Electronic component and method of mounting the same

An electronic component achieves significantly improved adhesion strength between an external electrode and a substrate body and includes an insulative substrate body, at least one groove disposed in at least one main surface of the substrate body, at least one external electrode disposed on the at least one main surface of the substrate body, wherein a portion of the at least one external electrode is disposed in at least a portion of the groove.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electronic components and, more particularly, to an electronic component including an external electrode.

2. Description of the Related Art

In a wiring board in which an external electrode is formed on a substrate body made of, for example, resin or ceramics, it is necessary to ensure the adhesion strength of the external electrode on the substrate body so that the external electrode is not detached from the substrate body after the wiring board is mounted.

For example, in a multilayer substrate100shown in a cross-sectional view inFIG. 9, the surface roughness of a surface that is in contact with a substrate body110made of resin of each external electrode121that is externally exposed on the front and rear surfaces of the substrate body110is set to a value higher than the surface roughness of the internal electrode pattern. Accordingly, the anchor effect for the substrate body110is increased to improve the adhesion strength of the external electrode121(for example, refer to Japanese Unexamined Patent Application Publication No. 2006-344828).

However, since the surfaces of copper foils each having a thickness of 35 μm are roughened by, for example, surface treatment to be used as the external electrodes in this multilayer substrate, the surface roughness in the multilayer substrate is not so great. Particularly, when the external electrodes are reduced in size, the external electrodes may not have a sufficient adhesion strength with the multilayer substrate. In addition, since the surfaces of the copper foils are uniformly roughened by the surface treatment or the like, the external electrodes have a direction that is weak in an impact applied from, for example, a side surface of the multilayer substrate mounted on a printed circuit board or the like due to the shapes of the electrodes and the chips, and the improvement effect of the adhesion strength against the impact from the direction is reduced.

SUMMARY OF THE INVENTION

In order to solve the above problems, preferred embodiments of the present invention provide an electronic component having a further improved adhesion strength between an external electrode and a substrate body.

According to a preferred embodiment of the present invention, an electronic component includes an insulative substrate body, at least one groove formed in at least one main surface of the substrate body, and at least one external electrode arranged on the at least one main surface of the substrate body and a portion of which is disposed in at least a portion of the groove.

Since the portion of the external electrode disposed on the one main surface of the substrate body in the above configuration is disposed in at least a portion of the groove or the entire groove to increase the resistance force, compared with the case in which the surface of the external electrode toward the substrate body is roughened, the adhesion strength between the external electrode and the substrate body is significantly increased.

The adhesion strength between the external electrode and the substrate body is greatly increased particularly against a force vertical to the direction in which the groove extends. Accordingly, forming the groove so as to extend vertically relative to the direction in which the adhesion strength between the external electrode and the substrate body is small allows the adhesion force to be increased especially in the direction in which the adhesion strength is small.

Preferably, the substrate body includes at least one set of grooves that are formed in the one main surface and that extend in parallel or substantially in parallel to each other.

Preferably, at least two sets of grooves that extend in parallel or substantially in parallel to each other are provided and the grooves in one set intersect with the grooves in the other set. Also preferably, the portion of the external electrode is disposed in at least a portion of the grooves in the one set and at least a portion of the grooves in the other set.

In the above case, the adhesion strength can be increased in multiple directions due to the grooves that intersect with each other. For example, the above configuration is effective in a case in which the adhesion strength is small in multiple directions. In addition, the adhesion strength can be entirely increased in all the directions.

More preferably, the grooves in the one set are perpendicular or substantially perpendicular to the grooves in the other set.

The grooves that are perpendicular or substantially perpendicular to each other can be easily formed, compared with the grooves that intersect with each other at an angle.

Preferably, the one main surface of the substrate body has a rectangular or substantially rectangular shape having one pair of longer sides and one pair of shorter sides. Also preferably, the at least one groove is arranged so as to extend in parallel or substantially in parallel to the longer sides of the one main surface of the substrate body.

When one main surface of the substrate body of an electronic component has a rectangular or substantially rectangular shape, the adhesion strength between the external electrode and the substrate body when a force perpendicular or substantially perpendicular to the longer sides of the one main surface of the substrate body is exerted along the one main surface of the substrate body may be smaller than the adhesion strength between the external electrode and the substrate body when a force perpendicular or substantially perpendicular to the shorter sides of the one main surface of the substrate body is exerted along the one main surface of the substrate body due to, for example, the difference in length of the moment arm.

In contrast, when multiple external electrodes are arranged on the longer sides of the one main surface of the substrate body, the adhesion strength between the external electrode and the substrate body when a force perpendicular or substantially perpendicular to the shorter sides of the one main surface of the substrate body is exerted may be smaller than that when a force perpendicular or substantially perpendicular to the longer sides of the one main surface of the substrate body is exerted.

When the groove extends vertically to the exerted force and a portion of the external electrode is disposed in the groove in the above case, as in the above configuration, the resistance force applied when a force perpendicular or substantially perpendicular to a certain side of the one main surface of the substrate body is exerted along the one main surface of the substrate body can be increased to increase the adhesion strength between the external electrode and the substrate body.

Preferably, the one main surface of the substrate body has a rectangular or substantially rectangular shape having one pair of longer sides and one pair of shorter sides, the external electrode is disposed on each of the pair of shorter sides of the substrate body, and the at least one groove is formed so as to extend in parallel or substantially in parallel to the longer sides of the one main surface of the substrate body.

Preferably, the external electrode has a main surface of a rectangular or substantially rectangular shape having one pair of longer sides and one pair of shorter sides. Also preferably, the at least one set of grooves is arranged so as to extend in parallel or substantially in parallel to the longer sides of the main surface of the external electrode.

When the main surface of the external electrode has a rectangular or substantially rectangular shape, the adhesion strength between the external electrode and the substrate body when a force perpendicular or substantially perpendicular to the longer sides of the main surface of the external electrode is exerted along the main surface of the external electrode may be smaller than that when a force perpendicular or substantially perpendicular to the shorter sides of the main surface of the external electrode is exerted along the main surface of the external electrode.

When the groove extends in parallel or substantially in parallel to the longer sides of the external electrode and a portion of the external electrode enters the groove in the above case, as in the above configuration, the resistance force applied when a force perpendicular or substantially perpendicular to the longer sides of the external electrode is exerted along the main surface of the external electrode can be increased to increase the adhesion strength between the external electrode and the substrate body.

Preferably, the substrate body has a rectangular or substantially rectangular shape, a plurality of external electrodes are arranged so as to extend in parallel or substantially in parallel to at least one side of the substrate body, and the at least one groove is arranged so as to be substantially perpendicular to the direction in which the plurality of external electrodes extend.

Preferably, the one main surface of the substrate body includes a high-density distribution area in which the external electrodes are distributed at a relatively high density and a low-density distribution area in which the external electrodes are distributed at a relatively low density. Also preferably, the interval between the grooves where the portion of the external electrodes in the low-density distribution area is disposed therein is shorter than the interval between the grooves where the portion of the external electrodes in the high-density distribution area is disposed therein.

Decreasing the interval of the grooves corresponding to the external electrodes in the low-density distribution area allows the number of the grooves to be increased and allows the adhesion strength per unit area of the external electrodes in the low-density distribution area to be greater than the adhesion strength per unit area of the external electrodes in the high-density distribution area. Stress, such as an impact, tends to increase in the external electrodes in the low-density distribution area and tends to decrease in the external electrodes in the high-density distribution area. Accordingly, making the adhesion strength per unit area of the external electrodes in the low-density distribution area greater than that of the external electrodes in the high-density distribution area allows the adhesion strength to be entirely increased.

Preferably, the grooves are located near a peripheral line of the one main surface of the substrate body.

When the electronic component is mounted on another substrate, the stress between the external electrode and the substrate body is maximized near the peripheral line of the main surface at the mounting side. Configuring the electronic component so that the groove is disposed in the area where the maximum stress is applied and a portion of the external electrode is disposed in the groove allows the adhesion strength between the external electrode and the substrate body to be increased.

Preferably, the depth of the grooves relatively close to the peripheral line of the one main surface of the substrate body is greater than the depth of the grooves relatively far from the peripheral line of the one main surface of the substrate body.

The adhesion strength of the external electrodes can be increased with the increasing depth of the grooves where a portion of the external electrodes is disposed therein. Since the stress applied between the external electrode and the substrate body is increased with the decreasing distance from the peripheral line of the main surface of the substrate body, the depth of the grooves is increased with the decreasing distance from the peripheral line of the main surface of the electronic component to increase the adhesion strength between the external electrode and the substrate body. This allows the adhesion strength to be made uniform as much as possible.

Preferably, the external electrode is a land grid array (LGA) electrode, for example.

Since it is difficult to increase the electrode area to increase the adhesion strength in the LGA electrode having a smaller electrode area, adopting the configuration in which a portion of the external electrode is disposed in the grooves to increase the adhesion strength has a particularly large effect.

In addition, another preferred embodiment of the present invention provides a method of mounting the electronic component having any of the above configurations, in which the one main surface of the substrate body where the groove is provided is used as a mounting surface.

According to various preferred embodiments of the present invention, since at least a portion of the external electrode is disposed in the groove provided in the substrate body, it is possible to further increase the adhesion strength between the external electrode and the substrate body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary preferred embodiments of the present invention will herein be described with reference toFIGS. 1 to 8C.

First Preferred Embodiment

An electronic component10of a first preferred embodiment will now be described with reference toFIGS. 1 to 3B.

As shown in a cross-sectional view inFIG. 1, the electronic component10of the first preferred embodiment is a surface mount device in which external electrodes20are provided at both sides of a substrate body12. The substrate body12includes multiple grooves14that are parallel or substantially parallel to each other in a rear surface12a, which is one main surface at a side where the electronic component10is mounted. The grooves14are preferably located in areas close to a peripheral line12kof the rear surface12aof the substrate body12. Each external electrode20is formed so that portions24of the external electrode20enter the grooves14.

For example, when the substrate body12is a ceramic multilayer substrate, the grooves14are formed in advance on a ceramic green sheet by, for example, laser processing; a rear electrode22is arranged so that the material of the electrode enters the grooves14; the ceramic green sheet is laminated on other ceramic green sheets; and the ceramic green sheets are fired. After the ceramic multilayer substrate subjected to the firing is divided into chips, the external electrode20is preferably arranged on a front surface12band/or an end surface12c, if needed.

The material of the substrate body12is not limited to ceramics and the substrate body12may be made of any material, such as resin or glass, which is generally used as the material of insulating layers and/or dielectric layers of electronic components. In addition, the substrate body12may have a single layer or multiple layers.

The method of forming the grooves14is not limited to the laser processing, and the grooves14may be formed by any method in which a cutting blade, such as a dicing blade, can be used to make cuts each having arbitrary depth and shape at arbitrary portions, for example.

When the grooves are formed by the laser processing, the laser may be scanned to form the grooves or successive depressions are formed with the laser to form the grooves. When the grooves are formed from the depressions, adjacent depressions may be overlapped with each other to form each groove or the depressions may be spaced apart by a predetermined distance to form each groove.

The external electrode20may be formed by printing and applying a paste, may be formed of a thin film by, for example, sputtering, or may be formed by spraying with, for example, an inkjet device.

The grooves14and the external electrode20may be formed at any timing. For example, the grooves14and the external electrode20may be formed on sheets before the lamination, may be formed after the lamination, or may be formed after the substrate is divided in the chips. In addition, the grooves14and the external electrode20may be formed before the firing or after the firing.

For example, with the lamination method, as shown in a cross-sectional view inFIG. 3A, grooves14smay be formed in the state of sheets11ato11dbefore the lamination. Alternatively, as shown in a cross-sectional view inFIG. 3B, grooves14tmay be formed in a multilayer body11resulting from integration of laminated sheets.

The configuration in which the portions24of the external electrode20are disposed in the grooves14, as in the electronic component10, is applicable to every chip size and every terminal arrangement. The configuration is also applicable to a land grid array (LGA)-type electronic component, for example.

The grooves14may be formed at any portions where the external electrode20can be joined. Specifically, the portion where the grooves14are formed is not limited to the rear surface12aand may be formed on the front surface12bor the end surface12c. The number and direction of the grooves14are not particularly specified or limited.

When the surface of the external electrode toward the substrate body is roughened, the adhesion strength is increased with the increasing contact area to increase the fixing force. In contrast, when the grooves14are formed in the manner in the first preferred embodiment, the contact area is increased and the resistance force against a force that is applied in parallel or substantially in parallel or vertically to the mounting surface, that is, the rear surface12ais applied because the portions24of the external electrode20enter the grooves14. Accordingly, the adhesion strength between the external electrode20and the substrate body12is significantly increased.

When the electronic component10is mounted on another substrate, the stress between the external electrode20and the substrate body12is maximized in the area close to the peripheral line12kof the rear surface12a, which is the main surface at the mounting side. Configuring the electronic component so that the grooves14are formed in the area close to the peripheral line12kwhere the maximum stress is applied and the portions24of the external electrode20disposed in the grooves14allows the adhesion strength between the external electrode20and the substrate body12to be increased.

A graph inFIG. 2illustrates an example of the result of experiments indicating the relationship between the adhesion force of the external electrode and the surface treatment state. Referring toFIG. 2, ♦ denotes each value in a case in which the surface of the external electrode toward the substrate body is not particularly processed, ▪ denotes each value in a case in which the surface of the external electrode toward the substrate body is processed at a surface roughness of about 3 μm, ▴ denotes each value in a case in which the surface is processed so that a portion of the external electrode is disposed in the grooves that each have a depth of about 8 μm and that are formed in the substrate body, and x denotes each value in a case in which the surface is processed so that a portion of the external electrode is disposed in the grooves that each have a depth of about 13 μm and that are formed in the substrate body. A broken line connects the average values in the respective cases. The electrode adhesion force represented as the vertical axis indicates the measured value of the magnitude of each force applied when a force that is parallel or substantially parallel to the mounting surface and that is opposite to the force applied to the mounting surface is exerted between a sample and another substrate in a state in which the external electrode of the sample is mounted on the other substrate to cause the external electrode of the sample to be detached from the substrate body.

The graph inFIG. 2shows that the configuration in which a portion of the external electrode enters the grooves has an adhesion strength greater than that of the configuration in which the surface of the external electrode is roughened. In addition, the variation in the adhesion strength is reduced in the configuration in which a portion of the external electrode is disposed in the grooves to improve the quality of the electronic component. Furthermore, the graph inFIG. 2shows that the adhesion strength is increased with the increasing depth of the grooves. In order to achieve an electrode adhesion force of about 30 N or greater, it is sufficient to set the depth of the grooves to a value not lower than about 5 μm, for example. It is more preferable to form the grooves having a depth of about 8 μm or higher, for example.

The adhesion strength of the external electrode20can be increased with the increasing depth of the grooves14where the portions24of the external electrode20are disposed therein. Since the stress applied between the external electrode and the substrate body12is increased with the decreasing distance from the peripheral line12kof the rear surface12aof the substrate body12, the depth of the grooves14may be increased with the decreasing distance from the peripheral line12kto increase the adhesion strength between the external electrode20and the substrate body12. In this case, it is possible to make the adhesion strength as uniform as possible.

Second Preferred Embodiment

An electronic component of a second preferred embodiment will now be described with reference toFIG. 4.

FIG. 4is a perspective view of the main portion, schematically showing an external electrode23and grooves15disposed in the substrate body. The multiple grooves15are preferably arranged so as to be parallel or substantially parallel to each other. A portion of the external electrode23is disposed in the grooves15in a portion where the grooves15are covered with the external electrode23.

The adhesion strength of the external electrode23is increased against a force indicated by an arrow18inFIG. 4, that is, a force that is vertically exerted with respect to the direction in which the grooves15extend, compared with the case where the grooves15are not formed. Accordingly, the grooves15that vertically extend with respect to the direction in which the adhesion strength of the external electrode23is small are disposed in the area of the substrate body where the external electrode23is located.

The fixing force of an electronic component is varied due to the effect of, for example, the chip size, the arrangement of terminals, the area (width) of the external electrode, and/or the configuration of the external electrode (the presence of an end surface electrode portion). Configuring the electronic component so that the grooves are arranged so as to vertically extend with respect to the direction in which the adhesion strength of the external electrode is small and a portion of the external electrode is disposed in the grooves allows the adhesion strength to be increased especially in the direction in which the adhesion strength of the external electrode is small.

Third Preferred Embodiment

An electronic component of a third preferred embodiment will now be described with reference toFIG. 5.

As schematically shown in a perspective view of the main portion inFIG. 5, grooves15a,15c, and15cin multiple directions are provided in the substrate body and the grooves15a,15b, and15care covered with the external electrode23. A portion of the external electrode23is disposed in the grooves15a,15c, and15cin portions where the grooves15a,15c, and15care covered with the external electrode23. The multiple grooves15a,15c, and15care preferably arranged so as be parallel or substantially parallel to each other. The grooves are preferably arranged in two or more directions, and the directions of the grooves may be perpendicular or substantially perpendicular to each other, for example.

The adhesion strength of the external electrode23is increased against forces in the directions indicated by arrows18a,18b, and18cinFIG. 5, that is, forces that are vertically exerted with respect to the respective directions in which the grooves15a,15b, and15cextend.

The formation of the grooves in the multiple directions allows the adhesion strength to be entirely increased not only in a specific direction where the adhesion strength of the external electrode is small but also in all the directions.

Fourth Preferred Embodiment

An electronic component of a fourth preferred embodiment will now be described with reference toFIGS. 6A-6C.

FIG. 6Ais a perspective view of the main portion, schematically showing the relationship between grooves15xand15ydisposed in the substrate body and the external electrode23.FIG. 6Bis a cross-sectional view of the main portion, showing the cross section of the grooves15xprovided in the substrate body12.FIG. 6Cis a cross-sectional view of the main portion, showing the cross section of the grooves15yprovided in the substrate body12.

As shown inFIG. 6A, in the substrate body12, the multiple grooves15xare preferably arranged in parallel or substantially parallel to each other along the longer side of the rectangular external electrode23and the multiple grooves15yare arranged in parallel or substantially in parallel to each other along the shorter side of the external electrode23. Although the grooves15xand15yare preferably configured to have a V shape, for example, that is, the widths of the grooves15xand15yare decreased with the increasing depths, as shown inFIGS. 6B and 6C, the grooves15xand15ymay have a constant width regardless of the depths, as in the first preferred embodiment.

When the grooves are arranged in multiple directions, the grooves are preferably formed so that the depth of the grooves vertically extending with respect to the direction in which the adhesion strength of the external electrode23is small is greater than the depth of the other grooves. For example, when the adhesion strength of the external electrode23is small against the force in the longitudinal direction inFIG. 6A, the grooves15xare arranged so that the depth of the grooves15xlaterally extending inFIG. 6Ais greater than the depth of the other grooves15y.

Varying the depths of the grooves in multiple directions depending on the directions of the grooves allows the adhesion strength of the external electrode23to be completely improved and allows for the improvement especially in the direction in which the adhesion strength of the external electrode23is small.

When the external electrode23has a rectangular or substantially rectangular main surface, the adhesion strength between the external electrode23and the substrate body12when a force perpendicular or substantially perpendicular to a longer side23xof the main surface of the external electrode23is exerted along the main surface of the external electrode23may be smaller than that when a force perpendicular or substantially perpendicular to a shorter side23yof the main surface of the external electrode23is exerted along the main surface of the external electrode23.

When a portion of the external electrode23is caused to enter the grooves15xextending in parallel or substantially in parallel to the longer side23xof the external electrode23in the above case, it is possible to increase the resistance force against the force that is exerted along the main surface of the external electrode23and that is perpendicular or substantially perpendicular to the longer side23xof the external electrode23, thus increasing the adhesion strength between the external electrode23and the substrate body12.

In addition, the grooves15xand15ythat are perpendicular or substantially perpendicular to each other can be easily formed, compared with the grooves that intersect with each other at an angle with respect to each other.

Fifth Preferred Embodiment

An electronic component10aof a fifth preferred embodiment will now be described with reference toFIG. 7.

As shown in a cross-sectional view inFIG. 7, the electronic component10aof the fifth preferred embodiment preferably is an LGA component in which each external electrode20ais disposed inwardly from the peripheral line12kof the rear surface12aof the substrate body12by a distance12s. The substrate body12is preferably constructed so that the multiple grooves14that are parallel or substantially parallel to each other are arranged in areas close to the peripheral line12kand portions24aof each external electrode20aare disposed in the grooves14, as in the electronic component10of the first preferred embodiment.

Since the area of the electrodes cannot be increased in the LGA component, it is difficult to ensure the adhesion strength of the external electrodes. However, configuring the LGA component so that the grooves are provided in the substrate body and portions of the external electrodes are disposed in the grooves allows the adhesion strength of the external electrodes to be increased.

Particularly, as shown inFIG. 10, there are cases in which the external electrodes20bare not uniformly distributed on one main surface12aof the substrate body12in the LGA component. In such cases, it is preferred that the interval of the grooves15sand15twhere portions of the external electrodes20benter in a low-density distribution area12L in which the external electrodes20bare distributed at a relatively low density be shorter than the interval of the grooves15sand15twhere portions of the external electrodes20benters in a high-density distribution area12H in which the external electrodes20bare distributed at a relatively high density. As used herein, the term “density” means the percentage of a particular area, i.e., the low-density distribution area12L or the high-density distribution area12H, that is occupied by the external electrode(s).

The LGA electrode may preferably include the end surfaces of via holes. In such a case, the grooves may be arranged in the end surfaces of the via holes in order to increase the adhesion strength of the LGA electrode.

As shown inFIG. 10, decreasing the interval of the grooves15sand15tcorresponding to the external electrodes20bin the low-density distribution area12L allows the number of the grooves to be increased and allows the adhesion strength per unit area of the external electrodes20bin the low-density distribution area12L to be greater than the adhesion strength per unit area of the external electrodes20bin the high-density distribution area12H. Stress, such as an impact, tends to increase in the external electrodes20bin the low-density distribution area12L and tends to decrease in the external electrodes20bin the high-density distribution area12H. Accordingly, making the adhesion strength per unit area of the external electrodes20bin the low-density distribution area12L greater than that of the external electrodes20bin the high-density distribution area12H allows the adhesion strength to be entirely increased.

Sixth Preferred Embodiment

An electronic component10bof a sixth preferred embodiment will now be described with reference toFIGS. 8A-8C.

FIG. 8Ais a plan view of the electronic component10b.FIGS. 8B and 8Care plan views of the substrate body12of the electronic component10a.

As shown inFIG. 8A, in the electronic component10b, four rectangular or substantially rectangular external electrodes21a,21b,21c, and21dare disposed on the rectangular or substantially rectangular rear surface12aof the substrate body12. As shown inFIG. 8B, straight grooves15sand15tthat are perpendicular or substantially perpendicular to each other are provided in areas corresponding to the areas where the external electrodes21a,21b,21c, and21dare disposed in the rear surface12aof the substrate body12.

As shown inFIG. 8C, the grooves15sand15tmay be arranged so as to protrude outwardly from the areas where the external electrodes21a,21b,21c, and21dare provided. When the grooves are also provided in areas other than the areas where the external electrodes are disposed in the above manner, advantages in processing may be achieved. For example, the necessity of processing accuracy of the grooves can be alleviated.

When the substrate body12of the electronic component10bhas the rectangular or substantially rectangular rear surface12a, the adhesion strength between the external electrodes21ato21dand the substrate body12when a force perpendicular or substantially perpendicular to a longer side12xof the rear surface12ais exerted (exerted longitudinally in the drawings) along the rear surface12aof the substrate body12may be smaller than the adhesion strength between the external electrodes21ato21dand the substrate body12when a force perpendicular or substantially perpendicular to a shorter side12yof the rear surface12ais exerted (exerted laterally in the drawings) along the rear surface12aof the substrate body12due to, for example, the difference in length of the moment arm.

When the grooves15sextend in parallel or substantially in parallel to the longer side12xof the rear surface12aof the substrate body12and a portion of the external electrodes21ato21dis caused to be disposed in the grooves15sin the above case, it is possible to increase the resistance force against the force that is exerted along the rear surface12aof the substrate body12and that is perpendicular or substantially perpendicular to the longer side12xof the rear surface12a(longitudinally in the drawings), thus increasing the adhesion strength between the external electrodes21ato21dand the substrate body12.

As described above, configuring the electronic component so that the grooves are provided in the substrate body and portions of the external electrodes are disposed in the grooves allows the adhesion strength between the external electrodes and the substrate body against, for example, the force vertical to the direction in which the grooves extend to be significantly increased, compared with the case in which the surfaces of the external electrodes toward the substrate body are roughened.

The present invention is not restricted to the above preferred embodiments and may be embodied in various modes.