JP2018152390A - Electronic component and method of manufacturing electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic component capable of improving the reliability of solder connection.SOLUTION: An electronic component includes an insulating mold containing an electronic element and an external electrode electrically connecting between the electronic element and the outside. The external electrode has a main surface substantially parallel to the bottom surface of the mold and a bent inclined surface increased in width from the bottom surface toward the top surface. The bent inclined surface is a surface between the main surface of the external electrode and the side of the mold, and is a curved surface increased in width from the bottom surface toward the top surface. The bent inclined surface is a curved surface, so that a surface area is increased as compared with the case where the same place is flat.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electronic component and a method for manufacturing the electronic component.

  There are two types of surface mount electronic component packages, one with a lead and one without a lead. In the manufacture of a package having leads, in many cases, after each package is molded, a lead shape is formed using a mold, and an end surface is cut by shearing. In this case, it is necessary to prepare a mold for molding and a mold for lead molding, which increases the cost. On the other hand, a type of package having no lead is generally manufactured by a method in which a plurality of packages are collectively molded and then cut and separated into pieces by a dicer. For this reason, the mold | die and process for lead molding can be omitted, and it can supply cheaply. For these reasons, in recent years, in small electronic components, packages such as QFN and SON that do not have leads protruding from the mold are increasing. Here, QFN is an abbreviation for Quad_Flat_Non-lead_package, and SON is an abbreviation for Small_Outline_Non-leaded_package.

  As described above, in general manufacture of QFN and SON, the mold is usually separated into pieces by dicing. At this time, a full cut method is generally used in which the dicing tape is attached to the back surface, and the dicing blade cuts halfway through the dicing tape so that the mold is completely cut. When cut by such a full cut method, the package end face and the electrode cutting end face on the same plane are perpendicular to the bottom face. Further, the electrodes of the package are collectively formed before dicing, and lead plating applied to improve the solder wettability of the electrodes is also collectively performed before dicing. For this reason, the electrode cutting end face of the package separated into pieces by dicing is exposed to an electrode base material without plating, and the solder wettability is remarkably inferior. However, in QFN and SON, the presence / absence of the fillet and the formation height greatly affect the reliability of the solder connection portion. For this reason, ensuring solder wetting to the electrode cutting end face is an issue.

  A method for solving this problem is disclosed in Patent Document 1, for example. In this technique, a tapered surface is formed on the end surface of the electronic component on the mounting side, and an external connection electrode that can be soldered is provided on the tapered surface. Then, the external connection electrode and the land on the mounting substrate side are opposed to each other and solder-connected. As a result, the angle formed by the connection electrode surface and the solder mounting surface of the land surface becomes an acute angle. In this way, the solder wetting force becomes a resultant force of the force that rises in the vertical direction and the force that spreads in the horizontal direction, and the wetness of the molten solder to the electrode end surface is improved. As a result, the mounting reliability of the electronic component is improved.

JP-A-5-175354

  However, the size of electronic components is constantly being reduced, and the electrode area is decreasing year by year. Under such circumstances, it is difficult to ensure the reliability of solder connection only by the technique of Patent Document 1. For this reason, a technique for further improving the reliability of solder connection is required.

  An object of this invention is to provide the electronic component which can improve the reliability of solder connection.

  In order to solve the above problems, an electronic component includes an insulating mold that encloses an electronic element, and an external electrode that electrically connects the electronic element and the outside. The external electrode has a main surface that is substantially parallel to the bottom surface of the mold and a curved inclined surface that becomes wider from the bottom surface toward the upper surface. The bending inclined surface is a surface between the main surface of the external electrode and the side surface of the mold, and is a curved surface that becomes wider from the bottom surface toward the upper surface. Since the curved inclined surface is a curved surface, the surface area is larger than when the same place is a flat surface.

  An effect of the present invention is to provide an electronic component that can improve the reliability of solder connection.

It is a top view which shows the electronic component of 1st Embodiment. It is sectional drawing which shows the electronic component of 1st Embodiment. It is a top view which shows the example of another electronic component of 1st Embodiment. It is sectional drawing which shows an example of the solder connection structure of 2nd Embodiment. It is sectional drawing which shows another example of the solder connection structure of 2nd Embodiment. It is sectional drawing which shows another example of the solder connection structure of 2nd Embodiment. It is sectional drawing which shows the electronic component of 3rd Embodiment. It is sectional drawing which shows an example of the soldering connection structure of the electronic component of 3rd Embodiment. It is a plane schematic diagram which shows a part of manufacturing method of the electronic component of 4th Embodiment. It is a cross-sectional schematic diagram which shows a part of manufacturing method of the electronic component of 4th Embodiment. It is a plane schematic diagram which shows the cutting method of the electronic component of 4th Embodiment. It is a cross-sectional schematic diagram which shows the cutting method of the electronic component of 4th Embodiment. It is a cross-sectional schematic diagram which shows the modification of the manufacturing method of the electronic component of 4th Embodiment. It is a cross-sectional schematic diagram which shows another modification of the manufacturing method of the electronic component of 4th Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the preferred embodiments described below are technically preferable for carrying out the present invention, but the scope of the invention is not limited to the following. In addition, the same number is attached | subjected to the same component of each drawing, and description may be abbreviate | omitted.

(First embodiment)
FIG. 1 is a plan view showing an electronic component 10 according to the first embodiment. The electronic component 10 includes an insulating mold 1 that encloses an electronic element, and an external electrode 2 that electrically connects the electronic element and the outside. The external electrode 2 has a main surface 2a substantially parallel to the bottom surface 1a of the mold 1 and a bent inclined surface 2b that becomes wider from the bottom surface 1a toward the top surface.

  FIG. 2 is a cross-sectional view of the electronic component 10 taken along the line AA ′ of FIG. The bending inclined surface 2b is a surface between the main surface 2a of the external electrode 2 and the side surface 1c of the mold 1, and is a curved surface that becomes wider from the bottom surface 1a to the upper surface 1b. Since the curved inclined surface 2b is a curved surface, the surface area is larger than when the same place is a flat surface. For this reason, at the time of solder joining, the area where the solder and the external electrode 2 come into contact is increased, and the reliability of solder connection is improved.

  FIG. 1 shows an example of the SON type having the external electrodes 2 on the two sides of the mold 1, but is not limited thereto. FIG. 3A shows an example applied to the QFN_10a having the external electrodes 2 on the four sides of the mold 1. FIG. In this example, the external electrode 2 is disposed at the end portions of the four sides of the mold 1, and the bending inclined surface 2 b is formed at the end portion of the external electrode 2. FIG. 3B shows an example applied to a chip component 10b having external electrodes 2 at two ends of a rectangular parallelepiped. In this example, a bent inclined surface 2 b is provided at the end of the external electrode 2.

  As described above, according to the present embodiment, an electronic component that can improve the reliability of solder connection can be provided.

(Second Embodiment)
FIG. 4 is a cross-sectional view illustrating a state in which the external electrode 2 of the electronic component 10 according to the first embodiment and the land 4 provided on the substrate 3 are connected by the solder 5. The substrate 3 is a printed wiring board in which wiring and lands 4 are printed on an insulating substrate, for example.

  The external electrode 2 has a bent inclined surface 2b having a concave shape with respect to the outside between the main surface 2a and the end. Further, the bent inclined surface 2b has an inclination in which the angle formed with the land 4 is an acute angle.

  The solder connection can be performed, for example, by printing a solder paste on a predetermined portion including the land 4, mounting the external electrode on the land 4, and performing reflow. At this time, since the external electrode 2 has the above-described bent inclined surface 2b, the wetted solder 5 is better wetted, and the solder 5 reaches the upper portion of the bent inclined surface 2b. Thereby, a good fillet 5b having a sufficient height is formed. Furthermore, since the contact area between the external electrode 2 and the solder 5 is increased as compared with the case where the same portion is a plane, the connection strength of the solder is improved.

  The bending inclined surface 2b may be formed as a convex surface. FIG. 5 is a cross-sectional view showing an example in which the external electrode 2 having the bent inclined surface 2 b _ 1 that protrudes outward and the land 4 are connected by the solder 5. Also in this case, the wettability of the solder is improved, the contact area between the solder 5 and the external electrode 2 is increased, and the connection strength of the solder can be improved.

  4 and 5 show an example in which the bending inclined surface 2b is at the end of the mold 1, the bending inclined surface 2b may be formed inside the end of the mold 1. FIG. 6 is a cross-sectional view showing an example of such a configuration. The bending inclined surface 2b_2 is formed inside the external electrode 2. In this example, the bent inclined surface 2b_2 is concave toward the outside, but conversely it may be convex. In this configuration, the main fillet 5 b is formed inside the end of the mold 1.

  As described above, according to the present embodiment, a good fillet can be formed in the solder connection portion, and the reliability of the solder connection can be improved.

(Third embodiment)
FIG. 7 is a cross-sectional view showing the electronic component 11 of the present embodiment. In the electronic component 11, in addition to the configuration of FIG. 1, the plating 6 is formed on the surface of the main surface 2 a of the external electrode 2.

  When the external electrode 2 is formed of, for example, a Cu alloy, a surface having good compatibility with solder can be formed by using, for example, Sn plating or Ni / Au plating as the plating 6.

  FIG. 8 is a cross-sectional view showing an example in which the electronic component 11 of FIG. The shape and the like of the fillet 5b are the same as in the example of FIG. 2, but since the affinity between the plating 6 and the solder 5 is good, the connection strength is improved as compared with the case of FIG. Although not shown, if the plating 6 can be formed also on the bending inclined surface 2b, the connection strength can be further increased.

  As described above, according to the present embodiment, it is possible to obtain a solder connection structure for an electronic component having high connection strength and high reliability.

(Fourth embodiment)
In the present embodiment, a method for manufacturing the electronic component described in the first to third embodiments will be described.

  Here, an example of a SON having external electrodes at the two side ends of the mold will be described, but the present invention is not limited to this, and the present invention can be similarly applied to an electronic component having another leadless type structure.

  FIG. 9 is a plan view schematically showing the process of mounting the Si chip 30 on the lead frame 20 and sealing with the mold 50. Here, in order to simplify the description, an example in which the Si chips 30 are arranged in a row is illustrated, but a structure in which the Si chips are two-dimensionally arranged may be used. In FIG. 9A, the Si chip 30 is die mounted on the die 20 a of the lead frame 20, and the Si chip 30 and the inner lead 20 a are connected by wire bonding using a wire 40. In FIG. 9B, a mold is formed on the mounting surface side of the Si chip 30. The mold is formed by, for example, using a mold and injection molding a mold resin. Rather than molding individual packages, the entire package forming part of the lead frame can be covered at once.

  FIG. 10 is a cross-sectional view showing the manufacturing process of the electronic component. The position of the cross section corresponds to BB ′ in FIG. First, a lead frame 20 having a cross section as shown in FIG. The lead frame 20 in this example has a shape in which die pads 20a and inner leads 20b are alternately arranged. For example, a Cu alloy can be used for the lead frame 20. Since the surface of the inner lead 20b on the Si chip mounting side requires wire bonding, surface treatment such as Ni / Au plating is preferable. Since the opposite surface is a surface on which soldering is performed, a surface treatment that improves the affinity with solder is preferable. For this purpose, for example, Sn plating or Ni / Au plating can be performed. Further, the Cu alloy surface may be coated with a preflux without plating.

  Next, as shown in FIG. 10B, the Si chip 30 is mounted on the die pad 20a, and the Si chip 30 and the inner lead 20b are connected by wire bonding.

  Subsequently, as shown in FIG. 10C, a mold 50 is formed on the Si chip mounting surface side of the lead frame 20. As described above, in the formation of the mold 50, the mold can be used, the mold resin can be injection molded, and the entire package forming part of the lead frame 20 can be covered at once.

  Next, the lead frame 20 on which the mold 50 is formed is attached to the dicing tape 60. Then, as shown in a schematic diagram in FIG. 11, the cutting portion 51 is formed by cutting with a dicing blade 70 from the lead frame 20 side, and cut into individual pieces. At this time, a dicing blade 70 having a bent portion 71 at a predetermined position is used. Thereby, an external electrode having a bent inclined surface can be formed.

  FIG. 12 is a cross-sectional view schematically showing a dicing process. As shown in FIG. 12A, the cutting part 51 a is formed with the dicing blade 70. At this time, for example, the mold 50 and the lead frame 20 are fully cut so that the dicing blade 70 cuts to the dicing tape 60. At this time, since the dicing blade 70 has an outwardly convex bent portion 71, a bent inclined surface is formed in the cutting portion 51.

  When the dicing is completed, the dicing tape 60 is peeled from the mold 50 as shown in FIG. In this way, the electronic components 10 separated individually can be obtained. At this time, the external electrode 2 has a shape having a concave inclined surface 2b which is concave with respect to the outside.

  In FIG. 12, the depth direction is not shown because it is shown in a schematic diagram of a cross section. However, in the case of QFN, the direction perpendicular to the cutting portion 51 in FIG. And Although an example in which a Si chip is mounted as an electronic component is shown here, it may be replaced with another electronic element or circuit. Moreover, although the example which mounts the whole bottom face of Si chip in the conductor part of a lead frame was used, it may be a part.

  In the examples of FIGS. 11 and 12, the curved inclined surface has a concave shape with respect to the outside, but may be convex. FIG. 13 is a cross-sectional view schematically showing how dicing is performed using a dicing blade 70a having a concave bent portion 71a with respect to the outside. In this case, the cutting part 51a having a convex shape is formed by the bent part 71a that is concave with respect to the outside. As a result, the external electrode is formed with a curved inclined surface that is convex outward.

  FIG. 14 is a cross-sectional view showing an example in which dicing is performed twice. First, as shown in FIG. 14A, a dicing blade 70b having an arc-shaped bent portion 71c with a convex tip is used to form a concave shape with respect to the outside at a position corresponding to the end portion of the external electrode 2. The cutting part 51b having a shape is formed. Next, as shown in FIG. 14B, using a dicing blade 70c that is narrower than the dicing blade 70b, a cutting part 51c that cuts in the middle of the dicing tape 60 is formed, and the mold 50 is fully cut. In this example, dicing needs to be performed twice. However, since only a dicing blade having a simple shape is used, there is an advantage that an inexpensive dicing blade can be used.

  The present invention has been described above using the above-described embodiment as an exemplary example. However, the present invention is not limited to the above embodiment. That is, the present invention can apply various modes that can be understood by those skilled in the art within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1,50 Mold 2 External electrode 2a Main surface 2b Bending inclined surface 3 Substrate 4 Land 5 Solder 6 Plating 10, 11 Electronic component 20 Lead frame 30 Si chip 40 Wire 60 Dicing tape 70 Dicing blade

Claims (10)

An insulating mold enclosing the electronic element;
An external electrode for electrically connecting the electronic element and the outside,
The external electrode is
Formed within the outer shape of the mold,
A surface substantially parallel to the bottom surface of the mold;
An electronic component comprising: a bent inclined surface that becomes wider from the bottom surface toward the upper surface. The electronic component according to claim 1, wherein the bent inclined surface has a shape that is concave with respect to the outside. The electronic component according to claim 1, wherein the bent inclined surface has a shape that is convex toward the outside. The electronic component according to any one of claims 1 to 3, wherein the external electrode has plating on at least a part of its surface. The electronic component according to any one of claims 1 to 4, wherein the bent inclined surface is formed at an outer end portion of the external electrode. An electronic component according to claim 1 to claim 5,
A wiring board in which wiring is formed on an insulating substrate;
An electronic device comprising: solder for connecting the electronic component and the wiring board. An insulating mold enclosing the electronic element;
A method of manufacturing an electronic component having an external electrode for electrically connecting the electronic element and the outside,
A bending inclined surface is formed on at least one end portion of the external electrode. Mount multiple electronic elements on the lead frame,
Forming a mold for covering the lead frame and the electronic element so that a part of the lead frame is exposed;
The mold is diced and divided,
The method of manufacturing an electronic component according to claim 7, wherein the bent inclined surface is formed in a cutting portion of the lead frame by the dicing. The method of manufacturing an electronic component according to claim 8, wherein the dicing is performed using a dicing blade having a bent portion. Print the solder paste on the wiring board on which the wiring is formed on the insulating substrate,
The electronic component according to claim 1 is mounted,
A method for manufacturing an electronic device, comprising: reflowing the wiring board and the electronic component.

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