JP2003273308A - Electronic part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an electronic part to be mounted on a substrate with a sufficient strength only by means of a solder dip process, even if there is a burr caused during formation on the lead frame of the electronic part. <P>SOLUTION: In the electronic part comprising a lead frame 1B, with which the electronic part is mounted on the surface of a substrate by solder dip, a recess 2 the depth of which becomes deeper toward the edge of the lead frame 1B is formed on the lead frame 1B in order to guide the solder from the edge of the lead frame 1B onto the lead frame during solder dip. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a lead frame (electrode terminal) in a semiconductor device or electronic component.

[0002]

2. Description of the Related Art FIG. 3 is a perspective view schematically showing a semiconductor device or an electronic component (hereinafter simply referred to as an electronic component). The electronic component 1 is composed of an electronic component body 1A and a lead frame (electrode terminal) 1B which is continuous with the bottom surface of the body 1A and protrudes outward from the opposite side surface thereof.
In the upper island, surface mounting is performed by dipping (immersing) the lead frame in the applied solder.

The lead frame 1B, which serves as an electrode when mounting electronic components on a substrate, is formed by etching or stamping using Cu, Fe--Ni material or the like as a base material. Burr inevitably occurs. 3B and 3C are views for explaining burrs that occur when a lead frame is formed by etching or stamping, respectively, and are enlarged cross-sectional views of a circle T portion in FIG. 3A. That is, when etching is performed, a burr 1c having a shape in which a side surface near the upper surface of the lead frame 1B is protruded in an eaves shape is generated as shown in FIG. 3B. Further, when stamping is performed, as shown in FIG. 3C, a protruding burr 1d is generated at the upper end of the cross section of the lead frame.

FIG. 4 is a sectional view of the lead frame taken along the line XX in FIG. 3A. When the lead frame 1B having burrs 1d is solder-dipped on the substrate 3, the solder 5 is left on the lead frame 1B. It is the figure which showed the state which turned around. As shown, lead frame 1B
When the solder (Pb-Sn eutectic or the like) is dipped, the solder applied on the island is prevented from wrapping around at the burr 1d, so that the solder concentration at that part becomes thin. Therefore, the solder applied to the substrate cannot get over this portion, resulting in a problem that the adhesiveness between the electronic component and the substrate is insufficient.

For this reason, conventionally, the lead frame 1B is subjected to a solder plating treatment so as to promote the wraparound of the solder so as to be able to get over the burrs 1c or 1d. Not only the cost is increased, but also a plating process is added, which causes new problems such as the complicated manufacturing.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to apply a solder applied to a substrate by simply performing a dipping process without performing an expensive solder plating process even if the lead frame has burrs. Is sufficiently mounted on the lead frame so that the adhesiveness between the electronic component and the substrate does not become insufficient.

[0007]

According to a first aspect of the present invention, there is provided an electronic component comprising a lead frame, and the lead frame is surface-mounted on a substrate by solder dipping. The electronic component is characterized in that it is provided with a guide means for guiding the solder onto the lead frame.

According to a second aspect of the present invention, in the electronic component according to the first aspect, the solder guiding means is a recess formed on the lead frame and communicating with the outside of the lead frame. It is an electronic component that

According to a third aspect of the present invention, in the electronic component according to the second aspect, the recess has a depth of about 1/20 to 2/3 of the thickness of the lead frame. It is a part.

According to a fourth aspect of the present invention, in the electronic component according to the first aspect, the solder guiding means is a molding surface formed by crushing an upper edge of the lead frame. It is a part.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The embodiments of the present invention shown in the drawings will be described. 1 shows an electronic component according to a first embodiment of the present invention, FIG. 1A is a perspective view thereof, and FIG. 1B is FIG. 1A.
2 is a cross-sectional view taken along line XX of FIG. In this embodiment, the recess 2 is formed on the upper surface of the lead frame (electrode terminal) 1B of the electronic component, and when the lead frame 1B is solder-dipped, the solder applied to the substrate 3 is placed in the recess 2. It flows along and easily wraps around the lead frame 1B to improve solderability. The same parts as those in FIG. 3 are designated by the same reference numerals.

Specifically, as shown in FIGS. 1A and 1B, a recess 2 is provided on the lead frame, and the recess 2 includes a central portion 2B and a lead frame 1B from the central portion 2B. Groove-shaped recess 2 extending to the tip and left and right ends
It consists of A. As shown in the cross section of FIG. 1B, each groove-shaped recess 2A is formed such that the central portion is the shallowest and the depth becomes deeper toward the ends. By forming the cross-sectional shape of the groove-shaped recess 2A in this way, even if burrs as shown in FIGS. 3B and 3C are generated in the lead frame 1B, when the lead frame 1B is solder-dipped,
The solder flows into the central recess 2B through the groove-shaped recess 2A, and a sufficient amount of solder can flow around the lead frame 1B. Therefore, when mounting the lead frame 1B on the substrate 3, the solderability to the substrate 3 can be improved by simply performing a dipping process without performing expensive solder plating on the lead frame 1B. Further, by adopting this configuration, even if the melting point of the solder becomes high due to Pb-free, the soldering temperature can be relatively lowered without impairing the solderability, and even in that case, the soldering temperature on the lead frame is also reduced. Sufficient soldering strength can be secured by wrapping the solder around.
In the above structure, the depth of the recess is about 1/2 of the thickness of the lead frame when the width of the recess is predetermined.
It is preferable that the depth is in the range of 0 to 2/3 in view of the strength of the lead frame and the soldering strength.

FIG. 2 shows a second embodiment of the present invention. In this embodiment, after the lead frame 1B is molded, for example, the upper surfaces of the three end surfaces other than the end portion where the lead frame 1B is joined to the main body are crushed and R processing is performed to form the crushed molded portion 4. . In this way, the lead frame 1B
When the lead frame 1B is soldered by dipping the lead frame 1B by subjecting the end portion to the R processing, the solder can easily get over the crushed forming portion 4 of the R processed end surface. The effect of burr can be eliminated. The processing of the end portion of the lead frame 1B is not limited to the R processing, and in short, when the lead frame 1B having burrs is dipped in the solder applied to the island, the shape can easily go around the lead frame 1B. The upper edge may be molded so that

[0014]

According to the present invention, since electronic components are surface-mounted on a board, even if burrs are generated on the lead frame when the lead frame is solder-dipped on the island of the board, it is affected by the burrs. The solder can be easily guided onto the lead frame without the need. for that reason,
The electronic component can be fixed to the substrate with a sufficient fixing force by simply performing the solder dip without performing expensive solder plating as in the conventional case.

[Brief description of drawings]

1 shows an embodiment of a lead frame of the present invention, FIG. 1A is a perspective view of an electronic component, and FIG. 1B is a sectional view showing a recess of the lead frame.

FIG. 2 is a perspective view of an electronic component including a lead frame according to another embodiment of the present invention.

FIG. 3 shows a conventional electronic component, FIG. 3A is a perspective view of an electronic component including a conventional lead frame, and FIG.
C indicates burrs respectively generated on the lead frame.

FIG. 4 is a cross-sectional view when a lead frame of a conventional electronic component is solder-dipped.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic component, 1A ... Electronic component main body, 1B ... Lead frame, 2 ... Recess, 3 ... Substrate, 4 ... Crush molding part, 5 ... Solder.

Claims (4)

[Claims] 1. An electronic component comprising a lead frame, wherein the lead frame is surface-mounted on a substrate by solder dipping, wherein the lead frame guides the solder onto the lead frame when the solder dipping is performed. An electronic component characterized by having. 2. The electronic component according to claim 1, wherein the solder guiding means is a recess formed on the lead frame and communicating with the outside of the lead frame. 3. The electronic component according to claim 2, wherein the recess is about 1/20 to 2 of the plate thickness of the lead frame.
An electronic component having a depth of / 3. 4. The electronic component according to claim 1, wherein the solder guiding means is a molding surface formed by crushing an upper edge of the lead frame.