JPH0279455A - Bending method for lead of electric parts - Google Patents

Abstract

PURPOSE:To suppress initiation of cracks at the bend of a lead by applying compression stress to the bend in its radial direction at the time of bending the lead, and thereby allowing the compression stress to restrain possible plastic deformation resulting from tensile stress to be generated on the outside of the bend. CONSTITUTION:In operating procedure of the bending process, the roots or its adjacencies of a plurality of leads 2 which are straight with respect to the semiconductor body 1 are first pinched by a projecting curvature 3b of a die 3 and the convex of a stripper 4, and thus the leads 2 are fixed. A press applies a pressing from the periphery of the bend of each lead 2 to the protruding curvature 3b of die. Thereby the lead 2 is pushed to be bent into specified angle, and at this time of bending, a compression punch 7 applies a compression stress in the radial direction of the bend. A tensile stress is generated on the outside of the bend by this bending process, and transfer will be made into the plastic deformation region when this value of tensile stress attains a certain limitation. If a compression stress in the radial direction is added to this condition, the mentioned compression stress acts in the form of restraining the plastic deformation caused by the tensile stress. This suppresses initiation of cracks at the bend of the lead 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for bending a lead drawn out from an electrical component such as a resin-molded semiconductor body.

[Conventional technology]

Figure 2 is a sectional view illustrating a conventional method for bending leads pulled out from the body of this type of semiconductor device. In Figure 0, (1) is a resin-molded semiconductor body; A lead drawn out from the semiconductor body (1), (3) and (4) a die and a stripper as molds for holding the lead (2), and (5) a roller for applying bending stress to the lead (21). It is.

Although FIG. 2 shows the state of the final step of bending, the conventional bending method will be explained from the first step. First of all,
The semiconductor body (1) has a plurality of leads (
With die (3) pulled out straight from side to side,
It is fitted into the recess (3a) and positioned. next,
The stripper (A) is lowered from the top by the press,
The convex parts formed on the ends of both (3) and (4) lead
Pinch and tighten the base of 2. In this state, the cylindrical roller (51) is pushed down in the direction of arrow A from a position above the stripper (4) by a press, and the lead (2)
Apply bending stress to. As the roller descends, the bending angle of the reed opening increases, and the reed is finally bent to an angle of about 80 to 85 degrees, as shown in FIG.

[Problem to be solved by the invention]

As the degree of integration of a semiconductor device increases, the width dimension of the semiconductor body (1) also increases, but the external dimensions of the semiconductor device including the leads (2) must be kept within a constant value according to the standard. Therefore, in order to absorb the increase in size of the main body (1), it is required to reduce the radius of curvature of the bent portion of the lead (2) by that amount.

By the way, Figure 3 shows the distribution of stress generated inside the lead (21) when the lead (2) is bent with a radius R. As can be seen from the figure, the stress distribution in the radial direction of the bent part of the lead (2) Tensile stress acts on the outer part from the center, and compressive stress acts on the inner part from the center.This stress value increases as the radius of curvature R becomes smaller, and eventually this tensile stress becomes the lead ( There was a problem in that when the breaking strength of 2) was exceeded, cracks (6) occurred as shown in FIG. 4, and the commercial value as a semiconductor device was lost.

This invention was made to solve the above-mentioned problems, and aims to provide a bending method in which cracks are less likely to occur in the lead even if the radius of curvature is reduced.

[Means and operations for solving the problem] First, the lead is fixed by clamping the vicinity of the base of the lead with a convex curved surface formed on a mold. Next, the lead is bent by pressing a presser whose tip has a concave curved surface from the outer periphery of the bent portion of the lead toward the curved surface of the mold. As a result, compressive stress is applied in the radial direction of the bent portion of the lead, which restrains the plastic deformation of the lead due to the tensile stress generated in the outer portion of the bent portion during bending, thereby suppressing the occurrence of cracks.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) to 4) are the same as in FIG. However, both ends (3b) of the die (3) are formed into convex curved surfaces to serve as the inner shape of the bent portion of the lead (2). (7) is a compression punch as a presser, and its tip 1 (7a) is formed into a concave curved surface to serve as the outer shape of the bent portion of the lead (2).

Next, the work procedure will be explained. First, as in the conventional case, the convex curved surface portion (3) of the die 8) is connected to the vicinity of the base of the plurality of leads (2) that are straight with respect to the semiconductor body (1).
b) and the convex part of the stripper (4) to remove the lead (2).
Next, the compression punch (7) is pressed in the direction of arrow B, that is, from the outer circumferential side of the bent portion of the lead (21) toward the convex curved surface (3b) of the die (3).

As a result, the lead (2) is pressed and bent to the same angle as in the conventional case, as shown in FIG. However, in this embodiment, when the lead (2) is bent, compressive stress is applied by the compression puncher in the direction of arrow B, that is, in the radial direction of the bent portion. By the way, as shown in Fig. 3, tensile stress is generated in the outer part of the bent part of the lead (a) due to bending, and when the value reaches a certain limit value, the tensile stress tends to shift to the plastic deformation region. However, as mentioned above, when radial compressive stress is added to this state, this compressive stress acts in a manner that restrains the plastic deformation caused by the previous tensile stress.As a result, the bent portion of the lead (2) The occurrence of cracks will be suppressed.

Although the above embodiment describes the case where the leads of a semiconductor device are bent, the present invention is not limited to this, and is widely applicable to the case where a lead pulled out from an electrical component is bent near its base. It is applicable.

〔Effect of the invention〕

As described above, in this invention, when bending the lead,
Since compressive stress is applied in the radial direction of the bent portion of the lead, the plastic deformation due to the tensile stress that occurs on the outside of the bent portion of the lead is restrained by the compressive stress, which prevents cracks in the bent portion of the lead. Occurrence is suppressed.

[Brief explanation of the drawing]

Fig. 1 is a sectional view illustrating a lead bending method according to an embodiment of the present invention, Fig. 2 is a sectional view illustrating a conventional bending method, and Fig. 3 is a sectional view illustrating a lead bending method according to an embodiment of the present invention. FIG. 4 is a perspective view illustrating the state of cracks that occur in the lead due to the conventional bending method. In the figure, (1) is the semiconductor body as an electrical component, (
2) is a lead, (3) and 4) are a gooey and a stripper as a mold, respectively, (3b) is a convex curved part formed on the die (3), (7) is a compression punch as a holding tool, (7a) is a concave curved surface portion formed at the tip of the compression punch (7). Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Masuo Oiwa, Patent Attorney Figure 3, Figure 4, Co.

Claims (1)

[Claims] In a method of bending a lead pulled out from an electrical component near its base, the lead is held near its base by a convex curved surface formed in a mold, and the tip of the lead is bent by a concave curved surface. A compressive stress is applied in the radial direction of the bent portion of the lead during bending of the lead by pressing a presser formed on the lead from the outer periphery of the bent portion of the lead toward the curved surface of the mold. A method for bending an electrical component lead, characterized in that: