JPS644347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a lead frame used for assembling a semiconductor device.

The first step is to assemble a resin molded semiconductor device.
A lead frame as shown in the figure is used. This lead frame 1 is formed by partially removing a thin metal plate by etching or stamping. The lead frame 1 has a frame 2 made of a rectangular frame, and has a rectangular tab 3 approximately in the center of the frame 2 to which a circuit element is attached. The tab 3 is supported at both ends by two tab leads 4 extending from the center of the pair of inner walls of the frame 2 toward the center of the frame 2. Further, a large number of thin leads extend from the inner wall of the frame frame 2 toward the tab 3. Since this lead frame 1 is a lead frame for a dual-in-line type semiconductor device, leads 5 extend from the inner wall portions of a pair of opposing frames.
There is also a structure in which it extends. Further, each lead 5 is supported by a dam piece 6 that prevents resin from flowing out during resin molding. This dam piece 6 also serves as a reinforcing member.

In the case of such a lead frame 1, after the circuit element 7 is fixed on the tab 3, each electrode (not shown) of the circuit element 7 and the inner end of the lead 5 corresponding to these electrodes is connected with a wire 8. After that, the mold area 9 inside the dam piece 6 is molded with resin, and the circuit element 7, the wire 8, and the inner end of the lead are covered with a resin package 10. Further, the unnecessary dam piece 6 and frame frame 2 are cut and removed, and the leads 5 protruding from the resin package cage 10 are removed.
A dual in-line resin molded semiconductor device is manufactured by bending the outer end of the semiconductor device downward.

Incidentally, depending on the product, wires may also be connected on the tab lead 4. In this case, in the case where the lead frame 1 is manufactured by stamping, a special wire bonding area is not secured, so as shown in FIG. There is a strong tendency for the surface of the tab lead 4 to become rounded 11. This is particularly noticeable when the lead frame is made of copper and is relatively thick, for example, 0.5 mm thick. Therefore, if the surface of the wire bonding area of the tab lead 4 is rounded, the wire will not be crimped sufficiently, resulting in a connection failure.

Therefore, a method of partially flattening the tab lead surface by crushing the wire bonding area of the tab lead by coining may also be considered. However, in such a method, the tab rises and flops due to the crushing deformation, which is not preferable for connecting circuit elements and wires. Further, depending on the lead frame pattern, the inner lead may also serve as a tab lead, but in this case, it is expected that coining will have an adverse effect on the dimensional stability of the leads of the lead frame.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a lead frame in which the surface of the wire bonding area of a tab lead is flat.

To achieve this object, the present invention provides a frame by partially punching out a thin metal plate, a rectangular tab located in the center of the frame and to which a circuit element is attached, and a rectangular tab extending from the frame. In the method for manufacturing a lead frame having two tab leads supporting both ends of the tab lead and a plurality of leads extending from the frame frame and having inner ends facing the periphery of the tab, after punching a lead frame pattern, a part of the tab lead is A V-groove is formed along an interface that defines a region corresponding to a wire bonding region, and then the region surrounded by the V-groove is coined and flattened to form a wire bonding region, and the method described below is performed. The invention will be explained by way of example.

FIG. 3 is a plan view showing a lead frame manufactured by the method of the present invention. This lead frame has a structure in which a wire bonding area is newly provided in a part of the tab lead in the lead frame shown in FIG. Therefore, the explanation of each part will be omitted, and the names and symbols will be used as they are. This lead frame 1 is patterned by stamping a thin metal plate (for example, copper-based metal). After that, the wire bonding area 12 of the tab lead 4 is
form. That is, as shown in Figure 5a,
A V groove having a V-shaped cross section extending in the width direction is provided on both ends of the wire bonding region 12 of the tab lead 4, in other words, on the longitudinal side of the tab lead 4, by coining. In this case, the V-groove is provided along the edge of the area of the tab lead 4 corresponding to the wire bonding area 12, that is, along the interface. Moreover, the flat surface 13 due to coining is
Since the grooves 15 are provided over the entire width of the tab lead 4, a pair of V grooves, that is, the grooves 15 are provided in parallel along the width of the tab lead 4 so as to sandwich the wire bonding area. Thereafter, as shown in FIG. 1B, the wire bonding region 12 sandwiched between the pair of V-grooves is partially crushed by coining to form a flat surface 13. The deformation 14 due to coining rises into the space of the V-groove 15 and protrudes outward as shown in Figure 5 (b) and Figures 4 (a) and (b), so deformation due to coining occurs in the lower base material of the tab lead. do not. In this case, it is necessary to specify the depth of the coining or V-groove 15 to such an extent that the base material is not deformed. Therefore, the tab lead 4 is not warped, twisted, or otherwise deformed.

Such a lead frame 1 has a tab lead 4.
Since the wire bonding region 12 is flattened by coining, the roundness of the tab lead surface caused by stamping during lead frame formation, which is particularly noticeable in copper-based metals, is eliminated. Therefore, as shown in FIG. 4b, wire bonding is performed reliably and the reliability of the bonding is also good. Therefore, in a semiconductor device using this lead frame 1, the yield of wire bonding is improved and the reliability is also improved.

Note that the present invention is not limited to the above embodiments. That is, the groove for absorbing material deformation during coining in the wire bonding region 12 is not limited to the V-shaped cross-section groove. Furthermore, one or more wire bonding regions 12 may be provided on each tab lead 4, and the lead frame shape may also be in another pattern.

As described above, according to the present invention, it is possible to provide a lead frame in which the surface of the wire bonding region of the tab lead is flat.

[Brief explanation of the drawing]

Figure 1 is a plan view showing a conventional lead frame.
FIG. 2 is an enlarged sectional view of the tab lead, FIG. 3 is a plan view of a lead frame according to an embodiment of the present invention, and FIGS. , Figure 5 a, b
2 is an enlarged view showing the tab lead coining method. 1...Lead frame, 4...Tab lead, 7
...Circuit element, 8...Wire, 11...Roundness, 1
2... Wire bonding area, 13... Flat surface, 14... Deformation, 15... Groove.

Claims (1)

[Scope of Claims] 1. A frame made by partially punching out a thin metal plate, a rectangular tab located at the center of the frame and to which a circuit element is attached, and two tabs extending from the frame and supporting both ends of the tab. A method for manufacturing a lead frame having a tab lead and a plurality of leads extending from a frame frame and having inner ends facing the periphery of the tab, wherein after punching out a lead frame pattern, a plurality of leads corresponding to a wire bonding area of a part of the tab lead are formed. A method for manufacturing a lead frame, comprising: forming a groove along an interface that divides a region, and then coining and flattening a region surrounded by the groove to form a wire bonding region. 2. The method of manufacturing a lead frame according to claim 1, wherein the groove is a V-groove.