JPH0798226B2 - Semiconductor lead bending method - Google Patents

Description

The present invention relates to a method of bending an external lead of a resin-molded semiconductor.

[Conventional technology]

An outline of a conventional semiconductor package manufacturing method and a semiconductor lead bending method in a semiconductor package manufacturing process will be described with reference to FIGS.

FIG. 5 is a manufacturing process diagram of the semiconductor package, and FIG. 6 is a plan view of a lead frame punched with a pattern in the initial manufacturing process of the semiconductor package. As shown in FIG. 6, a lead frame material (for example, a thin metal plate of 2% Sn-Cu alloy) is punched into a predetermined pattern by a press to obtain a lead frame 1 as shown in FIG. The lead frame 1 is
External lead 2, internal lead 3, tab 4, dam 5
A range surrounded by a chain double-dashed line in the figure is a mold range to be molded in a later step. Then, before the molding step, a semiconductor pellet (not shown) manufactured in a separate step is mounted and adhered on the tab 4 of the lead frame 1 to connect the semiconductor pellet and the internal lead 3, and then the semiconductor resin encapsulation. The molding range of the lead frame 1 is molded by a casting metal fitting for. FIG. 7 is a perspective view showing a state after the molding step. As shown in FIG. 7, the semiconductor pellet on the tab 4 and the inner lead 3 are resin-sealed in the molding portion 7 by the molding resin. Then, after cutting the dam burr 6 of the mold resin and the dam of the lead frame 1 protruding from the casting mold for semiconductor resin encapsulation, the outer lead 2 is bent downward, and through the above manufacturing process, A semiconductor package 8 as shown in the semiconductor package sectional view of FIG.

By the way, in such a lead bending process, if the bending process is performed without mechanically restraining the outer lead 2, the bending force is transmitted to the inner lead 3 and the molding portion 7, and as a result, as shown in FIG. ), Tensile stress acts on the interface between the mold portion 7 and the upper surface of the inner lead 3 to cause peeling, and eventually a gap 9 may be generated between the inner lead 3 and the mold portion 7. The gap 9 has a gap δ of several μm to several tens of μm and a depth l ₁ of several hundred μm. When such a gap 9 is generated, moisture enters from the outside into the gap 9 and corrodes the internal wiring of the semiconductor package. ∙ Disconnection may occur and cause malfunction.

Therefore, conventionally, in order to prevent the occurrence of a gap in the semiconductor package, as shown in, for example, Japanese Patent Publication No. 49-49107, mechanically restraining the vicinity of the external lead to be bent at the time of bending the lead from above and below. I was taking measures such as.

FIG. 9 shows a local sectional view of a conventional lead bending process for preventing the occurrence of such a gap. The same parts as those in FIG. 8 (b) described above are designated by the same reference numerals. is there.
That is, 2 is an external lead, 3 is an internal lead, and 7 is a mold part. Conventionally, during lead bending, the lead bending portion of the external lead 2 is machined by the upper surface restraint jig 10 and the lower surface restraint jig 11. The bending force is applied to the external lead 2 in a downward direction (lead bending load) while the binding force P is applied from above and below and the bending force is transmitted to the internal lead 3 and the molding portion 7. To prevent the occurrence of a gap at the interface between the inner lead 3 and the mold 7.

[Problems to be solved by the invention]

In such a lead bending method, the lead member 2
Since the lead bending load required for the lead bending process differs depending on the material, shape, size, etc. of the above, it is necessary to change the mechanical restraining force P applied to the restraining jigs 10, 11 according to the magnitude of the lead bending load. However, there is a limit to the magnitude of this type of restraint force P, and if the restraint force P becomes too large, the restraint site of the external lead 2 may be damaged. In particular, the force that prevents the bending process force from being transmitted to the inside of the mold 7 is determined by the product of the lead pressing width l ₂ (see FIG. 9) of the restraint jigs 10 and 11 and the restraint force P. When the value of the lead pressing width l ₂ is set to be small during bending, the restraining force P must be increased in inverse proportion to that, and as a result, the surface pressure applied to the restraining surface of the lead 2 is limited. Value is exceeded, yield stress occurs in lead 2 and lead 2
There is a problem in that lead bending that requires a large bending load cannot be performed with high accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lead bending method capable of effectively preventing the formation of a gap at the interface between a mold portion and an internal lead during lead bending while solving the above-mentioned problems of the prior art.

[Means for solving problems]

The purpose of the above is to perform a lead bending process for bending an external lead protruding from the mold part of a semiconductor by placing the external lead on the support part of the lower mold to hold the semiconductor in the lower mold and lowering the upper mold to raise the upper mold. With a slight gap maintained between the die pressing surface and the upper surface of the mold part, apply a bending load in the direction of the lower mold to the external lead parts outside the support part of the lower mold, and apply this bending load. The upper surface of the displacing mold part is brought into contact with the pressing surface of the upper mold to restrain the displacement of the mold part, whereby the bending moment of the part of the external lead protruding from the mold part is the bending moment of the part supported by the supporting part. This is achieved by bending the outer leads while keeping them sufficiently small compared with the above, to form the outer leads into a predetermined shape.

[Action]

The operation of the lead bending method of the present invention is shown in FIG.
A description will be given based on (b). FIG. 1 (a) is a principle diagram of the lead bending method of the present invention. In the figure, 2 is an external lead of a semiconductor, 3 is an internal lead, 7 is a mold portion, 12 is a lead lower surface restraint point, and 13 is Mold top restraint jig, P _M is lead bending load.

Then, the lower part of the semiconductor outer lead 2 is supported by the lead lower surface restraint point 12, and the upper surface of the mold portion 7 is pressed by the mold portion upper surface restraint jig 13 while restraining the upward displacement of the mold portion 7. Perform lead bending. External lead 2
As the bending deformation of the mold progresses, the force to lift the mold part 7 increases, but since the upward displacement of the mold part 7 is restricted, the mold part 7 does not lift up and is kept in a constant state. Be drunk External lead 2 at this time
The bending moment distribution inside the mold part 7 is shown in FIG. 1 (b). That is, as shown in FIG. 1 (b), when a lead bending load P _M is applied, a negative bending moment M ₁ for bending the lead 2 is generated in the outer lead 2, but inside the mold part 7. Is a force that restrains the upward displacement of the mold portion, so that a negative bending moment is not generated, the moment is almost zero, and the moment generated in the lead near the end 14 of the mold portion 7 is almost the same. It becomes zero. Therefore, the semiconductor leads are not deformed near the ends of the mold, so that no gap is generated between the mold part 7 and the inner leads 3.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS.

FIG. 2 is a front view of a lead bending apparatus for carrying out the lead frame bending method according to the present invention, showing a state before bending, and FIG. 3 shows a state after bending of the lead bending apparatus. FIG. 4 is a front view showing the state, and FIG. 4 is a partially omitted perspective view in which the portion A of FIG. 1 is enlarged and evaluated.

In FIG. 2, reference numeral 20 is a lower die for setting the semiconductor package 8 during bending, and the lower die 20 is provided with an accommodation groove 21 for accommodating the mold portion 7 of the semiconductor package 8.
A lower surface support portion 22 for supporting the lower surface side of the bending point of the outer lead 2 is formed on both side edges of the.

Reference numeral 23 is an upper die for restraining the upward displacement of the mold portion 7 of the semiconductor package 8. The upper die 23 is for restraining the upward displacement of the mold portion 7 by the pressing force of the air cylinder 24. As shown in FIG. 4, the upper die 23 is a pressing surface that presses and restrains the upper surface of the mold portion 7 of the semiconductor package 8.
Having 25. Further, a plurality of concave portions 26 and convex portions 27 are arranged on the side edge of the pressing surface 25 in a comb-teeth shape, and when the upper die 23 reaches the lowest point by the action of the air cylinder 24, the concave portion 26 is the upper surface of the external lead 2. And the convex portion 27 is in contact with the upper surface of the support portion 22 of the lower die 20. When the convex portion 27 contacts the support portion 22, the upper surface of the mold portion 7 and the pressing surface of the upper die 23 are pressed.
It is set so that a slight gap can be maintained between the mold 25 and 25, so that the force of the air cylinder 24 does not directly act on the mold portion 7 before the lead bending process.

Reference numeral 28 denotes a bending roller mechanism that applies a bending load (vertical load) to the outer lead 2. In the bending roller mechanism 28, a pair of roller members 28a and 28b reciprocate up and down along the left and right side surfaces of the upper mold 23 and the lower mold 20. The lead bending load P _M is generated by the movably adhered members and the downward force of the roller members 28a and 28b.

Next, a lead bending process using the lead bending apparatus of this embodiment will be described.

When performing the lead bending process, first, the semiconductor package 8 is set on the lower die 20, and the lower surface side of the bending point of the external lead 2 is positioned on the support portion 22. Next, the air cylinder 24
To lower the upper mold 23. When the upper mold 23 goes down to the lowest point,
The convex portion 27 of the upper die 23 comes into contact with the support portion 22 of the lower die 20, and the pressing surface
25 is positioned above the mold portion 7 of the semiconductor package with a slight gap. The pressure applied to the air cylinder 24 at this time is the same as that of the mold portion 7 in the subsequent lead bending process.
It is made large enough so that the upper mold 23 cannot be lifted by the force acting from. When the bending roller mechanism 28 is lowered in the direction of the arrow B with the pressure applied to the air cylinder 24 in this manner, the lead bending load P _M is applied to the outer lead 2 and the outer lead 2 is bent and deformed. As the bending deformation progresses, the mold portion 7 is slightly lifted by a small gap between the pressing surface 25 and the mold portion 7, and the upper surface of the mold portion 7 contacts the pressing surface 25 of the upper die 22. Further, as the lead bending deformation progresses, the force that tries to lift the mold part 7 upward increases, and the upward pressure applied to the pressing surface rises.
Since sufficient pressure is applied to restrain the displacement in the upward direction, the upper mold 23 does not lift. The state after lead bending is shown in FIG. Therefore, according to the lead bending process of the present embodiment, as already described in the [Operation] section of the invention, the pressure applied from the air cylinder 24 causes the mold portion 7 to move upward in the mold portion 7 in the upward direction. Since a force that restrains the displacement of the lead acts, a negative bending moment is not generated, which prevents the lead from bending and deforming to the inside of the mold portion 7, and prevents a gap from being formed at the interface between the inner lead and the mold portion. Can be prevented. Furthermore, according to this embodiment, it is not necessary to apply a large mechanical restraint force to the external lead by the restraint jig as in the conventional case, and proper lead bending can be performed only by the displacement restraint force on the upper surface of the mold portion. It is possible to prevent lead damage without causing a yield stress on the outer leads. Further, according to the present embodiment, the force applied to the mold portion 7 may be any restraining force that prevents the mold portion 7 from being lifted during lead bending processing, and the set restraining force does not require strictness. Bending control can be easily performed.

〔The invention's effect〕

As described above, according to the present invention, at the time of bending a lead, the bending deformation of the lead is prevented from reaching the inside of the mold portion, thereby preventing a gap from being generated at the interface between the mold portion and the internal lead, and performing the bending work. It is possible to eliminate the problem that leads are sometimes damaged.

[Brief description of drawings]

1 (a) and 1 (b) are schematic views showing the principle of the lead bending method of the present invention, and FIG. 2 is a front view of the main parts of a lead bending apparatus used in the lead bending method of the present invention. 3 is a front view of a main part of the lead bending apparatus shown in FIG. 2 after bending, FIG. 4 is a partial perspective view showing an enlarged part A of FIG. 2, and FIG. 5 is a semiconductor package. Manufacturing process diagram of
FIG. 6 is a partially omitted plan view of a lead frame used in the lead bending process of the present invention, FIG. 7 is a partially omitted perspective view showing a state of a semiconductor package during a manufacturing process, and FIGS. b) and FIG. 9 are cross-sectional views of the main part of the semiconductor package after the lead bending is performed by the conventional lead bending method. 2 …… External lead 3 …… Internal lead 7 …… Mold part 8 …… Semiconductor package 12 …… Surface support point 13 …… Mold part top restraint jig P _M …… Lead bending load.

Front Page Continuation (72) Inventor Kei Ueno, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd., Production Engineering Research Laboratory, Hitachi, Ltd. Musashi Factory (56) References

Claims (1)

[Claims] 1. A lead bending method for bending an external lead protruding from a mold part of a semiconductor, wherein the external lead is mounted on a support part of a lower die, and the semiconductor is held by the lower die. The upper die is lowered to maintain a small gap between the pressing surface of the upper die and the upper surface of the mold portion, and the outer lead portion outside the support portion of the lower die is arranged in the lower die direction. A bending load is applied, and the upper surface of the mold portion, which is displaced by applying the bending load, is brought into contact with the pressing surface of the upper mold to restrain the displacement of the mold portion, and the displacement is restrained so that the external By bending the outer lead while keeping the bending moment of the portion of the lead projecting from the mold portion sufficiently smaller than the bending moment of the portion supported by the support portion, the outer lead is located. A lead bending method for semiconductors, characterized by forming into a fixed shape.