solder precoat is formed on each of the plurality of first lands. A method for manufacturing an electronic component mounting substrate, wherein the distance between the first lands corresponding to each of the first electronic components soldered adjacent to each other on the first land is 0.02 mm or more and 0.10 mm or less. (Technical 2) A method for manufacturing an electronic component mounting substrate according to Technical 1, wherein the pair of first terminals are arranged only on the pair of end faces and the bottom surface. (Technical 3) A method for manufacturing an electronic component mounting substrate according to Technical 1 or 2, wherein the thickness of the solder plating is 1 μm or more and 10 μm or less.(Technology 4) The method for manufacturing an electronic component mounting substrate according to any one of Techniques 1 to 3, wherein the circuit board further includes a plurality of second lands on which a solder precoat is formed, in the first step, solder flux is further applied to the solder precoat formed on each of the plurality of second lands, in the second step, an electronic component is further mounted on each of the plurality of second lands via the solder flux, in the third step, the electronic component is further soldered to each of the plurality of second lands, the electronic component has an electronic component body having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and a pair of terminals arranged on both end faces of the electronic component body in contact with at least the lower surface, and the pair of terminals are soldered to the second lands in the third step by melting and solidifying the solder contained in the solder precoat.

[0059] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0060] The method for manufacturing an electronic component mounting substrate according to this disclosure can be used in applications where it is required to suppress the formation of solder bridges between adjacent electronic components.

[0061] 1: Circuit board, 1a: Board portion, 2: Land, 2A: First land, 2B: Second land, 3: Solder flux, 4: Solder precoat, 4a: Solder portion, 5: First electronic component, 5a: Electronic component body, 5b: First terminal, 6: Solder plating, 6a: Solder portion, 7: Second electronic component, 7a: Electronic component body, 7b: Second terminal

Claims

1. The process comprises: a first step of applying solder flux to at least a portion of each of a plurality of first lands on a circuit board; a second step of mounting a first electronic component of size 0402 or smaller as defined by JIS standards on each of the plurality of first lands via the solder flux; and a third step of heating the circuit board on which the first electronic components are mounted in the second step to solder the first electronic components to each of the first lands, wherein the first electronic component comprises an electronic component body having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and a pair of first terminals disposed on at least the pair of end faces and the lower surface of the electronic component body and having solder plating on their surfaces, wherein the pair of first terminals are soldered to the first lands in the third step by melting and solidifying the solder contained in the solder plating, and no solder precoat is formed on each of the plurality of first lands. A method for manufacturing an electronic component mounting substrate, wherein the distance between the first lands corresponding to each of the first electronic components soldered adjacent to each other on the first land is 0.02 mm or more and 0.10 mm or less.

2. The method for manufacturing an electronic component mounting substrate according to claim 1, wherein the pair of first terminals are arranged only on the pair of end faces and the bottom surface.

3. The method for manufacturing an electronic component mounting substrate according to claim 1 or 2, wherein the thickness of the solder plating is 1 μm or more and 10 μm or less.

4. The circuit board further includes a plurality of second lands on which a solder precoat is formed; in the first step, solder flux is further applied to the solder precoat formed on each of the plurality of second lands; in the second step, an electronic component is further mounted on each of the plurality of second lands via the solder flux; in the third step, the electronic component is further soldered to each of the plurality of second lands; the electronic component has an electronic component body having a pair of end faces, an upper surface, a lower surface, and a pair of side surfaces, and a pair of terminals arranged on both end faces of the electronic component body in contact with at least the lower surface; the pair of terminals are soldered to the second lands in the third step by melting and solidifying the solder contained in the solder precoat. The method for manufacturing an electronic component mounting board according to claim 1 or 2.

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