JPH11233703A - Lead terminal of electronic component and processing method thereof - Google Patents

Abstract

(57) [Abstract] [Problem] To improve the wettability of molten solder to a lead terminal,
A highly reliable lead terminal for an electronic component and a method for processing the lead terminal by increasing the bonding strength of the lead terminal and eliminating bridging between the lead terminals due to molten solder. SOLUTION: In a lead terminal of an electronic component which is fixed to a land portion 2 of a wiring board 1 by soldering, an edge portion of a lead leg piece 6 of a lead terminal 5 mounted on the land portion 2 has an inclined surface 7 having a round shape. The contact angle between the land and the land 2 is reduced by the formation of the slope 7, so that the wet solder of the molten solder to the lead leg 6 is improved.
And a method of processing the lead terminal 5 having the slope 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead terminal of an electronic component which is fixed to a land of a printed wiring board by soldering, and a method of processing the lead terminal. The contact angle between the tip of the lead and the land surface is reduced, so that the molten solder wets to the lead terminals and improves the bonding strength with the land. Things.

[0002]

2. Description of the Related Art Conventionally, as a general method for mounting a chip component such as an IC or an LSI on a wiring board, a solder 3 is printed and formed on a land portion 2 of the wiring board 1 as shown in FIG.
Each lead terminal 5 of the chip component 4 is provided on each of these land portions 2.
Is mounted. When the wiring board 1 on which the chip components 4 are mounted is conveyed into a reflow furnace, the solder 3 is melted and swells to the lead terminal 5 side, and the land portion 2 and the lead terminal 5 are connected by the solder 3 and electrically connected. Connection can be made.

More specifically, the action of the molten solder on the land portion 2 swelling on the lead terminal 5 is to adhere to the lead terminal 5 by the action of the surface tension of the solder itself, and the solder adheres to the lead terminal. This is called solder wettability. Therefore, conventionally, in order to securely connect the lead terminal 5 of the chip component to the land portion 2, it is required to improve the wettability of the land portion 2 and the lead terminal 5 together with the solder material itself.

[0004]

By the way, the lead terminal 5 of a conventional chip component is generally formed by bending a lead terminal made of chromium plating or the like on a flat copper material in the case of an IC or an LSI, etc. Has a lead leg piece 6 which makes surface contact with the land portion 2. The tip of the lead leg piece 6 is a vertically cut lead end face 6a.

FIG. 8 is an enlarged view of the above-mentioned conventional lead terminal 5 placed on the land portion 2 before the solder 3 is melted. Therefore, as can be seen from this figure, the contact angle θ between the lead end face 6a at the tip of the lead leg piece 6 and the land is 90 °.

In the case of the lead terminal 5 having such a shape, the wettability of the solder to the lead leg piece 6 when the solder 3 is melted by the reflow furnace is not optimal. That is, since the lead end face 6a at the tip end of the lead leg piece 6 rises vertically, the effect of the surface tension of the solder is also reduced due to the own weight of the solder. Therefore, as shown in FIG. The wet-up remains on the respective vertical surfaces of the lead leg pieces 6, and as a result, there is a problem in that the solder fixing strength of the lead terminal 5 and the reliability of the quality are lacking.

In addition, the decrease in the wettability of the solder to the lead terminals means that the solder that has not been soldered but melted and remains on the land 2 does not wet. If the space between the lands 2 and 2 is extremely small, the unsoldered solder may cause a solder bridge between the adjacent lands 2 and 2, which may cause a decrease in reliability such as a defective mounting of chip components. This was an obstacle to improving productivity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an object to improve the wettability of molten solder to a lead terminal, increase the bonding strength of a lead terminal, and to improve the molten solder between lead terminals. And to obtain a highly reliable lead terminal of an electronic component and a method of processing the same.

[0009]

In order to achieve the above-mentioned object, a lead terminal of an electronic component according to the present invention has a slope formed at an edge portion of a leading end of a lead terminal mounted on a land portion. The contact angle between the tip and the land surface is reduced.

[0010] With this configuration, the molten solder easily gets wet from the inclined surface of the tip end of the lead terminal, and a strong solder connection with the land can be made possible. In addition, since no excess molten solder remains on the lands, bridges between adjacent lands due to the molten solder can be eliminated.

Further, in the method for processing a lead terminal of an electronic component according to the present invention, the bending of the lead terminal and the processing of the slope at the edge of the tip of the lead placed on the land are performed by a single press. It is intended to be molded.

According to such a processing method, the bending of the lead terminal and the processing of the slope on the edge portion of the tip of the lead can be simultaneously formed by a single pressing.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a lead terminal of an electronic component according to an embodiment of the present invention;

FIG. 1 is a perspective view of a wiring board and chip components,
FIG. 2 is an enlarged view of a lead terminal placed on a land portion before solder melting, and the same components as those described in the conventional example are denoted by the same reference numerals.

Land portions 2 made of a copper foil pattern are formed on a wiring board 1, and solder 3 is formed on each land portion 2 by printing or the like. IC or L mounted on the wiring board 1
In the chip component 4 made of SI or the like, the lead leg pieces 6 of each lead terminal 5 are placed on the land portion 2 and fixed by soldering.

According to the present invention, in order to improve the wetting of the solder to the lead terminal, the lead leg piece 6 of the lead terminal 5 is used in the present invention.
An inclined surface is formed at the edge portion of the lead portion so that the molten solder can be surely wet from the land portion 2 to the lead leg piece 6.

In FIG. 2, as an example of the slope, the edge portion of the tip of the lead leg piece 6 is formed on a slope 7 having a round shape, and the contact angle θ ₁ between the slope 7 and the surface of the land 2 is reduced. Things. The contact angle theta ₁ is set at a gentle angle of 30-45 °, and is in the molten solder wetting easily as inclined.

Thus, when the above-mentioned lead leg piece 6 is placed on the land portion 2 and transported to the reflow furnace, the solder 3 on the land portion 2 is melted, and the molten solder is inclined by its own surface tension. The gently sloped surface 7 gets wet and reaches the upper surface of the lead leg 6, and as shown in FIG.
Can be attached to the entire surface of the substrate. Thus, the lead terminals 5 and the lands 2 can be firmly solder-bonded.

Further, since the molten solder wets over the entire surface of the lead leg piece 6, the unsoldered molten solder does not remain on the land portion 2. 2 can also eliminate the solder bridge with the unsolder.

Here, the slope formed at the tip of the lead leg 6 is a flat slope 8 at the tip of the lead leg 6 as shown in FIG. Alternatively, the contact angle θ ₂ formed with the surface of the land portion 2 may be reduced. Contact angle theta ₂ In this case is set to a gentle angle of 30-45 °. It should be noted that there is almost no difference in the wetting action of the molten solder between the rounded slope 7 and the flat slope 8, but the flat slope 8 is somewhat easier to shape. Points.

In the case of an inclined surface 7 having an R-shaped surface as an example, as shown in FIG. 5, except that the inclined surface 7 is formed at the edge portion of the tip end of the lead leg 6, as shown in FIG. It is also possible to form the inclined surfaces 7a, 7a having a round shape also at the edge portion. In this manner, the action of the molten solder wetting the lead leg pieces 6 is increased by the respective slopes 7, 7.
This can be performed simultaneously from steps a and 7a, and the reflow conveyance time can be shortened by reducing the time of wetting as well as more reliable wetting.

FIG. 6A shows a method of processing the above-mentioned lead terminal. A press forming machine including an upper mold 10 having a concave mold 10a for bending and forming the upper surface shape of the lead terminal 5 and a lower mold 11 having a convex mold 11a for bending and forming the lower surface shape of the lead terminal 5 is used. Here, the lead leg piece 6
The inclined surface 7 of the round surface is the inclined surface 10b of the upper mold 10.
It is formed by processing.

A flat lead terminal material 5a before press working
Are pressed by the pressing operation of the upper mold 10 to form the concave mold 10a and the convex mold 1a.
1a, the bending of the lead terminal 5 and the upper mold 10
The slope 7 is formed by the slope forming surface 10b of FIG. At the same time as this pressing operation, the remaining portions of the lead terminal material 5a are removed from the edges 10c, 11c and 10d, 11 of the two dies 10, 11.
It is cut and separated by d.

By using the press molding machine described above,
The bending of the lead terminal 5 and the formation of the inclined surface 7 for improving the wet-up of the molten solder can be performed by a single pressing operation. Further, it is also possible to perform the press forming of the lead terminal during the lead terminal forming step.

The present invention is not limited to the embodiment described above and shown in the drawings, and various modifications can be made without departing from the scope of the invention.

The lead terminal according to the present invention can be used for an IC or an LSI.
It is extremely suitable to be used for a lead terminal composed of multiple terminals of a chip component such as the one described above, and is also widely applicable to a case where a lead terminal composed of a single terminal is fixed to a land by soldering.

[0027]

As described above, the lead terminal of the electronic component according to the present invention has a slope formed at the edge of the tip of the lead terminal mounted on the land to reduce the contact angle with the land surface. By reducing the size, the molten solder easily wets up from the slope, the amount of solder attached to the lead terminal increases, and a strong solder connection with the land can be performed. Thereby, it is possible to improve the reliability of the quality of the solder connection of the lead terminals and the productivity. In addition, since the molten solder does not remain as unsoldered on the lands, bridges between adjacent lands due to the molten solder can be eliminated. Further, since the bridge between the lands is not generated by the solder, the post-repair process such as repair can be simplified.

Further, the method for processing lead terminals of an electronic component according to the present invention comprises a step of bending a lead terminal and a step of forming a slope at an edge portion of a tip end of a lead placed on a land. By forming the lead terminal by a single press working, the bending of the lead terminal and the forming of the slope can be formed simultaneously, so that the forming can be shortened and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a chip component having lead terminals according to the present invention and a land portion of a wiring board.

FIG. 2 is an enlarged view of a state where a lead terminal is mounted on a land according to the present invention.

FIG. 3 is a perspective view of a state in which molten solder wets to a lead terminal according to the present invention;

FIG. 4 is an enlarged view of another example of a lead terminal according to the present invention mounted on a land portion.

FIG. 5 is a perspective view of another example of the lead terminal.

FIG. 6A is a sectional view of a press die for processing a lead terminal according to the present invention. B is a diagram of the lead terminal of the present invention processed by a press die.

FIG. 7 is a perspective view of a conventional chip component having lead terminals and a land portion of a wiring board.

FIG. 8 is an enlarged view of a conventional lead terminal mounted on a land.

FIG. 9 is a perspective view showing a state in which molten solder wets to a conventional lead terminal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Wiring board, 2 land parts, 3 solders, 4 chop parts, 5 lead terminals, 6 lead leg pieces, 7, 7a, 8
Slope, 10 Upper mold, 10b Slope molding surface, 11 Lower mold

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 1/18 H05K 1/18 H

Claims (3)

[Claims] 1. A lead terminal of an electronic component fixed to a land portion of a printed wiring board by soldering, wherein a slope is formed at an edge portion of a tip end portion of the lead placed on the land portion, A lead terminal for an electronic component, wherein a contact angle with a land portion surface is reduced to make molten solder wet to the lead terminal. 2. The lead terminal of an electronic component according to claim 1, wherein said inclined surface is formed on at least one edge of said lead tip. 3. A method of processing a lead terminal of an electronic component to be solder-fixed to a land portion of a printed wiring board, wherein the lead terminal is bent, and a slope is formed on an edge portion of a tip end of the lead placed on the land portion. And forming the lead terminal of the electronic component by a single press working using a forming die.