Solder junction structure, touch sensor for steering wheel, and method for forming solder junction structure

Abstract

To provide a solder junction structure with an excellent joint quality, a touch sensor for a steering wheel, and a method for manufacturing a solder junction structure while suppressing or preventing damages of a net-like conductive material.SOLUTION: The solder junction structure is formed by joining a plate-like electrode and a net-like conductive material by a solder to form a laminate. The solder junction structure has a solder site having a solder joint layer formed by joining the plate-like electrode and the solder with each other in an electrode position which corresponds to a part of openings of the net-like conductive material, and also has an electrode exposure site in which the plate-like electrode is exposed in the electrode positions which correspond to the other openings.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a solder joint structure, a touch sensor for a steering wheel, and a method for forming the solder joint structure, and more particularly to a solder joint structure in which a plate-shaped electrode and a mesh-shaped conductive material are laminated and joined via solder, a steering wheel touch sensor having the same, and a method for forming the solder joint structure. [Background technology]

[0002] Patent Document 1 discloses an inexpensive circuit device and a manufacturing method thereof, which is provided by establishing a method of directly ultrasonically bonding a lead terminal to a thin conductor. In this manufacturing method of the circuit device, the lead terminal of an electronic component is placed on a conductor mainly composed of copper or silver formed by screen printing on a ceramic substrate, and a load is applied from above using an ultrasonic vibration horn. When the ultrasonic vibration horn is ultrasonically vibrated in the surface direction of the lead terminal while applying the load, friction occurs at the bonding interface between the conductor and the lead terminal. When the oxide films formed at the bonding interface between the conductor and the lead terminal are removed by friction, a metal bond occurs at the bonding interface between the conductor and the lead terminal due to the generated plastic flow. As a result, the lead terminal is directly ultrasonically bonded to the conductor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-86717 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in ultrasonic vibration bonding as described in Patent Document 1, if the strength or heat resistance of the lead terminal is insufficient to withstand, for example, the above-mentioned load or friction caused by ultrasonic vibration, the lead terminal may be damaged and it may not be possible to connect the lead terminal to the conductor.

[0005] The present invention has been made in consideration of the problems associated with such conventional technology, and aims to provide a solder joint structure having excellent joint quality while suppressing or preventing damage to the mesh-like conductive material, a touch sensor for a steering wheel, and a method for forming a solder joint structure. [Means for solving the problem]

[0006] As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that the above-mentioned objective could be achieved by providing a solder portion having a solder bonding layer formed by bonding a plate-shaped electrode and solder at electrode positions corresponding to some of the openings in the mesh-like conductive material, and providing an electrode exposed portion in which the plate-shaped electrode is exposed at electrode positions corresponding to the remaining openings, thereby completing the present invention.

[0007] That is, the solder joint structure of the present invention is a solder joint structure in which a plate-shaped electrode and a mesh-shaped conductive material are laminated and joined via solder. The solder joint structure has a solder portion having a solder joint layer formed by joining a plate-shaped electrode and solder at an electrode position corresponding to some of the openings of the mesh-like conductive material, and has an electrode exposed portion where the plate-shaped electrode is exposed at an electrode position corresponding to the remaining openings.

[0008] Moreover, the steering wheel touch sensor of the present invention is a steering wheel touch sensor provided on a steering wheel. The steering wheel touch sensor comprises an insulating sheet and a mesh-like conductive material provided on both sides of the insulating sheet, and a part of the steering wheel touch sensor has a solder joint structure in which a plate-like electrode and the mesh-like conductive material are laminated and joined via solder, and the plate-like electrode is positioned on the insulating sheet side. The solder joint structure has a solder portion having a solder joint layer formed by joining a plate-shaped electrode and solder at an electrode position corresponding to some of the openings of the mesh-like conductive material, and has an electrode exposed portion where the plate-shaped electrode is exposed at an electrode position corresponding to the remaining openings.

[0009] Furthermore, the method for forming a solder joint structure of the present invention is a method for forming a solder joint structure in which a plate-shaped electrode and a mesh-shaped conductive material are layered and joined via solder, and a solder portion having a solder joint layer formed by joining the plate-shaped electrode and solder is provided at an electrode position corresponding to some of the openings of the mesh-shaped conductive material, and an electrode exposed portion in which the plate-shaped electrode is exposed is provided at an electrode position corresponding to the remaining openings. In the method for forming a solder joint structure, when forming the solder joint structure, a mesh conductive material is placed on a plate electrode having a solder plating formed on its surface, and a plurality of convex parts of an ultrasonic vibrator having openings in the mesh conductive material are inserted through the openings of the mesh conductive material to apply pressure to the solder plating while ultrasonically vibrating the convex parts, melting the solder plating into molten solder, and some of the plurality of convex parts are ultrasonically vibrated while applying pressure to the plate electrode while other of the convex parts are ultrasonically vibrated in the molten solder. Effect of the Invention

[0010] According to the present invention, a solder portion having a solder joint layer formed by joining a plate-shaped electrode and solder is provided at electrode positions corresponding to some of the openings in the mesh-shaped conductive material, and an electrode exposed portion in which the plate-shaped electrode is exposed is provided at electrode positions corresponding to the remaining openings.This makes it possible to provide a solder joint structure with excellent joint quality, a steering wheel touch sensor, and a method for forming a solder joint structure, while suppressing or preventing damage to the mesh-shaped conductive material. [Brief description of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram illustrating a steering wheel touch sensor according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an explanatory diagram illustrating a schematic diagram of the solder joint structure shown in FIG. [Diagram 3] 13 is a plan view showing a schematic view of another embodiment of a solder joint structure as viewed from the mesh-shaped conductive material side. FIG. [Figure 4] 1A to 1C are explanatory diagrams illustrating an embodiment of a method for forming a solder joint structure of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The solder joint structure, steering wheel touch sensor, and method for forming the solder joint structure of the present invention will be described in detail below with reference to the drawings. Note that hereinafter, the "steering wheel touch sensor" may be simply referred to as the "touch sensor." Also, the dimensional ratios of the drawings cited below are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0013] [Touch sensor, solder joint structure] The upper view of Fig. 1 is a plan view showing an example of an application position of the touch sensor 10 of this embodiment in a steering wheel 1. The lower view of Fig. 1 is a partial cross-sectional view showing a state where the solder joint structure 10A of the touch sensor 10 shown in the upper view of Fig. 1 is cut along line AA and developed. Furthermore, the upper view of Fig. 2 is a plan view showing a state where the solder joint structure 10A is seen from the mesh-like conductive material 13 side. Furthermore, the lower view of Fig. 2 is a cross-sectional view showing a state where the solder joint structure 10A is cut along line BB shown in the upper view of Fig. 2.

[0014] As shown in Fig. 1, the touch sensor 10 of this embodiment is provided in the shaded area of ​​the annular steering wheel 1. The touch sensor 10 detects whether or not the driver's hand is touching the steering wheel from a change in electrostatic capacitance of a mesh-like conductive cloth, which will be described in detail later. More specifically, the touch sensor 10 is provided on the outer diameter side of the steering wheel main body 2 in a cross section of the cylindrical steering wheel 1 perpendicular to the circumferential direction of the steering wheel 1. Normally, in the steering wheel 1, a steering wheel cover 3 is provided on the outer diameter side of the touch sensor 10.

[0015] The touch sensor 10 also includes an insulating sheet 15 and a mesh-like conductive material 13 such as conductive cloth provided on both sides of the insulating sheet 15. Here, a film formed of, for example, polyimide (PI) or polyethylene terephthalate (PET) can be suitably used as the insulating sheet. Also, a woven fabric formed of coated fibers in which a metal such as copper is plated on a polymer fiber such as PET, or a woven fabric formed of a polymer fiber such as PET plated with a metal such as copper can be suitably used as the conductive cloth.

[0016] The touch sensor 10 has a solder joint structure 10A in which a plate electrode 11 made of a metal such as copper and a mesh-shaped conductive material 13 are laminated and joined via solder 14 (see FIG. 2), and the plate electrode 11 is located on the insulating sheet 15 side. The size (length x width) of the plate electrode 11 is about 10 mm x 10 mm. The thickness of the plate electrode 11 is about 0.1 mm to 1 mm. The conductive wire 12 has, for example, an insulating coating on its surface, and connects the plate electrode 11 to an electronic control device (not shown) of the touch sensor 10. The touch sensor 10 preferably includes, for example, a metal base material 16 that supports the solder joint structure 10A.

[0017] 2, the solder joint structure 10A of the present embodiment has a solder portion 10a1 having a solder joint layer 14A formed by joining the plate electrode 11 and the solder 14 at an electrode position corresponding to a part of the openings 13a of the mesh conductive material 13 in a plan view from the mesh conductive material 13 side, and has an electrode exposed portion 10a2 at which the plate electrode 11 is exposed at an electrode position corresponding to the remaining openings 13a. Here, when the plate electrode is made of copper, the solder joint layer 14A usually contains an intermetallic compound of copper and tin. Note that, in the electrode exposed portion 10a2, it is sufficient that the plate electrode 11 is exposed even a little, and the solder joint layer 14A or the solder 14 may be present in a part thereof. Here, the thickness of the mesh conductive material 13 is about 0.05 mm to 0.2 mm. Also, the opening size (length x width) of the mesh conductive material is about 0.2 mm x 0.2 mm.

[0018] 2, the plate electrode 11 has a rough surface portion 11A in the electrode exposed portion 10a2, and the surface roughness of the surface 11a of the plate electrode 11 in the electrode exposed portion 10a2 is preferably rougher than the surface roughness of the surface 11a of the plate electrode 11 in the solder portion 10a1. For example, the surface roughness Ra2 of the surface 11a of the plate electrode 11 in the electrode exposed portion 10a2 is preferably 2 to 3 times the surface roughness Ra1 of the surface 11a of the plate electrode 11 in the solder portion 10a1. Moreover, the surface roughness Ra1 of the surface 11a of the plate electrode 11 in the solder portion 10a1 is preferably 0.05 to 0.1 μmRa, for example.

[0019] 2, the plate electrode 11 has an uneven structure, and the surface height of the plate electrode 11 at the electrode exposed portion 10a2 is preferably higher than the surface height of the plate electrode 11 at the solder portion 10a1. When the surface of the plate electrode 11 on the side opposite to the side where the mesh conductive material 13 is disposed is flat, the difference between the surface height of the plate electrode 11 at the electrode exposed portion 10a2 and the surface height of the plate electrode 11 at the solder portion 10a1 is preferably 0.01 mm to 0.1 mm.

[0020] 2, it is preferable that the solder joint structure 10A has a solder joint layer 14A formed by joining the plate electrode 11 and the solder 14 at an electrode position corresponding to the mesh conductive material 13 in a plan view from the mesh conductive material 13 side. In addition, although not shown, it is preferable that the solder joint structure 10A has a solder joint layer formed by joining the mesh conductive material 13 and the solder 14 at the interface between the mesh conductive material 13 and the solder 14.

[0021] Furthermore, as shown in FIG. 2, it is preferable that the mesh-like conductive material 13 is embedded in the solder 14.

[0022] Next, the advantages of this embodiment will be described. According to this embodiment, the electrode positions corresponding to some of the openings 13a of the mesh-like conductive material 13 have solder portions 10a1 having solder joint layers 14A formed by joining the plate-like electrode 11 and the solder 14, and the electrode positions corresponding to the remaining openings 13a have electrode exposed portions 10a2 where the plate-like electrode 11 is exposed, so that it is possible to suppress or prevent damage to the mesh-like conductive material and realize excellent joint quality.

[0023] Furthermore, according to this embodiment, the surface roughness of the surface 11a of the plate electrode 11 in the electrode exposed portion 10a2 is rougher than the surface roughness of the surface 11a of the plate electrode 11 in the solder portion 10a1, which has the advantage of making it easier to ensure a solder bonding layer.

[0024] Furthermore, according to this embodiment, the surface height of the surface 11a of the plate electrode 11 at the electrode exposed portion 10a2 is higher than the surface height of the surface 11a of the plate electrode 11 at the solder portion 10a1, which has the advantage of making it easier to ensure a solder bonding layer.

[0025] Furthermore, according to this embodiment, when viewed in a plan view from the mesh conductive material 13 side, the solder joint structure 10A has a solder joint layer 14A formed by joining the plate electrode 11 and solder 14 at the electrode position corresponding to the mesh conductive material 13, thereby achieving better joint quality.

[0026] Furthermore, according to this embodiment, the solder joint structure 10A has a solder joint layer formed by joining the mesh conductive material 13 and the solder 14 at the interface between the mesh conductive material 13 and the solder 14, so that better joint quality can be achieved.

[0027] Furthermore, according to this embodiment, since the mesh-like conductive material 13 is embedded in the solder 14, better joint quality can be achieved.

[0028] Fig. 3 is a diagram illustrating another embodiment of the solder joint structure, and Fig. 4 is a diagram illustrating one embodiment of a method for forming the solder joint structure. In the following description, the same components as those described above are given the same reference numerals, and detailed descriptions of the invention are omitted.

[0029] As shown in Figure 3, the solder joint structure 10B of this embodiment has a configuration similar to that of the above-mentioned solder joint structure 10A, except that, when viewed in a planar view from the mesh-like conductive material 13 side, it has an electrode exposed portion 10a2 in the central portion 10c and a solder portion 10a1 in the outer peripheral edge portion 10e.

[0030] Next, the advantages of this embodiment will be described. According to this embodiment, in plan view from the mesh-like conductive material 13 side, the central portion 10c has the electrode exposed portion 10a2, and the outer peripheral edge portion 10e has the solder portion 10a1. In addition to the advantages of the solder joint structure 10A described above, the amount of current flowing to the central portion when the solder joint structure is used can be reduced, and heat can be prevented from being trapped in the solder joint structure, improving the joint reliability.

[0031] [Method of forming solder joint structure] As shown in Fig. 4(A), a mesh-like conductive material 13 is placed on a plate electrode 11 having a solder plating 20 formed on its surface. Here, the plate electrode 11 has a rough surface portion 11A at a portion that will become the electrode exposed portion 10a2 in the solder joint structures 10A and 10B. The rough surface portion can be formed, for example, by a conventionally known etching method. Also, the height of the surface 11a of the plate electrode 11 at the portion where the rough surface portion 11A is formed is relatively higher than the height of the other portions.

[0032] Next, as shown in FIG. 4(B), the solder plating 20 (see FIG. 4(A)) is pressurized with a pressure of about 1 kgf by multiple protrusions 30A of the ultrasonic vibrator 30 inserted through the openings 13a of the mesh-like conductive material 13, while the protrusions 30A are ultrasonically vibrated at about 20 kHz to 100 kHz to melt the solder plating 20 into molten solder 21.

[0033] Furthermore, as shown in FIG. 4(C), while pressure is continued to be applied to the plate electrode 11 by some of the multiple protrusions 30A, the protrusions 30A are continued to be ultrasonically vibrated, and the other parts of the protrusions 30 are continued to be ultrasonically vibrated in the molten solder 21.

[0034] The molten solder is then solidified to form the solder joint structure described above.

[0035] Next, the advantages of this embodiment will be described. According to this embodiment, since the above-mentioned predetermined process is performed, the molten solder is secured by the portion where the surface height of the rough surface portion 11A is relatively high, while the oxide film and dirt can be removed by the cavitation effect in the other portions. This makes it possible to form a solder joint structure with excellent joint quality with a good yield while suppressing or preventing damage to the mesh-like conductive material. In addition, since fine vibrations are applied to the molten solder, voids that occur during normal solder jointing can be removed.

[0036] Although the present invention has been described above with reference to some embodiments, the present invention is not limited to these, and various modifications are possible within the scope of the gist of the present invention.

[0037] In the present invention, in order to provide a solder joint structure, a steering wheel touch sensor, and a method for forming a solder joint structure having excellent joint quality while suppressing or preventing damage to the mesh conductive material, the gist of the present invention is that a solder portion having a solder joint layer formed by joining a plate-shaped electrode and solder is provided at an electrode position corresponding to some of the openings in the mesh conductive material, and an electrode exposed portion where the plate-shaped electrode is exposed is provided at an electrode position corresponding to the remaining openings.

[0038] Therefore, in the above embodiment, a general conductive cloth is used as the mesh-like conductive material, but the present invention is not limited to this. For example, a metal cloth may be used as the mesh-like conductive material.

[0039] In the above embodiment, copper is used as an example of the metal in the plate electrode and the mesh-like conductive material, but the present invention is not limited to this. For example, a metal that can be joined by a type of solder can be used. The type of solder is not particularly limited, and although it is preferable to use lead-free solder, it is also possible to use lead-containing solder.

[0040] In the above embodiment, the mesh-like conductive material is described as being completely buried by self-alignment or the ultrasonic transducer, but the present invention is not limited to this. For example, the mesh-like conductive material may be partially buried.

[0041] Furthermore, for example, the above-mentioned components are not limited to the configurations shown in each embodiment, and it is possible to change the details of the specifications and materials of the plate electrode, mesh-like conductive material, solder, insulating sheet, and metal substrate, or to combine the components of one embodiment with the components of another embodiment. [Explanation of symbols]

[0042] 1 Steering wheel 2 Steering wheel body 3 Steering wheel cover 10 Touch Sensor 10A, 10B Solder joint structure 10a1 solder part 10a2 electrode exposed area 10c central part 10e Outer edge 11 Plate electrode 11A Rough surface area 11a surface 12 Conductor 13 Mesh-like conductive material (conductive cloth) 13a aperture 14 Solder 14A solder joint layer 15 Insulation sheet 16 Metal substrate 20 Solder plating 21 Molten solder 30 Ultrasonic transducer 30A Convex

Claims

1. A solder joint structure in which a plate-shaped electrode and a mesh-shaped conductive material are laminated and joined via solder, The conductive mesh material has a solder portion having a solder joint layer formed by joining the plate electrode and the solder at electrode positions corresponding to some of the openings of the conductive mesh material, and an electrode exposed portion where the plate electrode is exposed at electrode positions corresponding to the remaining openings. A solder joint structure comprising:

2. 2. The solder joint structure according to claim 1, wherein the surface roughness of the plate electrode at the electrode exposed portion is greater than the surface roughness of the plate electrode at the solder portion.

3. 3. The solder joint structure according to claim 2, wherein a surface height of the plate electrode at the electrode exposed portion is higher than a surface height of the plate electrode at the solder portion.

4. A solder joint structure described in any one of claims 1 to 3, characterized in that, when viewed in a plane from the mesh-shaped conductive material side, the electrode exposed portion is located in the center and the solder portion is located in the outer circumferential edge portion.

5. A steering wheel touch sensor provided on a steering wheel, The insulating sheet has a mesh-like conductive material provided on both sides of the insulating sheet. a solder joint structure in which a plate-shaped electrode and the mesh-shaped conductive material are laminated and joined to a part of the touch sensor via solder, and the plate-shaped electrode is located on the insulating sheet side; The solder joint structure has a solder portion having a solder joint layer formed by joining the plate-like electrode and the solder at an electrode position corresponding to some of the openings of the mesh-like conductive material, and has an electrode exposed portion where the plate-like electrode is exposed at an electrode position corresponding to the remaining openings. A touch sensor for a steering wheel.

6. When forming a solder joint structure in which a plate electrode and a mesh conductive material are laminated and joined via solder, and a solder portion having a solder joint layer formed by joining the plate electrode and the solder is provided at electrode positions corresponding to some of the openings of the mesh conductive material, and an electrode exposed portion where the plate electrode is exposed is provided at electrode positions corresponding to the remaining openings, A mesh-shaped conductive material is placed on a plate-shaped electrode having a solder-plated surface; a plurality of protrusions of an ultrasonic vibrator are inserted through the openings of the mesh-like conductive material, the protrusions are ultrasonically vibrated while applying pressure to the solder plating, and the solder plating is melted into molten solder; While applying pressure to the plate-shaped electrode with some of the plurality of protrusions, the protrusions are ultrasonically vibrated, and the other protrusions are ultrasonically vibrated in the molten solder.

1. A method for forming a solder joint structure comprising the steps of:

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