JPH0371785B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a lead frame, and more particularly to a tie bar (dam bar) that can effectively prevent resin burrs from appearing and damage the diver's cutter. The present invention relates to a lead frame that can be easily removed without cutting or using a knife.

(Prior art and its problems) Some lead frames used in resin-sealed packages are equipped with a dam bar that connects the external leads to prevent the resin from being pushed out into the gaps between the external leads during resin sealing. be.

As shown in FIG. 1, the dam bar 10 is removed by being cut with a knife 12 after being sealed with resin, but the dam bar 10 is removed from the outside line of the resin body 14 to prevent the knife 12 from biting the resin body 14 during cutting. 0.3mm
They are placed approximately 0.4mm apart. However, if such a dam bar 10 is provided apart from the resin body 14, the resin will naturally be pushed out into the gap as a resin burr 16, and the blade 12 will also cut a part of this resin burr 16 at the same time. However, since ceramics, glass, etc. are mixed into the resin, there is a problem in that it damages the knife and significantly shortens its life.

Further, after cutting the dam bar 10, a finishing step is required to remove the resin burr 16, and its original function as a dam bar is also diminished.

Furthermore, in recent years, as external leads have become increasingly multi-pinned and the gaps between the leads have become smaller, making it difficult to cut with a knife, there is a strong demand for a method for removing dam bars without using a knife.

The present invention was made in response to the above-mentioned needs, and its purpose is to effectively prevent the occurrence of resin burrs and to easily remove the dam bar without damaging the cutter or without using a cutter. We can provide lead frames.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes the following configuration.

In other words, it is used for resin-sealed packages.
In a lead frame having a plurality of external leads that lead electrical conduction to the outside, a tie bar connecting the external leads is provided so that its inner edge touches the outer line of the resin sealing area, and a tie bar on the diver The present invention is characterized in that a semi-sheared portion is provided at least on the side of the resin-sealed region at the planned side line position of the external lead, in which the tie bar is shifted in the thickness direction with respect to the external lead and pushed back.

(Function) Since the half-sheared portion is formed by shifting the tie bar in the thickness direction with respect to the external lead and pushing it back, no groove is formed in the half-sheared portion, and no resin burrs are generated during resin sealing.

Furthermore, the tie bar is easy to remove, and can be easily removed without or even using a cutting blade. In addition, if the semi-sheared part is provided on the resin sealing area side and not on the far side,
The strength of the tie bar can be ensured, resin burrs do not occur, and even when cutting with a knife a part that is not formed in a semi-sheared part, the part is on the side far from the resin sealing part. Therefore, there is no risk of the cutting blade biting the resin.

In addition, since the tie bar does not protrude from the external lead surface, the tie bar does not get caught when being progressively fed, for example, with a progressive die, which is convenient.

Note that it is necessary to provide the semi-sheared portion with enough strength to prevent the tie bar from falling off during the intermediate process of resin sealing.

(Embodiments) Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a schematic diagram showing an example of a lead frame 20 according to the present invention. 22 is the external lead,
24 is an internal lead following the external lead 22, and 26 is a dam bar that connects the plurality of external leads 22 and connects to the rail section 28. A stage 30 is an element mounting section, and is connected to the rail section 28 by a stage support bar 32.

As shown in FIG. 3, the lead frame 20 is resin-sealed after a semiconductor element 34 is assembled on a stage 30, wire bonding is performed, and a protective film 36 is formed.

In the present invention, the position where the dam bar 26 is provided is such that its inner edge 38 is located at the outer line 40 of the resin body 40.
It is set to match. The resin-sealed area is indicated by a chain line in FIG.

Further, in the present invention, a semi-sheared portion is provided on the dam bar 26 at a position of a side line 44 (FIG. 4) where external leads are planned.

The structure of the half-shear section is shown in FIG. FIG. 5a is a sectional view taken along the line XX in FIG. 4, and FIG. 5b is a sectional view taken along the line YY in FIG. In this embodiment, the dam bar 26 is pressed against the external lead 22 by a male mold 46 and a female mold 48 in the thickness direction so that it is lifted up from the surface of the external lead 22 by about half the thickness of the plate, as shown in FIG. As shown in FIG. 2, the dam bar 26 is pushed back to match the height of the external lead 22 to form a semi-sheared portion. Although this half-sheared part has the necessary strength because the dam bar 26 and the external lead 22 are connected at a part of the half-sheared plane 60, the metal structure is shifted along the half-sheared plane. It is in a state where it is easily detached by external force from the thickness direction.

Note that the degree of this semi-shearing process needs to be adjusted so that the dam bar 26 does not fall off when handling the lead frame after the process.

FIG. 6 is an explanatory diagram showing a case where resin sealing is performed using the lead frame 20 in this state. Since the dam bar 26 is pushed back to the surface of the external lead 22 again, the resin does not protrude and functions as a dam bar. Fulfilling. The dam bar 26 that has been pushed back in the opposite direction to the shearing direction is in a state where it is easier to detach, and in the subsequent process, it can be removed by hand, with a thruster (not shown), or with a sandplast, etc., without using a knife. It is easily removed.

Furthermore, when the external leads 22 are bent and formed after resin sealing, the dam bar 26 can be dropped during the bending.

FIG. 8a shows an example in which the above-mentioned shearing process is applied to a part of the scheduled external lead side line 44 (on the resin main body side), and corresponds to the XX sectional view in FIG. 4. In this case as well, the dam bar 26 is raised and pushed back to form a semi-sheared portion, as described above. In this embodiment, the strength of the dam bar 26 can be maintained constant.

FIG. 9 shows another embodiment of the half-shear section, and the figure a
The dam bar 26 is partially or completely sheared so that the resin body 40 side is inclined with respect to the surface of the external lead 22. In Figure b, the resin main body 40 side is processed so that it is a completely sheared surface, the middle part is a semi-sheared surface, and the base is not sheared. In the case of this embodiment, the connection strength differs along the fracture surface, and there is an effect that it is easy to set the necessary connection strength for the dam bar 26 as a whole.

In the embodiments shown in FIGS. 8 and 9b above, a knife may be necessary to remove the dam bar 26, but the cutting point should be a non-sheared part on the side far from the resin body 40. Since it is only necessary to cut, there is no risk of the blade biting the resin body 40 during cutting.

The present invention has been variously explained above with reference to preferred embodiments, but the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. That's true.

(Effects of the Invention) As described above, according to the lead frame according to the present invention, the dam bar is once shifted in the thickness direction with respect to the external lead and then pushed back again, so that the tie bar is not lifted up from the external lead surface. This is convenient because the tie bars do not get caught on other members during progressive feeding with a progressive die or during continuous plating processing. In addition, when the tie bar is pushed back as it is, there are no concave grooves or the like in the semi-sheared part, so there is no resin burr, and the tie bar can be removed relatively easily without using a knife or even with a knife. Can be detached.

Furthermore, even if a semi-sheared part is provided on the side of the resin sealing area at the planned side line position of the external lead of the tie bar, resin burrs do not occur and can be easily removed without chewing the resin using a knife. I can do it.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a state in which a dam bar of a lead frame in a conventional resin-sealed package is cut. FIG. 2 is a plan view showing an example of a lead frame according to the present invention, FIG. 3 is an explanatory cross-sectional view when resin-sealed, and FIG. 4 is an explanatory view showing planned side lines of external leads. 5 and 7 are cross-sectional views showing the structure of the half-sheared portion of the dam bar, and FIG. 6 is an explanatory view showing a state in which an element is assembled into a lead frame and placed in a resin-sealed mold. FIG. 8 is a cross-sectional view of a part of the dam bar subjected to semi-shearing, and FIG. 9 is a cross-sectional view of the dam bar tilted and semi-sheared. 10... Dam bar, 12... Cutler, 14... Resin body, 16... Resin burr, 20... Lead frame, 22... External lead, 24... Internal lead, 26... Dam bar, 28... Rail section , 30
... Stage, 34 ... Semiconductor element, 36 ... Protective coating, 38 ... Inner edge, 40 ... Resin body, 4
2...External line, 44...External lead planned lateral line, 4
6...Male type, 48...Female type, 50...Upper type, 52
...lower mold.

Claims (1)

[Claims] 1. In a lead frame used for a resin-sealed package that has multiple external leads that lead electrical conduction to the outside, tie bars that connect the external leads are connected so that the inner edge of the tie bar is in contact with the outer line of the resin-sealed area. A lead frame characterized in that a half-sheared portion is provided at least on the resin-sealed region side of a planned side line position of an external lead on the tie bar, the tie bar being shifted in the thickness direction with respect to the external lead and pushed back.