Laminate printed board and manufacturing method thereof

The present invention provides a laminate printed board having a novel structure that is able to ensure alignment accuracy of the interboard terminals soldered to one printed board and that is also able to achieve a simplification of the process of soldering the interboard terminals. Through-hole lines in which a plurality of through-holes extend in lines are formed on a first printed board. Additionally, a press-fitting fastener hole is formed within the through-hole lines and a first end of an interboard terminal is press-fitted and fastened to the press-fitting fastener hole. Additionally, first ends of others of the interboard terminals are inserted through and flow soldered to through-holes on the first printed board.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 of Japanese Application No. 2011-185598, filed on Aug. 29, 2011, the disclosure of which is expressly incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laminate printed board in which two printed boards are laminated and connected by a plurality of interboard terminals, and a manufacturing method thereof

2. Description of Related Art

Conventionally, a laminate printed board in which two printed boards are laminated and mutually connected by a plurality of interboard terminals, such as that described in Japanese Patent Laid-open Publication No. 2009-26464 (Related Art 1), for example, has been used as an internal circuit in an electrical connection box, such as a junction box mounted in an automobile.

In this type of laminate printed board, first ends of a plurality of interboard terminals are inserted through and soldered to one set of respective through-holes on a first printed board. Also, second ends are inserted through and soldered to another set of respective through-holes on a second printed board. Thus, should the plurality of interboard terminals not be accurately positioned at the stage of soldering to the first printed board, there is a risk that insertion through the through-holes of the second printed board will become difficult.

Supporting the plurality of interboard terminals with a synthetic resin base has been suggested in the laminate printed board described in Related Art 1. However, such a configuration leads to an increase in the number of components due to the necessity of a base as a separate component. In addition, there is a risk that the base may thermally expand from heat of soldering or the like, pulling on the interboard terminals and producing positional drift. Good alignment accuracy thus cannot necessarily be ensured and cracks may occur in the soldering portions of the interboard terminals.

In addition, soldering the interboard terminals to the two printed boards requires the first ends of the interboard terminals first be in a state inserted through the through-holes of the first printed board, immersing the bottom surface of the printed board in a soldering pot to be flow soldered, then inserting the second ends through the through-holes of the second printed board to form an assembly, and inverting the assembly to immerse in the soldering pot the bottom surface of the second printed board, on which the second ends project, to be flow soldered once more. The process had been cumbersome and required time and effort. In particular, in a case where the electronic components mounted on the printed board are of a surface-mounted type only, a flow soldering process must be performed to solder only the interboard terminals, separate from the reflow soldering process for the surface-mounted components, and there is a risk that this may lead to a decrease in manufacturing efficiency.

SUMMARY OF THE INVENTION

The present invention was provided with the above-described situation as background. In order to address the problem, a laminate printed board having a novel structure is provided that is able to ensure alignment accuracy of the interboard terminals soldered to one printed board without leading to an increase in the number of components, and that is also able to achieve a simplification of the process of soldering the interboard terminals. In addition, a novel manufacturing method for the laminate printed board is provided which can be favorably used to manufacture such a laminate printed board.

One aspect of the laminate printed board is a laminate printed board in which a first printed board and a second printed board are spaced apart. In addition, the first printed board and the second printed board are mutually connected by a plurality of interboard terminals, both ends of which are inserted through and soldered to a plurality of through-holes provided thereon. The plurality of through-holes are formed in a line on the first printed board, and within the line of through-holes, at least one press-fitting fastener hole is formed passing through the first printed board. Of the plurality of interboard terminals, a first end of one of the interboard terminals is press-fitted and fastened to the press-fitting fastener hole and, in addition, the first ends of the other interboard terminals are inserted through and reflow soldered to the through-holes on the first printed board, while second ends of the plurality of interboard terminals are inserted through and flow soldered to the through-holes on the second printed board.

According to the laminate printed board having a configuration according to the present aspect, a press-fitting fastener hole to which the interboard terminal is able to press-fit and fasten is provided within the through-hole line on the first printed board. Accordingly, the plurality of interboard terminals are prepared as a chain terminal connected in parallel with a belt-like carrier and, by press-fitting and fastening one of the interboard terminals in the chain terminal to the press-fitting fastener hole, the other interboard terminals connected by the carrier can be held in a state inserted through the through-holes on the first printed board. As a result, the plurality of interboard terminals are fixed in position with respect to the first printed board and can be soldered with reflow soldering without requiring a special component such as a base. In particular, in a case where surface-mounted components are reflow soldered to the first printed board, the interboard terminals can be soldered simultaneously with the reflow soldering process of the surface-mounted components. Accordingly, soldering of the interboard terminals can be performed with a simple process, without requiring cumbersome effort such as, similar to convention, following a reflow soldering process for the surface-mounted components, the first ends of the interboard terminals are flow soldered to the first printed board, then the second ends are inserted through the through-holes of the second printed board and the resulting assembly is inverted, the bottom surface of the second printed board then being immersed again in the soldering pot. In addition, because a base supporting the interboard terminals is rendered unnecessary, no increase in the number of parts is involved, either. Moreover, risks can be reduced such as the work of inserting the interboard terminals into the through-holes on the second printed board becoming difficult when the alignment accuracy of the interboard terminals degrades due to thermal expansion of the base, or soldering cracks developing, and better manufacturing quality can be obtained.

One press-fitting fastener hole may be formed in the through-hole line, and a plurality may also be formed. Moreover, the formation location of the press-fitting fastener hole in the through-hole line is not particularly limited. One press-fitting fastener hole may, for example, be formed in a central portion of the through-hole line, two press-fitting fastener holes may be formed at both end portions of the through-hole line, or the like.

Another aspect of the laminate printed board is the press-fitting fastener hole in which a land is formed on a circumferential edge of an opening, on a side where the second ends of the interboard terminals project, and in which the interboard terminal press-fitted into the press-fitting fastener hole is reflow soldered to the land.

According to the present aspect, by forming the land on the press-fitting fastener hole, the interboard terminal press-fitted and fastened to the press-fitting fastener hole can be reflow soldered along with the other interboard terminals and can be affixed by soldering to the first printed board. Accordingly, the interboard terminal press-fitted into the press-fitting fastener hole can be fastened more strongly thereto. As a result, the other interboard terminals can be held in position more securely with respect to the first printed board and, in addition, the risk can be reduced that manufacturing apparatuses and other components may be negatively affected by the interboard terminal press-fitted in the press-fitting fastener hole slipping free.

Another aspect of the laminate printed board is the press-fitting fastener hole formed in the central portion of the through-hole line on the first printed board.

According to the present aspect, when the chain terminal, in which the plurality of interboard terminals are connected in parallel by the belt-like carrier, is inserted through the through-holes on the first printed board, for example, the interboard terminal positioned in the central portion of the plurality of parallel interboard terminals can be press-fitted and fastened to the press-fitting fastener hole. Thereby, the plurality of interboard terminals connected by the belt-like carrier can be held with good balance by the interboard terminal positioned in the central portion.

Another aspect of the laminate printed board is the press-fitting fastener hole as one of the plurality of through-holes which are electrically connected to printed wirings on the first printed board.

According to the present aspect, the press-fitting fastener hole can be effectively used as a through-hole configuring an electrical circuit on the first printed board. As a result, space on the first printed board can be employed more effectively and, in addition, the interboard terminal press-fitted and fastened to the press-fitting fastener hole can also be employed more effectively as a conductive path electrically connecting the first printed board and the second printed board.

An embodiment relating to a manufacturing method of the laminate printed board is a manufacturing method for a laminate printed board in which a first printed board and a second printed board are spaced apart and, in addition, the first printed board and the second printed board are mutually connected by a plurality of interboard terminals, both ends of which are inserted through and soldered to a plurality of through-holes provided thereon. The manufacturing method of the laminate printed board is a process of forming a plurality of through-holes in a line on the first printed board; a process of forming at least one press-fitting fastener hole passing through the first printed board within the line of through-holes; a process of preparing a chain terminal in which the plurality of interboard terminals are separably connected in parallel by a belt-like carrier; a process in which a first end of one interboard terminal in the chain terminal is press-fitted and fastened to the press-fitting fastener hole and, in addition, the first ends of the other interboard terminals connected by the carrier are inserted through and reflow soldered to the through-holes on the first printed board; and a process in which second ends of the plurality of interboard terminals in the chain terminal are inserted through and flow soldered to the through-holes on the second printed board.

In the manufacturing method according to the present embodiment, the plurality of interboard terminals connected by the belt-like carrier are inserted through the through-holes on the first printed board and, in addition, at least one of the interboard terminals is press-fitted and fastened to the press-fitting fastener hole formed on the first printed board. Thereby, the plurality of interboard terminals prior to soldering can maintain position in a state inserted through the through-holes on the first printed board without requiring a special component such as a base. As a result, an increase in the number of components can be avoided to achieve a reduction in manufacturing costs and, in addition, a decrease in alignment accuracy and an occurrence of cracks in solder due to positional drift of the interboard terminals caused by thermal expansion of the base can be inhibited. An improvement in manufacturing quality can thus be achieved.

Also, the first ends of the interboard terminals are inserted through and reflow soldered to the through-holes on the first printed board. Therefore, the time and effort to flow solder the first ends of the interboard terminals to the first printed board, then invert the assembly of the second printed board on the second ends of the interboard terminals and immerse the bottom surface of the second printed board once more in a soldering pot to perform flow soldering, as in a case where both end portions of the interboard terminals are flow-soldered, is not necessary and the soldering process can be simplified. In particular, in a case where surface-mounted components are reflow soldered to the first printed board, the interboard terminals can be reflow soldered to the through-holes on the first printed board in the same process as a reflow soldering process for the surface-mounted components, and better manufacturing efficiency can be obtained.

In the present embodiment relating to the laminate printed board, the press-fitting fastener hole is formed within the line of through-holes on the first printed board and the first end of the interboard terminal is press-fitted and fastened to the press-fitting fastener hole. In addition, the first ends of the other interboard terminals are inserted through and reflow soldered to the through-holes on the first printed board, while the second ends of the interboard terminals are inserted through and flow soldered to the through-holes on the second printed board. Thereby, one interboard terminal of the chain terminal, in which the plurality of interboard terminals are connected in parallel by the belt-like carrier, is press-fitted and fastened to the press-fitting fastener hole. Accordingly, prior to soldering, the other interboard terminals can maintain position via the carrier in a state inserted through the through-holes of the first printed board. As a result, alignment accuracy of the plurality of interboard terminals soldered to the first printed board can be ensured and insertion through the through-holes of the second printed board can be performed more easily and reliably, without requiring a special component such as a base. In addition, the first ends of the interboard terminals are reflow soldered to the through-holes on the first printed board, and thus the soldering process can be further simplified, as compared to a case where both end portions are flow soldered.

In the present embodiment relating to the manufacturing method of the laminate printed board, the press-fitting fastener hole is formed within the line of through-holes on the first printed board, and one of the interboard terminals in the chain terminal, in which the plurality of interboard terminals are connected by the belt-like carrier, is press-fitted and fastened to the press-fitting fastener hole. Thereby, the interboard terminal fastened to the press-fitting fastener hole and the plurality of interboard terminals connected via the carrier can maintain position and be soldered in a state inserted through the through-holes on the first printed board without using a special component such as a base. Accordingly, an improvement in manufacturing costs can be achieved through a reduction in the number of components. In addition, positional drift of the interboard terminals caused by expansion of the base or the like can be avoided, and thus the alignment accuracy of the interboard terminals can be ensured with better accuracy and the work of insertion through the through-holes on the second printed board can be performed more easily. Further, the first ends of the interboard terminals are reflow soldered, and thus the soldering process can be further condensed, as compared to the case where both end portions are flow soldered.

DETAILED DESCRIPTION OF THE INVENTION

Hereafter, an embodiment of the present invention is described with reference to the figures.

First,FIG. 1illustrates a laminate printed board10for the embodiment of the present invention. The laminate printed board10is accommodated within a case of an electrical connection box not shown in the drawings, and configures an internal circuit of the electrical connection box. The laminate printed board10is configured by a first printed board12and a second printed board14being disposed in a laminate state opposing each other, spaced apart, and mutually connected by a plurality of interboard terminals16.

FIG. 2illustrates the first printed board12. The first printed board12according to the present embodiment is produced by forming a plurality (four inFIG. 2) of first printed boards12in a connected state on one board17and cutting out each one. The first printed board12has a substantially longitudinal rectangular shape. In an outer peripheral portion of the first printed board12, on one long side portion and a pair of short side portions, through-hole lines20a,20b, and20care respectively formed, in which a plurality of through-holes18aare formed in lines along the outer peripheral edges of the first printed board12. Each of the through-hole lines20a,20b, and20chas a substantially similar configuration to one another, and thus the through-hole line20awill be described below as an example.

In the through-hole line20a, a plurality of through-holes18aare formed in one line. As shown inFIG. 3, the through-holes18a, as conventionally known, are formed of a circular through-hole passing through the first printed board12. At the through-holes18a, a land24is formed on a circumferential edge of an opening on a surface22on the first printed board12facing the second printed board14and, in addition, an inner peripheral surface is plated. Also, each of the through-holes18ais connected to a printed wiring26formed on the first printed board12.

Further, on the first printed board12, one press-fitting fastener hole28is formed at a central portion in each of the through-hole lines20a,20b, and20c. The press-fitting fastener hole28has a circular through-hole shape passing through the first printed board12. The inner diameter measurement φ of the press-fitting fastener hole28is made smaller compared to the inner diameter measurement φ′ of the through-holes18a, and the press-fitting fastener hole28is set to a size so that the interboard terminal16inserted therethrough is press-fitted to contact the inner circumferential surface of the press-fitting fastener hole28.

The press-fitting fastener hole28in the present embodiment in particular, similar to the rest of the plurality of through-holes18aformed in the through-hole line20a, is formed of a through-hole electrically connecting the second printed board14with the first printed board12via the interboard terminal16. Therefore, in the press-fitting fastener hole28, the land24is formed on the circumferential edge of the opening on the surface22. In addition, the inner peripheral surface is plated, and the press-fitting fastener hole28is connected to the printed wiring26formed on the first printed board12.

Moreover, the inner diameter measurement φ of the press-fitting fastener hole28is made smaller than the inner diameter measurement φ′ of the other through-holes18a; however, the inner diameter measurement φ of the press-fitting fastener hole28may also have an inner diameter measurement made smaller by making a diameter of a bore-hole from a drill or the like when piercing the through-holes18ain the first printed board12smaller than the through-holes18a, for example. Alternatively, as in the present embodiment, in a case where the press-fitting fastener hole28is also used as a through-hole, the diameter of the bore hole is made equal to the through-holes18aand a thickness measurement of the plating deposited on the inner circumferential surface is made thicker than the through-holes18a. Thereby, the inner diameter measurement φ of the press-fitting fastener hole28can also be made smaller, or the like, than the inner diameter measurement φ′ of the through-holes18a. When done in this way, the press-fitting fastener hole28can also be bored with the same drill as the through-holes18awithout requiring changing of the drill. In addition, plating thickness is ensured and thus a risk of the plating peeling during press-fitting of the interboard terminal16can also be reduced.

Meanwhile, the second printed board14is conventionally known, and has a longitudinal rectangular shape larger than the first printed board12. Though a detailed illustration is omitted, through-holes18bare respectively pierced in the second printed board14in positions corresponding to each of the through-holes18a, which include the press-fitting fastener hole28, on the first printed board12.

The first printed board12and the second printed board14are mutually connected by the plurality of interboard terminals16. A chain terminal32is favorably used as the interboard terminals16, as shown inFIG. 4, in which the plurality of interboard terminals16are connected in parallel by a belt-like carrier30. Each of the interboard terminals16has a straight shape formed by a metallic wire rod having a substantially square shape in cross-section and being cut at a predetermined length. A pair of nub-like abutments34projecting to both outward sides are formed at both end portions in a length direction of the interboard terminal16by crushing or the like.

The plurality of such interboard terminals16are connected by the carrier30in a parallel state extending in parallel to one another. The carrier30is formed from a thin metallic plate and is successively formed with a plurality of unit portions36. In addition, the carrier30is made to be easily severable between each of the unit portions36. As shown inFIG. 5, latching portions38rising up perpendicularly are formed curving at both terminal edges of each unit portion36. The interboard terminal16is made so as to fit into and be held within cutaways40formed on the latching portions38. Further, between the latching portions38on each of the unit portions36, a fastener clip42having substantially an L-shape in cross-section is formed by being cut away, and the interboard terminal16is fastened and held with the fastener clip42. Moreover, the fastener clip42partially overlaps with the interboard terminal16and, by pulling the carrier30away downward inFIG. 5, a latched state between the interboard terminal16and the fastener clip42can be easily released and thus the interboard terminal16is made easily separable from the carrier30. In addition, the chain terminal32, in which the plurality of interboard terminals16are connected in parallel by the carrier30, is configured by the interboard terminals16being held by each of the unit portions36. Furthermore, in a state connected to the carrier30, a placement interval Pc for each of the interboard terminals16is made to equal a placement interval Pt of the through-holes18aand18b, including the press-fitting fastener holes28, on the first printed board12and the second printed board14(seeFIG. 3).

In addition, in a state connected to the carrier30, the interboard terminals16can be cut away to the same number as the through-holes18a, including the press-fitting fastener hole28, in the through-hole lines20a,20b, and20con the first printed board12by the carrier30in this type of chain terminal32being severed. The first ends of each of the interboard terminals16are then inserted through the through-holes18a, including the press-fitting fastener hole28, in each of the through-hole lines20a,20b, and20c. Furthermore, the amount of insertion of the interboard terminals16into the through-holes18ais regulated by the abutments34touching the first printed board12. As shown inFIG. 6, the interboard terminal16inserted through the press-fitting fastener hole28is fastened in a state projecting from the first printed board12by being press-fitted into the press-fitting fastener hole28, without requiring soldering. Furthermore, in the present embodiment, the inner diameter measurement φ of the press-fitting fastener hole28is made smaller than the inner diameter measurement φ′ of the through-holes18aby increasing the thickness of the plating on the inner circumferential surface. In addition, the inner diameter measurement φ of the press-fitting fastener hole28is made smaller than a maximum outer shape measurement of an axially-perpendicular cross-section at the end portion of the interboard terminal16inserted through the press-fitting fastener hole28. Thereby, the interboard terminal16inserted through the press-fitting fastener hole28is press-fitted and fastened while scraping away the plating on the inner circumferential surface of the press-fitting fastener hole28. In addition, the first ends of the other interboard terminals16are held in position in a state inserted through each through-hole18awithout requiring any particular press-fitting force due to being connected by the carrier30to the interboard terminal16press-fitted and fastened to the press-fitting fastener hole28. Under these conditions, by being reflow soldered in the state inserted through each of the through-holes18a, including the press-fitting fastener hole28, each of the interboard terminals16is electrically connected to each of the through-holes18a, including the press-fitting fastener hole28, and is provided projecting from the first printed board12.

In addition, due to the overlap of the first printed board12, on which the interboard terminals16are projectingly provided, with the second printed board14, the second ends of the interboard terminals16projecting from the first printed board12are inserted through each of the through-holes18bon the second printed board14. Furthermore, the amount of insertion of the interboard terminals16into the through-holes18bis regulated by the abutments34touching the second printed board14. Further, on the second printed board14, a plurality of connector terminals44, relays46, and the like connected to fuses, connectors, and the like are inserted through through-holes not shown in the drawings. The end portions of the interboard terminals16inserted through the through-holes18bare flow soldered along with the connector terminals44and the relays46. Thereby, the laminate printed board10is configured in which the first printed board12and the second printed board14are mutually connected by the plurality of interboard terminals16.

Furthermore, the laminate printed board10of this type is favorably manufactured as below, for example. First, the first printed board12and the second printed board14are prepared. Using a conventionally known procedure, the first printed board12is formed with the plurality of through-holes18ain a line, thereby forming the through-hole lines20a,20b, and20c. Further, as described above, the press-fitting fastener hole28is formed within each of the through-hole lines20a,20b, and20c, for example by making the bore-hole diameter of a drill smaller than the through-holes18a, or by making the thickness measurement of the plating larger than the through-holes18a. In addition, the chain terminal32is prepared and, by severing the carrier30in the chain terminal32, the interboard terminals16are prepared by being cut away in a state where connection to the carrier30is maintained, to the same number as the through-holes18a, including the press-fitting fastener hole28, in the through-hole lines20a,20b, and20con the first printed board12.

Next, as shown inFIG. 7, first ends of each of the interboard terminals16are inserted through each of the through-holes18a, including the press-fitting fastener hole28, in the through-hole lines20a,20b, and20con the first printed board12. Furthermore, although omitted from the drawings, a cream solder in a paste form for reflow soldering is printed on the first printed board12. Further, surface-mounted components such as an LSI are disposed on the surface22of the first printed board12, as necessary. Moreover, inFIG. 7, by inserting each of the interboard terminals16through each of the through-holes18aon four of the first printed boards12prior to cutting away from the board17, soldering of the interboard terminals16to four of the first printed boards12is performed simultaneously. During this insertion, the interboard terminal16inserted through the press-fitting fastener hole28is fastened in a press-fitted state to the press-fitting fastener hole28. Accordingly, the other interboard terminals16are connected by the carrier30to the interboard terminal16press-fitted and fastened to the press-fitting fastener hole28and are held in a state inserted through each of the through-holes18a. In addition, by dropping the first printed board12, in which the interboard terminals16have been inserted through the through-holes18a, into a reflow kiln and by melting the solder, each of the interboard terminals16is reflow soldered to the first printed board12, along with the surface-mounted components. As described above, in the present embodiment, reflow soldering of four of the first printed boards12is performed simultaneously and, after reflow soldering of the interboard terminals16is completed, each of the first printed boards12is individually cut away from the board17.

Next, as shown inFIG. 1, in addition to inserting the connector terminals44and the relays46through the through-holes (not shown in the drawing) of the second printed board14, the first printed board12obtained previously is overlapped on the second printed board14, and the second ends of the interboard terminals16projecting from the first printed board12are respectively inserted through the corresponding through-holes18bof the second printed board14. Moreover, in this state, each of the interboard terminals16is preferably maintained in a state connected to the carrier30. Also, by immersing the reverse surface of the second printed board14in a soldering pot filled with liquid solder, the interboard terminals16are flow soldered to the second printed board14along with the connector terminals44, the relays46, and the like. Thereafter, by peeling away the carrier30connecting the interboard terminals16, the laminate printed board10can be obtained.

According to the laminate printed board10having such a configuration, the press-fitting fastener hole28capable of press-fitting and fastening the interboard terminal16is formed in each of the through-hole lines20a,20b, and20con the first printed board12. Thereby, in a state where the plurality of interboard terminals16are connected to the carrier30, by press-fitting and fastening one of the interboard terminals16to the press-fitting fastener hole28, the other interboard terminals16can be held via the carrier30in a state inserted through each of the through-holes18a. As a result, the plurality of interboard terminals16can be held in a state inserted through the through-holes18awithout requiring a special component such as a base. In addition, the plurality of interboard terminals16are reflow soldered to the first printed board12in a state inserted through the through-holes18a. Thereby, as in a case where the interboard terminals16are flow soldered to both the first printed board12and the second printed board14, for example, the time and effort of immersing in the soldering pot the reverse surface of the first printed board12on which the first ends of the interboard terminals16project, and then once again immersing in the soldering pot the reverse surface of the second printed board14on which the second ends project becomes unnecessary, and a simplification of the soldering process can be achieved. In particular, in a case where the surface-mounted components are provided on the surface22of the first printed board12, the interboard terminals16can be soldered to the first printed board12in the reflow soldering process of the surface-mounted components, and further efficiency of the manufacturing process can be achieved.

In particular, in the present embodiment, the land24is formed on the press-fitting fastener hole28, and the interboard terminal16press-fitted and fastened to the press-fitting fastener hole28is also fastened by soldering to the land24. Thereby, the interboard terminal16can be fastened more securely to the press-fitting fastener hole28, and the risk can be reduced that the interboard terminal16inserted through the press-fitting fastener hole28may slip free and become a foreign body with respect to manufacturing apparatuses, and thus impart a negative effect. Further, by connecting the press-fitting fastener hole28to the printed wiring26as well, the press-fitting fastener hole28can also be used as a through-hole configuring an electrically conductive path, and further efficient use of the first printed board12can be achieved.

The press-fitting fastener hole28is formed in a central portion of each of the through-hole lines20a,20b, and20c. Thereby, by fastening the central portion of the plurality of the interboard terminals16connected by the carrier30to the press-fitting fastener hole28, the plurality of interboard terminals16on both sides of the interboard terminal16fastened to the press-fitting fastener hole28can be supported with good balance. Moreover, only one press-fitting fastener hole28is formed in each of the through-hole lines20a,20b, and20c. When the plurality of interboard terminals16are inserted through the through-holes18a, only one of the interboard terminals16is press-fitted into the press-fitting fastener hole28, and thus the first printed board12can be easily assembled, without requiring an excessive press-fitting force.

An embodiment of the present invention was described above; however, the present invention is not limited to this specific description. For example, a press-fitting fastener hole is not required to be a through-hole configuring a conductive path, and may be a simple through-hole passing through the first printed board. When made in such a way, even where there is a risk of damaging the press-fitting fastener hole during press-fitting of the interboard terminal, there is no need to weigh a reduction in reliability of the electrical connection. Further, the land formed on the press-fitting fastener hole is not strictly required, either. However, the land alone may be formed, without being connected to the printed wiring. When made in such a way, the interboard terminal press-fitted and fastened to the press-fitting fastener hole is soldered to the land and can ensure a stronger fastening force.

Further, the shape of the opening of the press-fitting fastener hole is not limited to a specific shape, so long as the inserted interboard terminal can be press-fitted and fastened thereto. Therefore, in a case where the interboard terminal has a flattened shape in cross-section or the like, for example, the press-fitting fastener hole may have a long hole shape, or the like. Moreover, a plurality of the press-fitting fastener holes may be formed in the through-hole lines, and are not limited necessarily to being formed in the central portion of the through-hole lines. Therefore, for example, two of the press-fitting fastener holes may be formed at both end portions of the through-hole lines, or the like.