JP2020161782A - Electronic component and electronic component mounting substrate with the same - Google Patents

Abstract

To provide an electronic component comprising a terminal electrode capable of securing a high joint intensity even if a reflow is performed at a plural time.SOLUTION: An electronic component 1 comprises: a main body part 10 having a component surface 10a; and a flat plan-like terminal electrode 20 which is provided so as to be projected from the component surface 10a, and has a main surface 21 and a side surface 22 in parallel to the component surface 10a. The terminal electrode 20 includes a part in which a diameter becomes small as approach to the component surface 10a. Thus, at least one part of the side surface 22 has an overhang shape. When a solder or the like is entered into a connection conductive material into the overhang shape of the terminal electrode, and high jointing intensity can be secured even in the case of performing reflow at a plural time.SELECTED DRAWING: Figure 2

Description

The present invention relates to electronic components, and more particularly to electronic components mounted on a substrate via solder or conductor paste. The present invention also relates to an electronic component mounting substrate on which such electronic components are mounted.

In recent years, modularization of electronic components mounted on circuit boards has progressed. Therefore, a certain electronic component is not only reflowed in the surface mounting process when it is modularized, for example, but also reflowed in the surface mounting process when it is mounted on a circuit board after being modularized. As described above, as modularization progresses, the same electronic component is reflowed twice or more, so that the joint strength of the joint portion using solder or the like may decrease.

As a method for increasing the bonding strength of the solder bonding, as described in Patent Document 1, a method of adding a thermosetting resin composition to the flux, or as described in Patent Document 2, a special composition is used. One way is to use solder.

Japanese Unexamined Patent Publication No. 2012-84845 Japanese Patent Publication No. 2016-500178

However, in the method described in Patent Document 1, when the reflow is performed a plurality of times, the thermosetting resin composition is denatured and the bonding strength is lowered. Further, in the method described in Patent Document 2, since solder having a special composition is used, there is a problem that the manufacturing cost increases.

Therefore, an object of the present invention is to provide an electronic component provided with a terminal electrode capable of ensuring high bonding strength even when reflowing a plurality of times while suppressing an increase in manufacturing cost. Another object of the present invention is to provide an electronic component mounting substrate on which such electronic components are mounted.

The electronic component according to the present invention includes a main body portion having a mounting surface and a flat plate-shaped terminal electrode provided so as to project from the mounting surface and having a main surface and a side surface parallel to the mounting surface, and the terminal electrode is provided on the mounting surface. It has a portion whose diameter decreases as it approaches, so that at least a part of the side surface has an overhang shape.

According to the present invention, since at least a part of the side surface of the terminal electrode has an overhang shape, when a connecting conductor material such as solder is wrapped around this part to perform reflow a plurality of times. Even if there is, it is possible to secure high bonding strength.

The electronic component according to the present invention may further include a connecting conductor material that is provided on the main surface of the terminal electrode and has a melting point lower than that of the terminal electrode. According to this, it is possible to wrap the connecting conductor material around the side surface by reflowing after mounting the electronic component on the circuit board. That is, in the state before the reflow, the connecting conductor material may be present only on the main surface of the terminal electrode, and after the reflow, the connecting conductor material may cover the side surface of the terminal electrode having an overhang shape.

The electronic component mounting substrate according to the present invention includes a substrate having a land pattern and the above-mentioned electronic components mounted on the substrate, and the land pattern and the terminal electrode are connected via a connecting conductor material. To do. According to the present invention, it is possible to increase the bonding strength between the substrate and the electronic component via the connecting conductor material.

In the present invention, the thickness of the connecting conductor material located between the land pattern and the terminal electrode may be 30 μm or less. When the thickness of the connecting conductor material is reduced to 30 μm or less, the stress absorption capacity of the connecting conductor material is reduced and cracks and delamination are likely to occur in the connecting conductor material, but the connecting conductor material covers the overhang portion of the terminal electrode. If so, it is possible to suppress the occurrence of cracks and delamination.

As described above, according to the present invention, it is possible to sufficiently secure the bonding strength between the substrate and the electronic component via the connecting conductor material even when the reflow is performed a plurality of times. Moreover, since it is not necessary to use solder having a special composition, an increase in manufacturing cost is suppressed.

1A and 1B are views showing a structure of an electronic component 1 according to a preferred embodiment of the present invention, in which FIG. 1A is a schematic plan view and FIG. 1B is a schematic cross-sectional view taken along the line AA shown in FIG. is there. FIG. 2 is an enlarged view of the region B shown in FIG. 1 (b). FIG. 3 is a schematic cross-sectional view of the electronic component mounting substrate 2 on which the electronic component 1 is mounted on the substrate 3. FIG. 4 is an enlarged view of the region C shown in FIG. FIG. 5 is a schematic cross-sectional view showing a state in which the connecting conductor material 5 is formed on the terminal electrode 20. FIG. 6 is a schematic diagram for explaining a state in which exposure is performed on the positive photoresist 31P. FIG. 7 is a schematic view showing the shape of the photoresist 31P / 31N after development. FIG. 8 is a schematic diagram for explaining a state in which exposure is performed on the negative type photoresist 31N. FIG. 9 is a schematic plan view showing a circular terminal electrode 20. FIG. 10 is a schematic plan view of the terminal electrode 20 having an overhang shape only on a part of the side surface 22a. FIG. 11 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the first modification. FIG. 12 is a schematic diagram for explaining a state in which exposure is performed on the positive photoresist 31P. FIG. 13 is a schematic view showing the shape of the photoresist 31P / 31N after development. FIG. 14 is a schematic diagram for explaining a state in which exposure is performed on the negative type photoresist 31N. FIG. 15 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the second modification. FIG. 16 is a schematic view showing the shape of the photoresist 31P / 31N after development. FIG. 17 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the third modification. FIG. 18 is a schematic diagram for explaining a state in which exposure is performed on the negative type photoresist 31N. FIG. 19 is a schematic view showing the shape of the photoresist 31N after development. FIG. 20 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the fourth modification. FIG. 21 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the fifth modification. FIG. 22 is a schematic cross-sectional view showing an example in which the electronic component 1 and the electronic component 1A are connected by the connecting conductor material 5.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1A and 1B are views showing a structure of an electronic component 1 according to a preferred embodiment of the present invention, in which FIG. 1A is a schematic plan view and FIG. 1B is a schematic cross-sectional view taken along the line AA shown in FIG. is there.

The electronic component 1 according to the present embodiment is a surface mount type chip component, and as shown in FIG. 1, includes a main body portion 10 and a terminal electrode 20 provided on the mounting surface 10a of the main body portion 10. The type of the electronic component 1 is not particularly limited, and may be a passive circuit component such as a capacitor, an inductor, a resistor, or a filter, or an active circuit component such as a transistor or a semiconductor IC. Further, it may be a module component in which a plurality of passive circuit components and a plurality of active circuit components are integrated, or may be a wiring board on which a wiring layer is formed.

In the example shown in FIG. 1, the main body 10 is composed of a substrate 11 made of nickel (Ni) or the like, a functional layer 12 made of a capacitor or the like provided on the substrate 11, and an insulating layer 13 covering the functional layer. .. The surface of the insulating layer 13 constitutes the mounting surface 10a, and the terminal electrode 20 is provided on the mounting surface 10a. The terminal electrode 20 is connected to the functional layer 12 via a connecting portion 14 provided so as to penetrate the insulating layer 13. The terminal electrode 20 is a flat plate-shaped electrode provided so as to project from the mounting surface 10a, and has a main surface 21 and a side surface 22 parallel to the mounting surface 10a.

FIG. 2 is an enlarged view of the region B shown in FIG. 1 (b).

As shown in FIG. 2, the main surface 21 of the terminal electrode 20 is parallel to the mounting surface 10a, whereas the side surface 22 of the terminal electrode 20 is not perpendicular to the mounting surface 10a, and the mounting surface 10a and the side surface 22 are It has an inverted taper shape with an angle θ formed of less than 90 °. That is, the side surface 22 of the terminal electrode 20 has an overhang shape, and the diameter of the terminal electrode 20 decreases as it approaches the mounting surface 10a. The angle θ is preferably less than 80 °, and more preferably less than 60 ° in order to sufficiently obtain the effects described later. However, if the angle θ is too small, the shape of the terminal electrode 20 becomes unstable and it becomes difficult to form the terminal electrode 20. Therefore, it is preferably 30 ° or more, and more preferably 45 ° or more. preferable. When the side surface 22 is not a completely flat surface but a curved surface having a certain curvature, the angle θ is not uniquely determined and becomes a value having a predetermined range. Further, the overhang amount W, that is, the plane distance between the end portion of the side surface 22 on the mounting surface 10a side and the end portion of the side surface 22 on the main surface 21 side is preferably 0.5 μm or more and 30 μm or less, preferably 1 μm. As mentioned above, it is more preferably 15 μm or less. The thickness of the terminal electrode 20 is preferably 0.5 μm or more and 32 μm or less, and more preferably 1 μm or more and 25 μm or less. Regarding the plane size of the terminal electrode 20, the length of one side is preferably 0.01 mm or more and 4.5 mm or less, and more preferably 0.05 mm or more and 3.2 mm or less.

FIG. 3 is a schematic cross-sectional view of the electronic component mounting substrate 2 on which the electronic component 1 is mounted on the substrate 3.

As shown in FIG. 3, the substrate 3 has a land pattern 4, and is mounted on the substrate 3 so that the terminal electrode 20 of the electronic component 1 faces the land pattern 4. The terminal electrode 20 and the land pattern 4 are connected via a connecting conductor material 5 having a melting point lower than that of the terminal electrode 20 and the land pattern 4, such as solder or conductor paste. In the example shown in FIG. 3, the plane size of the land pattern 4 of the substrate 3 is larger than that of the terminal electrode 20 of the electronic component 1. Therefore, almost the entire surface of the terminal electrode 20 of the electronic component 1 is covered with the connecting conductor material 5, whereas a part of the main surface of the land pattern 4 of the substrate 3 is covered with the connecting conductor material 5. It is exposed without being exposed. The side surface of the land pattern 4 is also exposed without being covered with the connecting conductor material 5.

FIG. 4 is an enlarged view of the region C shown in FIG.

As shown in FIG. 4, when the electronic component 1 is mounted on the substrate 3, the connecting conductor material 5 such as solder or conductor paste includes not only the main surface 21 of the terminal electrode 20 but also the side surface 22 having an overhang shape. cover. As a result, for example, even if an external force in the horizontal direction is applied to the electronic component 1 and as a result, peeling occurs at the interface between the main surface 21 of the terminal electrode 20 and the connecting conductor material 5, this peeling occurs on the main surface 21 and the side surface 22. It is stopped by the sharp corners 23 that serve as boundaries, and it becomes difficult for peeling to proceed any further. Here, when the thickness of the connecting conductor material 5 located between the land pattern 4 and the terminal electrode 20 is sufficiently thick, even if an external force in the horizontal direction is applied to the electronic component 1, the connecting conductor material having a large thickness The stress can be absorbed to some extent by 5. However, when the connecting conductor material located between the land pattern 4 and the terminal electrode 20 is thin, especially when it is as thin as 30 μm or less, the stress absorption capacity of the connecting conductor material 5 decreases, and the connecting conductor material 5 cracks or delaminates. Is likely to occur. In particular, when the connecting conductor material 5 is lead-free solder, when the reflow is repeated a plurality of times, an alloy composed of a metal such as copper (Cu) constituting the terminal electrode 20 or the land pattern 4 and the lead-free solder grows and cracks occur. And delamination are likely to occur. Further, even when the connecting conductor material 5 is a conductive paste, if the reflow at a temperature exceeding the glass transition point is repeated a plurality of times, the adhesive strength is lowered. However, in the present embodiment, since the connecting conductor material 5 covers not only the main surface 21 of the terminal electrode 20 but also the side surface 22 having an overhang shape, it is possible to suppress the occurrence of cracks and delamination. It will be possible.

When the electronic component 1 is mounted on the substrate 3, as shown in FIG. 5, the connecting conductor material 5 is formed in advance on the terminal electrode 20 side of the electronic component 1, and in this state, the electronic component 1 is mounted on the substrate 3. After mounting, you can reflow. As a method of forming the connecting conductor material 5 on the terminal electrode 20, after preflux treatment for rust prevention is performed on the surface of the terminal electrode 20 made of copper (Cu) or the like, for example, a solder ball made of lead-free solder is used. The connecting conductor material 5 may be spread on the main surface 21 of the terminal electrode 20 by being mounted on the terminal electrode 20 and reflowing. The surface of the terminal electrode 20 may be nickel (Ni) plated or gold (Au) plated in advance. Further, at this point, the connecting conductor material 5 does not have to wrap around the side surface 22 of the terminal electrode 20.

The method for forming the terminal electrode 20 having the above-mentioned shape is not particularly limited, but as shown in FIG. 6, a positive photoresist 31P is formed on the main body 10 of the electronic component 1, and the light 33 is formed through the mask 32. The photoresist 31P is patterned into the shape shown in FIG. 7 by irradiating with. At the time of exposure, if the intensity of the light 33 is set to be weak so that the exposure width is gradually narrowed in the depth direction, the width becomes narrower in the depth direction as shown in FIG. 31a can be formed. Then, if the terminal electrode 20 is formed in the opening 31a by electrolytic plating, it is possible to form the terminal electrode 20 whose side surface 22 has an overhang shape.

Alternatively, as shown in FIG. 8, a negative type photoresist 31N is formed on the main body 10 of the electronic component 1, and the photoresist 31N is formed into the shape shown in FIG. 7 by irradiating the light 33 through the mask 32. Pattern. At the time of exposure, if the intensity of the light 33 is set to be stronger and the exposure width is adjusted to gradually increase in the depth direction, the opening becomes narrower in the depth direction as shown in FIG. 31a can be formed. Then, if the terminal electrode 20 is formed in the opening 31a by electrolytic plating, it is possible to form the terminal electrode 20 whose side surface 22 has an overhang shape.

The planar shape of the terminal electrode 20 is not particularly limited, and may be rectangular as shown in FIG. 1A or circular as shown in FIG. Further, it is not necessary that all the side surfaces 22 of the terminal electrode 20 have an overhang shape, and it is sufficient that at least a part of the side surfaces has an overhang shape. For example, the terminal electrode 20 shown in FIG. 10 has two opposite side surfaces 22a having an overhang shape, while the remaining side surfaces 22b do not have an overhang shape and are substantially vertical surfaces. Even in this case, if the connecting conductor material 5 is wrapped around the overhang portion, it is possible to suppress the occurrence of cracks and delamination.

FIG. 11 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the first modification.

As shown in FIG. 11, in the terminal electrode 20 according to the first modification, the side surfaces 22 are not all inclined, but the inclined surface 22A located on the mounting surface 10a side and the vertical surface 22 located on the main surface 21 side. It differs from the shape of the terminal electrode 20 shown in FIG. 2 in that it has a surface 22B. Even when the terminal electrode 20 has such a shape, the same effect as that of the above embodiment can be obtained.

The method for forming the terminal electrode 20 having the shape of FIG. 11 is not particularly limited, but as shown in FIG. 12, a positive photoresist 31P is formed on the main body 10 of the electronic component 1, and light is emitted through the mask 32. By irradiating 33, the photoresist 31P is patterned into the shape shown in FIG. At the time of development, if the photoresist 31P remains at the bottom of the opening 31a by setting the development conditions weakly, it is possible to form the opening 31a whose width becomes narrower from the middle in the depth direction. Then, if the terminal electrode 20 is formed in the opening 31a by electrolytic plating, it is possible to form the terminal electrode 20 having the side surface 22 including the inclined surface 22A and the vertical surface 22B.

Alternatively, as shown in FIG. 14, a negative type photoresist 31N is formed on the main body 10 of the electronic component 1, and light 33 is irradiated through the mask 32 to form the photoresist 31N into the shape shown in FIG. Patterning may be used. Also in this case, by setting the developing conditions weakly, it is possible to form the opening 31a whose width becomes narrower from the middle in the depth direction.

FIG. 15 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the second modification.

As shown in FIG. 15, the terminal electrode 20 according to the second modification has a portion where the diameter of the terminal electrode 20 decreases as it approaches the mounting surface 10a and a portion where the diameter of the terminal electrode 20 increases as it approaches the mounting surface 10a. have. That is, the side surface 22 has an inclined surface 22A corresponding to a portion where the diameter of the terminal electrode 20 decreases as it approaches the mounting surface 10a, and an inclined surface 22C corresponding to a portion where the diameter of the terminal electrode 20 increases as it approaches the mounting surface 10a. Consists of. In the example shown in FIG. 15, the inclined surface 22A is located on the main surface 21 side, and the inclined surface 22C is located on the mounting surface 10a side. Even when the terminal electrode 20 has such a shape, the same effect as that of the above embodiment can be obtained.

In order to form the terminal electrode 20 having the shape shown in FIG. 15, as described with reference to FIG. 6, the intensity of the light 33 is set to be stronger in the state where the positive photoresist 31P is formed, or As described with reference to FIG. 8, the shape of the opening 31a is formed by adjusting the development conditions to be weak after setting the intensity of the light 33 to be weak in the state where the negative photoresist 31N is formed. The shape shown in. Then, if the terminal electrode 20 is formed in the opening 31a by electrolytic plating, the terminal electrode 20 having the shape shown in FIG. 15 can be formed.

FIG. 17 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the third modification.

As shown in FIG. 17, the terminal electrode 20 according to the third modification is different from the second modification shown in FIG. 15 in that the positions of the inclined surface 22A and the inclined surface 22C are opposite to each other. Even when the terminal electrode 20 has such a shape, the same effect as that of the above embodiment can be obtained.

In order to form the terminal electrode 20 having the shape shown in FIG. 17, as shown in FIG. 18, the intensity of the light 33 is set to be weak in the state where the negative photoresist 31N is formed, and then the development conditions are weakened. By adjusting, the shape of the opening 31a is made into the shape shown in FIG. Then, if the terminal electrode 20 is formed in the opening 31a by electrolytic plating, the terminal electrode 20 having the shape shown in FIG. 17 can be formed.

FIG. 20 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the fourth modification.

As shown in FIG. 20, the terminal electrode 20 according to the fourth modification has a shape in which the diameter of the terminal electrode 20 changes at a certain thickness position. The side surface 22 is located on the main surface 21 side and corresponds to the large diameter portion of the vertical surface 22B _1, and is located on the mounting surface 10a side and corresponds to the small diameter portion of the vertical surface 22B ₂ and the vertical surface 22B _1. It is composed of a horizontal plane 22D connecting the vertical plane 22B ₂ and the vertical plane 22B ₂ . Even when the terminal electrode 20 has such a shape, the same effect as that of the above embodiment can be obtained. The terminal electrode 20 having such a shape can be obtained by performing exposure using a photoresist in two steps.

FIG. 21 is a cross-sectional view for explaining the shape of the terminal electrode 20 according to the fifth modification.

As shown in FIG. 21, the terminal electrode 20 according to the fifth modification has a portion where the diameter is constant regardless of the distance from the mounting surface 10a and a portion where the diameter of the terminal electrode 20 decreases as it approaches the mounting surface 10a. have. The side surface 22 is composed of a vertical surface 22B corresponding to a portion having a constant diameter, an inclined surface 22A corresponding to a portion having a reduced diameter, and a horizontal surface 22E connecting the vertical surface 22B and the inclined surface 22A. Even when the terminal electrode 20 has such a shape, the same effect as that of the above embodiment can be obtained. The terminal electrode 20 having such a shape can also be obtained by performing exposure using a photoresist in two steps.

In the present embodiment, the substrate on which the electronic component 1 is mounted does not have to be a simple circuit board, and may be another electronic component 1A as shown in FIG. The other electronic component 1A may be a passive circuit component such as a capacitor, an inductor, a resistor, or a filter, or may be an active circuit component such as a transistor or a semiconductor IC. Further, it may be a module component in which a plurality of passive circuit components and a plurality of active circuit components are integrated, or may be a wiring board on which a wiring layer is formed.

The terminal electrode 20 included in another electronic component 1A may have the same shape as the terminal electrode 20 of the electronic component 1. According to this, since both the overhang portion of the terminal electrode 20 of the electronic component 1 and the overhang portion of the terminal electrode 20 of the electronic component 1A are covered with the connecting conductor material 5, the electronic component 1 and the electronic component 1A are joined. It is possible to increase the strength.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention, and these are also the present invention. Needless to say, it is included in the range.

Twenty sample A of Example 1 were prepared by mounting thin film capacitors having the structures shown in FIGS. 1 and 2 on an evaluation organic substrate having a thickness of 1 mm. The plane size of the thin film capacitor is 1.6 mm × 0.8 mm, and the thickness is 0.8 mm. The plane size of the terminal electrode provided on the thin film capacitor is 0.4 mm × 0.7 mm. Further, the side surface of the terminal electrode having the reverse taper shape is curved rather than a completely flat surface, and the angle θ is in the range of 30 ° to 70 °. The height of the solder after mounting was controlled to 20 μm.

Twenty samples B1 of Comparative Example 1 having the same structure as the above sample A were prepared except that the side surfaces of the terminal electrodes were vertical.

Twenty samples B2 of Comparative Example 2 having the same structure as that of the above sample A were prepared except that they had a forward taper shape in which the angle θ of the side surface of the terminal electrode was 110 ° to 150 °.

After reflowing these samples A, B1 and B2 eight times at 250 ° C., they are fixed to an aluminum housing weighing 130 g with bolts, and from a height of 170 cm, in the x-direction, -x-direction, and y-direction. , -Y direction, z direction, and -z direction, 50 times each, for a total of 300 times, free-falling onto the concrete surface. The impact load of free fall in this test is estimated to be equivalent to 3000G.

After that, when an open failure check of the electrical connection was performed, it was confirmed that there was no failure in all 20 samples A of Example 1. On the other hand, sample B1 of Comparative Example 1 was found to have one failure per 20 pieces, and Sample B2 of Comparative Example 2 was found to have three failures per 20 pieces.

1,1A Electronic component 2 Electronic component mounting board 3 Board 4 Land pattern 5 Connection conductor material 10 Main body 10a Mounting surface 11 Board 12 Functional layer 13 Insulation layer 14 Connection 20 Terminal electrode 21 Main surface 22, 22a, 22b Side surface 22A Inclined Surface 22B Vertical surface 22B ₁ Vertical surface 22B ₂ Vertical surface 22C Inclined surface 22D Horizontal surface 22E Horizontal surface 23 Corner 31N photoresist (negative type)
31P photoresist (positive type)
31a opening 32 mask 33 light

Claims (5)

The main body with the mounting surface and
It is provided with a flat terminal electrode that is provided so as to project from the mounting surface and has a main surface and a side surface parallel to the mounting surface.
An electronic component characterized in that the terminal electrode has a portion whose diameter decreases as it approaches the mounting surface, whereby at least a part of the side surface has an overhang shape. The electronic component according to claim 1, further comprising a connecting conductor material provided on the main surface of the terminal electrode and having a melting point lower than that of the terminal electrode. The electronic component according to claim 2, wherein the connecting conductor material covers the side surface of the terminal electrode having an overhang shape. A substrate with a land pattern and
The electronic component according to claim 3 mounted on the substrate is provided.
An electronic component mounting substrate, characterized in that the land pattern and the terminal electrode are connected via the connecting conductor material. The electronic component mounting substrate according to claim 4, wherein the thickness of the connecting conductor material located between the land pattern and the terminal electrode is 30 μm or less.

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