JP2005044968A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board wherein, even if a solder under a connection terminal is re-melted when an external terminal is welded to the connection terminal on the circuit board, the melted solder can be prevented from being discharged to the side of electronic components. <P>SOLUTION: The opening 13a of a protection layer 13 is provided with a projection groove 13b for receiving a melted solder on at least one side among its four sides that do not face an electrode 14 for components and an electronic component 16. Because of such a construction, even if a solder BM under a connection terminal 15 is re-melted by a heat producing during welding of an external terminal 17 to the connection terminal 15, and it is discharged (scattered and run out) to the outside, the projection groove 13b of the opening 13 receives at least a part of the melted solder so that the melted solder can be prevented from being discharged to the side of the electronic component 16, and the shortcircuiting of the electrode 14 or a lead 16a in the electronic component 16 can be also prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit board including a terminal electrode to which a connection terminal is bonded and a component electrode to which an electronic component is bonded adjacently.
[0002]
[Prior art]
FIG. 1 shows such a conventional circuit board.
[0003]
The circuit board includes a substrate 1, a terminal electrode 2 provided on the substrate 1, and a protective layer 3 that covers the periphery of the terminal electrode 3 so that the surface of the terminal electrode 2 is partially exposed through the opening 3 a. And a plurality of component electrodes 4 provided adjacent to the terminal electrode 2 on the substrate 1 and a surface exposed portion 2a of the terminal electrode 2 exposed from the opening 3a of the protective layer 3 via a solder BM. And the electronic component 6 such as an IC in which the lead 6a is joined to the plurality of component electrodes 4 via the solder BM.
[0004]
In order to obtain this circuit board, first, as shown in FIGS. 2 (A) and 2 (B), a substrate 1 made of an insulating material such as ceramics or plastic is prepared, and the surface thereof is made of a metal material such as copper. A terminal electrode 2 having a rectangular upper surface shape is formed, and a plurality of component electrodes 4 having a rectangular upper surface shape made of the same material are formed.
[0005]
Then, a protective layer 3 made of an insulating material such as plastic or glass is formed so as to cover the periphery of the terminal electrode 2, and the center portion of the surface of the terminal electrode 2 is exposed (reference numeral 2a) through the rectangular opening 3a.
[0006]
Next, as shown in FIG. 3, the solder BM is printed on the surface exposed portion 2a of the terminal electrode 2 and the surface of each component electrode 4 by a method such as a screen printing method.
[0007]
Next, the connection terminal 5 is mounted on the terminal electrode 2 and the electronic component 6 is mounted on the component electrode 4, and this is put into a reflow furnace (not shown) to solder the connection terminal 5 and the electronic component 6. Join.
[0008]
[Patent Document 1]
JP 2003-23244 A [Patent Document 2]
JP-A-8-64939 [Patent Document 3]
Japanese Patent Laid-Open No. 11-177225
[Problems to be solved by the invention]
By the way, the connection terminal 5 is provided for welding an external terminal. As shown in FIGS. 4A and 4B, the connection terminal 5 is formed by a technique such as spot welding. The external terminal 7 is welded. Incidentally, the symbol WP in FIG. 4A indicates a welding point.
[0010]
However, in the circuit board shown in FIG. 1, the solder BM under the connection terminal 5 is remelted by heat generated when the external terminal 7 is welded to the connection terminal 5 and discharged to the outside (including scattering and outflow). 4A and 4B, there is a problem that a short occurs in the component electrode 4 or the lead 6a of the electronic component 6 due to the molten solder released in the direction indicated by the arrow in FIG. Incidentally, it is considered that the release of the remelted solder described above is due to the expansion of the volume of the internal voids (voids) accompanying the remelting of the solder BM, thereby increasing the internal pressure.
[0011]
The present invention was created in view of the above circumstances, and the purpose of the present invention is to melt even if the solder under the connection terminal is remelted when the external terminal is welded to the connection terminal provided on the circuit board. An object of the present invention is to provide a circuit board capable of suppressing the release of solder to the electronic component side.
[0012]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a substrate, a terminal electrode provided on the substrate, and a protective layer that covers the periphery of the terminal electrode so that the surface of the terminal electrode is partially exposed through the opening. , A component electrode provided adjacent to the terminal electrode on the substrate, a connection terminal bonded via solder to a surface exposed portion of the terminal electrode exposed from the opening of the protective layer, and bonded to the component electrode A circuit board including the electronic component, wherein a melting point that can be discharged to the outside when the solder existing between the connection terminal and the surface exposed portion of the terminal electrode is remelted at a joint portion of the connection terminal. The feature is that the molten solder receiving portion for receiving at least a part of the solder is provided in a direction not facing the component electrode and the electronic component.
[0013]
According to this circuit board, even when the external terminal is welded to the connection terminal, even if the solder under the connection terminal melts and is released to the outside (including scattering and outflow), it is released to the outside. By receiving at least a part of the obtained molten solder in the molten solder receiving portion, it is possible to suppress the molten solder from being released to the electronic component side.
[0014]
The above object and other objects, structural features, and operational effects of the present invention will become apparent from the following description and the accompanying drawings.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
FIG. 5 shows a first embodiment of a circuit board according to the present invention.
[0016]
The circuit board includes a terminal electrode 12 provided on the substrate 11, a protective layer 13 that covers the periphery of the terminal electrode 13 so that the surface of the terminal electrode 12 is partially exposed through the opening 13a, and the substrate 11 A plurality of component electrodes 14 provided adjacent to the terminal electrode 12 and a connection terminal joined via a solder BM to a surface exposed portion 12a of the terminal electrode 12 exposed through the opening 13a of the protective layer 13 15 and an electronic component 16 such as an IC in which a lead 16a is joined to a plurality of component electrodes 14 via solder BM.
[0017]
In order to obtain this circuit board, first, as shown in FIGS. 6A and 6B, a substrate 11 made of an insulating material such as ceramics or plastic is prepared, and a metal material such as copper is used on the surface thereof. A terminal electrode 12 having a rectangular upper surface shape is formed, and a plurality of component electrodes 14 having a rectangular upper surface shape made of the same material are formed.
[0018]
Then, a protective layer 13 made of an insulating material such as plastic or glass is formed so as to cover the peripheral edge of the terminal electrode 12, and the central portion of the surface of the terminal electrode 12 is exposed (reference numeral 12a) through the rectangular opening 13a. As can be seen from FIGS. 6A and 6B, the protective layer 13 has two sides (in FIG. 6A) that do not face the component electrode 14 and the electronic component 16 among the four sides of the opening 13a. A rectangular overhang groove 13b for receiving molten solder is provided at the center of the upper and lower sides), and a part of the peripheral edge of the surface of the terminal electrode 12 is exposed through the two overhang grooves 13b (reference numeral 12b). is doing. Incidentally, the overhang groove 13b corresponds to a “molten solder receiving portion” in the claims.
[0019]
Of course, the shape of the overhanging groove 13b is necessarily rectangular because it is sufficient that the discharge direction of the molten solder that can be discharged to the outside when the solder BM is re-melted can be regulated in a direction different from the direction in which the electronic component 16 is disposed. There is no. In addition, it is desirable to ensure that the overhang groove 13b has a size that can completely receive the remelted solder BM. However, as described above, the overhang groove 13b only needs to be able to regulate the discharge direction of the molten solder. Therefore, the intended purpose can be sufficiently achieved as long as it has a size and shape capable of receiving at least a part of the molten solder. Furthermore, the number of the overhanging grooves 13b can be changed as appropriate. For example, the number of overhanging grooves 13b is three and the openings 13a are respectively provided on the upper side, the lower side, and the left side in FIG. Alternatively, the number of the overhanging grooves 13b may be one and the openings 13a may be provided only on one of the upper side and the lower side in FIG. 6A or the left side.
[0020]
Next, as shown in FIG. 7, the solder BM is printed on the surface exposed portion 12 a of the terminal electrode 12 and the surface of each component electrode 14 by a method such as a screen printing method. In the conventional circuit board shown in FIG. 1, the solder printing area for the surface exposed portion 2a of the terminal electrode 2 is 100% of the area of the opening 3a of the protective layer 3 or a value close thereto, but here the terminal The amount of solder printing is limited by setting the solder printing area with respect to the surface exposed portion 12 a of the electrode 12 for use within the range of 70 to 20% of the area of the opening 13 a of the protective layer 13.
[0021]
Next, the connection terminal 15 is mounted on the terminal electrode 12 and the electronic component 16 is mounted on the component electrode 14, and this is put into a reflow furnace (not shown) to solder the connection terminal 15 and the electronic component 16. Join. In the conventional circuit board shown in FIG. 1, the thickness of the connection terminal 5 is in the range of 0.1 to 0.3 mm. Here, the thickness t of the connection terminal 15 is set to 0.3 mm <t ≦ A connection terminal 15 having a thickness larger than that of the conventional one is used as 1.0 mm. Further, because of the relationship in which the amount of solder printing is limited, the interface height between the connection terminal 15 and the solder BM is substantially coincident with the surface of the protective layer 13, and the adhesion area of the solder BM to the lower surface of the connection terminal 15 is the connection terminal 15. It falls within the range of 30 to 90% of the lower surface area.
[0022]
The connection terminal 15 is provided for welding an external terminal. As shown in FIGS. 8A and 8B, the connection terminal 15 is connected to the external terminal by a technique such as spot welding. 17 is welded. Incidentally, symbol WP in FIG. 8A indicates a welding point.
[0023]
According to the circuit board described above, the opening 13a of the protective layer 13 has the overhanging groove 13b for receiving molten solder on at least one side of the four sides that does not face the component electrode 14 and the electronic component 16. Therefore, even if the solder BM under the connection terminal 15 is remelted by the heat generated when the external terminal 17 is welded to the connection terminal 15 and released to the outside (including scattering and outflow), By receiving at least a part of the molten solder that can be discharged to the outside in the protruding groove 13 b provided in the opening 13, it is possible to suppress the molten solder from being discharged to the electronic component 16 side, and thereby the component electrode 14 or the electronic component 16. It is possible to prevent a short from occurring in the lead 16a.
[0024]
Further, according to the above-described circuit board, by limiting the solder printing amount by setting the solder printing area for the surface exposed portion 12a of the terminal electrode 12 within the range of 70 to 20% of the area of the opening 13a of the protective layer 13, The interface height between the connection terminal 15 and the solder BM is substantially coincident with the surface of the protective layer 13, and the adhesion area of the solder BM to the lower surface of the connection terminal 15 is in the range of 30 to 90% of the lower surface area of the connection terminal 15. Therefore, it is possible to prevent the solder BM under the connection terminal 15 from being remelted and released to the outside due to heat generated when the external terminal 17 is welded to the connection terminal 15 and to be melted solder. Is less likely to be released to the outside, and the short-circuit defect caused by the release of the molten solder can be more reliably prevented.
[0025]
Further, according to the above-described circuit board, the thickness t of the connection terminal 15 is in the range of 0.3 mm <t ≦ 1.0 mm and is thicker than the conventional one, so that heat during welding is transmitted to the solder BM. Since it is difficult, even when the heat at the time of welding the external terminal 17 to the connection terminal 15 is transmitted to the connection terminal 15, the solder BM under the connection terminal 15 is hardly remelted by this heat, causing the release of the molten solder. The short circuit that occurs can be prevented more reliably.
[0026]
It should be noted that the short-circuit occurrence rate when the external terminal 7 is welded to the connection terminal 5 of the conventional circuit board shown in FIG. 1, and the short-circuit occurrence rate when the external terminal 17 is welded to the connection terminal 15 of the circuit board described above. As a result of the verification, it was 8/10 in the former case and 0/10 in the latter case, and the intended purpose was sufficiently achieved by the configuration of the circuit board described above. Was confirmed.
[0027]
[Second Embodiment]
FIG. 9 shows a second embodiment of the circuit board according to the present invention.
[0028]
This circuit board is different from the circuit board of the first embodiment in that the dimension of the opening 13a ′ of the protective layer 13 in the horizontal direction in the drawing is about 3/5 of the opening 13a, and the terminal electrode 12 is formed through the opening 13a ′. The surface portion is exposed in a rectangular shape (reference numeral 12a ′) and the printing position of the solder BM is set to the left in the drawing so as to be within the exposed portion 12a ′ of the terminal electrode 12. Since other configurations are the same as those of the circuit board of the first embodiment, description thereof is omitted.
[0029]
According to this circuit board, the external terminal 17 is welded to the connection terminal 15 by reducing the area of the surface exposed portion 12 a ′ of the terminal electrode 12 and reducing the adhesion area of the solder BM to the lower surface of the connection terminal 15. Even if the heat is transmitted to the connection terminal 15, the solder BM under the connection terminal 15 can be prevented from being remelted by this heat. Other than that, the same effects as the circuit board of the first embodiment can be obtained.
[0030]
[Third Embodiment]
FIG. 10 shows a third embodiment of the circuit board according to the present invention.
[0031]
This circuit board is different from the circuit board of the first embodiment in that the overhanging groove 13b is excluded from the protective layer 13, and a through hole 12c having a circular cross section instead of the surface exposed portion 12a of the terminal electrode 12 is provided. A through hole 11a having a circular cross section corresponding to the through hole 12c is formed in the substrate 11 at the center or in the vicinity thereof. Since other configurations are the same as those of the circuit board of the first embodiment, description thereof is omitted. Incidentally, the through holes 12c and 11a correspond to the “molten solder receiving portion” in the claims.
[0032]
According to this circuit board, the solder BM under the connection terminal 15 is re-melted by the heat generated when the external terminal 17 is welded to the connection terminal 15 and discharged (including scattering and outflow). However, it is possible to suppress the molten solder from being discharged to the electronic component 16 side by receiving at least a part of the molten solder that can be discharged to the outside in the through holes 12c and 11a. Other than that, the same effects as the circuit board of the first embodiment can be obtained.
[0033]
The cross-sectional shapes of the through holes 12c and 11a are not necessarily circular, and rectangular through holes 12c ′ and 11a ′ as shown in FIG. 11 are employed, or through holes having other cross-sectional shapes are employed. It doesn't matter.
[0034]
[Fourth Embodiment]
FIG. 12 shows a fourth embodiment of a circuit board according to the present invention.
[0035]
This circuit board is different from the circuit board according to the first embodiment in that an insulating material that releases molten solder (including scattering and outflow) between the protective layer 13 and the component electrode 14 on the surface of the board 11 is used. The protrusion 18 is provided by a method such as screen printing. Since other configurations are the same as those of the circuit board of the first embodiment, description thereof is omitted.
[0036]
According to this circuit board, even if the solder BM under the connection terminal 15 is re-melted by the heat generated when the external terminal 17 is welded to the connection terminal 15 and released to the outside (including scattering and outflow), it is released. The molten solder received by the protrusion 18 can be prevented from reaching the component electrode 14 or the lead 16 a of the electronic component 16. Other than that, the same effects as the circuit board of the first embodiment can be obtained.
[0037]
In each of the above embodiments, the electronic component 16 is exemplified as a type in which the lead 16a is soldered. However, the electronic fixture 16 includes a flip chip type IC provided with gold bumps and a surface mountable electrode shape. There may be leadless electronic components such as transformers and inductors, and there are no particular restrictions on the number of electronic components to be mounted and the number of component electrodes, and the electronic components are connected to the component electrodes by a bonding material other than solder. It may be connected. In each embodiment, the effect of preventing the occurrence of a short circuit due to the external release of the molten solder has been described. However, according to each embodiment, it is possible to prevent the molten solder from being externally discharged, thereby preventing the molten solder from being added to the electronic component. The effect which can prevent that it adheres and becomes dirty is also acquired.
[0038]
【The invention's effect】
As described above in detail, according to the present invention, even when the external terminal is joined to the connection terminal provided on the circuit board by the welding method, even if the solder under the connection terminal is remelted, the molten solder is It is possible to prevent the short circuit from occurring in the component electrode or the electronic component by suppressing the release to the side.
[Brief description of the drawings]
FIG. 1 is a top view of a conventional circuit board and a sectional view taken along line a1-a1 of FIG. 2. FIG. 2 is a top view of the board showing a step of forming terminal electrodes, protective layers and component electrodes on the board, and a2- FIG. 3 is a cross-sectional view taken along line a2. FIG. 3 is a top view of the substrate showing a process of printing solder on the exposed surface of the terminal electrode and the surface of each component electrode. FIG. 4 is a connection terminal of the circuit board shown in FIG. FIG. 5 is a top view of a circuit board and a sectional view taken along the line a3-a3 for explaining a problem when the members are joined by a welding method. FIG. FIG. 6 is a top view of a substrate showing a process of forming a terminal electrode, a protective layer, and a component electrode on the substrate, and a b2-b2 sectional view of the substrate. FIG. FIG. 8 is a top view of a substrate showing a process of printing solder on the surface of a component electrode. FIG. 9 is a top view of a circuit board and a cross-sectional view taken along line b3-b3 for explaining the operation and effect when an external terminal is joined to a connection terminal of the board by a welding method. FIG. 10 is a top view of a circuit board, a cross-sectional view taken along line c1-c1 thereof, and a cross-sectional view taken along line d1-d1 and a cross-sectional view of essential parts of the circuit board according to a second embodiment of the present invention. 11 is a top view of a circuit board showing a modification of the circuit board shown in FIG. 10. FIG. 12 is a top view of the circuit board showing a third embodiment of the present invention and a cross-sectional view taken along line e1-e1.
DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 11a, 11a '... Through-hole, 12 ... Terminal electrode, 12a, 12a', 12b ... Surface exposed part, 12c, 12c '... Through-hole, 13 ... Protective layer, 13a, 13a' ... Opening, 13b DESCRIPTION OF SYMBOLS ... Overhang groove, 14 ... Electrode for components, 15 ... Connection terminal, 16 ... Electronic component, BM ... Solder, 17 ... External terminal, WP ... Welding point.

Claims (3)

A substrate, a terminal electrode provided on the substrate, a protective layer covering the periphery of the terminal electrode so that the surface of the terminal electrode is partially exposed through the opening, and adjacent to the terminal electrode on the substrate A circuit board comprising: a component electrode provided; a connection terminal joined via solder to a surface exposed portion of a terminal electrode exposed from the opening of the protective layer; and an electronic component joined to the component electrode. There,
A molten solder receiving portion for receiving at least a part of the molten solder that can be discharged to the outside when the solder existing between the connection terminal and the exposed portion of the surface of the electrode for the terminal is remelted is a component at the joint portion of the connection terminal. Provided in a direction that does not face the electrodes and electronic components,
A circuit board characterized by that. The molten solder receiving part is composed of an overhang groove provided at an opening edge of the protective layer.
The circuit board according to claim 1. The molten solder receiving portion is composed of the terminal electrode and a through hole provided in the substrate.
The circuit board according to claim 1.

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