JP2008130812A - Surface-mounting electronic component and mounting structure of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a dissipation property of a component by soldered junction in a bottom electrode of a surface-mounting electronic component and a printed circuit board, and to improve a junction property with the printed circuit board. <P>SOLUTION: The shape of the bottom electrode 4 in the surface-mounting electronic component is formed to be a salient with respect to a connection pad 2 of a printed wiring board 1. At the time of reflow-mounting, surface tension acts on a solder 5 by heat transmission, the surface tension to the solder 5 centrally acts on a portion where the peak apex 4a of the electrode 4 contacts with the solder 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface-mounted electronic component that is surface-mounted on a printed wiring board built in an electronic apparatus such as an information processing apparatus or a communication apparatus, and a mounting structure thereof.

  In recent years, with the progress of high-speed and high-performance electronic devices, the amount of heat generated by electronic components used in the electronic devices has increased, which has become a factor that hinders stable operation inside the electronic circuit.

  In surface-mount electronic components, in order to dissipate the heat generated in the component, an electrode is formed on the bottom of the component package and soldered to the printed wiring board to print the heat inside the component. There are an increasing number of parts that escape to the wiring board to dissipate heat.

  For example, Patent Document 1 has a configuration in which heat inside the component is released to the printed wiring board by solder bonding between the ground electrode provided on the bottom surface of the electronic component and the ground electrode of the printed wiring board.

JP2001-210737

  In order to mount a surface mount component on a printed circuit board, usually paste cream solder mixed with solder and flux is printed on the electrode pad on the printed circuit board, and then the cream solder is crushed. The lead is placed on the electrode pad. Next, the cream solder is melted by an overall heating method such as a reflow furnace or a partial heating method, and then the molten solder is cooled and solidified, whereby the lead is joined to the electrode pad.

  In solder bonding of the electrode portion on the bottom surface of the surface mount component package, the printed solder is dissolved between the electrode pad on the printed wiring board and the electrode on the bottom surface of the component during reflow. Since the solder once liquefied changes its shape between the electrode pad and the component electrode, when the solder is cooled and solidified in a state where the joint area is small, joint strength and heat dissipation are reduced.

  In addition, when the solder is solidified while air is entrained in the solder at the time of melting, voids that cause solder cracks are generated.

  The solder shape of the bottom part of the component after solder joining cannot be visually confirmed unlike when the solder fillet outside the part such as the lead part is confirmed. Therefore, in order to confirm whether the solder has been solidified in an appropriate shape, a special device such as X-rays is required, and there is a problem that the inspection cost increases.

  In addition, when reflow mounting with a printed wiring board with through-holes in the electrode pad to improve heat dissipation, if the melted solder comes into contact with the through-holes, solder shortage due to solder rubbing will occur and bonding strength will decrease. There was a problem.

  The present invention has been made to solve the above-described problems, and enhances the heat dissipation of the component by solder bonding between the bottom electrode of the surface-mount type electronic component and the printed wiring board, and the bonding with the printed wiring board. The purpose is to improve the performance.

  The surface-mount type electronic component according to the present invention is a surface-mount type electronic component that is surface-mounted on a printed wiring board. The surface-mount type electronic component has an electrode on a package bottom surface of the surface-mount type electronic component. It is formed in a convex shape protruding in the direction of the bonding pad surface of the plate.

  The surface-mount type electronic component according to the present invention is a surface-mount type electronic component that is surface-mounted on a printed wiring board. The surface-mount type electronic component has an electrode on the package bottom surface of the surface-mount type electronic component. Since it is formed in a convex shape that protrudes in the direction of the pad surface, the surface tension acts around the point where the apex of the bottom electrode is in contact with the solder, and after solder cooling, it becomes an appropriate solder shape, Generation | occurrence | production of a void can also be suppressed and the reliability of joining with a printed wiring board can be improved while improving the heat dissipation of components.

Hereinafter, embodiments of a surface-mount type electronic component according to the present invention will be described with reference to the drawings. In the drawings, the same reference numerals denote the same or corresponding parts.

Embodiment 1 FIG.
FIG. 1 is a side cross-sectional view of a state in which a surface-mounted electronic component according to Embodiment 1 of the present invention is mounted on a printed wiring board. In FIG. 1, 1 is a printed wiring board, 2 is a bonding pad of the printed wiring board 1, 3 is a surface-mounted electronic component, 4 is a bottom electrode of the surface-mounted electronic component, and 5 is solder. At the time of reflow mounting, surface tension acts on the solder 5 by applying heat. Since the shape of the bottom electrode 4 is formed in a convex shape with respect to the bonding pad 2 of the printed wiring board 1, the surface tension to the solder 5 is centered on the point where the apex 4 a of the bottom electrode 4 is in contact with the solder 5. Will act.

  FIG. 2 is a top perspective view of the bonding pad 2 and the solder 5 portion of the printed wiring board 1 in a state in which the surface-mounted electronic component 3 in FIG. 1 is mounted on the printed wiring board 1. FIG. FIG. 3 is a top perspective view of the bonding pad 2 and the solder portion of the printed wiring board 1 when the shape of the bottom electrode of the surface mount electronic component is parallel to the bonding pad 2.

  In the case where the shape of the conventional bottom electrode is parallel to the bonding pad 2 of the printed wiring board 1, it is cooled by an abnormal solder shape 6s with a small bonding area with the bonding pad 2 as shown in FIG. It will become. Further, the void 7 is generated by solidifying the air with the air inside.

  On the other hand, by forming the shape of the bottom electrode 4 to be convex with respect to the bonding pad 2 of the printed wiring board 1, the surface tension acts around the place where the vertex 4 a of the bottom electrode 4 contacts the solder 5, As shown in FIG. 2, after solder cooling, the solder shape is sufficiently large compared to the solder shape 6s of FIG. 3 to become an appropriate solder shape 5s, and further, the generation of voids can be suppressed, and the heat dissipation of the parts is improved. Bonding reliability with the printed wiring board 1 can be improved. Further, when the bottom electrode 4 is a ground electrode or a power supply electrode, it is possible to further reduce the difference in potential from the electrode on the printed wiring board 1 side, so that the electrical characteristics can be further improved. You can also.

  FIG. 4 is a bottom view of the surface-mount type electronic component according to Embodiment 1 of the present invention, and has a pyramid shape with the center 4b of the bottom electrode of the SOP (Small Outline Package) package as the apex. Note that the convex shape of the bottom electrode 4 is not limited to a pyramid shape, and any protrusion that affects the surface tension of the solder melted during reflow mounting may be used. Shape may be sufficient.

Embodiment 2. FIG.
FIG. 5 is a side cross-sectional view of a state in which the surface mount electronic component according to the second embodiment of the present invention is mounted on a printed wiring board. In FIG. 5, 11 is a printed wiring board, 12 is a bonding pad of the printed wiring board 11, 13 is a surface-mounted electronic component, 14 is a bottom electrode of the surface-mounted electronic component 13, 15 is solder, and 16 is the printed wiring board 11. Through hole. FIG. 6 is a top view of the bonding pad 12 before reflow in which the solder paste 17 is printed avoiding the through-through hole 16 of the printed wiring board 11 on the bonding pad 12.

  In FIG. 5, a plurality of convex portions of the bottom electrode 14 are formed, and when the surface mount electronic component 13 is mounted on the printed wiring board 11, the convex portion of the bottom electrode 14 is shown in FIG. 6 is disposed in correspondence with the printed portion of the solder paste 17.

  FIG. 7 is a top perspective view of the bonding pad 12 and the solder 15 portion of the printed wiring board 11 in a state where the surface-mounted electronic component 12 in FIG. 5 is mounted on the printed wiring board 11. FIG. 8 is a top perspective view of the bonding pad 12 and the solder portion of the printed wiring board 11 when the bottom electrode of the surface mount electronic component has no convex protrusion and the shape thereof is parallel to the bonding pad 12. The state where the solder bit 18 to the through through hole 16 is generated after the solder is cooled during reflow mounting is shown.

  On the other hand, when the shape of the bottom electrode 14 is formed in a convex shape with respect to the bonding pad 12 of the printed wiring board 11, the surface tension is centered on the place where each vertex 14 a, 14 b of the bottom electrode 14 contacts the solder 15. After the solder is cooled, the solder shape becomes an appropriate 15s as shown in FIG. 7, and it is possible to suppress the occurrence of solder scorching as shown in FIG. Can be improved.

It is side surface sectional drawing of the state which mounted the surface mounted electronic component which concerns on Embodiment 1 of this invention on the printed wiring board. FIG. 2 is a top perspective view of a bonding pad and a solder portion of a printed wiring board in a state where the surface-mount type electronic component in FIG. 1 is mounted on the printed wiring board. It is a top perspective view of a bonding pad and a solder portion of a printed wiring board in a state where a conventional surface mount electronic component is mounted on the printed wiring board. It is a bottom view of the surface mount electronic component which concerns on Embodiment 1 of this invention. It is side surface sectional drawing of the state which mounted the surface mount type electronic component which concerns on Embodiment 2 of this invention on the printed wiring board. It is a top view of the joint pad before reflow which printed the solder paste avoiding the through-hole of a printed wiring board to the joint pad which concerns on Embodiment 2 of this invention. FIG. 6 is a top perspective view of a bonding pad and a solder portion of a printed wiring board in a state where the surface-mount type electronic component in FIG. 5 is mounted on the printed wiring board. It is a top perspective view of a bonding pad and a solder portion of a printed wiring board in a state where a conventional surface mount electronic component is mounted on the printed wiring board.

Explanation of symbols

1 printed wiring board, 2 bonding pads, 3 surface mount electronic components, 4 bottom electrode,
4a Vertex of bottom electrode 5 Solder, 5s Proper solder shape,
6s abnormal solder shape 7 void, 11 printed wiring board, 12 bonding pad,
13 surface mount type electronic components, 14 bottom electrode, 14a-14b apex part of bottom electrode,
15 Solder, 15s Proper solder shape 16 Through hole,
17 Solder paste 18 Solder wire

Claims (6)

In surface-mount electronic components that are surface-mounted on printed wiring boards,
Having an electrode on the bottom of the package of the surface mount electronic component;
The surface mount type electronic component according to claim 1, wherein the electrode is formed in a convex shape protruding in a direction of a bonding pad surface of the printed wiring board. 2. The surface mount electronic component according to claim 1, wherein the shape of the convex electrode is a pyramid. The surface mount type electronic component according to claim 1, wherein the electrode formed in a convex shape is cylindrical. The surface-mount type electronic component according to claim 1, wherein a vertex of the convex portion exists in a central portion of the electrode formed in a convex shape. The surface-mount type electronic component according to claim 1, wherein a plurality of convex portion vertices exist in the convex electrode. In a surface mount electronic component mounting structure for mounting a surface mount electronic component on a printed wiring board having a through-hole in a bonding pad,
Having an electrode formed in a convex shape projecting in the direction of the bonding pad surface of the printed wiring board on the bottom surface of the package of the surface mount electronic component;
A surface-mount type electronic component mounting structure, wherein a convex portion of the electrode is disposed at a position other than on the through-hole in the bonding pad to the printed wiring board.

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