JPS6167250A - Lead frame - Google Patents

Abstract

PURPOSE:To eliminate the need for deburring at a portion between unit patterns on a lead frame and elaborate the edge portion of a resin seal, by providing an intermediate frame at said portion so as to be parallel to the outer frames. CONSTITUTION:An intermediate frame 11 is disposed between two tie bars 3 and also between two resin seal parts M in such a manner that the frame 11 extends parallel to two outer frames 2. In addition, the lateral edges of the intermediate frame 11 are in close proximity with the resin seal parts M, respectively. Thus, any molten resin which flows during a molding step is blocked by the intermediate frame 11, so that substantially no resin burr is formed. When support bars 5 are cut by means of pinch-cutting, the intermediate frame 11 is cut off, and any resin burr is simultaneously removed. Accordingly, it is made possible to reduce the number of burrs at the edge of each resin seal part M markedly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead frame used in a plastic mold-sealed semiconductor device.

Semiconductor devices that are sealed with thermosetting plastic resin such as epoxy resin (resin mold type) have higher production efficiency and can be manufactured at lower cost than other ceramic or can-sealed semiconductor devices. Currently, it is the main structure of most general-purpose semiconductor devices including ICs.

Such resin-molded semiconductor devices use a lead frame on which multiple semiconductor devices are assembled, a semiconductor chip is attached to the lead frame, wire bonding is performed, and finally a large number of lead frames are assembled simultaneously. Sealed with plastic resin.

Next, the unnecessary frame attached to the lead frame is cut and removed, and the leads are bent to complete the semiconductor device. At this time, there is no excess adhesion on the outside of the finished resin sealing part. Beautiful skin is desired.

[Prior Art] Usually, a lead frame is a long piece in which 8 to 10 semiconductor devices are assembled in a row in parallel in the horizontal direction, and is made of iron alloy or copper alloy and has a thickness of about 0.25 mm ( The patterning is performed by punching with a press die or by etching.

After the above-mentioned chip is attached to such a lead frame and wire bonding is performed, many lead frames are resin-sealed at once, but this resin sealing process (
The molding process involves casting heated and molten resin into a mold, and is a hatching process in which the lead frame is sandwiched between the upper and lower molds and the resin is injected.

In general, assembly processes such as bonding are automated assembly processes, while molding processes are batch processes, so a large number of lead frames are sealed at once using the largest possible mold. The method of stopping is more efficient. Therefore, in order to increase work efficiency, a large mold is generally used to perform the sealing work.

However, ICs have various external shapes, and in the case of small ICs, a large number of assembled small lead frames must be inserted into a mold, which requires a large number of man-hours and increases costs. Therefore, in addition to the conventional lead frame in which unit patterns (patterns forming one semiconductor device) are arranged horizontally in one row, multiple unit patterns are arranged in the vertical direction, and these are further arranged in the horizontal direction as in the past. Lead frames arranged side by side have come to be used.

FIG. 2(a) shows a plan view of a unit pattern of lead frames arranged horizontally in one row, and this example is a so-called dual-in-line package (DIT) type with 14 lead pins. This is a lead frame.

Furthermore, FIG. 2('b) is a plan view of a vertical two unit pattern of a lead frame in which two unit patterns are arranged in the vertical direction and these are paralleled in the horizontal direction, and this example has eight lead bins. This is a lead frame for a pan cage.

In each case, 8 to 10 such unit patterns are connected in parallel to form one lead frame. In the figure, the part M surrounded by the dotted line indicates the resin sealing part, and the two unit patterns shown in Figure 2) have two resin sealing parts M, and the two patterns are arranged in a vertical line. 2
This is a lead frame in which 8 to 10 patterns are arranged in parallel to form a total of 16 to 20 semiconductor devices. On the other hand, the lead frame shown in FIG. 2 ia+ is a lead frame in which 8 to 10 semiconductor devices in which 8 to 10 unit patterns are arranged in parallel are fabricated.

In these figures, 1 is a lead, 2 is a frame, 3 is a connecting strip (dam bar), 4 is a stage (a part for mounting a semiconductor chip), and 5 is a support bar (stage support bar).

[Problems to be Solved by the Invention] In the above molding process, the resin sealing part M is fixed with a molding resin material, but in that case, heated molten resin flows into the resin sealing part M, Since the resin flows out into the gap between the upper and lower molds for sealing and the lead frame is sandwiched in the gap, a firmness of the resin is created around the mold sealing part M by the thickness of the lead frame.

This gap appears on the four peripheries of the resin sealing part M and is formed in a frame-shaped part (see fat in FIG. 2; indicated by diagonal lines) bent by the frame 2 and the connecting strip 3. Structurally, this Paris F is unavoidable.

Therefore, conventionally, as a pre-treatment for cutting the frame 2 and the connecting strip 3 of the lead frame, the connecting strip 3 and the resin-sealed portion M
The edges are punched out with a punch. Here, the gap between the frame 2 and the resin sealing portion M is relatively narrow (although this portion is not deburred).

The above-described blanks are punched (the process is carried out by punching a lead frame with one vertical row of unit patterns shown in FIG. 2(a), and a lead frame with two vertical rows of unit patterns shown in FIG. 2(b)). Although it is similar to the lead frame, in the case of the lead frame shown in FIG.

However, this gap S is wider than other parts of the burr, and even if punching is performed in the same manner, it is difficult to completely remove the burr from the side edges of the resin sealing part M, as shown in FIG.
As shown in the plan view and perspective view of the semiconductor device shown in a) and (b), a large hole with a jagged fracture surface remains on one side of the resin sealing portion M.

The present invention proposes a lead frame structure that reduces the amount of particles that adhere to one side of the resin-sealed portion M.

[Means for Solving the Problem] The purpose is to provide a lead frame in which a plurality of lead frame unit patterns are vertically connected between two outer frames provided in parallel. This is achieved by a lead frame provided with an inner frame parallel to the outer frame.

Here, the lead frame unit pattern is one pattern for forming one semiconductor device.

[Function] That is, when the above-mentioned pre-treatment for punching out the holes is performed using the punch P, the firmness of the resin is not completely removed, so an intermediate frame is provided in this gap S of the lead frame, and This process eliminates the need for deburring and provides a fine finish to the edges of the resin, followed by pinch cutting to remove the inner frame.

[Example] Hereinafter, an example will be described in detail with reference to two drawings.

FIG. 1 shows a plan view of a two-row unit pattern of a lead frame according to the present invention, and the same members as in FIG. 2(b) are given the same symbols.

In the figure, reference numeral 11 denotes an intermediate frame according to the present invention, which is located between the two connecting strips 3 and between the two resin sealing parts M, and is provided parallel to the frames 2 on both sides. Furthermore, middle frame 1
The side end of 1 is provided close to the resin sealing part M, and in this way, when the molten resin flows during the molding process, the resin is blocked by the inner frame 11, and most of the resin particles are removed. It disappears.

Thus, when the support bar 5 is cut with a pinch force or a throat, the middle frame 11 is separated, and at the same time, a small amount of resin debris is removed, and the debris on this side of the resin sealing part M is extremely reduced. . That is, by using the lead frame according to the present invention, the jaggedness of the fractured surface is eliminated, and the number of cracks is reduced to the same level as or more than that of the side surface between the frame 2 and the resin sealing part M. Therefore, there is no external defect, the precision is improved, and the yield and quality of semiconductor devices are also improved.

In this case, the shaping process after resin sealing includes resin deburring, connecting strip cutting, lead bending, and support bar cutting (pinch cutting). Further, if the support bar is cut at the same time as the connecting strip, the work efficiency will be further improved.

[Effects of the Invention] Therefore, according to the present invention, in a resin-sealed IC, the sealing surface can be beautifully finished, and the quality of the semiconductor device can be extremely improved.

Although the above description has been given as an example of a lead frame having two unit patterns in the vertical direction, it is of course applicable to other lead frames, such as a lead frame having three unit patterns in the vertical direction. .

[Brief explanation of the drawing]

FIG. 1 is a plan view of a two-row unit pattern of a lead frame according to the present invention, FIG. 2 (a) is a plan view of a one-row unit pattern of a conventional lead frame, and FIG. A plan view of a two-column unit pattern of the frame, and FIGS. 3A and 3B are a plan view and a perspective view of a semiconductor device fabricated using the lead frame of FIG. 2 is the frame, 3 is the connecting strip (
dam bar or tie bar), 4 is the stage,
5 is a support bar, 11 is an intermediate frame according to the present invention, M is a resin sealing portion, and F and S are gaps where resin stiffness occurs. Agent Patent Attorney Hiroshi Matsuoka Part 4 Part 1 Figure 2 Figure 2 Figure 3

Claims (1)

[Claims] In a lead frame in which a plurality of lead frame unit patterns are vertically connected between two parallel outer frames, an intermediate frame parallel to the outer frame is provided between the lead frame unit patterns. A lead frame featuring