Method for manufacturing wiring board assembly, wiring board assembly, wiring module, and power storage module

Abstract

The present invention is provided with a first step for applying a plurality of solder paste portions 90a to 90d to a land 64 of a flexible printed wiring board 60, a second step for bringing a metal piece 70 into contact with the plurality of solder paste portions applied to the land 64, and a third step for heating the solder paste portions to form a plurality of solder connection parts 80a to 80d for joining together the land 64 and the metal piece 70. A surface 641 of the land 64 is provided with a plurality of solder connection regions SR1 to SR4 partitioned by virtual boundary lines BL1 and BL2. The solder connection regions SR1 to SR4 positioned adjacent to each other are directly connected to each other on the boundary lines BL1 and BL2. The first step includes applying the plurality of solder paste portions 90a to 90d to the plurality of solder connection regions SR1 to SR4, respectively.

Description

Method for manufacturing wiring board assembly, wiring board assembly, wiring module, and power storage module

[0001] The present invention relates to a method for manufacturing a wiring board assembly including a wiring board with lands and a metal piece joined to the lands via a solder connection, the wiring board assembly, and a vehicle wiring module and an energy storage module including the wiring board assembly. For designated countries where incorporation by reference is permitted, the content of Japanese Patent Application No. 2024-109194, filed in Japan on July 5, 2024, is incorporated herein by reference and made a part of the description of this specification.

[0002] A flexible printed circuit board is known that has a metal surface, lands with multiple soldering portions to which terminals are soldered, and non-metallic surface partition portions between the multiple soldering portions that separate adjacent soldering portions (see, for example, Patent Document 1).

[0003] International Publication No. 2021 / 084913

[0004] In the flexible printed circuit board, the multiple soldering sections are separated by partitions to prevent the terminals from shifting positions due to melting solder. However, in the flexible printed circuit board, the partitions are interposed between the multiple soldering sections, which reduces the area of ​​the lands onto which cream solder can be applied, resulting in a problem of reduced bonding strength between the terminals and the lands.

[0005] The problem that the present invention aims to solve is to provide a method for manufacturing a wiring board assembly, a wiring board assembly, a wiring module, and an energy storage module that can suppress the positional misalignment of the metal pieces while suppressing a decrease in the bonding strength between the land and the metal pieces.

[0006] [1] Aspect 1 of the present invention is a method for manufacturing a wiring board assembly, comprising a first step of applying a plurality of solder pastes to lands of a wiring board, a second step of contacting metal pieces with the plurality of solder pastes applied to the lands, and a third step of heating the solder pastes to form a plurality of solder connection portions that join the lands and the metal pieces, wherein the surface of the lands has a plurality of solder connection areas separated by imaginary boundary lines, and adjacent solder connection areas are directly connected to each other on the boundary lines, and the first step includes applying the plurality of solder pastes to each of the plurality of solder connection areas.

[0007] [2] A second aspect of the present invention may be the method for manufacturing a wiring board assembly according to the first aspect, wherein the first step includes applying the solder paste to each of the solder connection regions so that the aspect ratio of the planar shape of the solder paste satisfies the following formula (1): 1≦La / Lb≦4 (1) where La is the length of the solder paste and Lb is the width of the solder paste.

[0008] [3] Aspect 3 of the present invention may be a method for manufacturing a wiring board assembly according to Aspect 1 or 2, wherein the first step includes applying the plurality of solder pastes to the surface of the land at intervals so that a gap Ds between the solder pastes satisfies the following formula (2): 0.1 mm≦Ds≦0.7 mm (2)

[0009] [4] A fourth aspect of the present invention may be a method for manufacturing a wiring board assembly according to any one of the first to third aspects, wherein the first step includes applying the solder paste to each of the solder connection regions so that a height Hs of the solder paste satisfies the following formula (3): Hs≦0.2 mm (3)

[0010] [5] Aspect 5 of the present invention may be a method for manufacturing a wiring board assembly according to any one of aspects 1 to 4, wherein the surface of the land is a metal surface made of a metal material containing copper as a main component, and the metal surface of the land to which the solder paste is applied in the first step is directly covered with an organic coating made of an organic compound.

[0011] [6] A sixth aspect of the present invention is a wiring board assembly manufactured by any one of the manufacturing methods of the first to fifth aspects.

[0012] [7] Aspect 7 of the present invention is a wiring board assembly comprising a wiring board having a land and a metal piece joined to the land via a plurality of solder connection portions, the surface of the land having a plurality of solder connection areas separated by imaginary boundary lines, adjacent solder connection areas being directly connected to each other on the boundary lines, and the plurality of solder connection portions being formed in each of the plurality of solder connection areas.

[0013] [8] Aspect 8 of the present invention is a wiring board assembly according to aspect 6 or 7, wherein the wiring board assembly may be a wiring board assembly having a groove extending linearly between adjacent solder connection portions in a planar view.

[0014] [9] A ninth aspect of the present invention may be a wiring board assembly according to any one of the sixth to eighth aspects, wherein the land has a metal surface made of a metal material containing copper as a main component, and the solder connection portion is in direct contact with the metal surface.

[0015]

[10] A tenth aspect of the present invention is a wiring module for a vehicle, comprising: the wiring board assembly according to any one of aspects 6 to 9; and a frame that holds the wiring boards of the wiring board assembly.

[0016]

[11] Aspect 11 of the present invention is a vehicle energy storage module comprising the wiring module of aspect 10, a plurality of energy storage elements each having an electrode, and a connecting member that electrically connects the plurality of energy storage elements together, wherein the metal piece is joined to the connecting member.

[0017] In the present invention, the surface of the land is provided with a plurality of solder connection regions defined by imaginary boundaries, adjacent solder connection regions are directly connected to each other on the boundaries, and a plurality of solder pastes are applied to the plurality of solder connection regions, respectively. Furthermore, in the present invention, a plurality of solder connection portions are formed in the plurality of solder connection regions, respectively. Therefore, in the present invention, it is possible to suppress the positional displacement of the metal piece while suppressing a decrease in the bonding strength between the land and the metal piece.

[0018] FIG. 1 is a partial plan view showing an energy storage module according to an embodiment of the present invention. FIG. 2(a) is a plan view showing an enlarged portion of section II in FIG. 1, FIG. 2(b) is a cross-sectional view taken along line IIB-IIB in FIG. 2(a), and FIG. 2(c) is an enlarged view of section IIC in FIG. 2(b). FIG. 3(a) is an enlarged plan view showing a flexible printed wiring board before solder paste is applied, FIG. 3(b) is a cross-sectional view taken along line IIIB-IIIB in FIG. 3(a), and FIG. 3(c) is an enlarged view of section IIIC in FIG. 3(b). FIG. 4 is a bottom view showing a metal piece before being placed on solder paste. FIG. 5(a) is an enlarged plan view showing a flexible printed wiring board to which solder paste has been applied, and FIG. 5(b) is a cross-sectional view taken along line VB-VB in FIG. 5(a). Fig. 6(a) is an enlarged plan view showing a flexible printed wiring board and a metal piece stacked with solder paste interposed therebetween, and Fig. 6(b) is a cross-sectional view taken along line VIB-VIB in Fig. 6(a). Figs. 7(a) to 7(i) are schematic diagrams showing first to ninth modified examples of the solder connection region on the surface of a land in an embodiment of the present invention. Fig. 8 is a graph illustrating the effect of suppressing misalignment in an embodiment of the present invention.

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] Fig. 1 is a partial plan view showing the energy storage module of this embodiment. Fig. 2(a) is a plan view showing an enlarged portion of part II in Fig. 1, Fig. 2(b) is a cross-sectional view taken along line IIB-IIB in Fig. 2(a), and Fig. 2(c) is an enlarged view of part IIC in Fig. 2(b).

[0021] 1 , the energy storage module 1 in this embodiment includes a plurality of energy storage elements 10, a bus bar 20 that electrically connects the energy storage elements 10 to each other, and a wiring module 30 that is connected to the bus bar 20. Although not specifically shown, the energy storage module 1 is disposed inside a vehicle, for example, in the center of the vehicle. Specific examples of the vehicle include electrically driven vehicles such as electric vehicles (EVs) and hybrid electric vehicles (HEVs).

[0022] Each energy storage element 10 is, for example, a flat lithium ion battery, though not limited thereto. The energy storage element 10 has a pair of electrode terminals 11 (11a, 11b) exposed at both ends of the upper surface of the energy storage element 10. The multiple energy storage elements 10 are stacked on top of each other, inverted, so that the opposite polarity terminals 11 (11a, 11b) face each other. Capacitors may also be used as the energy storage elements 10. The number of energy storage elements 10 included in the energy storage module 1 can be set as desired depending on the required voltage, etc.

[0023] The busbar 20 is a plate-shaped member made of a metal material. The electrode terminals 11 of the energy storage elements 10 are joined to the busbar 20 at joints 21. Specific examples of the metal material constituting the busbar 20 include copper, copper alloys, aluminum, aluminum alloys, and stainless steel. Specific examples of methods for joining the busbar 20 and the electrode terminals 11 include, but are not limited to, laser welding, ultrasonic welding, and soldering. The busbar 20 corresponds to an example of a "connecting member" in this aspect of the present invention.

[0024] Adjacent energy storage elements 10 are electrically connected via the bus bar 20 by joining the positive electrode terminal 11 a of one energy storage element 10 and the negative electrode terminal 11 b of the other energy storage element 10 to the bus bar 20. Therefore, all of the energy storage elements 10 included in the energy storage module 1 are connected in series via the bus bar 20. Although not particularly shown, the outermost electrode terminal 11 of the multiple energy storage elements 10 connected in series in this manner is electrically connected to a device such as a vehicle inverter via an electric wire. Note that the connection method of the multiple energy storage elements 10 included in the energy storage module 1 is not particularly limited to the above, and for example, the multiple energy storage elements 10 may be connected in parallel via the bus bar 20.

[0025] The wiring module 30 includes a frame 40 and a wiring board assembly 50. The frame 40 is a member that holds the flexible printed wiring board 60 of the wiring board assembly 50. The frame 40 is made of, for example, a resin material or the like and has electrical insulation properties. The frame 40 is disposed on top of the plurality of energy storage elements 10. An opening 41 is formed in the frame 40. The bus bar 20 is exposed upward through the opening 41.

[0026] The wiring board assembly 50 includes a flexible printed wiring board 60 and a metal piece 70. The metal piece 70 is joined to the bus bar 20 exposed through the opening 41 of the frame 40 at a joint 71. Specific methods for joining the metal piece 70 and the bus bar 20 include, for example, laser welding, ultrasonic welding, and soldering. As described below, the metal piece 70 is soldered to a land 64 of the flexible printed wiring board 60. Therefore, the bus bar 20 and the flexible printed wiring board 60 are electrically connected via the metal piece 70. The flexible printed wiring board 60 corresponds to an example of a "wiring board" in accordance with the present invention. Note that, although two metal pieces 70 are connected to one bus bar 20 in the example shown in FIG. 1 , the number of metal pieces 70 connected to one bus bar 20 may be one.

[0027] 1 to 2B, the flexible printed circuit board (FPC) 60 includes a base film 61, a conductor layer 62, and a coverlay 65. For convenience, the coverlay 65 is not shown in FIG.

[0028] The base film 61 is a flexible film. The base film 61 is made of an electrically insulating material such as a resin material. Although not particularly limited, examples of the material that can be used to form the base film 61 include polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyetherimide (PEI), polyether ether ketone (PEEK), and aramid.

[0029] A conductor layer 62 is disposed on the base film 61. The conductor layer 62 is made of a metal material. The material constituting the conductor layer 62 is preferably a metal material containing copper as a main component, and the material constituting the conductor layer 62 may be copper. The conductor layer 62 is formed by etching copper foil laminated on the base film 61 into a predetermined shape. Specific methods for forming the conductor layer 62 include, for example, a subtractive method and a semi-additive method. Although not specifically shown, the conductor layer 62 is fixed to the base film 61 via an adhesive layer. Specific examples of such adhesives include epoxy adhesives and acrylic adhesives.

[0030] The conductor layer 62 includes wiring 63 and lands 64. The wiring 63 extends linearly on the base film 61. The land 64 is connected to one end of the wiring 63. Although not specifically shown, the other end of the wiring 63 is electrically connected to a monitoring unit via a wire harness. The monitoring unit monitors the states of the multiple energy storage elements 10, and monitors the voltage of each energy storage element 10 via the wiring module 30 and the bus bar 20, for example.

[0031] The coverlay 65 is laminated on the base film 61 so as to cover the conductor layer 62. Like the above-described base film 61, the coverlay 65 is a flexible film made of an electrically insulating material such as a resin material. Although not specifically shown, the coverlay 65 is fixed to the base film 61 via an adhesive layer, and the conductor layer 62 is interposed between the base film 61 and the coverlay 65. Specific examples of such adhesives include epoxy adhesives and acrylic adhesives.

[0032] The coverlay 65 may be formed using a dry film made of a photosensitive coverlay material instead of the above-mentioned resin film, or the coverlay 65 may be formed by applying a liquid photosensitive coverlay material to the base film 61 and then exposing and developing it. Alternatively, the coverlay 65 may be formed by printing a liquid coverlay ink on the base film 61.

[0033] Alternatively, the coverlay 65 may be made of so-called solder resist. Specifically, the coverlay 65 may be formed using a dry film made of a photosensitive resist material. Alternatively, the coverlay 65 may be formed by applying a liquid photosensitive resist material onto the base film 61, followed by exposure and development. Alternatively, the coverlay 65 may be formed by printing a liquid solder resist ink onto the base film 61.

[0034] Specific examples of the above-mentioned photosensitive coverlay material and photosensitive resist material include those containing polyester, epoxy, acrylic, polyimide, polyurethane, etc. Specific examples of the above-mentioned coverlay ink and solder resist ink include those based on polyimide or epoxy.

[0035] The coverlay 65 has openings 651 at positions corresponding to the lands 64 of the conductor layer 62. The lands 64 are exposed from the coverlay 65 through the openings 651. A plurality of solder connection portions 80a to 80d are formed on the lands 64. The lands 64 and the metal piece 70 are joined via the plurality of solder connection portions 80a to 80d. In this embodiment, the solder connection portions 80a to 80d are collectively referred to as "solder connection portions 80."

[0036] The metal piece 70 is, for example, a plate-shaped member made of a metal material. Specific examples of the metal material making up the metal piece 70 include nickel, nickel alloy, copper, copper alloy, aluminum, aluminum alloy, and stainless steel.

[0037] The surface 641 of the land 64 exposed through the opening 651 of the coverlay 65 is located on the imaginary boundary line BL １ , BL ２ By this, a plurality of solder connection regions (sections) SR １ ~SR ４ The plurality of solder connection regions SR １ ~SR ４ are arranged in a matrix in a plan view. The plurality of solder connection portions 80a to 80d are the plurality of solder connection regions SR １ ~SR ４ The surface 641 of the land 64 is formed with a plurality of solder connection regions SR １ ~SR ４ By dividing the solder connection region SR into two regions, it is possible to prevent the metal piece 70 from being displaced as described later, and also to easily adjust the amount of solder paste to an appropriate amount, and to prevent the flux contained in the solder paste from flowing out of the land 64. １ ~SR ４ are collectively referred to as the "solder connection region SR", and the boundary line BL １ , BL ２ are collectively referred to as the "boundary line BL."

[0038] Specifically, the boundary line BL １ is a virtual boundary line extending in the X direction, and this boundary line BL １The surface 641 of the land 64 is virtually divided into two in the Y direction by the boundary line BL ２ is a virtual boundary line extending in the Y direction, and this boundary line BL ２ As a result, the surface 641 of the land 64 is virtually divided into two in the X direction by two boundary lines BL １ , BL ２ As a result, the surface 641 of the land 64 is virtually divided into four solder connection regions SR １ ~SR ４ These four solder connection regions SR １ ~SR ４ are arranged in a matrix of two rows and two columns. １ ~SR ４ Solder connection portions 80a to 80d are formed on the respective substrates.

[0039] Adjacent solder connection regions SR in the Y direction １ , S.R. ２ The boundary line BL １ Therefore, in a plan view, the solder connection region SR １ , S.R. ２ There is no electrically insulating partition between the solder connection regions 80a and 80b, and there is no partition between the solder connection regions 80a and 80b. １ , S.R. ２ The solder connection portions 80a and 80b also directly face each other.

[0040] Similarly, the solder connection regions SR adjacent in the Y direction ３ , S.R. ４ Comrades, boundary line BL １ Therefore, in a plan view, the solder connection region SR ３ , S.R. ４ There is no electrically insulating partition between the solder connection regions SR and 80c, and there is no partition between the solder connection regions 80c and 80d. ３ , S.R. ４The solder connection portions 80c and 80d also directly face each other.

[0041] In addition, the solder connection regions SR adjacent to each other in the X direction １ , S.R. ３ The boundary line BL ２ Therefore, in a plan view, the solder connection region SR １ , S.R. ３ There is no electrically insulating partition between the solder connection regions 80a and 80c, and there is no partition between the solder connection regions 80a and 80c. １ , S.R. ３ The solder connection portions 80a and 80c also directly face each other.

[0042] Similarly, the solder connection regions SR adjacent to each other in the X direction ２ , S.R. ４ Comrades, boundary line BL ２ Therefore, in a plan view, the solder connection region SR ２ , S.R. ４ There is no electrically insulating partition between the solder connection regions 80b and 80d, and there is no partition between the solder connection regions 80b and 80d. ２ , S.R. ４ The solder connection portions 80b and 80d also directly face each other.

[0043] In this way, the solder connection region SR １ ~SR ４ are directly connected to each other, and the solder connection region SR １ ~SR ４ Therefore, a large contact area can be secured between the land 64 and the solder connection portions 80a to 80d, and a decrease in the bonding strength between the land 64 and the metal piece 70 can be suppressed.

[0044] The number of boundary lines BL that define the surface 641 of the land 64 is not particularly limited to the above, and the surface 641 of the land 64 may be defined by three or more boundary lines BL. Also, the surface 641 of the land 64 may be defined only by boundary lines BL that extend parallel to each other, without any other boundary lines BL that intersect at right angles with the boundary lines BL. Furthermore, the number of solder connection regions SR on the surface 641 of the land 64 is not particularly limited to the above, as long as there are multiple.

[0045] Also, the solder connection region SR １ ~SR ４ The solder connection portions 80a to 80d are individually formed in the solder paste 80a, 80b, so that a linear groove 81 penetrates between adjacent solder connection portions 80a, 80b in the Y direction. This groove 81 also penetrates linearly between adjacent solder connection portions 80c, 80d in the Y direction. Similarly, a linear groove 82 penetrates between adjacent solder connection portions 80a, 80c in the X direction. This groove 82 also penetrates linearly between adjacent solder connection portions 80b, 80d in the X direction. Outgassing generated when the solder paste melts can be discharged to the outside through these grooves 81, 82, thereby reducing voids generated within the solder connection portions 80a to 80d. Note that if one end of the groove 81 is open to the outside, the other end of the groove 81 may be closed. Similarly, if one end of the groove 82 is open to the outside, the other end of the groove 82 may be closed. Alternatively, as long as at least one end of one groove 81 (or 82) is open, both ends of the other groove 82 (or 81) communicating with that groove 81 (or 82) may be closed.

[0046] As described above, the material constituting the conductor layer 62 is preferably a metal material containing copper as a main component, and in this case, the surface 641 of the land 64 is also made of the same metal material. Therefore, as shown in FIG. 2( c), the solder connection portion 80 is in direct contact with the metal surface 641 made of this metal material containing copper as a main component. Therefore, no metal material (e.g., gold, tin, nickel, palladium, etc.) other than the metal material containing copper as a main component is interposed between this metal surface 641 and the solder connection portion 80. By forming the surface 641 of the land 64 from a metal material containing copper as a main component, when the solder paste 90 is applied in portions onto the land 64, the solder does not wet and spread too much, and the solder connection region SR １ ~SR ４ This can prevent the molten solders on the respective surfaces from joining together and becoming one.

[0047] Next, a method for manufacturing the wiring board assembly 50 of this embodiment will be described with reference to FIGS.

[0048] FIG. 3(a) is an enlarged plan view showing the flexible printed wiring board 60 before the solder paste 90 is applied, FIG. 3(b) is a cross-sectional view taken along line IIIB-IIIB in FIG. 3(a), and FIG. 3(c) is an enlarged view of part IIIC in FIG. 3(b). FIG. 4 is a bottom view showing the metal piece 70 before it is placed on the solder paste 90. FIG. 5(a) is an enlarged plan view showing the flexible printed wiring board 60 to which the solder paste 90 has been applied, and FIG. 5(b) is a cross-sectional view taken along line VB-VB in FIG. 5(a). FIG. 6(a) is an enlarged plan view showing the flexible printed wiring board 60 and the metal piece 70 stacked with the solder paste 90 interposed therebetween, and FIG. 6(b) is a cross-sectional view taken along line VIB-VIB in FIG. 6(a).

[0049] 3A to 4, a flexible printed wiring board 60 and a metal piece 70 are prepared. The flexible printed wiring board 60 is formed by etching the copper foil of a copper clad laminate (CCL) into a predetermined shape to form a conductor layer 62, and then bonding a coverlay 65 to a base film 61 so as to cover the conductor layer 62.

[0050] As described above, in this embodiment, a copper-based metal material is exposed on the surface 641 of the land 64 to slow the spreading of solder. However, this surface 641 is susceptible to oxidation. To prevent this oxidation, an organic coating 66 is formed on the surface 641 of the land 64, as shown in FIG. 3C. This organic coating 66 directly covers the surface 641 of the land 64, which is made of a copper-based metal material. This organic coating 66 is made of an organic compound such as an imizodal compound. This organic coating 66 is formed by immersing the surface 641 of the land 64 in an aqueous solution containing an organic compound as a main component. Although not particularly limited, this organic coating 66 has a thickness T of 0.2 μm to 0.5 μm (0.2 μm≦T≦0.5 μm).

[0051] 4, a surface treatment layer 73 is formed on the lower surface 72 of the metal piece 70 in the region where the solder connection portion 80 is joined. This surface treatment layer 73 has the function of preventing oxidation of the lower surface 72 of the metal piece 70 and the function of promoting the wetting and spreading of the solder. Specific examples of this surface treatment layer 73 include a tin-plated layer, a gold-plated layer, and a nickel-plated layer. Note that this surface treatment layer 73 does not necessarily have to be formed on the lower surface 72 of the metal piece 70.

[0052] 5(a) and 5(b), the solder paste is applied in portions to the surface 641 of the land 64. That is, in this embodiment, a plurality of solder pastes 90a to 90d are applied to the surface 641 of the same land 64. In this embodiment, the solder pastes 90a to 90d are collectively referred to as "solder paste 90."

[0053] This solder paste 90 is, for example, a lead-free solder paste. Although not particularly limited, for example, a solder paste having a composition of Sn-3.0Ag-0.5Cu can be used as this solder paste 90. Furthermore, specific methods for applying the solder paste 90 to the lands 64 include a method of printing the solder paste 90 using a metal mask and a method of applying the solder paste 90 using a dispenser.

[0054] Although not particularly limited, the solder paste 90 is applied to each solder connection region SR so that the aspect ratio of the planar shape of the solder paste 90 satisfies the following formula (4): In formula (4), La is the major axis (length) of the solder paste 90, and Lb is the minor axis (width) of the solder paste 90. The major axis La of the solder paste 90 is the length of the solder paste 90 along the longitudinal direction of the solder paste 90, and is the distance between the short sides of the solder paste 90. The minor axis Lb of the solder paste 90 is the length of the solder paste 90 along the lateral direction of the solder paste 90, and is the distance between the long sides of the solder paste 90. By limiting the aspect ratio of the solder paste 90 within the range of formula (4), it is possible to further suppress misalignment of the metal piece 70 in the major axis direction of the solder paste 90. 1≦La / Lb≦4 (4)

[0055] The solder paste 90 printed on the lands 64 has a convex (mountain-like) shape with a peak 91 at its top. Although not particularly limited, the solder paste 90 is applied to each solder connection region SR so that the height Hs of the solder paste 90 satisfies the following formula (5). By setting the height Hs of the solder paste 90 to 0.2 mm or less, it is possible to prevent adjacent solder from merging together when the solder paste 90 melts: 0.05 mm≦Hs≦0.2 mm (5)

[0056] When the solder paste 90 is printed using a metal mask, the thickness of the metal mask can be changed to change the height Hs of the solder paste 90. When the solder paste 90 is applied using a dispenser, the height Hs of the solder paste 90 can be changed by changing the shape of the nozzle tip of the dispenser, the size of the nozzle opening, or the pressure at which the solder paste is discharged from the dispenser.

[0057] As described above, the surface 641 of the land 64 is defined by the imaginary boundary line BL １ , BL ２ The four solder connection areas SR １ ~SR ４ These four solder connection areas SR １ ~SR ４ The solder pastes 90a to 90d are individually applied to the respective solder pastes 90a to 90d. Therefore, the four solder pastes 90a to 90d are arranged in a matrix in plan view.

[0058] These four solder pastes 90a to 90d are applied at intervals so as not to come into contact with one another. As described above, since there are no partitions between adjacent solder connection regions SR in a plan view, there are also no partitions between adjacent solder pastes 90 in a plan view. In other words, adjacent solder pastes 90 directly face each other in a plan view, and the entire surfaces of adjacent solder pastes 90 face each other.

[0059] Although not particularly limited, a plurality of solder pastes 90 are applied to the surface 641 of the land 64 at intervals so that the gap Ds between adjacent solder pastes 90 satisfies the following formula (6): 0.1 mm≦Ds≦0.7 mm (6)

[0060] By setting the gap Ds between the solder paste 90 to 0.1 mm or more, it is possible to prevent adjacent solder from merging together when the solder paste 90 melts. On the other hand, by setting the gap Ds between the solder paste 90 to 0.7 mm or less, it is possible to interpose a large amount of solder between the land 64 and the metal piece 70.

[0061] Furthermore, this gap Ds can be set according to, for example, the shape and thickness of the metal piece 70, the material constituting the metal piece 70, the amount of solder paste for other electronic components (e.g., fuses, connectors, etc.) to be mounted on the flexible printed wiring board 60, and the melting state of the solder of the metal piece 70 and other electronic components.

[0062] 6(a) and 6(b), the metal piece 70 is brought into contact with the plurality of solder pastes 90 applied to the same land 64. Specifically, the flexible printed wiring board 60 is placed in the recess 101 of the jig 100, and the metal piece 70 is placed on the upper surface 102 of the jig with the surface treatment layer 73 of the metal plate 70 facing the land 64. This ensures a predetermined distance between the land 64 and the metal piece 70, and the metal piece 70 comes into contact with the solder pastes 90a to 90d.

[0063] In this state, the solder paste 90 is heated and melted to form the solder connection portion 80 (see FIGS. 2( a) and 2(b)). Examples of means for heating the solder paste 90 include a heating furnace, laser reflow, and a soldering iron.

[0064] As described above, the solder paste 90 printed on the lands 64 has a convex shape with peaks 91. Therefore, when the metal pieces 70 are in contact with the solder paste 90 (the state shown in FIGS. 6( a) and 6(b)), the metal pieces 70 are in contact only with the peaks 91 of the convex solder paste 90, and the position of the metal pieces 70 is maintained by the multiple peaks 91. Therefore, even if the solder paste 90 melts due to heating and spreads from this state, the multiple peaks 91 continue to maintain the position of the metal pieces 70, so that displacement of the metal pieces 70 can be suppressed.

[0065] Furthermore, as described above, by forming the surface 641 of the land 64 from a metal material containing copper as a main component, the wetting and spreading of the solder on the surface 641 is slowed. This makes it possible to prevent adjacent solder from merging together when the solder paste 90 melts. Meanwhile, by forming the surface treatment layer 73 on the lower surface 72 of the metal piece 70, the wetting and spreading of the solder on the lower surface 72 is promoted, ensuring a wide contact area between the metal piece 70 and the solder connection portion 80.

[0066] The organic coating 66 covering the surface 641 of the land 64 disappears when the solder paste 90 is heated to melt. Therefore, when the step of heating the solder paste 90 is completed, the surface 641 made of a metal material containing copper as a main component and the solder connection portion 80 are in direct contact (see FIG. 2( c)), and the organic coating 66 is not interposed between the surface 641 and the solder connection portion 80. Furthermore, no metal material (e.g., gold, tin, nickel, palladium, etc.) other than the metal material containing copper as a main component is interposed between the metal surface 641 and the solder connection portion 80.

[0067] In this embodiment, as described above, the surface 641 of the land 64 is divided into four solder connection regions SR arranged in a matrix of two rows and two columns. １ ~SR ４ However, the number of solder connection regions SR on the surface 641 of the land 64 and the arrangement of the solder connection regions SR are not particularly limited to this. For example, the surface 641 of the land 64 may be divided as shown in Figures 7(a) to 7(i). Figures 7(a) to 7(i) are schematic diagrams showing first to ninth modified examples of the solder connection regions SR on the surface 641 of the land 64 in this embodiment.

[0068] Specifically, as in a first modified example shown in Fig. 7(a), the surface 641 of the land 64 may be partitioned into six solder connection regions SR in a matrix of three rows and two columns, or as in a second modified example shown in Fig. 7(b), the surface 641 of the land 64 may be partitioned into eight solder connection regions SR in a matrix of four rows and two columns, or as in a third modified example shown in Fig. 7(c), the surface 641 of the land 64 may be partitioned into nine solder connection regions SR in a matrix of three rows and three columns.

[0069] Alternatively, as in the fourth to ninth modified examples shown in Figures 7(d) to 7(i), the surface 641 of the land 64 may be partitioned only by boundary lines BL extending parallel to one another, without any other boundary lines BL perpendicular to the boundary lines BL. In these fourth to ninth modified examples shown in Figures 7(d) to 7(i), the surface 641 of the land 64 is partitioned into three to eight solder connection regions SR, respectively.

[0070] Wiring board assemblies having solder connection portions arranged as shown in FIG. 2(a) and FIG. 7(a) to FIG. 7(i) were fabricated under the same reflow conditions, and the rotational misalignment of metal piece 70 relative to land 64 was measured. The results are shown in FIG. 8. FIG. 8 is a graph illustrating the misalignment suppression effect of this embodiment. The numbers on the horizontal axis in FIG. 8 indicate the arrangement of the solder connection portions, with No. 1 being the arrangement in FIG. 2(a) and Nos. 2 to 10 being the arrangements in FIG. 7(a) to FIG. 7(i), respectively. The vertical axis in FIG. 8 indicates the rotational misalignment (degrees) at ±3σ (standard deviation).

[0071] 8, the rotational deviation of Nos. 1 to 4, in which the solder connection regions SR are arranged in a matrix, is less than ±0.5 degrees. In contrast, the rotational deviation of Nos. 5 to 10, in which the solder connection regions SR are arranged in only one direction, is close to or exceeds ±1 degree. In other words, by arranging the solder connection regions SR in a matrix, it is possible to effectively suppress the positional deviation of the metal piece 70.

[0072] The number of solder connection regions SR on the surface 641 of the land 64 and the arrangement of the solder connection regions SR can be set according to, for example, the shape and thickness of the metal piece 70, the material constituting the metal piece 70, the occurrence of voids when the solder paste 90 melts, the amount of solder paste 90 that flows out, and the amount of flux contained in the solder paste 90 that flows out, etc.

[0073] The wiring module 30 is fabricated by fixing the wiring board assembly 50 fabricated as described above to the frame 40. Specifically, as shown in FIG. 1 , the flexible printed wiring board 60 is attached to the upper surface of the frame 40 so that the metal piece 70 protrudes into the opening 41 of the frame 40.

[0074] Next, the plurality of energy storage elements 10 are inverted and stacked on top of each other so that the different polarity terminals 11 (11a, 11b) face each other, and the different polarity terminals 11 (11a, 11b) of adjacent energy storage elements 10 are connected to each other by bus bars 20. Then, the wiring module 30 is arranged on the plurality of energy storage elements 10 and fixed thereto so that the bus bars 20 are exposed from the openings 41 of the frame 40.

[0075] Next, the bus bar 20 positioned within the opening 41 of the frame 40 is joined to the metal piece 70, thereby completing the energy storage module 1. At this time, since the plurality of solder pastes 90a to 90d applied to the same land 64 suppress misalignment of the metal piece 70, there is no need to adjust the positions of the bus bar 20 and the metal piece 70 when joining them, which makes it easier to manufacture the energy storage module 1.

[0076] As described above, in this embodiment, the surface 641 of the land 64 is located on the virtual boundary line BL １ , BL ２ A plurality of solder connection regions SR partitioned by １ ~SR ４ and the solder connection regions SR are adjacent to each other. １ ~SR ４ The boundary line BL １ , BL ２ The solder connection regions SR are directly connected to each other on the １ ~SR ４ A plurality of solder pastes 90a to 90d are applied to the plurality of solder connection regions SR. １ ~SR ４ A plurality of solder connection portions 80a to 80d are formed on the land 64, respectively. Therefore, it is possible to suppress a decrease in the bonding strength between the land 64 and the metal piece 70, and also to suppress positional deviation (rotational deviation) of the metal piece 70.

[0077] Furthermore, when a partition is provided on the land, the width of the partition must be extremely narrow. This may result in a meandering partition being formed on the land, which may reduce the yield of the flexible printed wiring board. In contrast, in this embodiment, the solder connection region SR １ ~SR ４are directly connected to each other, and the solder connection region SR １ ~SR ４ Since no partition is interposed between the flexible printed wiring board 60 and the flexible printed wiring board 60, a good yield can be ensured.

[0078] Furthermore, when partitions are provided on the lands, the solder paste may overflow from the gaps formed between the metal mask and the lands by the partitions during printing, and adjacent solder pastes may connect to each other. １ ~SR ４ Since there is no partition between them, there is no risk of the solder paste spilling out when printing the solder paste.

[0079] It should be noted that the above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, the elements disclosed in the above embodiments are intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0080] REFERENCE SIGNS LIST 1... Energy storage module 10... Energy storage element 11... Electrode terminal 11a... Positive electrode terminal 11b... Negative electrode terminal 20... Bus bar 21... Joint portion 30... Wiring module 40... Frame 41... Opening 50... Wiring board assembly 60... Flexible printed wiring board 61... Base film 62... Conductive layer 63... Wiring 64... Land 641... Surface SR, SR １ ~SR ４ ...Solder connection area BL, BL １ ~BL ４ Boundary line 65: Coverlay 651: Opening 66: Organic coating 70: Metal piece 71: Joint 72: Lower surface 73: Surface treatment layer 80, 80a to 80d: Solder connection 81, 82: Groove 90, 90a to 90d: Solder paste 91: Top 100: Jig 101: Recess 102: Upper surface

Claims

1. A method for manufacturing a wiring board assembly, comprising: a first step of applying multiple solder pastes to lands of a wiring board; a second step of bringing metal pieces into contact with the multiple solder pastes applied to the lands; and a third step of heating the solder pastes to form multiple solder connections that join the lands and the metal pieces, wherein the surface of the lands has multiple solder connection areas separated by imaginary boundary lines, and adjacent solder connection areas are directly connected to each other on the boundary lines, and the first step includes applying the multiple solder pastes to each of the multiple solder connection areas.

2. A method for manufacturing a wiring board assembly according to claim 1, wherein the first step includes applying the solder paste to each of the solder connection areas so that the aspect ratio of the planar shape of the solder paste satisfies the following formula (1): 1≦La / Lb≦4 ... (1) where La is the length of the solder paste and Lb is the width of the solder paste.

3. A method for manufacturing a wiring board assembly according to claim 1 or 2, wherein the first step includes applying the plurality of solder pastes to the surface of the land at intervals so that the gap Ds between the solder pastes satisfies the following formula (2): 0.1 mm≦Ds≦0.7 mm ... (2) 4. A method for manufacturing a wiring board assembly according to any one of claims 1 to 3, wherein the first step includes applying the solder paste to each of the solder connection areas so that the height Hs of the solder paste satisfies the following formula (3): Hs≦0.2 mm ... (3) 5. A method for manufacturing a wiring board assembly according to any one of claims 1 to 4, wherein the surface of the land is a metal surface made of a metal material containing copper as a main component, and the metal surface of the land onto which the solder paste is applied in the first step is directly covered with an organic coating made of an organic compound.

6. A wiring board assembly manufactured by the manufacturing method according to any one of claims 1 to 5.

7. A wiring board assembly comprising: a wiring board having a land; and a metal piece joined to the land via a plurality of solder connection portions, wherein the surface of the land has a plurality of solder connection areas separated by imaginary boundary lines, adjacent solder connection areas are directly connected to each other on the boundary lines, and the plurality of solder connection portions are formed in each of the plurality of solder connection areas.

8. A wiring board assembly according to claim 6 or 7, wherein the wiring board assembly is provided with grooves that extend linearly between the solder connection portions that are adjacent to each other in a plan view.

9. A wiring board assembly according to any one of claims 6 to 8, wherein the land has a metal surface made of a metal material containing copper as a main component, and the solder connection portion is in direct contact with the metal surface.

10. A wiring module for a vehicle, comprising: a wiring board assembly according to any one of claims 6 to 9; and a frame for holding the wiring boards of the wiring board assembly.

11. An electric storage module for a vehicle, comprising: the wiring module according to claim 10; a plurality of electric storage elements each having an electrode; and a connecting member that electrically connects the plurality of electric storage elements together, wherein the metal piece is joined to the connecting member.

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