JPS60121750A - Lead frame - Google Patents

Abstract

PURPOSE:To facilitate the separation of dam leads by a method wherein a tab lead extending from the vicinity of a tab corner toward a dam piece is branched, and the tab lead is provided with grooves in the neighborhood of the dam pieces. CONSTITUTION:The square tab 12 where a semiconductor element is mounted is supported by tab leads 13 supported by the dam pieces arranged so as to surround the tab 12. The lead 13 extending to this dam piece is branched into separated leads 19. This lead 19 is provided with a V-groove 20 at the cutting point in the neighborhood of the dam piece. This manner enables the leads 19 to be easily cut after molding.

Description

[Detailed description of the invention] The present invention relates to lead frames.

Metal lead frames are used to assemble resin molded semiconductor devices. This lead frame is formed by punching out a thin metal plate with a press or by etching, and its shape is as shown in FIG.
It consists of a tab lead 3 that supports a rectangular tab 2 to which it is attached at its inner end, a plurality of glued leads 4 whose inner ends face the periphery of the tab 2, and a rectangular frame that supports these leads 4 and the outer ends of the tab lead 3. a frame portion 5 and a frame portion 5. It consists of a dam piece 6 that connects each lead 4 and tab lead 3 and prevents melted resin from flowing out during resin molding. In addition, the frame portion 5
Guide holes 7 are provided at regular intervals on both sides of the lead frame, and the guide holes 7 are used as positioning holes and hooking and transport holes during assembly and transportation using the lead frame.

To assemble a semiconductor device using such a lead frame, first attach the semiconductor element l onto the tab 2, and then connect each electrode of the semiconductor element 1 to the inner end of the corresponding lead 4 using the wire 8. Thereafter, the inner regions of the dam pieces 6 arranged along the rectangular frame are molded with resin, and the semiconductor elements 1 and the like are covered with the mold part 9. Then, the dam piece 6 and the frame portion 5 are cut and removed to obtain a flat lead semiconductor device.

Further, in order to obtain an in-line type semiconductor device, the part 4 protruding from the mold part 9 is bent in the middle.

By the way, since the tab is supported by thin tab leads on both sides, its strength is weak.

In particular, as the number of leads increases recently, and in order to maintain miniaturization, the width of the leads (tab leads) must also become narrower. Also, narrow the lead width (for example, 0,
3 width), the material used to make the lead frame has to be thinner than before (for example, 0.3 mm width) due to problems in the punching process.
15mm). As a result, the tabs, like the leads, can easily tilt or lift even with a small external force, causing trouble in assembly. For example, when attaching a semiconductor element, the tab swings, resulting in incomplete bonding, and during wire bonding, incomplete bonding and wire breakage occur. In addition, during resin molding, the tab may tilt and move due to the flowing resin, causing the wire to break, or the vortex generated by the tab tilting may cause air bubbles to remain inside the mold or on the surface, reducing moisture resistance or creating dents. This results in a bad appearance.

However, the purpose of the present invention is to provide a lead frame with excellent rigidity in which the tabs do not easily move during assembly, and
An object of the present invention is to provide a lead frame that can improve assembly yield.

In order to achieve such an object, the present invention assembles a semiconductor device using a lead frame in which the four corners of a rectangular tab on which a semiconductor element is attached are supported by tab leads. Detailed explanation.

FIG. 2 is a plan view showing an embodiment of the lead frame devised by the present inventor, and FIG. 3 is a plan view of a semiconductor device assembled using the lead frame according to the present invention shown in FIG.
FIG. 4 (1al, tb) is a plan view and a partially enlarged view showing the state during one process of assembly. First, the shape of the lead frame will be explained. This lead frame is made from a metal plate with a thickness of 0.15 mm by punching or etching. The shape is such that a rectangular tab 12 for attaching a semiconductor element (bellet) 11 is provided at the center of a frame portion 10 that forms a rectangular frame as a whole, although there are portions with different widths. This tab 12 is supported at its four corners by the inner ends of thin tab leads 13 whose outer ends are connected to the corners of the frame 10, respectively. Further, a plurality of leads 14 extend toward this tab 12 from four directions, and their tips (inner ends) face near the periphery of the tab 12. In addition, leads 14 extending in four directions
The rear ends of each are connected to the inside of the frame portion 10.

It also prevents melted resin from flowing out during resin molding.
To this end, a dam piece 15 extending between each lead and between the lead and the frame portion 10 is arranged to surround the tab 12.

Further, a guide hole 16 is bored in the frame portion 10 as in the conventional case.

When assembling a semiconductor device using such a lead frame, as shown in FIG. Wire (as shown in Figure 3')
Then, as shown in FIG. 4 la, the inside of the dam piece 15 is molded with resin, and the semiconductor element 11 and the like are covered with the resin mold part 17. At this time, as shown in FIG. 4 tl)l, the mold intersects with the tab lead 13.

The corner portion (corner portion) of the portion 17 is molded into a chamfered state having a cutout surface 18 perpendicular to the tab lead 13.

This is a result of consideration taken to prevent chipping when cutting the corners of the mold part when the tab lead is subsequently cut at the base of the mold part. Next, the tab lead 13 is cut at the base of the mold part 17, and the unnecessary dam piece 15 and frame part 10 are cut and removed to obtain a flagged semiconductor device. In addition, if necessary, a portion "14" may be provided that protrudes from the mold part 17 for a long time.
An in-line type semiconductor device is made by bending it from the middle.

In this embodiment, the tab 12 is supported at its four corners by the tab leads 13, so it is difficult to move and has excellent rigidity. Therefore, it does not tilt or lift off the work table during each assembly operation. Therefore, reliable connection (bonding) can be achieved during pellet bonding or wire bonding. Further, during resin molding, the tab is not tilted by the inflowing resin, so no vortices are generated due to the shadow of the flow, and no air bubbles are generated. Furthermore, since the tab does not tilt, strong force is not applied to the wire and the wire does not break.

Note that the present invention is not limited to the above embodiments. for example,
The tab lead may be provided with a 7-shaped groove such as +c3;5 on the periphery of the mold part at a position that is the boundary with the mold part, so that the tab lead can be easily separated from the 7-shaped groove when cutting the tab lead.

Further, one or more of the plurality of tab leads may be used as leads.

In addition, in the case of a structure in which the corners of the mold part are not chamfered, as shown in FIGS.
Alternatively, the middle of the separation lead 19 may intersect with the outer circumferential surface of the mold part so that the corner of the mold part is not damaged when the tab lead is cut. The separation lead 19 is cut at the single-point chain M portion shown in FIG. 6 1al. Further, the cut portion may also be divided as shown in FIG. 6 1al, and a V-shaped groove 20 may be provided for ease of separation.

In addition, as shown in FIG. 7 1al, the space formed by the two Y-shaped separation leads 19 and the frame 10 (dam piece 15) is widened toward the frame, and a large hole is inserted into the resin. If the gate 21 is used for resin injection during molding, it is shown in Fig. 7 (
As shown in b), there is a step on the runner 22, and when the mold part and runner are separated, stress is concentrated on this step, and the runner separates at this step (separation occurs as shown in the dashed line shown in FIG. 7 1al). Become.). Therefore, the shape of the lunch separation part in the molded product is constant, and the problem of irregular separation parts can be prevented.

Furthermore, even though this lead frame has a structure in which the tab portion is lowered, the strength (steel column) is high.

As described above, according to the present invention, since the tab has high strength, it does not easily move during assembly. For this reason,
Bonding such as wire bonding and pellet bonding can be performed reliably and with high reliability. In addition, since no air bubbles are generated inside or on the surface of the mold during resin molding, it has excellent moisture resistance and does not damage its appearance. Furthermore, since the tab does not tilt or move during resin molding, no large force is applied to the wire, so the wire does not break.

Because of the stiffness, it is possible to assemble semiconductor devices with excellent characteristics, and the yield in assembly is also improved. In addition, the thickness of the lead frame is thinner than before, and the tab does not move during resin molding, so the desired sealing can be achieved even if the mold is thin, resulting in many effects such as making the product more compact. .

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a conventional lead frame, FIG. 2 is a plan view showing an embodiment of the lead frame devised by the inventor, and FIG. 3 is a plan view showing an embodiment of the semiconductor device of the present invention. 4, 1al and tbl are a plan view and partially enlarged view of a semi-finished product in one work step in manufacturing the semiconductor device of the present invention, and FIG. 5 is a plan view of another embodiment of the lead frame of the present invention. 181, tbl is an explanatory view of the molded state and a partially enlarged perspective view of the tab lead, and FIG. 7 (al, ibl is an enlarged plan view of the resin injection gate part of the lead frame and the state at the time of molding) It is an explanatory diagram. 1... Semiconductor element, 2... Tab, 3... Tab lead, 4... Lead, 5... Frame, 6... Dam piece,
7... Guide hole, 8... Wire, 9... Mold part, 10... Frame part, 11... Semiconductor element, 12...
Tab, 13...Tab lead, 14...Lead, 15
...Dam piece, 16...Guide hole, 17...Mold part, 18...Cut out surface, 19...Separation lead, 20...7-shaped groove, 21...Resin injection gate for,
22...Lunch. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A tab lead that supports a square-shaped tab on which a semiconductor element is attached, a plurality of leads whose inner ends protrude near the periphery of the tab, and a dam that supports the tab lead and the plurality of leads. and a frame portion that supports at least the plurality of leads on the outside of the dam piece, wherein the tab lead extends from near a corner of the tab and is separated into two parts in the middle. lead frame. 2. A lead frame characterized in that the bifurcated tab lead according to claim 1 is connected to a dam piece and has a groove near the dam piece.