JP2823328B2 - External lead forming method and external lead forming apparatus for resin-sealed semiconductor device - Google Patents

Description

The present invention relates to an external lead forming method and an external lead forming apparatus for a resin-encapsulated semiconductor device.

(Prior Art) In a conventional method of manufacturing a resin-encapsulated semiconductor device (hereinafter simply referred to as a semiconductor device), a semiconductor chip is joined to a stage portion of a lead frame, and resin-sealing is performed by wire bonding.

 After that, the dam bar is cut.

Subsequently, in the state of being supported on the rails with the suspending pins, the external leads of the semiconductor device are individually cut so as to be free, and the external leads are bent.
Thereafter, the semiconductor device was separated from the rail.

When bending the external leads of the semiconductor device while the semiconductor device is separated from the rail, the semiconductor device is separated from the rail after resin sealing, and the separated semiconductor device is transferred to each process. And was working on it.

(Problems to be Solved by the Invention) However, the synthetic resin forming the resin sealing portion of the semiconductor device described above shrinks with a decrease in the resin temperature, and causes warping and twisting of the resin sealing portion. For example, as shown in FIG. 5, the entire resin sealing portion 2 warps as the resin sealing portion 2 contracts. This is because a stress difference occurs between the upper part and the lower part of the resin sealing part 2. For this reason, a deviation occurs in the height position of the external lead.

When the external lead 3 of the semiconductor device is bent in the semiconductor device in which the resin sealing portion 2 is warped as described above,
The external leads 3 are not uniformly bent, causing variations in the height direction, and errors in the lead pitch of the external leads 3.

In a specific processing example, when bending the external lead 3 of the resin-sealed semiconductor device, the shoulder 3a of the external lead 3 is used.
Is strongly held by the die 5 having a flat surface and the knockout 6, and the external leads are bent by the punch 7 in a state where there is no large variation in the height direction (see FIG. 6). Therefore, when the semiconductor device is taken out of the mold,
The shoulder 3a of the external lead 3 returns to the state of being dispersed again in the height direction, and the trajectory drawn by the tip of the external lead 3 becomes arc-shaped (see FIG. 5).

That is, due to the warpage of the semiconductor device 1, the external leads 3b located at the ends of the external leads 3 arranged side by side produce a deviation 1 from the position assuming that the resin sealing portion does not warp, and H is generated as a positional deviation in the height direction. When the semiconductor device 1 having such deviations l and h is mounted on a printed circuit board, all the external leads 3 cannot be mounted uniformly,
It may cause poor contact. In particular, it is more remarkable in a semiconductor device having many external leads,
Further, there is a problem that the deviations l and h increase with the increase in the number of external leads of the semiconductor device, and the reliability is lacking.

Further, the dam bar connecting the middle part of the external lead of the semiconductor device is cut and removed after sealing with resin. As shown in the cross-sectional view of the cut-out portion of the dam bar shown in FIG. Remains as burr 3c. As shown in FIG. 6, when the external lead 3 is bent, the external lead 3 is bent so as to be clamped from above and below. As a result, the bending is performed in a state where the external lead 3 is lifted up by the burr 3c, and uniform bending cannot be performed. Was.

Furthermore, although the external leads are plated with solder, it is difficult to make this plating layer uniform in thickness, and the thickness differs. The unevenness of the thickness of the solder plating causes a variation in the bending process.

Due to the burrs 3c and the uneven thickness of the solder plating, the tips of the external leads 3 become uneven as shown in FIG.

Therefore, an object of the present invention is to provide an external lead molding method and an external lead molding device for a resin-encapsulated semiconductor device, in which even if the resin encapsulation portion of the semiconductor device is warped, the external leads are aligned and molded. I do.

(Means for Solving the Problems) The present invention has the following configuration to achieve the above object.

The method for forming an external lead of a resin-encapsulated semiconductor device according to the present invention includes a preliminary bending step of bending an external lead extending from a resin-encapsulated portion downward to bend outward (so-called external lead is folded in a Z-shape). A bending step of correcting the outer lead by pressing the outer lead in such a manner that the tip of the outer lead is aligned with a free bending state while supporting the base of the bent outer lead. And characterized in that:

In the correction bending step, the base of the external lead may be clamped so that the tip of the external lead is in a free state. Further, when clamping the base of the external lead, it is preferable to clamp the base of the external lead with a force that does not deform the external lead.

An apparatus for realizing the above molding method includes a die extending from a resin sealing portion, bending downward, further supporting the base of the external lead bent outward, and setting the tip of the external lead in a free state. And a knockout for holding the base of the external lead while holding the external lead supported by the die, and a modified bending punch for pressing the free end of the external lead and further bending it. It is characterized by.

Further, in the above-mentioned external lead forming apparatus, a concave portion may be formed at an appropriate position in a support portion of a die for supporting a base of the external lead.

(Operation) Next, the operation of the present invention will be described.

The external lead extending from the resin sealing portion is bent in a Z-shape, and while the base of the external lead bent in the Z-shape is supported, the tip of the external lead remains in a free state.
The external lead is bent more than a predetermined position by the correction bending punch.

Then, by releasing the bending force of the modified bending punch, the tip positions of the external leads are aligned.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The bending method according to the present invention, in which the external lead extending from the resin sealing portion of the semiconductor device is bent downward and further bent outward (bent-shaped). In addition to the description of the bending method, an apparatus used for the method will be described.

First, the preliminary bending step will be described with reference to FIG.

The resin-sealed semiconductor device 10 is separated from the lead frame, and after cutting and removing dam bars and resin burrs, the semiconductor device 10 is mounted on the bending die 20 of the preliminary bending device.

Then, a shoulder 14a, which is the base of the external lead 14 extending from the resin sealing portion 12 of the semiconductor device 10, is held between the bending die 20 and the knockout 24. The bending die 20 and the knockout 24 are formed with concave portions 20a and 24a for accommodating the resin sealing portion 12 of the semiconductor device 10, respectively. Further, a step portion 25 which is a tapered surface whose lower side is widened is provided in the middle of both side surfaces of the knockout 24.

Note that the knockout 24 has a cushion mechanism supported by a spring material from above.

Reference numerals 28a and 28b denote bending punches supported to move up and down against both outer side surfaces of the knockout 24. Bending punch 28a, 2
8b is formed in a rectangle, knocked out on the upper inner wall side
A roller 30 that rolls in contact with the outer wall of the knockout 24 is rotatably supported, and a support shaft 32 that drives up and down in parallel with the center line of the knockout 24 is provided at a substantially central position. Bending punch 28a, 28b
Moves up and down at the same timing due to the above configuration.
In the drawing, the bending punch 28a on the right side from the center line position is in contact with the external lead 14, and the bending punch 28a on the left side from the center line position is in a state where the external lead 14 is bent in a Z shape.

Knockout 24 has external leads 14 between bending die 20
When the bases are clamped, the bending punches 28a and 28b start descending.

Then, when the bending punches 28a and 28b descend, the roller 30 contacts the outer wall surface of the knockout 24 and rolls, and further descends so that the roller 32 rides on the outer wall surface of the step portion 25.
Then, with the support shaft 32 as a fulcrum, the upper side of the bending punches 28a, 28b is opened, and the lower side is lowered so as to move inward, and the external leads 14 are sandwiched between the bending die 20 and Z-shaped. Fold it into a shape.

In the preliminary bending step, the external leads 14 are slightly shallowly bent without bending to the final dimensions.

The modified bending of the semiconductor device 10 in which the external lead 14 is formed by the above-mentioned nominal bending device will be described.

Semiconductor device with external leads processed in the pre-bending step
10 is sent to the correction bending process which is the next second bending process.

The correction bending step is for correcting the external leads 14 bent in the bending step. In particular, in the pre-bending step, external leads are provided by the bending punches 28a and 28b and the bending die 20.
14 ... are sandwiched and formed in a Z-shape. As described in the above-mentioned conventional example, the bending position of the tip of the external lead 14 is reduced due to the warpage of the resin sealing portion 12 or the burr of the dam bar. Not aligned (see Fig. 8). Aligning the bending positions of the outer leads 14...

As shown in FIG. 2, the semiconductor device 10 having undergone the pre-bending step is placed on the modified bending die 40.

The modified bending die 40 is provided with a support die portion 40a that supports the base of the external lead 14, and a recess 40b surrounded by the support die portion 40a is a storage portion of the resin sealing portion 12 of the semiconductor device 10. . The recess 40b is formed in such a size that the resin sealing portion 12 does not touch the die.

A knockout 44 has a cushion mechanism supported by a spring material or the like, but has a very small spring force. On the lower surface of the knockout 44, external leads 14 of the semiconductor device 10 mounted on the correction bending die 40 are provided.
A support portion 44a is formed to hold the semiconductor device 10 with the support die portion 40a of the correction bending die 40, and a recess 44b for accommodating the resin sealing portion 12 of the semiconductor device 10 is formed. The recess 44b is formed in a size that does not make contact with the resin sealing portion 12.

That is, since the shoulders 14a of the external leads 14 of the semiconductor device 10 are only clamped by the correction bending die 40 and the knockout 44 with a small force, the variation of the shoulders 14a of the external leads 14 is not largely corrected. Shoulder 14a of external lead 14
It is clamped and supported in the state of variation.

On the side surface of the knockout 44, a correction bending punch 48 that moves up and down against the knockout 44 is provided. The modified bending punch 48 starts descending after the knockout 44 clamps the shoulder 14a of the external lead 14... With the modified bending die 40.

The correction bending punch 48 descends vertically and presses the external lead 14 downward. Note that the supporting die portion 40a of the modified bending die 40
Is largely open, so that even when the external lead 14 is pressed downward by the correction bending punch 48, a space 40c where the tip of the external lead 14 does not hit the correction bending die 40 is secured.

In FIG. 2, the external lead 14 indicated by a two-dot chain line shows a processing state in the pre-bending step, and in this state, there is a vertical variation at the tip of the external lead 14.

The modified bending punch 48 is lowered, and the external lead 14 shown by the two-dot chain line is bent to the position shown by the solid line. Then, the shoulder 14a of the external lead 14 where plastic work hardening has not occurred, especially the shoulder not clamped by the modified bending die 40 and the knockout 44.
The portion A of FIG. 14a is bent due to stress concentration, and the external lead 14 is positioned at the bent position.
The tips are aligned. In other words, in the pre-bending process, external leads
The tips of the external leads 14 are further pushed down from the position where the tips 14 are all the lowest, and the tips of the external leads 14 are aligned at the pushed-down position.

In the above-described correction bending of the tip of the external lead 14, the external lead 14 may slightly return from the once bent position due to spring back. Consider this case.

The correction bending punch 48 is lowered, and the external lead 14 shown by the two-dot chain line is bent to the position shown by the broken line. In the pre-bending step, the outer die 14 and the supporting die 40 of the modified bending die 40 are used.
Although the angle formed between the outer surface of a bent up theta _1,
In modified bending step and bending until the angle becomes theta ₃ from theta _1.

When the correction bending punch 48 is raised, the outer leads 14 return to the positions of the outer leads 14 indicated by solid lines by the spring bag. External lead 14 and support die 40a
The angle formed between the outer surface so that the return to theta ₂ of.

In the pre-bending step, the two bent portions 14b and 14c of the external lead 14 have undergone plastic work hardening. Therefore, when the tip of the external lead 14 is pushed down by the modified bending punch 48, the portion A of the shoulder portion 14a of the external lead 14 where plastic work hardening has not occurred as described above is bent. In the case where the external lead 14 causes springback, the correction bending process is performed plural times,
It is also possible to further reduce the 14 variations.

As described above, in the modified bending step, the bent portion 14c of the external lead 14 has undergone work hardening regardless of whether the external lead 14 has caused springback or not. The angle α of the bent portion does not change. The correction bending step is a step of bending the external lead 14 whose base has been bent shallowly in the preliminary bending step to an angle (θ ₂ ), and corrects the irregularly arranged external leads 14... By largely bending downward with the bending punch 48, the heights of the external leads 14 can be made uniform. In other words, the correction bending step can reduce variations (flatness) of the external leads 14...

For example, when the semiconductor device 10 is placed on a flat surface, the height (standoff) between the tip of each external lead 14 and the lower surface of the resin sealing portion 12 can be set to a predetermined length. That is, when the semiconductor device 10 is mounted on the horizontal plate, all the external leads 14
Is in contact with the horizontal plate.

 Next, a modified example of the modified bending die 40 will be described.

If there is a vertical variation in the shoulder 14a of the external lead 14 of the semiconductor device 10, the semiconductor device
It is not stable when 10 is placed. Also, modify bending die 40
The outer die 14 is supported by the support die 40a and the knockout 44.
When the outer lead 14 is clamped, the position of the tip of the outer lead 14 is formed in a state where the vertical variation of the outer lead 14 is corrected, and the outer lead 14 is modified and bent.
In some cases, the position of the shoulder 14a of the external lead 14 is restored when the external lead 14 is removed. This is the semiconductor device 10
Is not able to be held horizontally.

Therefore, as shown in FIG. 3, when the shoulder portion 14a of the external lead 14 has an arc shape due to the warpage of the resin sealing portion 12, a concave portion 41 is formed on the upper surface of the support die portion 40a of the modified bending die 40. Preferably, the base of the external lead 14 can be stably mounted in a horizontal state.

That is, in the concave portion 41 on the upper surface of the support die portion 40a of the correction bending die 40, the shoulder portions 14a... Of the external leads 14 located at the central portion of the parallel external leads 14 are supported by the support die portion 40a. And the semiconductor device 10 can be supported horizontally. Then, even if the knockout 44 (shown by a dotted line) is lowered, the external lead 14 located in the concave portion 41 is not pinched and has play. Therefore, even if the external leads 14 are sandwiched between the support die portion 40a of the modified bending die 40 and the knockout 44, the external leads 14
In the state where the variation in the vertical direction of a is not corrected,
The positions of the tips can be aligned, so that the positions of the tips of the external leads 14 of the semiconductor device 10 after being taken out from the correction bending die 40 can be kept in the same state.

That is, by forming the concave portion 41 on the upper surface of the support die portion 40a corresponding to a portion where the variation of the external leads 14 is likely to occur, the variation of the external leads 14 is escaped and the semiconductor device 10 is supported horizontally. Can be done. Therefore, it goes without saying that a plurality of recesses 41 may be formed.

As described above, by performing the preliminary bending step and the correction bending step on the external lead 14, the flatness can be reduced, the standoff can be kept constant, and a semiconductor device with higher dimensional accuracy can be formed. .

 Next, a modification of the above embodiment will be described.

After the resin sealing portion 12 is formed on the lead frame 50 and through a predetermined process (see FIG. 4 (a)), when cutting the ends of the external leads 14, the ends of the external leads 14 are connected. Piece
Cut from the lead frame 50 with the connection at 52
Then, the external leads 14 may be formed by the preliminary bending process and the correction bending process of the above embodiment. After bending the external leads 14, the connecting piece 52 at the tip of the external lead 14 is cut off.

Alternatively, after the preliminary bending step is performed in a state where the external leads 12 are connected by the connecting pieces 52, the connecting pieces 52 may be cut off, and then the modified bending step may be performed.

As described above, by performing the bending process in a state where the external leads 14 are connected, even when an external force is applied to a part of the external leads, the forces are released and averaged. In addition, positional deviations of the external leads 14 due to warpage of the resin sealing portion 12 and the like can be averaged while absorbing each other, and variations in the external leads 14 can be prevented.

In each of the above-described embodiments, the correction bending step is performed by clamping the base of the external lead 14. However, without clamping the external lead, the correction bending step is performed only by placing and supporting on the correction bending die 40. The correction bending may be performed by the punch 48.

The semiconductor devices to which the above embodiments are applied are applicable to semiconductor devices in which external leads extend from corresponding two sides (so-called SOP) and semiconductor devices in which external leads extend from four sides (so-called QFP). It is. Further, each semiconductor device 10 may be formed with external leads while being supported by the rails of the lead frame, or may be formed with each semiconductor device cut off from the lead frame.

The present invention is not limited to the above-described embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the present invention.

(Effect of the Invention) The present invention is configured as described above, and after bending the external lead of the semiconductor device once into a Z-shape with a predetermined dimension, the external lead is pushed down while the external lead is kept free. Therefore, the tip of the external lead can be set at a flat bending position without being affected by burrs of the dam bar or uneven thickness due to plating.

In the correction bending step, only the outer lead base is supported without forcibly holding the resin sealing portion flat, so that the resin sealing portion is not affected by warping or twisting.

Therefore, a remarkable effect such as improvement in flatness of the tip of the external lead of the semiconductor device can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a bending step of a resin-sealed semiconductor device, FIG. 2 is an explanatory view showing a modified bending step, FIG. 3 is an explanatory view showing a modified example of a modified bending die, and FIG. FIGS. 5A and 5B are a partial plan view showing a part of the lead frame after resin sealing, and a plan view showing a state where the tips of the external leads of the semiconductor device are separated from the lead frame in a connected state. Side view illustrating a warped semiconductor device, FIG.
FIG. 7 is an explanatory view showing a method of bending an external lead of a conventional semiconductor device. FIG. 7 is a cross-sectional view of a dam bar portion of the external lead.
FIG. 8 shows a semiconductor device in which the tips of the external leads are irregular. 10 ... Semiconductor device, 12 ... Resin seal, 14 ... External lead, 20 ... Bending die, 24 ... Knockout, 28a, 28b ... Bending punch, 40 ... Correct bending die, 40a ... Support Die, 41 ... recess, 44 ... knockout, 48 ... modified bending punch, 50 ... lead frame.

Claims (5)

(57) [Claims] 1. A preliminary bending step of bending an external lead extending from a resin sealing portion downward and bending outward, and a tip of the external lead in a state of supporting a base of the bent external lead. In a free state, with a modified bending punch,
A method of forming the external lead of the resin-encapsulated semiconductor device, the method further comprising a step of pressing and correcting the external leads so that the tips of the external leads are aligned. 2. The method of molding an external lead of a resin-encapsulated semiconductor device according to claim 1, wherein in the correcting bending step, the base of the external lead is held and the tip of the external lead is set in a free state. 3. The method according to claim 2, wherein the external leads are clamped with a force that does not deform the external leads when the base of the external leads is clamped. 4. A die which extends from a resin sealing portion, bends downward, and further supports a base portion of an external lead bent outward to make a tip of the external lead in a free state. A resin-encapsulated semiconductor comprising: a holding knockout for holding and supporting a base of an external lead in a supported state; and a bending punch for pressing and further bending the tip of a free external lead. External lead forming equipment for the equipment. 5. The external lead molding apparatus for a resin-encapsulated semiconductor device according to claim 4, wherein a concave portion is formed at an appropriate position in a supporting portion of the die for supporting a base of the external lead.