Method of manufacturing electronic component module and electronic component module

A method of manufacturing an electronic component module and the electronic component module manufactured by the manufacturing method includes bumps, each including a thicker portion having a relatively large thickness and a thinner portion having a relatively small thickness and formed on one surface of the substrate. When looking at the electronic component in a mounted state in a plan view, the thicker portion is positioned on a side of a corresponding outer terminal closer to a center of the electronic component and the thinner portion is positioned on the opposite side of the corresponding outer terminal. In the plan view, joining portions joining the outer terminals respectively to the bumps are formed such that a height of each joining portion on the opposite side is lower than a height of the joining portion on the side closer to the center of the electronic component.

TECHNICAL FIELD

The technical field relates to a method of manufacturing an electronic component module, the method being used to respectively join a plurality of outer terminals of an electronic component to a plurality of bumps provided on one surface of a substrate, and also relates to the electronic component module manufactured by the manufacturing method.

BACKGROUND

Japanese Unexamined Patent Application Publication No. 2004-228375 (Patent Document 1) discloses a method of forming bumps when a semiconductor is joined to a substrate with the bumps interposed between them.FIG. 1is a schematic sectional view illustrating a related-art method of manufacturing an electronic component module. In Patent Document 1, as illustrated inFIG. 1(a), a bump6is formed on a surface electrode10of a substrate9by ejecting a metal paste4from an ink head3and by drying the metal paste4.

Next, as illustrated inFIG. 1(b), outer terminals2of a bare IC (i.e., an electronic component provided with outer terminals)1are aligned to face the bumps6on the substrate9, respectively. Furthermore, as illustrated inFIG. 1(c), the bare IC1is placed on the substrate9, and the outer terminals2are joined to the bumps6, respectively, by applying pressure and heat to such an extent that the bumps6are deformed. The bare IC1is thus mounted to the substrate9.

SUMMARY

The present disclosure provides a method of manufacturing an electronic component module in which joining portions joining a plurality of outer terminals of an electronic component and a plurality of surface electrodes of a substrate are not contacted with a lateral surface of the electronic component, and to provide the electronic component module manufactured by the manufacturing method.

In an embodiment the present disclosure, a method of manufacturing an electronic component module, the method being used to join a plurality of outer terminals of an electronic component respectively to a plurality of bumps provided on one surface of a substrate, the method comprising the steps of forming, on the one surface of the substrate, the plural bumps such that each bump includes a thicker portion having a relatively large thickness and a thinner portion having a relatively small thickness, and that, when looking at the electronic component in a mounted state in a plan view, the thicker portion is positioned on side closer to a center of the electronic component relative to corresponding one of the outer terminals, and the thinner portion is positioned on opposite side away from the center of the electronic component relative to the corresponding outer terminal, and forming a plurality of joining portions, which join the plural outer terminals respectively to the plural bumps, having been formed in the preceding step, through deformation of the bumps, such that a height of each joining portion on the opposite side away from the center of the electronic component when looking at the mounted electronic component in a plan view is lower than a height of the joining portion on the side closer to the center of the electronic component.

With the feature mentioned above, each of the plural bumps includes the thicker portion having a relatively large thickness and the thinner portion having a relatively small thickness. Each bump is formed on one surface of the substrate such that, when looking at the electronic component in a mounted state in a plan view, the thicker portion is positioned on the side closer to a center of the electronic component relative to corresponding one of the outer terminals, and the thinner portion is positioned on the opposite side away from the center of the electronic component relative to the corresponding outer terminal. The plural joining portions joining the plural outer terminals respectively to the plural bumps, having been formed in the preceding step, through deformation of the bumps are formed such that a height of each joining portion on the opposite side away from the center of the electronic component when looking at the mounted electronic component in a plan view is lower than a height of the joining portion on the side closer to the center of the electronic component. Therefore, the joining portions are avoided from contacting with lateral surfaces of the electronic component. Thus, even when an internal wiring of the electronic component is exposed at the lateral surfaces of the electronic component due to dicer cutting, characteristics of the electronic component do not degrade.

In a more specific embodiment of the method of manufacturing the electronic component module, each of the plural bumps may be formed in a stepped shape.

With the feature mentioned above, since the plural bumps are each formed in a stepped shape, the joining portions can be formed such that the height of each joining portion on the opposite side away from the center of the electronic component when looking at the mounted electronic component in a plan view is lower than the height of the joining portion on the side closer to the center of the electronic component. Therefore, the joining portions are avoided from contacting with the lateral surfaces of the electronic component. Thus, even when the internal wiring of the electronic component is exposed at the lateral surfaces of the electronic component due to dicer cutting, characteristics of the electronic component do not degrade.

In the method of manufacturing the electronic component module according to the present invention, preferably, the plural bumps are formed by an ink jet method.

In another embodiment, an electronic component module includes a substrate, a plurality of bumps provided on one surface of the substrate, an electronic component having a plurality of outer terminals, and a resin sealing surroundings of a plurality of joining portions which join the plural outer terminals respectively to the plural bumps through deformation of the bumps. The plural joining portions are formed such that a height of each joining portion on opposite side away from a center of the electronic component when looking at the electronic component module in a plan view is lower than a height of the joining portion on side closer to the center of the electronic component module.

In a more specific embodiment of the electronic component module, preferably, the plural bumps are formed in pairs at opposed positions symmetrical with respect to the center of the electronic component when looking at the electronic component in a plan view.

DETAILED DESCRIPTION

The inventors realized that with the related-art manufacturing method described above with respect to Patent Document 1, for example, when the bump6is formed in a relatively large thickness, there is a possibility that the deformed bump6may extend up to a lateral surface of the bare IC1, and electrical conduction may occur between the surface electrode10of the substrate9and an internal wiring of the bare IC1. Thus, the electronic component module manufactured by the related-art manufacturing method, described above, has a risk that characteristics of the bare IC1may degrade.

FIG. 2is a sectional view illustrating a structure of the electronic component module manufactured by the related-art manufacturing method. When the bump6is formed in a relatively large thickness, a joining portion7between the outer terminal2of the bare IC1and the surface electrode10of the substrate9is caused to extend up to the lateral surface of the bare IC1, and the joining portion7comes into contact with the lateral surface of the bare IC1. If chipping occurs in dicer cutting of the bare IC1, the internal wiring is often exposed at the lateral surface of the bare IC1. In such a case, the contact of the joining portion7with the lateral surface of the bare IC1causes electrical conduction between the surface electrode10of the substrate9and the internal wiring of the bare IC1. As a result, the characteristics of the bare IC1degrade.

An exemplary embodiment of the present disclosure that can address the above shortcomings will now be described in detail with reference to the drawings.

FIG. 3is a sectional view illustrating a structure of an electronic component module, in a state before mounting of a bare IC, according to an exemplary embodiment. As illustrated inFIG. 3, a surface electrode10is provided on one surface of a substrate9, and a bump6is formed in a stepped shape on the surface electrode10.

In more detail, the bump6includes a thinner portion61having a relatively small thickness, and a thicker portion62having a relatively large thickness. The thicker portion62and the thinner portion61are formed on the one surface of the substrate9such that, when an electronic component is mounted, the thicker portion62is positioned on the side closer to a center of the electronic component relative to a corresponding outer terminal2when looking at the mounted electronic component in a plan view, and the thinner portion61is positioned on the opposite side away from the center of the electronic component relative to the corresponding outer terminal2when looking at the mounted electronic component in a plan view. The following description is made in connection with an example in which a bare IC in the form of an electronic component provided with outer terminals is mounted.

FIG. 4is a sectional view illustrating a structure of the electronic component module according to the exemplary embodiment. After aligning the outer terminals2of a bare IC1to face the bumps6on the substrate9, respectively, the bare IC1is placed on the substrate9, and the outer terminals2are joined to the bumps6, respectively, by applying pressure and heat to such an extent that the bumps6are deformed, as illustrated inFIG. 4. The bare IC1is thus mounted to the substrate9.

In this embodiment, a portion joining the outer terminal2and the bump6to each other through deformation of the bump6is denoted by a joining portion7. The joining portion7is formed in a state having a lower height in its region on the opposite side away from the center of the bare IC1when looking at the mounted bare IC1in a plan view than that in its region on the side closer to the center of the substrate9when looking at the mounted bare IC1in a plan view. Accordingly, the deformed bump6is avoided from extending up to a lateral surface of the bare IC1. As a result, even when chipping occurs in dicer cutting of the bare IC1and an internal wiring of the bare IC1is exposed at the lateral surface of the bare IC1, electrical conduction between the surface electrode10of the substrate9and the internal wiring of the bare IC1is not caused. Hence characteristics of the bare IC1do not degrade.

A method of manufacturing the electronic component module according to this embodiment will be described in detail below.FIG. 5is an enlarged sectional view illustrating a part of the substrate9. The substrate9is formed of a flexible resin. As illustrated inFIG. 5, the surface electrode10is provided on the one surface of the substrate9. The surface electrode10is constituted by forming an Au plating101over a nickel layer102and a copper layer103, the latter two serving as ground coatings.

The bump6is formed in a desired shape on the Au plating101by ejecting a metal paste from an ink head. For example, an Ag paste is used as the metal paste. The thinner portion61and the thicker portion62having different thicknesses from each other can be easily formed by adjusting the number of times the metal paste is ejected.

Of course, a method of forming the bump6is not limited to the ink jet method. As another example, the bump6may be formed by the screen printing method. When the bump6is formed by the screen printing method, it is required to, after forming the thinner portion61, dry the printed thinner portion61and then form the thicker portion62on a part of the thinner portion61after replacing a screen plate. On the other hand, when the bump6is formed by the ink jet method, the thinner portion61and the thicker portion62can be both formed in a continuous step, and the production cost can be reduced.

The outer terminal2of the bare IC1has the shape of an inverted truncated cone and is formed by providing an Au wire bump on an Al pad that is an outer electrode of the bare IC1. In this embodiment, the Au wire bump has an outer diameter of 85 μm and a height of 25 μm. An Au plated bump, a Cu wire bump, or a Cu plated bump may be used instead of the Au wire bump. Furthermore, the outer terminal2may be formed in a disk-like shape with a plated bump.

FIGS. 6(a) to 6(e)are schematic sectional views illustrating a method of manufacturing the electronic component module according to the exemplary embodiment. As illustrated inFIG. 6(a), a metal paste4is first ejected from an ink head3onto the surface electrode10of the substrate9, thereby forming the thinner portion61as illustrated inFIG. 6(b). More specifically, the metal paste4is ejected while a table on which the ink head3or the substrate9is placed is moved. An Ag paste is used as the metal paste4, and one dot of the Ag paste ejected from the ink head3has a volume of 1 pl (1×10−15m3). In this embodiment, the thinner portion61having a thickness of 20 μm is formed by ejecting the metal paste4two times while the table on which the ink head3is placed is moved in the horizontal direction (right-to-left direction inFIG. 6).

Next, the thicker portion62is formed as illustrated inFIG. 6(c). When forming the thicker portion62, the metal paste4is ejected eight times while the table on which the ink head3is placed is moved in the horizontal direction. As a result, the bump6is formed with a thickness of 100 μm in its portion on the side closer to the center of the bare IC1when looking at the mounted bare IC1in a plan view. The formed bump6is then dried. Because the ejected metal paste4is a minute droplet, the formed bump6may be naturally dried without employing a special drying apparatus.

While a ratio of the thickness of the thicker portion62and the thickness of the thinner portion61is about 5:1 in this embodiment, the ratio is not limited to such a value. For example, the ratio may be set to, for example, 2:1 insofar as the deformed bump6is avoided from extending up to the lateral surface of the bare IC1when the bare IC1is mounted. Furthermore, in this embodiment, the thicker portion62has a width of 50 μm and the thinner portion61has a width of 100 μm in the horizontal direction (right-to-left direction inFIG. 6). However, the respective widths of the thicker portion62and the thinner portion61are not limited to those values, and the width of the thicker portion62may be set to 10 μm, for example.

After drying the formed bumps6, the outer terminals2of the bare IC (electronic component provided with outer terminals)1are aligned to face the bumps6on the substrate9, respectively. Next, as illustrated inFIG. 6(d), the bare IC1is placed on the substrate9, and the external terminals2are joined to the bumps6, respectively, by applying pressure and heat to such an extent that the bumps6are deformed. The bare IC1is thus mounted to the substrate9. In the above-mentioned alignment of the outer terminals2, a center of each outer terminal2of the bare IC1is positioned to be not overlapped with the thicker portion62. With such an arrangement, the deformed bump6is made less apt to extend up to the lateral surface of the bare IC1.

FIG. 7is a plan seeing-through view illustrating an arrangement of the bumps6in the electronic component module according to the exemplary embodiment. InFIG. 7, the outer terminals2of the bare IC1are each denoted by a white circle, and the bumps6are each denoted by a hatched area. The plural bumps6are arranged in pairs at opposed positions symmetrical with respect to a center71of the bare IC1when looking at the bare IC1in a plan view.

The thicker portions62of the bumps6are also formed in pairs at opposed positions symmetrical with respect to the center71of the bare IC1when looking at the bare IC1in a plan view. Accordingly, when the bare IC1is mounted, a pressing force can be applied in a balanced state, and the plural bumps6can be deformed in similar ways. It is hence possible to avoid bonding strength from being locally changed.

The shape of the bump6in a plan view is not limited to a rectangle as illustrated inFIG. 7.FIG. 8is a plan seeing-through view illustrating an arrangement of the bumps6in the electronic component module according to a modification of the exemplary embodiment when the bumps6have a different shape from that inFIG. 7. As illustrated inFIG. 8, the bump6may have a substantially elliptic shape in a plan view, by forming the thinner portion61having a substantially elliptic shape in a plan view, and the thicker portion62having a substantially elliptic shape in a plan view. In such a case, the bumps6are formed, similarly to the above-mentioned case, in pairs at opposed positions symmetrical with respect to the center71of the bare IC1when looking at the bare IC1in a plan view. Moreover, the thicker portions62of the bumps6are also formed in pairs at opposed positions symmetrical with respect to the center71of the bare IC1when looking at the bare IC1in a plan view.

The number of the outer terminals2is not limited to any particular one, and the least necessary number of the outer terminals2is two.FIG. 9is a plan seeing-through view illustrating an arrangement of the bumps6in the electronic component module according to the embodiment of the present invention when the bare IC1has two outer terminals2.

As illustrated inFIG. 9, when the number of the outer terminals2is two, the outer terminals2are each formed in a rectangular shape, when viewed in a plan view, in many cases from the viewpoint of mounting the bare IC1in a stable state. A similar advantageous effect to that described above is expected by forming the bump6in such a stepped shape that the thicker portion62is positioned on the side closer to the center of the bare IC1when looking at the bare IC1in a plan view than a center line of the outer terminal2extending in the lengthwise direction thereof, and that the thinner portion61is positioned on the opposite side with respect to the center line of the outer terminal2.

Returning toFIG. 6, the surroundings of the joining portion7are finally sealed by an insulating resin8as illustrated inFIG. 6(e), whereby the electronic component module is completed.

According to this embodiment, as described above, the plural joining portions7joining the plural outer terminals2respectively to the plural bumps6, having been formed in the preceding step, through deformation of the bumps6are each formed such that the height of the joining portion7on the opposite side away from the center of the bare IC1when looking at the bare IC1in a plan view is lower than the height of the joining portion7on the side closer to the center of the bare IC1when looking at the bare IC1in a plan view. Therefore, the joining portion7is avoided from contacting with the lateral surface of the bare IC1. Thus, even when the internal wiring of the bare IC1is exposed at the lateral surface of the bare IC1due to dicer cutting, characteristics of the bare IC1do not degrade.

While, in the embodiment described above, the bump6is formed in a two-step shape including the thicker portion62and the thinner portion61, the shape of the bump6is not particularly limited to the two-step shape.FIGS. 10(a) and 10(b)are sectional views illustrating a structure of the electronic component module, in a state before mounting of the bare IC1, according to an exemplary embodiment when the bumps6have other different shapes.

FIG. 10(a)illustrates an example in which the bump6is formed in a three-step shape including a thicker portion, an intermediate portion, and a thinner portion. As a matter of course, the bump6is formed such that those three portions have thicknesses gradually increasing toward the side closer to the center of the bare IC1when looking at the mounted bare IC1in a plan view. Alternatively, when an amount of the metal paste4ejected from the ink head3can be finely controlled, the bump6may be formed in a sloped shape having a thickness that gradually increases toward the side closer to the center of the bare IC1when looking at the mounted bare IC1in a plan view, as illustrated inFIG. 10(b).

An embodiment consistent with the present disclosure is not limited to the above-described embodiment, and it may be variously modified and improved without departing from the scope of the present disclosure. For example, applications of the present invention are not limited to an electronic component module in which an electronic component, e.g., a bare IC, is mounted to a substrate, and embodiments according to the present disclosure is also applicable to an electronic component module in which a medium-sized electronic component incorporating a small-sized electronic component therein is mounted to a substrate. As one example, the present disclosure can be applied to an electronic component module in which, after resin-molding a small-sized electronic component together with a substrate, an electromagnetic shield portion is formed on a top surface or a lateral surface of the electronic component module.

With the features of the method of manufacturing an electronic component module described above, each of the plural bumps includes the thicker portion having the relatively large thickness and the thinner portion having the relatively small thickness. Each bump is formed on one surface of the substrate such that, when looking at the electronic component in a mounted state in a plan view, the thicker portion is positioned on the side closer to the center of the electronic component relative to the corresponding outer terminal, and the thinner portion is positioned on the opposite side away from the center of the electronic component relative to the corresponding outer terminal. The plural joining portions joining the plural outer terminals respectively to the plural bumps, having been formed in the preceding step, through deformation of the bumps are formed such that the height of each joining portion on the opposite side away from the center of the electronic component when looking at the mounted electronic component in a plan view is lower than the height of the joining portion on the side closer to the center of the electronic component. Therefore, the joining portions are avoided from contacting with the lateral surfaces of the electronic component. Thus, even when the internal wiring of the electronic component is exposed at the lateral surfaces of the electronic component due to dicer cutting, characteristics of the electronic component do not degrade.

With the feature mentioned above, since the plural joining portions are formed such that the height of each joining portion on the opposite side away from the center of the electronic component when looking at the electronic component in a plan view is lower than the height of the joining portion on the side closer to the center of the electronic component, the joining portions are avoided from contacting with the lateral surfaces of the electronic component. Thus, even when the internal wiring of the electronic component is exposed at the lateral surfaces of the electronic component due to dicer cutting, characteristics of the electronic component do not degrade.

In an embodiment of the disclosed method of manufacturing the electronic component module in which, preferably, the plural bumps are each formed in a stepped shape, since the plural bumps are each formed in a stepped shape, the joining portions can be formed such that the height of each joining portion on the opposite side away from the center of the electronic component when looking at the mounted electronic component in a plan view is lower than the height of the joining portion on the side closer to the center of the electronic component. Therefore, the joining portions are avoided from contacting with the lateral surfaces of the electronic component. Thus, even when the internal wiring of the electronic component is exposed at the lateral surfaces of the electronic component due to dicer cutting, characteristics of the electronic component do not degrade.

In an embodiment of the method of manufacturing the electronic component module in which, preferably, the plural bumps are formed by an ink jet method, since the plural bumps are formed by an ink jet method, the thinner portion and the thicker portion having different thicknesses can be easily formed by adjusting the number of times a metal paste is ejected. Furthermore, the thinner portion and the thicker portion can be both formed in a continuous step, and the production cost can be reduced.

With the feature of the electronic component mentioned above, since the plural joining portions are formed such that the height of each joining portion on the opposite side away from the center of the electronic component when looking at the electronic component in a plan view is lower than the height of the joining portion on the side closer to the center of the electronic component, the joining portions are avoided from contacting with the lateral surfaces of the electronic component. Thus, even when the internal wiring of the electronic component is exposed at the lateral surfaces of the electronic component due to dicer cutting, characteristics of the electronic component do not degrade.

In embodiment of the electronic component module where the plural bumps are formed in pairs at opposed positions symmetrical with respect to the center of the electronic component when looking at the electronic component in a plan view, since the plural bumps are formed in pairs at opposed positions symmetrical with respect to the center of the electronic component when looking at the electronic component in a plan view, a pressing force can be applied in a balanced state and the plural bumps can be deformed evenly when the electronic component is mounted. It is hence possible to avoid bonding strength from being locally changed.