JPH0745769A - Lead cutting method for resin-sealed semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] When cutting a lead from a lead frame that has undergone resin sealing and surface treatment with solder, it is possible to reduce the exposed portion of the lead material on the cut surface and improve solder wettability. To provide a method of cutting a lead of a resin-encapsulated semiconductor device which can be performed. A lead frame 29 having a solder plating layer 3 of a resin-encapsulated semiconductor device is pressed by a lead clamp 9 from the side opposite to the mounting surface of the lead 13, and the mounting surface of the lead is supported by a notch forming die 8 to form a notch. A step of forming a notch 4 on the surface opposite to the mounting surface of the lead by the molding punch 7 and extending the solder plating layer 3 in the notch 4, and the lead frame 29 on the side opposite to the mounting surface of the lead 13. From the cutting die 11 and the mounting surface of the lead 13 is supported by the lead clamp 12, and the cutting punch 10 is acted from the mounting surface side of the lead 13 to extend the solder plating layer 3 and cut off the lead frame 30. Includes and.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead cutting method for a resin-sealed semiconductor device.

[0002]

2. Description of the Related Art When mounting a resin-sealed semiconductor device on the surface of a printed circuit board, the side surface of the tip of the lead, which is separated from the lead frame which has been resin-sealed and soldered, is mounted on the printed circuit board. It is mounted by pressing against the electrode pad on the surface and fixed by soldering. At this time,
It is necessary to improve the soldering performance by minimizing the dropout of the solder plating layer on the surface of the tip of the lead when cutting from the lead frame.

7A and 7B are views for explaining a conventional lead cutting method. FIG. 7A shows a state before cutting the leads from the lead frame, and FIG. 7B shows a state after cutting the leads from the lead frame. .

In the conventional lead cutting method shown in FIG. 7A, the lead frame 29 having the solder plating layer 3 on the surface of the lead material portion 2 is near the resin sealing portion 1 and the lead clamper 12 is used from the upper surface thereof. It is clamped and its lower surface is supported by the cutting die 11, and the cutting line 10 is cut by the cutting punch 10.
At 1, the lead 13 is cut. Although the drawing shows the order drawing work for cutting the lead frame 29 when the cutting punch 10 descends from the upper side on the side opposite to the mounting surface of the lead 13, the reverse punching for cutting the lead frame 29 from the lower side on the mounting surface side. Work is also being done.

FIG. 8 is a diagram for explaining a conventional lead cutting method as described in JP-A-2-158162, (a).
Shows the state before cutting the leads from the lead frame, and (b) shows the state after cutting the leads from the lead frame.

In the conventional lead cutting method shown in FIG. 8, when a lead frame 29 is manufactured, a step 27 corresponding to a half of the lead plate thickness is formed at a portion which can be a cut surface of the lead 13 in advance.
Is provided on the side opposite to the mounting surface, soldering is performed, and leads are cut, and the other work procedure is similar to that shown in FIG. Since the step 27 is to cut a part that can be a cut surface in advance and the side surface of the cut portion is plated with solder, the solder plating remains on a part of the cut portion at the time of cutting. Will be. Therefore,
The cutting stroke is shortened and the material exposed on the lead cutting surface is reduced. FIG. 9 is a diagram for explaining a conventional lead cutting method as described in JP-A-2-270360.
(A) shows a state before cutting the leads from the lead frame, and (b) shows a state after cutting the leads from the lead frame.

In the conventional lead cutting method shown in FIG. 9, when the lead frame 29 is manufactured, a notch 28 having a thickness of about 1/3 of the lead plate thickness is formed at a portion which can be a cut surface of the lead 13 in advance on the mounting surface side. It is a method of cutting the leads by performing a soldering process from the above, and thus the same effect as the method shown in FIG. 8 is obtained.

[0008]

However, in the conventional method shown in FIG. 7, in the cutting plane, the lead plate thickness of 9 is used.
Since 0% to 95% is the exposed portion 6 of the lead material, there is a problem that when mounting, the solder wettability is poor, the solder is hard to attach, and the soldering strength is weak.

In addition, Japanese Unexamined Patent Publication No. 2-15816 of FIGS.
In the conventional lead cutting method as described in No. 2 and Japanese Patent Laid-Open No. 2-270360, it is necessary to previously form the step 27 or the notch 28 at a portion which can be a cut surface of the lead when the lead frame is manufactured. Step 27 or notch 2
No. 8 significantly reduces the strength of the lead frame, warps or bends of the lead frame are likely to occur during transportation, and transportation problems are likely to occur. Due to the deformation of the lead frame caused by the transport trouble, it becomes difficult to align the positions when cutting the leads, and the accuracy of the cutting dimension does not meet the standard.

The step 27 or the notch 2 formed
In the inner corner portion of 8, the thickness of the solder plating layer is large and the amount of solder is large, so that many solder scraps are generated, and the solder is attached to the leads and the cutting punch 10 and the cutting die 11 are often worn. There was a problem.

FIG. 10 is a cross-sectional view for explaining a defective soldering state of a lead caused by the conventional cutting method, (a) shows the lead by the conventional cutting method shown in FIG. 7, and (b) shows FIG.
9 shows a lead by the conventional cutting method shown in FIG. 9, and FIG. 9C shows a lead by the conventional cutting method shown in FIG.

FIG. 10 is a sectional view showing a state in which the leads cut by the conventional cutting method are bent and soldered to the electrode pads 23 of the printed circuit board 22 to be mounted.
(A) (b) (c) The lead 13 cut by any of the conventional cutting methods has a lead material exposed portion 6 at its end face, that is, a portion 6 where the solder plating layer on the surface has fallen off.
Indicates that the solderability is poor. On the contrary, in each case, the fillet 24 is sufficiently formed.

In the case of FIG. 10C, since the lead material exposed portion 6 exists in the upper half of the lead end surface, the fillet 24
In some cases, the bonding strength between the leads 13 and the printed circuit board 22 may be sufficient even if the formation of the lead is insufficient. The inspection device used for the visual inspection after mounting illuminates the light and converts the reflected light from the object to be measured into effective information, which is used as judgment data. When the lead material is exposed, the amount of reflected light changes extremely, so that it is erroneously determined to be defective. Further, in the work of visually confirming the soldering, the exposed portion 6 of the lead material is detected, and it is determined as a defective product without solder. If defective products occur, reconfirmation work is required, and there is a problem in that work efficiency cannot be improved.

The present invention has been made in view of the above points. When cutting a lead from a lead frame which has been resin-sealed and surface-treated with solder, the exposed portion of the lead material on the cut surface is reduced. An object of the present invention is to provide a lead cutting method for a resin-encapsulated semiconductor device capable of improving solder wettability.

[0015]

In order to solve the above-mentioned problems, the present invention is to hold a lead frame having a solder plating layer of a resin-encapsulated semiconductor device from the side opposite to the mounting surface of the lead with a lead clamp and to A step of supporting the mounting surface with a notch forming die, forming a notch on the surface opposite to the mounting surface of the lead by a notch forming punch, and extending a solder plating layer in the notch, and mounting the lead frame on the lead. Pressing the cutting die from the side opposite to the surface and supporting the mounting surface of the lead with a lead clamp, cutting the lead frame frame while extending the solder plating layer by operating a cutting punch from the mounting surface side of the lead. It is characterized by including.

[0016]

[Operation] A notch forming punch is applied to the semiconductor device that has been subjected to the solder treatment from above on the side opposite to the mounting surface in the previous step,
Then, in the subsequent process, the punch for cutting is applied from below the mounting surface side, so that the solder plating layer extends from the mounting surface side and the non-mounting surface side to the cut end surface of the lead, and the exposed portion of the lead material is reduced. The wettability is improved, and the soldering performance when mounting the semiconductor device on the printed circuit board is improved.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic structure of a semiconductor cut by the lead cutting method of a resin-sealed semiconductor device of the present invention. (A) is a perspective view, (b) is a line AA of (a). FIG.

The semiconductor device comprising the resin sealing portion 1 shown in FIG. 1 and the lead frame 29 having the solder plating layer 3 on the surface is cut at an arbitrary position in the longitudinal direction of the lead frame 29 to cut the lead frame frame. The case of dropping will be described.

FIGS. 2A to 2E are views for explaining the lead cutting method of the resin-sealed semiconductor device of the present invention in the order of steps.

2A to 2E, the lead frame 29 of the semiconductor device is the die 8 for forming the notch of the cutting device.
After being pinched and fixed from the lower surface, that is, the lead mounting surface, and the lead clamper 9 from the upper surface, that is, the surface opposite to the lead mounting surface, the notch forming punch 7 is formed.
As shown in FIG. 2C, the V notches 4 are formed on the upper surface of the lead frame 29 by lowering. The notch forming punch 7 has a minute R processing at its tip, and the notch depth is about 1/2 to 1/3 of the lead thickness. During the time from when the descending notch forming punch 7 comes into contact with the lead to the bottom dead center, the lead frame 2
The solder plating layer 3 of 9 is extended into the V notch 4 from the upper surface side.

In FIGS. 2D and 2E, the V notch 4 is formed.
The lead frame 29 having the above is clamped and fixed from the lower surface by the lead clamper 12 of the cutting device and from the upper surface by the cutting die 11, and then the cutting punch 10 is provided with the lead 1.
It is cut by rising from the lower surface of 3, and at this time, the solder plating layer is extended from the lower surface side to the cut surface, that is, the end surface of the lead 13. In this way, the lead frame frame 30 is cut off from the leads 13 connected to the resin sealing portion 1.

3A and 3B are views showing the state of the tip end of the lead cut by the lead cutting method of the resin-sealed semiconductor device of the present invention. FIG. 3A is a longitudinal sectional view of the lead, and FIG. It is a front view of the front-end | tip part.

As shown in FIG. 3, in order to form the sag 5 by extending the solder plating layer 3 on the end face of the tip of the lead 13, the clearance between the cutting punch 10 and the cutting die 11 is set to 10% of the lead plate thickness. It is suitable to be -15%.
At this time, the material exposed portion 6 between the upper and lower sags 5 is minimized. In this way, the clearance between the cutting punch and the cutting die can be set to be large, so that the durability of the cutting punch and the cutting die is improved and the maintainability is improved.

FIG. 4 is a sectional view showing a state in which the leads cut by the lead cutting method of the resin-sealed semiconductor device of the present invention are mounted on a printed board.

The leads 13 cut by the above method are bent, and the side surfaces thereof are electrode pads 2 of the printed circuit board 22.
FIG. 4 shows a state of being mounted by soldering to No. 3. It can be seen that in this state, the lead material is not exposed to the outside, the fillet 24 is sufficiently formed between the lead 13 and the printed board 22, and good soldering is performed.

FIG. 5 is a sectional view showing another embodiment of the lead cutting method for the resin-sealed semiconductor device of the present invention.

In the embodiment shown in FIG. 5, the notch-forming punch 14 has a single-edged tip, and the tip of the single-edged blade is finely rounded.
The pressing amount of can be made as deep as ⅔ to ½ of the lead plate thickness, and the solder plating layer 3 can be extended into the notch longer. Other work steps are shown in Figure 2.
It is the same as that described in (a) to (e). Also in the embodiment shown in FIG. 5, the exposed area of the lead material can be made smaller as in the case of FIG.

FIG. 6 is a sectional view showing a state in which the leads cut by the lead cutting method of the resin-sealed semiconductor device of the present invention shown in FIG. 5 are mounted on a printed board.

In FIG. 6, it is apparent that the fillet 24 is sufficiently formed between the lead 13 and the printed circuit board 22, good soldering is performed, and the lead material is not exposed to the outside.

[0031]

As described above, according to the present invention, by the notch processing step and the lead cutting step before the leads are individually separated from the lead frame whose surface has been resin-sealed and soldered, the mounting surface side is formed on the cut surface of the leads. And the solder plating layer extends from both the non-mounting surface side and the exposed portion of the lead material on the cut surface, resulting in improved solder wettability and good soldering quality during board mounting. The visual inspection after attachment becomes easy.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a semiconductor cut by a lead cutting method for a resin-sealed semiconductor device of the present invention, FIG.
Is a perspective view, and (b) is a cross-sectional view taken along the line AA of (a).

2A to 2E are views for explaining a lead cutting method for a resin-sealed semiconductor device of the present invention in the order of steps.

FIG. 3 is a diagram showing a state of the tip portions of the leads cut by the lead cutting method for a resin-sealed semiconductor device of the present invention,
(A) is a longitudinal sectional view of the lead, and (b) is a front view of the tip of the lead.

FIG. 4 is a cross-sectional view showing a state in which the leads cut by the lead cutting method of the resin-encapsulated semiconductor device of the present invention are mounted on a printed board.

FIG. 5 is a cross-sectional view showing another embodiment of the lead cutting method of the resin-sealed semiconductor device of the present invention.

FIG. 6 is a cross-sectional view showing a state in which the leads cut by the lead cutting method of the resin-sealed semiconductor device of the present invention are mounted on a printed board.

FIG. 7 is a diagram for explaining a conventional lead cutting method, (a)
Shows the state before cutting the leads from the lead frame, and (b) shows the state after cutting the leads from the lead frame.

FIG. 8 is a diagram for explaining a conventional lead cutting method, (a)
Shows the state before cutting the leads from the lead frame, and (b) shows the state after cutting the leads from the lead frame.

FIG. 9 is a diagram for explaining a conventional lead cutting method, (a)
Shows the state before cutting the leads from the lead frame, and (b) shows the state after cutting the leads from the lead frame.

FIG. 10 is a cross-sectional view illustrating a defective soldering state of a lead caused by a conventional cutting method, (a) showing a lead by the conventional cutting method shown in FIG. 7, and (b) showing a conventional lead shown in FIG. The lead by the cutting method is shown, and (c) shows the lead by the conventional cutting method shown in FIG.

[Explanation of symbols]

 3 Solder Plating Layer 4 Notch 7 Notch Forming Punch 8 Notch Forming Die 9 Lead Clamp 10 Cutting Punch 11 Cutting Die 12 Lead Clamp 13 Lead 29 Lead Frame 30 Lead Frame Frame

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[Procedure amendment]

[Submission date] April 6, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

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[Claims]

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[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

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[0015]

In order to solve the above-mentioned problems, the present invention is to hold a lead frame having a solder plating layer of a resin-encapsulated semiconductor device from the side opposite to the mounting surface of the lead with a lead clamp and to The step of supporting the mounting surface with a notch forming die, forming a notch on the surface opposite to the mounting surface of the lead by a notch forming punch, and extending the solder plating layer in the notch, and mounting the lead frame on the lead Pressing the cutting die from the side opposite to the surface and supporting the mounting surface of the lead with a lead clamp, cutting the lead frame while extending the solder plating layer by operating a cutting punch from the mounting surface side of the lead. It is characterized by including. In addition, the tip shape of the notch forming punch
The shape is double-edged or single-edged. Also, the tip of the blade die is very small
R processing has been applied.

Claims (1)

[Claims] 1. A notch forming punch in which a lead frame having a solder plating layer of a resin-encapsulated semiconductor device is held by a lead clamp from the side opposite to the lead mounting surface and the lead mounting surface is supported by a notch forming die. The step of forming a notch on the surface opposite to the mounting surface of the lead and extending the solder plating layer in the notch, and pressing the lead frame from the side opposite to the mounting surface of the lead with a cutting die and mounting the lead. A step of cutting off the lead frame frame while extending the solder plating layer by applying a cutting punch from the mounting surface side of the lead while supporting the surface with a lead clamp. Lead cutting method.