JPS5933982B2 - Lead frame manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a lead frame, and in particular, an object of the present invention is to prevent meandering that occurs when a lead frame for a semiconductor device is connected to a band-shaped metal plate.

2. Description of the Related Art In the manufacture of semiconductor devices such as power transistors and ICs, there is a step of arranging elements on a lead frame and leading out electrodes of the elements.

The above lead frames are made of copper, copper alloy, iron, iron-nickel alloy, etc., and power transistors, power ICs, etc. are made of copper, copper alloy, iron, iron-nickel alloy, etc.
Copper alloys are mainly used, but due to the problem of bending strength of the outer leads as semiconductor devices, the hardness of copper and copper alloy strips is lowered to satisfy this requirement. Figure 1 shows one example of a frame-shaped lead, which is connected to a second
The shape shown in the figure is punched out using a press. At this time, the distance A between the spout holes of the side edge bar 1 with the wide width w and the distance B between the spout holes of the side edge bar 2 with the narrow width w are B.
>A, and while A is equal to the mold dimension, B is several microns to several tens of microns longer than the mold dimension. In this way, a ``curvature'' occurs over the entire length of the lead frame, and the length deviation shown in the figure is seen at the center. The above is actually 16 cm long with 14 connected leads and the hardness of the strip is -H (JIS) O, 05u)
When the hardness is -H, it reaches 0.3 degrees.

Moreover, this tendency becomes more pronounced as the difference in width of the side edge bars provided on the side edges of the strip increases, and deformation is unavoidable, resulting in the following drawbacks. That is, the positioning accuracy of the lead frame is deteriorated in each machine used in the die bonder, wire bonder, encap, preform, etc. processes of the semiconductor assembly process.

As a result, the yield of semiconductor assembly is significantly reduced. The present invention provides an improved lead frame manufacturing method to eliminate the above-mentioned conventional drawbacks.

That is, the present invention applies press working to a relatively soft metal strip to form a lead frame having side edge bars of different widths on both sides of the metal strip. It is characterized by having a process for processing coins.

Next, the present invention will be explained in detail regarding a lead frame manufacturing method according to an embodiment.

FIG. 3 shows an example of punching a lead frame by pressing. That is, die cutting is performed in the direction shown by the arrow in the figure. "Cutting die" with dense diagonal lines in the figure (Ila, ll
b...) is provided at m/c, and the mold 12 is dotted with dots.
, 12', and 13 are "pressing molds", and 12, 12' are for bending a part of the lead, and 13 is a "coin processing part" as shown in cross section in FIG. This is used by experimentally adjusting the machining depth t, groove opening degree θ, and groove end diameter r depending on the material of the lead frame (particularly hardness less than -H) and selecting appropriate values. The lead frame formed in this way is shown in FIG.
It becomes something without "one song". That is, in this case, the distance A' between the spout holes in the side edge bar 21 with the wide width w and the distance B' between the spout holes in the side edge bar 22 with the narrow width w are B'2N, and both of the mold The size of the particles is several microns to several tens of microns, but there are no "wand curves". For this type of lead frame, even if the pitch is as large as above, it will not cause any problem in semiconductor assembly. However, for lead frames that pose a problem, the mold dimensions should be made shorter by several microns to several tens of microns per pitch in advance, and after coin processing, All you have to do is match it to the regular pitch, and this can be easily accomplished. The present invention has the following advantages.

(1) If the material of the lead frame is a soft copper material, copper alloy material, or other material with hardness below -H quality, it can be manufactured without "curving".

(2) Since the lead frame can be made of a soft material, a semiconductor device using the lead frame has high bending strength.

(3) Since there is no bending, each meter/
The positioning accuracy at c becomes better. (4) As mentioned above, since the positioning accuracy is good, the accuracy of each assembly process is greatly improved. Furthermore, auto bonding requires a high-precision lead frame with no curvature, but this can also be satisfactorily handled.

[Brief explanation of the drawing]

FIG. 1 is a front view of a frame-shaped lead 1, FIG. 2 is a front view of a conventional lead frame, and FIG.
Fig. 3 is a diagram for explaining the press working of the lead frame of one embodiment, Fig. 4 is a sectional view for explaining the coin processing, and Fig. 5 is a front view of the lead frame of the embodiment. be. 13... Coin processing section, 21... Wide side edge bar,
22... Narrow width side edge bar.

Claims (1)

[Claims] 1. A lead frame characterized in that, in a press working process for forming a lead frame having side edge bars of different widths on both sides of a metal band, coin-processed portions in the width direction of the band are formed on wide side edge bars. Production method.