Printed substrate and printed substrate with terminal using same

The present invention provides a printed substrate having a novel structure in which substrate terminals can be fixed to the printed substrate without needing a base, and the substrate terminals can be press-fitted into through-holes without applying pressing force to printed wiring and a plating layer in the through-holes, and also provides a printed substrate with terminals that uses this printed substrate. A printed substrate includes through-holes into which the first end portions of substrate terminals are to be inserted. The through-holes each include press-fitting regions into which the first end portion of a substrate terminal is to be press-fitted, and conduction regions arranged so as to oppose the outer circumferential surfaces of the first end portion of the substrate terminal via gaps in directions perpendicular to the axis. Printed wiring is connected to the conduction regions, and a plating layer is adhered to the conduction regions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase of PCT/JP2015/055390 filed Feb. 25, 2015, which claims priority to Japanese Patent Application JP 2014-052559 filed Mar. 14, 2014.

FIELD OF THE INVENTION

The present invention relates to a printed substrate, and to a printed substrate with terminals in which substrate terminals are provided upright by insertion of first end portions thereof into through-holes of the printed substrate of the present invention.

BACKGROUND OF THE INVENTION

Conventionally, in order to allow a printed substrate for use in an electrical connection box of an automobile or the like to be connected to an external electrical component, a substrate with terminals has been provided in which multiple substrate terminals, which are provided upright, are connected to printed wiring of a printed substrate by inserting first end portions of the substrate terminals into through-holes provided in the printed substrate and then performing soldering.

Incidentally, in order to hold the substrate terminals in an upright state on the printed substrate, the substrate terminals are held in a state of passing through a base made of a synthetic resin, thus positioning and holding the substrate terminals on the printed substrate via the base, as shown in JP 2008-35669A, for example.

However, with this conventional structure, a separate component, namely the base, needs to be prepared, and the operation of press-fitting the substrate terminals into clearance holes of the base needs to be performed, thus having a problem in that an increase in the number of components and an increase in cost cannot be avoided. There is also a problem in that solder cracks are readily formed due to a difference between the linear expansion coefficients of the base and the printed substrate.

Also, as shown in JP 2003-338333A, there has been a proposal to both connect substrate terminals to a printed wiring and hold the substrate terminals in an upright state on the printed substrate by press-fitting first end portions of substrate terminals into through-holes of a printed substrate without using a base.

However, with the method of press-fitting first end portions of the substrate terminals into through-holes, it is not possible to avoid cases where a plating layer in the through-holes becomes detached during press-fitting of the substrate terminals, and the printed wiring, which is made up of copper foil or the like provided in an inner layer of the printed substrate, undergoes deformation due to pressing force during press-fitting of the terminals. Also, due to pressing force that is applied to the printed wiring (inner-layer copper foil) and the like in an inner layer during press-fitting, so-called measling occurs in which glass fibers become detached due to thermal stress in a subsequent soldering step or the like, and this has the possibility of leading to a circuit failure in the printed substrate with terminals. As a result, this has brought about the problem of degradation in the product accuracy of the printed substrate with terminals.

The present invention has been achieved in light of the above-described situation, and a problem to be solved by the present invention is the provision of a printed substrate having a novel structure in which substrate terminals can be fixed to the printed substrate without needing a base, and the substrate terminals can be press-fitted into through-holes with a reduced amount of pressing force applied to printed wiring and a plating layer in the through-holes, and also the provision of a printed substrate with terminals that uses the same printed substrate.

SUMMARY

A first aspect of the present invention related to a printed substrate is a printed substrate including a through-hole into which a first end portion of a substrate terminal is to be inserted, the through-hole including press-fitting regions into which the first end portion of the substrate terminal is press-fitted, and conduction regions arranged so as to oppose outer circumferential surfaces of the first end portion of the substrate terminal via gaps in directions perpendicular to the axis, and printed wiring being connected to the conduction regions, and a plating layer being adhered to the conduction regions, wherein in the through-hole, the conduction regions protrude outward in the directions perpendicular to the axis relative to the press-fitting regions.

According to the printed substrate of this aspect, the through-hole is provided with the press-fitting regions into which the substrate terminal is press-fitted and the conduction regions that oppose the substrate terminal via gaps, and the conduction regions are provided with printed wiring and the plating layer. Accordingly, a function of press-fitting and fixing the substrate terminal to the printed substrate can be realized with merely the press-fitting regions, and this function can be separated from the conduction regions. Accordingly, even in a state where the substrate terminal is press-fitted and fixed to the printed substrate, a situation in which pressing force exerted during press-fitting of the substrate terminal is applied to the printed wiring and the plating layer provided in the conduction regions is avoided. Accordingly, detachment of the plating layer and deformation of the printed wiring in an inner layer (inner-layer copper foil) can be prevented, and, even if a step of soldering to the through-hole is performed thereafter, it is possible to advantageously prevent the occurrence of measling and the occurrence of solder lifting defects caused by plating detachment. Furthermore, in this aspect, the conduction regions bulge outward in the direction perpendicular to the axis relative to the press-fitting regions, thus making it possible to ensure a larger opposing surface distance between the outer circumferential surfaces of the substrate terminal fitted into the through-hole and the conduction regions of the through-hole. As a result, it is possible to stably ensure insertion regions for the solder when soldering the substrate terminal to the through-hole, and it is possible to realize an improvement in a solder lifting property and a resulting improvement in connection stability.

Moreover, by press-fitting the first end portion of the substrate terminal into the press-fitting regions of the through-hole, the substrate terminal can be positioned and held in an upright state on the printed substrate, thus making it possible to eliminate the need for a conventional base. Accordingly, it is possible to reduce the number of components and number of manufacturing steps, and also manufacturing cost. Moreover, eliminating the base, eliminates the formation of solder cracks, thus making it possible to also improve connection reliability between the printed substrate and the substrate terminal.

Note that the printed wiring connected to the conduction regions includes printed substrate provided both as an inner layer and an outer layer. In particular, in the case where the printed wiring is provided as an inner layer, measling prevention can be advantageously achieved.

A second aspect of the present invention related to a printed substrate is the printed substrate according to the first aspect, wherein the press-fitting regions are provided at at least three locations that are separated from each other in a circumferential direction of the through-hole, and the conduction regions are respectively provided between pairs of press-fitting regions that are adjacent in the circumferential direction.

According to this aspect, the press-fitting regions are provided at at least three locations that are separated in the circumferential direction, thus making it possible for the substrate terminal to be press-fitted into and held on the printed substrate in a stable manner, and making it possible to improve precision regarding terminal alignment and rolling. Moreover, the conduction regions are respectively provided between pairs of adjacent press-fitting regions, thus making it possible to put the substrate terminal into conduction with the plating layer of the through-hole by soldering with stability in the circumferential direction.

Note that by providing the press-fitting regions at four locations that are separated with an equal pitch in the circumferential direction, the corner portions of an existing substrate terminal having a square cross-section can be press-fitted and held in a stable manner. Also, a configuration is possible in which by changing the pitch of the four locations, the corner portions of an existing substrate terminal having a rectangular cross-section can be press-fitted and held in a stable manner.

A first aspect of the present invention related to a printed substrate with terminals is a printed substrate with terminals in which a substrate terminal is provided upright by a first end portion thereof being inserted into a through-hole of a printed substrate, the printed substrate according to the first or second aspect being used as the printed substrate, the first end portion of the substrate terminal being press-fitted into the press-fitting regions of the through-hole, and corner portions of the first end portion being pressure welded to the press-fitting regions, and outer circumferential surfaces of the first end portion of the substrate terminal being arranged so as to oppose the conduction regions of the through-hole via gaps in directions perpendicular to the axis, and the substrate terminal and the printed wiring being put into conduction by filling the gaps with solder, wherein in the through-hole, the conduction regions protrude outward in the directions perpendicular to the axis relative to the press-fitting regions.

According to the printed substrate with terminals of this aspect, the printed substrate according to the first or second aspect of the present invention related to a printed substrate is used, and therefore all of the effects described in the first or second aspect of the present invention related to a printed substrate are effectively exhibited when the first end portion of the substrate terminal is press-fitted into and fixed to the through-hole of the printed substrate and then soldered.

A second aspect of the present invention related to a printed substrate with terminals is the printed substrate with terminals according to the first aspect, wherein the press-fitting regions are provided at three locations that are separated from each other in a circumferential direction of the through-hole, and the conduction regions are respectively provided between pairs of press-fitting regions that are adjacent in the circumferential direction, and the first end portion of the substrate terminal has a triangular cross-sectional shape, and three corner portions of the first end portion of the substrate terminal are pressure welded to the press-fitting regions.

According to this aspect, the first end portion of the substrate terminal has a triangular cross-sectional shape, and the three corner portions are pressure welded to the press-fitting regions separated from each other in the circumferential direction. Accordingly, the substrate terminal is press-fitted into and fixed to the through-hole in a stable manner. Moreover, due to the first end portion of the substrate terminal having a triangular cross-sectional shape, the dimension, in the direction perpendicular to the axis, of the gaps between the conduction regions of the through-hole and the outer circumferential surfaces of the first end portion of the substrate terminal that face the conduction regions can be set larger than in the case of a terminal whose cross-sectional shape has four or more sides. Accordingly, without causing the conduction regions of the through-hole to bulge outward in directions perpendicular to the axis, it is possible to ensure a sufficient gap dimension, and an improvement in the solder lifting property can be ensured with the cross-sectional shape of the small through-hole.

A third aspect of the present invention related to a printed substrate with terminals is the printed substrate with terminals according to the first or second aspect, wherein the substrate terminal is provided with an abutting portion that positions the first end portion in an axial direction of the through-hole by abutting against the printed substrate.

According to this aspect, the abutting portion of the substrate terminal abuts against the upper surface of the printed substrate, thus making it possible to position the substrate terminal in the axial direction of the through-hole. Accordingly, it is possible to further position and hold the substrate terminal stably on the printed substrate.

According to the present invention, the through-hole is provided with the press-fitting regions into which the substrate terminal is press-fitted and the conduction regions that oppose the substrate terminal via gaps, and the conduction regions are provided with printed wiring and the plating layer. Accordingly, even in a state where the substrate terminal is press-fitted and fixed to the printed substrate, a situation in which pressing force exerted during press-fitting of the substrate terminal is applied to the printed wiring and the plating layer provided in the conduction regions is avoided, thus making it possible to prevent detachment of the plating layer and deformation of the printed wiring in an inner layer, and making it possible to advantageously avoid the occurrence of measling and the occurrence of solder lifting defects caused by plating detachment. Moreover, given that the substrate terminal can be positioned and held in an upright state on the printed substrate, it is possible to eliminate the need for a conventional base, thus making it possible to reduce the number of components and number of manufacturing steps, and also manufacturing cost. Moreover, eliminating the use of a base, also eliminates the formation of solder cracks, thus making it possible to also improve connection reliability between the printed substrate and the substrate terminal.

DETAILED DESCRIPTION

First,FIGS. 1 to 4show a printed substrate10serving as a first embodiment of the present invention, and a printed substrate with terminals18in which substrate terminals14are provided upright by first end portions16thereof being inserted into through-holes12of the printed substrate10. Note thatFIGS. 1 and 2show a state before soldering, andFIGS. 3 and 4show a state after soldering. Also, in the following description, the front side refers to the left side ofFIG. 1, the rear side refers to the right side ofFIG. 1, the upward direction refers to the upward direction ofFIG. 1, and the downward direction refers to the downward direction ofFIG. 1.

As shown inFIG. 3, the printed substrate10includes an insulated substrate20that is shaped as an approximately rectangular flat plate and is formed using a known insulating material such as a glass epoxy resin. The insulated substrate20has a laminated structure in which an inner layer26is interposed between a top layer22aand a bottom layer22b. An outer layer conductor pattern24aserving as printed wiring is formed on the upper surface of the top layer22a, and an outer layer conductor pattern24bis formed on the lower surface of the bottom layer22b. Inner layer conductor patterns28aand28bserving as printed wiring are provided on the upper surface and the lower surface of the inner layer26as well. Also, the majority of the outer surfaces of the outer layer conductor patterns24aand24bis covered by a protective coating30made of a synthetic resin for the purpose of oxidation prevention and the like, and the protective coating30has been removed from the outer layer conductor patterns24aand24bin the vicinity of the through-holes12such that the outer layer conductor patterns24aand24bare connected with a large area, that is to say with a low resistance, to the first end portions16of the substrate terminals14when flow soldering is performed.

As shown inFIGS. 1 to 4, the through-holes12of the printed substrate10are each configured by a clearance hole32that has a circular cross-sectional shape and four conduction regions34that are recessed grooves that bulge outward, in directions perpendicular to the axis, from the inner circumferential surface of the clearance hole32with an approximately hemispherical cross-sectional shape at positions that are separated from each other with a pitch of 90 degrees. The inner circumferential surface of the clearance hole32is scooped out by the four conduction regions34, and the remaining portions of the inner circumferential surface configure four press-fitting regions36at positions that are separated from each other in the circumferential direction. Specifically, the press-fitting regions36are provided at four locations that are separated from each other in the circumferential direction of the through-hole12, and the conduction regions34are respectively provided between pairs of press-fitting regions36that are adjacent in the circumferential direction. Furthermore, a plating layer38is adhered over the entirety of the interior of each of the through-holes12. Also, the outer layer conductor patterns24aand24band the inner layer conductor patterns28aand28bserving as printed wiring are connected to the portions of the plating layer38provided on the four conduction regions34.

The substrate terminals14are provided upright by inserting the first end portions16thereof into the through-holes12of the printed substrate10configured as described above. As shown inFIGS. 1 to 4, the substrate terminals14are each an integrally molded article obtained by forming a substrate press-fitting portion42in a first end portion16of a bar-shaped metal fitting40and forming a connection portion46in a second end portion44.

The bar-shaped metal fitting40is formed by cutting a metallic square wire member48to a predetermined length. A member that has rigidity to the extent that a spring property can be given by shape machining is preferably applied as the metallic square wire member48, and as one example, the metallic square wire member48is a wire member that is formed from iron, a copper alloy such as tough pitch copper or brass, or the like, and that extends with a constant approximately square cross-sectional shape. Note that a plating layer is provided over the entirety of the outer surfaces around the metallic square wire member48.

The substrate press-fitting portion42is formed in the first end portion16of the bar-shaped metal fitting40cut from the metallic square wire member48. A diagonal dimension W of the substrate press-fitting portion42is larger than an inner diameter dimension R of the through-hole12(seeFIG. 4). Note that a tip tapered portion50that has a tapered shape is formed on the tip edge portion of the substrate press-fitting portion42, similarly to conventionally-used terminals.

Also, the bar-shaped metal fitting40is provided with a pair of approximately rectangular abutting portions52,52on the central side (upper side inFIG. 1), with respect to the length direction (up-down direction inFIG. 1), of the substrate press-fitting portion42. The pair of abutting portions52,52are shaped as protrusions that protrude in the plate width direction (left-right direction inFIG. 2) of the bar-shaped metal fitting40. The pair of abutting portions52,52are formed by the two side edge portions of the metallic square wire member48being crushed in the plate thickness direction so as to protrude outward in the plate width direction. Note that although the abutting portions52of the present embodiment are shaped as protrusions that have an approximately rectangular cross-section, there are no limitations on the specific shape of the abutting portions52, and an approximately triangular cross-sectional shape or the like is possible.

Also, a connection portion46is formed on the second end portion44side of the bar-shaped metal fitting40. The connection portion46is given a desired cross-sectional shape by the two side edge portions of the metallic square wire member48on the second end portion44side being cut in the width direction, as necessary. Whereas the connection portion46has an approximately square cross-sectional shape in the present embodiment, a rear end tapered portion54that has a tapered shape is formed on the tip edge portion of the connection portion46, similarly to conventionally-used terminals.

As shown inFIG. 1, the substrate press-fitting portion42side of the first end portions16of the substrate terminals14having the above-described structure are inserted into the through-holes12of the printed substrate10. The insertion amount of the first end portion16of a substrate terminal14into a through-hole12is defined by the pair of abutting portions52,52abutting against the printed substrate10. In other words, due to the pair of abutting portions52abutting against the printed substrate10, the first end portion16of the substrate terminal14is positioned in the axial direction of the through-hole12. Note that when the first end portion16of the substrate terminal14is inserted into the through-hole12of the printed substrate10, the first end portion16of the substrate terminal14is positioned such that the protruding direction of the pair of abutting portions52is the front-rear direction as shown inFIGS. 1 and 2. As shown inFIG. 4, due to the diagonal dimension W of the first end portion16(substrate press-fitting portion42) of the substrate terminal14inserted into the through-hole12being set larger than the inner diameter dimension R of the through-hole12, the first end portion16of the substrate terminal14is press-fitted into the press-fitting regions36of the through-hole12in a state where four corner portions56of the first end portion16of the substrate terminal14are pressure welded to corresponding press-fitting regions36. Also, at this time, outer circumferential surfaces58of the first end portion16of the substrate terminal14are arranged so as to oppose the conduction regions34of the through-hole12via gaps60in directions perpendicular to the axis. By filling these gaps60with solder62, the substrate terminal14is put into conduction with the plating layer38and the outer layer conductor patterns24aand24band the inner layer conductor patterns28aand28bserving as printed wiring as shown inFIG. 3.

According to the printed substrate10having such a structure, the press-fitting regions36are provided at four locations that are separated from each other in the circumferential direction of the through-hole12, and the conduction regions34are respectively provided between pairs of press-fitting regions36that are adjacent in the circumferential direction. For this reason, when the substrate terminal14is press-fitted into and fixed to the printed substrate10, it is possible to avoid a situation in which pressing force exerted during press-fitting of the substrate terminal14is applied to the plating layer38and the outer layer conductor patterns24aand24band inner layer conductor patterns28aand28bserving as printed wiring, which are provided on the conduction regions34. Accordingly, deformation of such printed wiring (particularly the inner layer conductor patterns28aand28b) and detachment of the plating layer38can be prevented, thus making it possible to advantageously prevent the occurrence of measling and the occurrence of solder lifting defects caused by plating detachment in the step of soldering to the through-hole12.

As a result, by merely press-fitting the first end portions16of the substrate terminals14into the through-holes12of the printed substrate10and performing soldering, the substrate terminals14can be positioned and held in an upright state on the printed substrate10, thus making it possible to eliminate the need for a conventionally-needed base. For this reason, it is possible to reduce cost by reducing the number of components and the number of manufacturing steps, and, due to the need for a base being eliminated and the problem of solder crack formation is also eliminated, it is possible to also improve the connection reliability between the printed substrate10and the substrate terminals14. Additionally, the pair of abutting portions52are provided as protrusions on the substrate terminals14that are to be provided upright on the printed substrate10. These pairs of abutting portions52abut against the upper surface of the printed substrate10, and therefore the substrate terminals14can be positioned in the axial direction of the through-holes12, thus making it possible to further stably position and hold the substrate terminals14on the printed substrate10.

Also, the press-fitting regions36are provided at four locations that are separated with an equal pitch in the circumferential direction, and therefore the corner portions56of an existing substrate terminal14have a square cross-section that can be press-fitted and held in a stable manner, thus making it possible to improve precision regarding substrate terminal14alignment and rolling. Furthermore, the conduction regions34are arranged so as to oppose the outer circumferential surfaces58of the substrate terminals14via the gaps60in directions perpendicular to the axis, thus making it possible to stably ensure insertion regions for the solder62when soldering the substrate terminals14to the through-holes12, and making it possible to realize an improvement in a solder lifting property and a resulting improvement in connection stability. Moreover, in the present embodiment, the conduction regions34are formed so as to bulge outward in directions perpendicular to the axis relative to the press-fitting regions36, thus making it possible to ensure large insertion regions for the solder62when soldering the substrate terminals14to the through-holes12, and making it possible to realize a further improvement in a solder lifting property and an accompanying improvement in connection stability.

UsingFIGS. 5 to 8, the following describes details of a printed substrate64serving as a second embodiment of the present invention and a printed substrate with terminals70in which substrate terminals68are provided upright by first end portions16thereof being inserted into through-holes66of the printed substrate64. Members and portions having structures similar to the above-described embodiment are denoted in the figures by the same reference signs as in the above-described embodiment, thereby omitting detailed descriptions for them. Note thatFIGS. 5 and 6show a state before soldering, andFIGS. 7 and 8show a state after soldering. Specifically, in the printed substrate64, the four press-fitting regions36are provided with different pitches in the circumferential direction of the through-hole66, the conduction regions34are provided at two locations where the separation distance between adjacent press-fitting regions36is large (seeFIG. 6), the first end portion16of the substrate terminal14has an approximately rectangular cross-sectional shape, and the four corner portions56are provided at locations that correspond to the four press-fitting regions36. Accordingly, by the four corner portions56of an existing substrate terminal68having a rectangular cross-section being press-fitted into and pressure welded to the four press-fitting regions36of the through-hole66of the printed substrate64, the substrate terminal68can be press-fitted into and held in the through-hole66in a stable manner. Note that in the present embodiment as well, the structure of the through-hole12of the printed substrate10in the above embodiment is merely changed so as to conform to the cross-sectional shape of the first end portion16of the new substrate terminal68, and therefore effects similar to the above embodiment can of course be obtained.

Furthermore, usingFIGS. 9 and 10, the following describes details of a printed substrate72serving as a third embodiment of the present invention and a printed substrate with terminals78in which substrate terminals76are provided upright by first end portions16thereof being inserted into through-holes74of the printed substrate72. Members and portions having structures similar to the above-described embodiments are denoted in the figures by the same reference signs as in the above-described embodiments, thereby omitting detailed descriptions for them. Note thatFIG. 10shows a state after soldering. Specifically, in the printed substrate72, the press-fitting regions36are provided at three locations that are separated from each other in the circumferential direction of the through-hole74, and the conduction regions34are respectively provided between pairs of press-fitting regions36that are adjacent in the circumferential direction, but this embodiment is different from the first embodiment in that the first end portion16of the substrate terminal76has a triangular cross-sectional shape, and the three corner portions56of the first end portion16of the substrate terminal76are pressure welded to the press-fitting regions36. Accordingly, the substrate terminal76can be stably press-fitted into and held in the through-hole74, and it is possible to improve precision regarding substrate terminal76alignment and rolling. Moreover, due to the first end portion16of the substrate terminal76having a triangular cross-sectional shape, a dimension L3, in the direction perpendicular to the axis, of the gaps60between the conduction regions34of the through-hole74and the outer circumferential surfaces58of the first end portion16of the substrate terminal76that face the conduction regions34can be set larger than with a substrate terminal whose cross-sectional shape has four or more sides. In other words, it is possible to ensure a larger dimension L3than the dimensions L1and L2of the gaps between the inner circumferential surfaces of the clearance hole32and the outer circumferential surfaces58of the first end portion16of the substrate terminals14and68in the first and second embodiments, for example. Accordingly, without causing the conduction regions34of the through-hole74to bulge outward in directions perpendicular to the axis, an improvement in the solder lifting property can be ensured even with the cross-sectional shape of the small through-hole74as in the present embodiment. Note that in the present embodiment as well, the structure of the through-hole12of the printed substrate10in the first embodiment is merely changed so as to conform to the cross-sectional shape of the first end portion16of the new substrate terminal76, and therefore effects similar to the above embodiment can of course be obtained.

Although embodiments of the present invention have been described above, they are merely examples, and the present invention is not intended to be interpreted in a limiting manner, in any way, by the specific descriptions in the embodiments. For example, although the outer layer conductor patterns24aand24band the inner layer conductor patterns28aand28bserving as printed wiring are all connected to the four conduction regions34in the above embodiments, it is sufficient that at least one printed wiring is connected. Also, although the first end portions16of the substrate terminals14are mounted to the through-holes12of the printed substrate10by flow soldering in the above embodiments, they may be mounted by reflow soldering. Note that lead-free solder not containing lead may be employed as the solder62.

Additionally, although the conduction regions34of the through-holes12are configured so as to bulge outward in directions perpendicular to the axis in the first embodiment, the conduction regions34may be provided in the inner circumferential surface of the circular clearance hole32without bulging outward in directions perpendicular to the axis. Also, although the above embodiments have been described taking the example of the substrate terminals14,68, and76whose cross-sectional shapes are triangular, square, and rectangular, it goes without saying that the present invention can be applied to substrate terminals having any cross-sectional shape by providing a printed substrate with through-holes that are in accordance with the cross-sectional shape. Furthermore, although the plating layer38is adhered over the entirety of the interior of the through-holes12in the above embodiments, it is sufficient that the plating layer38is adhered to at least the conduction regions34.