JPH03216222A - Manufacture of lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a positional deviation for a internal lead by making a clearance of former process side of a die between a punch and a die on the side punching process larger than that of a rear process side. CONSTITUTION:The clearance C1 between the punch 21 and the die 23 on the 1st process on the punching layout, the clearance C2 of the 2nd process and the clearance C3 on the 3rd process are made as the relation of C1 > C2 > C3. The internal lead 24 is applied with the force so as to bend the lead 24 on the punching time. Next, when the side of the lead 24 opposite to the side which is already punched is punched, the lead 24 is apt to bend to the arrow direction. The forces generated on each drawing are made equal by changing the clearances between the punch 21, 26 and the die 23, 27, or mutually counterbalanced because they are operating to the opposite direction. There is the effect to prevent the positional deviation.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention... Especially regarding the manufacturing method of lead frames. The present invention is applied to a method for manufacturing lead frames for semiconductor devices.

(Prior Art) A conventional method for manufacturing a lead frame for a semiconductor device will be described based on the drawings. FIG. 4 shows an example of a lead frame for a semiconductor device. Diver 42 is Guipat 41
is hanging. A plurality of internal leads 43 are arranged around the die butt 41.

When manufacturing such a lead frame for a semiconductor device, it is manufactured with a punched layout as shown in FIG. The flow direction is to the right. 11 to m each indicate the punching shape from the initial process to the m process. In each of these processes, the material Since both the material thicknesses are the same, the internal leads of lead frames for semiconductor devices are. The punch and die clearance was the same from the first process to the mth process.

(Problem to be Solved by the Invention) However, in such a lead frame manufacturing method, the internal leads punched from the initial process to the final process cannot be used in the subsequent process after the tips are cut off and the internal stress is released. There was a drawback that the position would shift in the direction in which the punch was punched.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a lead frame in which the internal leads do not shift in position even when the shapes of both sides of the internal leads are punched out alternately, and the internal leads are held in their normal positions. It is said that

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a method for manufacturing a lead frame for a semiconductor device. It is formed by press working. One internal lead of a semiconductor device having multiple internal leads is formed in two or more punching processes, and the clearance between the punch and die in the punching process of the side surface punched in the previous process is the same as that of the punch and die in the punching process in the later process. This was made larger than the clearance between the punch and the die in the side punching process.

(Function) The method for manufacturing the above lead frame for semiconductor devices is as follows. 6th
As shown in Figure (a), when punching out one side of the internal lead 64, as shown by the arrow. Punch 61
A force that tries to move the internal lead 64 from its normal position in the direction of . This takes advantage of the fact that it changes depending on the clearance C and presser force. In other words. Figure 6 (
As shown in a), when pulling out one side of the internal lead 64, the force to press the internal lead 64 is large because the stopper 62 and die 63 press the material 65. but. As shown in Figure 6(b), in the subsequent steps. The force for pressing the internal lead 64 becomes small because only the internal lead is pressed.
Also, the force that tries to move the internal lead from its normal position is... The larger the clearance C, the thicker it becomes, and the smaller the clearance C, the smaller it becomes. The force holding down the internal lead differs between the front and back processes, and in order to offset this difference, the punching (side clearance) is made smaller in the post process than the punching (side clearance) in the front process. The internal lead can be held in the correct position.

Examples of the present invention will be described below based on the drawings. 1st
The diagram is. This is a diagram showing the layout of internal leads. From the first step of punching out the center internal lead to the nth step of cutting off the tips of the internal leads, the internal leads, tie bars, and gouging pads are formed by punching outward from the center in order. Each internal lead, tie bar, and guide pad is formed in two or three steps.

The clearance of the first process l of this punching layout is CI
, the clearance of the second process 2 is C2, the clearance of the third process 3 is C3, the clearance of the fourth process 4 is C4, the clearance of the fifth process 5 is C5, the clearance of the nth process is C5, and the respective clearances are CI>C2
The relationship is >C3>C4>C5.

The effect that the clearance and punching order configured in this way have on the corresponding internal lead will be explained with reference to FIG. FIG. 2(a) is a cross section of the bunch 21 punching out the side surface of the internal lead 24, the die 23 paired with it, and the stopper 22 that guides the bunch 2l and presses the material. FIG. 2(b) is a sectional view of the punch 26, die 27, and stopper 22 for punching the opposite side of the internal lead 24 punched in FIG. 2(a).

When the internal lead 24 is punched out as shown in FIG. A force is applied to bend the internal lead 24 in the direction of the arrow. Next, as shown in FIG. 2(b), when the side surface of the internal lead 24 on the opposite side that has already been punched out is punched out, the internal lead 24 receives a force that tends to bend the lead in the direction shown by the arrow. The force generated in Figure 2(a) and the force generated in Figure 2(b) become equal by changing the clearance, and... Since they act in opposite directions, they cancel each other out.

FIG. 3 is a layout diagram showing another embodiment of the present invention.

The clearance for the first process 1 and second process 2 is Cl, and the clearance for the third process is Cl.
Step 3 The clearance of the nth step is C5.

Here again, the relationship is CI>C5. If the clearance is configured as shown in 2, the force generated during punching will act on the leads in the same way as in the previous embodiment, so the punching layout of the internal leads will be a regular punching layout in which the internal leads are punched outward one by one from the center. There is no need to create a layout, and even if several shapes are punched in one process, the lead position can be maintained at the correct position.

(Effects of the Invention) The present invention is as described above. When forming internal leads by press working, the clearance of the side surfaces of the punching in the post-process was made smaller than the clearance of the sides of the punching in the pre-process. This has the effect of preventing the internal read from shifting by one position. In particular, internal leads are concentrated. This is effective when the strength of the internal lead is low.

[Brief explanation of drawings]

Fig. 1 is a punched layout diagram showing an embodiment of the present invention, and Fig. 2 is a cross-sectional view when punching shows an embodiment of the present invention. FIG. 3 is a cutout layout diagram showing another embodiment of the present invention. FIG. 4 is a plan view of a lead frame, FIG. 5 is a punched layout diagram showing a conventional technique, and FIG. 6 is a sectional view of the conventional technique during punching. 21.61...Punch 23.63...Die 24.64...Internal lead 26.66...Punch 27.67...Die 43...Internal lead

Claims (1)

[Claims] (1) In a method for manufacturing a lead frame for a semiconductor device that is formed by press working and has a plurality of internal leads, one internal lead is formed in two or more punching processes, and one internal lead is punched in the previous process. A method for manufacturing a lead frame for a semiconductor device, characterized in that a clearance between a punch and a die in a punching process for a side surface is larger than a clearance between a punch and a die in a punching process for a side surface to be punched in a subsequent process.