JPS6110984B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molding device for leads, particularly for lead frames used in the assembly process of semiconductor devices such as ICs and LSIs.

Normally, in the assembly of semiconductor devices, a lead frame 23 having a structure as shown in FIG. 1A is used. As shown in the figure, this lead frame 23 has a tab lead 2 in which a tab 28 is continuously provided in the center.
9, a plurality of leads arranged symmetrically around the tab and the tab lead, a dam 24 supporting the leads provided in a direction intersecting the plurality of leads, and the dam 24 and the tab lead 29.
Support frames 21a and 21 arranged above and below to support
A plurality of unit block portions consisting of b are successively arranged in the horizontal direction. In each unit block, a plurality of leads are arranged so as to extend near the periphery of the tab 28, and a tie bar 25 is provided between the unit blocks to connect the leads extending from both blocks. This figure shows a state in which a pellet 27 is mounted on the tab 28, the electrode portion of this pellet and the lead are connected by a gold wire, and a resin is molded to cover these. Below, the entire molded part is IC3
They are called a and 3b.

The assembly work using such a device is performed by sequentially passing through the steps of cutting the dam 24 (b in the figure), cutting the tie bars 25, and bending the leads downward at right angles (c). be exposed.

Incidentally, in the work of bending the leads downward, a device as shown in FIG. 2 is used.

As shown in FIG.
and a support rod 6 connected to this holding jig,
A compression spring 7 is provided between the tip of the support rod and the fixed part, and an upper mold for molding is located on the side of the lead holding jig and is slidably inserted into the support rod 6. It consists of a jig 4. This upper mold jig 4 is configured to be movable up and down by mechanical means (not shown). According to such a device, as shown in Figure b, the support rod 6 of the upper mold jig 4 slides down on the top, thereby forcing the leads 2a and 2b downward. It is made to press and bend. As a result, the leads 2a and 2b are bent downward at right angles. At this time, since the leads on both sides of the IC 3a are pressed by the lead pressing jig 5 due to the spring pressure, it is possible to prevent cracks from occurring in the IC during the above-mentioned bending operation.

However, in the above-mentioned apparatus, since the lead is squeezed by the upper mold jig 4,
As shown in FIG. 3, the plating on the surface of the bent part A of the lead often peels off, and there is a problem in that the exposed base metal part of the peeled part A rusts.

In order to solve this problem, an apparatus has been proposed in which rollers 8a and 8b are rotatably attached to the lower end of the upper mold jig 4 as shown in FIG. 4.
According to such an apparatus, as shown in FIG.
Since the rollers 8a and 8b in contact with b rotate,
The roller circumferential surface and the lead are in line contact, and smooth bending is performed without the squeezing action as shown in FIG. 2 above. Therefore, peeling of the plating can be prevented.

However, by using a frame in which multiple ICs are consecutively arranged on one frame as shown in Fig. 1a above, it is possible to perform dam cutting → lead tip cutting → lead bending in succession. type.
That is, in the case of continuous operation using an integrated automatic type, the diameter of the roller in the above-mentioned apparatus cannot be made very large. The reason is as follows. As shown in Figure 1c above, usually
The distance L ₀ between the centers of the ICs 3a and 3b is regulated to a certain length (approximately 20 mm), and along with this, the distance L ₁ between the tip of the left lead 2a and the bent part of the right lead 2c. is less than half (approximately 8 mm) of the above distance L ₀ . Considering the margin between the lead and the lead to be bent, the diameter of the roller must be extremely small (6 mm).

In this way, high-speed operation using small diameter rollers (in continuous operation using the above-mentioned integrated automatic type,
If this is carried out at a speed of 0.2 seconds/k to 1.0 seconds/k), a problem arises in that the rollers are severely worn and their durability deteriorates. Incidentally, according to experiments conducted by the present inventor, the rollers had to be replaced after 200,000 to 300,000 uses.

Therefore, it is an object of the present invention to provide a method and apparatus for forming a lead that does not cause peeling of the plating and can ensure durability even during high-speed operation. Another object of the present invention is to provide a lead forming method and apparatus suitable for an automatic continuous molding process.

The present invention will be specifically explained below using Examples.

FIG. 5 is a sectional view of a main part showing an embodiment of the apparatus used in the lead forming method according to the present invention.

The lead forming apparatus has two lead mounting jigs 9 and 10 that are arranged side by side with an interval L ₀ between the parts to be bent of the leads 2b and 2c extending from the ICs 3a and 3b formed on the frame. and corresponding to each of the mounting jigs 9 and 10,
Leads 2a, 2b, 2 placed on a mounting jig
Two lead holding jigs 11 and 12 are used to press c and 2d from above, and a lead holding jig 11 and 12 is provided between the holding jigs 11 and 12 and is moved downward to the bottom of the above-mentioned mounting jigs 9 and 10. A bearing plate 17 that is long in the vertical direction, and a diameter L ₁ that is rotatably supported above and below this bearing plate 17 and that is slightly shorter than the interval L ₀ of the mounting jig described above. It is composed of two rollers 18 and 19 having a diameter. Here, since the distance L ₀ between the jigs is usually about 15 mm, the diameter L ₁ of the roller can be designed to be about 10 to 12 mm. The above-mentioned mounting jigs 9 and 10 and lead holding jigs 11 and 12 both have concave tips, and when stacked facing each other, IC3
The structure is such that a and 3b are located in the center and the lead portions at both ends are sandwiched. In addition, the lead holding jigs 11 and 12 have support rods 13 and 14 that protrude from the upper center part thereof, and these support rods 1
The tips of 3 and 14 are fixed to the fixed part via compression springs 15 and 16. Further, the bearing plate 17 has a T-shape with a support portion 22 located at the upper part, and this support portion 22 is slidably inserted into the support rods 13 and 14 of the lead pressers 11 and 12. .
This T-shaped bearing plate 17 is made vertically movable by mechanical means (not shown).

Here, care must be taken in the arrangement of the two rollers 18 and 19. The lower roller 19 is
When the bearing plate 17 is lowered, the shaft is received at a position where it can contact only the inner side of the mounting jig 9, that is, at a position slightly shifted to the left with respect to the center of the bearing plate 17. The upper roller 18 is mounted on the shaft and placed at a position where it can contact only the inner side of the mounting jig 10 when the bearing plate 17 is lowered, that is, slightly to the right of the center of the bearing plate 17. Install the shaft in a position that is shifted to the opposite direction. The reason why the rollers are disposed mutually in this manner is to ensure smooth rotation of the rollers.

The lead forming method using this apparatus will be explained using the partially enlarged sectional view of FIG. 5b.

The bearing plate 17 provided with the rollers 18 and 19 is lowered linearly by mechanical or electrical means (not shown). Then, the lower roller 19, which is designed to come into contact only with the side surface of the left mounting jig 9, rotates downward so as to pinch the lead 2b. For this reason, the lead 2b is bent along the surface perpendicular to the upper end of the mounting jig 9. In this case, the bending operation brings the roller 19 into rotational contact with the lead so that it is in line contact with the lead, so that the plating does not peel off due to ironing. Note that at this time, the lead 2c on the right side is also moved to the roller 1.
9 and is bent, but since there is a certain distance between the side surface of the mounting jig 10 and the rollers 19, it is bent gently and not fully bent. . However, as the bearing plate 17 further descends, the upper roller 18 comes into contact with the side view of the mounting jig 10 on the right side with the lead 2c sandwiched between them, so the lead 2c is at a right angle at this stage. It is bent to FIG. 6 shows the relationship between the lead frame 23 and the roller 19 during such a bending operation. As shown in the figure, roller 19
is formed to have a diameter L ₁ that is slightly narrower than the distance L ₀ between the bent portions of the lead 2b of one IC 3a and the lead 2c of the other IC 3b. In the figure, the lead 2d of the IC 3b is shown in a state where the bending work has already been completed.

After the above-described bending operation is completed, the roller rises, escapes above the lead frame, and returns to its original position. In this state, the lead frame 23 is sent out one block to the right, and the same bending operation as described above is repeated again.

According to the method using the device as described above, since the lead and the forming roller are in line contact, there is no squeezing action and no peeling of the plating occurs. In addition, since a forming roller is provided between one IC3a and the other IC3b, the diameter of the roller can be made approximately twice as large (for example, 12 mm) as compared to the conventional type, which increases durability. A device with excellent performance can be obtained. Therefore, it is most suitable for high-speed operation using a continuous process of mold processing → dam section cutting → tie bar cutting → lead bending.

The invention is not limited to the above embodiments. For example, in the above embodiment, the support portion 22 of the bearing plate 17 is inserted into the support rods 13 and 14 of the lead holding jig, but the present invention is not limited to this. You can do it like this. Furthermore, the diameters of the rollers 18 and 19 are not the same, but may be different.

The present invention has particular significance when various lead forming processes are performed continuously, but it can also be used as an apparatus for independently bending leads.

[Brief explanation of the drawing]

1A to 1C are explanatory diagrams for explaining the assembly order of a semiconductor device using a lead frame;
Figures a and b are cross-sectional views showing a conventional lead bending device.
FIG. 3 is an explanatory diagram for explaining the peeling of the lead plating, FIGS. 4 a and b are sectional views showing other examples of conventional lead bending devices, and FIGS. 5 a and b are one embodiment of the present invention. FIG. 6 is a plan view showing the relationship between the lead frame and rollers. 1, 9, 10... mounting jig, 2a to 2d...
Lead, 3a, 3b... IC, 4... Molding jig, 5, 11, 12... Lead holding jig,
6, 13, 14...Support rod, 7, 15, 16...
Compression spring, 8a, 8b, 18, 19...roller,
17... Bearing plate, 21a, 21b... Frame outer frame, 22... Support part, 23... Lead frame,
24...Dam, 25...Tie bar, 26...Lead tip, 27...Pellet, 28...Tab, 29
...Tabreed.

Claims (1)

[Claims] 1. A method for bending leads in a lead frame in which a plurality of unit blocks each consisting of a mounting portion and leads extending to the left and right of the mounting portion are connected by a frame, By lowering the first and second rollers, which are installed at different levels in the upper center of the unit block and whose axes are eccentric to each other, the first roller bends one lead, and the second roller bends the lead. A lead forming method characterized by bending the other lead. 2. first and second lead mounting jigs arranged side by side at a predetermined interval and configured to support the portion of the elongated lead to be bent from below;
First and second lead holding jigs are positioned correspondingly to each of the mounting jigs and are adapted to press down from above the elongated leads placed on the mounting jigs; It is arranged between the first and second holding jigs, and includes a vertically long bearing plate that can be moved down to the bottom of the above-mentioned mounting jig, and It consists of first and second rollers that have a diameter slightly shorter than the distance between the first and second mounting jigs that are rotatably supported, and of these rollers, the first The rollers are arranged so that they can contact only the inner surface of the first mounting jig, and the second rollers are arranged so that they can contact only the inner surface of the second mounting jig. A lead forming device featuring: