JPS6214696Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a lead frame protection sheet that is inserted into a coiled lead frame that is a component of an integrated circuit package to prevent damage to the lead frame.

Generally, when manufacturing an integrated circuit (hereinafter abbreviated as IC) package, as shown in Figure 1, the central IC
A long lead frame 4 made of a thin steel plate is used, in which a large number of unit lead frames 3 consisting of a chip mounting portion 1 and a large number of terminals 2 surrounding the chip mounting portion 1 are successively formed. Note that the left and right rib portions 5 of the lead frame 4
A hole 6 for positioning is bored in the. Then, the IC package is made by pasting the IC chip on the IC chip attachment part 1 of the lead frame 4, welding conductive wires such as gold wires to each terminal 2 of the lead frame 4 and the terminal of the IC chip, and then welding the IC chip with synthetic resin. It is manufactured by molding and then cutting the lead frame 4. The lead frame 4 is made by continuously punching out a long sheet of thin steel plate wound into a coil shape with a predetermined width and a length of several hundred meters, for example, using a press, as shown in FIG. Although it is formed as shown, the punching itself is done in multiple steps, including a degreasing step and a plating step.
This lead frame 4 is wound and rewound several times. This lead frame 4
Since the IC chip mounting portion 1 is generally formed in a recessed manner as shown in FIG. 2, the IC chip mounting portion 1 is particularly susceptible to damage during the winding process.

For this reason, conventionally, when winding the lead frame 4 onto the drum 7, as shown in FIG. A protective sheet 8 is interposed between the overlapping surfaces.

However, with the paper protective sheet 8 interposed, a load is applied to the central IC chip mounting portion 1, so that the protective effect is not sufficient. Furthermore, since paper is easy to cut, the feeding speed of the lead frame must be slowed down in the lead frame processing process, which is an obstacle to improving production efficiency.

In order to eliminate the above-mentioned drawbacks, it is conceivable to use a protective sheet 11 made of soft plastic in which thick parts 10 are formed on both side edges of a thin part 9 by extrusion molding, as shown in cross section in FIG. . In this case, the step h between the thin part 9 and the thick part 10 is
Usually 0.3 to 0.4 to protect the IC chip mounting part 1.
mm is required, and the thin part 9 is, for example, 0.2 mm.
Although it is desired that the thickness be as thin as possible, such as less than mm, it is not easy to obtain the desired thickness even with the cross-sectional shape shown in FIG. 4 due to the characteristics of extrusion molding. That is, there is a limit to the minimum gap size that can be extruded in the cross section of the die nozzle, and the gap size in the thin wall portion 9 is set to this limit value, and the gap size in the thick wall portion 10 is set to a level difference from this limit value. Even if h is made larger, the cross-sectional area of the thick part 10 is wider than that of the thin part 9, so the extrusion resistance in the thick part 10 is small and the speed of the resin is high, resulting in molding. The desired thickness cannot be obtained in the thick portion 10, and therefore the step h of the desired size cannot be formed. Also,
If the gap size corresponding to the thick wall portion 10 is increased in order to obtain the step height h of the desired size, the total cross-sectional area of the die nozzle itself will increase, thereby increasing the extrusion amount, and only the thick wall portion 10 will be increased. As a result, the thin wall portion 9 is also formed thickly, and it is not easy to obtain a step h having a desired dimension. If an attempt is made to obtain a step h with a desired dimension, the thickness T of the protective sheet 11 will end up being too large, resulting in a waste of materials and other inconveniences such as the coiled lead frame becoming extremely bulky. arise.

This idea was made in view of the above circumstances,
The lead frame protection effect is sufficiently high, and
The object of the present invention is to obtain a lead frame protective sheet that can be formed thin as a whole and has sufficient strength.

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 5, the lead frame protection sheet 12 of the present invention is formed by joining strips 14 made of plastic along the tape length direction to both side edges of one side of a thin long tape 13. do. That is, the thin part of the protective sheet is formed with tape 13,
The thick portion is formed by a strip 14. The width of the tape 13 is preferably approximately the width of the lead frame 4, and the width of the strip 14 is preferably approximately the width of the rib portion 5.

The tape 13 may be, for example, paper coated with plastic on both sides, or paper impregnated with plastic. It is desirable that the tape 13 be as thin as possible while still providing strength, but since paper is extremely thin compared to plastic sheets, and its strength is reinforced by coating or impregnation with plastic, it should be 0.2 mm or less. It is easy to obtain a material with the required strength and thickness.

Further, the tape 13 may be made of nonwoven fabric, fabric, aluminum foil, or the like other than paper, as long as it has the required strength and can be made thin, for example, 0.2 mm or less.

The thickness of the strip 14 is the same as that of the lead frame 4.
In order to sufficiently protect the IC chip mounting part 1, that is, the recess, the thickness is set to, for example, 0.3 to 0.4 mm, and
For the material of the strip 14, it is preferable to use a soft plastic such as ethylene vinyl acetate copolymer, soft vinyl chloride, or soft polyethylene in order to protect the lead frame. Moreover, since the stripes 14 are bonded to the tape 13 by adhesive or heat fusion, it is preferable that the strips 14 have good adhesion or heat fusion properties to the tape 13. For example, the ethylene vinyl acetate copolymer has good adhesion to paper.

In addition, when paper is used for the tape 13, the plastic to be coated or impregnated is the strip 1.
It is preferable to use the same plastic as the material in step 4 from the viewpoint of adhesiveness and other aspects.

As shown in FIG. 3, the lead frame protection sheet 12 configured as described above is wound around the drum 7 so as to overlap the lead frame 4 to protect the lead frame 4. In other words, the left and right strips 14 form thick parts that contact the rib portions 5 of the lead frame 4, and the protective sheet 12 does not contact the central portion of the lead frame 4, which includes the IC chip mounting portion 1. It is interposed between the overlapping surfaces of the frame 4 and effectively protects the IC chip mounting portion 1 and the terminal 2 portion of the lead frame 4.

In the conventional method in which thick parts are simply formed on both side edges by extrusion molding of plastic, it is easy to make the thin parts sufficiently thin and to obtain the desired level difference h between the thin parts and the thick parts. However, in the protective sheet 12 of the present invention, the thin portion can be made sufficiently thin with the tape 13 made of paper or the like, and the thick portion can be made to have an arbitrary thickness with the strips 14, so that the lead A protective sheet having a step h necessary for frame protection and having a thin overall thickness T can be obtained very easily. Therefore, when the lead frame is wound around the protective sheet 12, the bulk of the lead frame is suppressed to a small level, and smooth winding is possible.

Also, unlike traditional paper protection sheets,
Since the plastic strip 14 serves as reinforcement, or the paper tape 13 is coated or impregnated with plastic, sufficient strength can be obtained, and therefore, when winding and unwinding the lead frame, There is very little possibility that the lead frame will be cut, and the feed rate of the lead frame in the lead frame processing process can be increased, thereby improving production efficiency. Moreover, it is economical because it can be used repeatedly.

Although the strip 14 in the above embodiment has a rectangular cross section, it may also have grooves 14a formed therein as shown in FIG.

When the groove 14a is formed in this manner, the remaining portion, that is, the protruding portion 14b, is easily bent, so that a softer cushioning effect is obtained, and the effect of protecting the lead frame is further improved.

As explained above, the lead frame protection sheet of the present invention is made by joining strips of plastic along the length of the tape to both edges of one side of a thin long tape. It is extremely easy to provide a step with a desired size and to form a thin overall structure. Therefore, the bulk of the lead frame wound into a coil can be suppressed, smooth winding is possible, and since the lead frame is not easily cut, the winding and unwinding speed of the lead frame can be increased to increase production efficiency. It is also economical because it can be used repeatedly.

[Brief explanation of the drawing]

Fig. 1 is a partial plan view of the lead frame, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is an explanatory diagram of the state in which the lead frame is wound together with a protective sheet, and Fig. 4 is a conventional protective sheet. 5th cross-sectional view of
The figure is a sectional view showing one embodiment of the protective sheet of the present invention, and FIG. 6 is a sectional view showing another embodiment. 4... Lead frame, 12... Lead frame protection sheet, 13... Tape, 14... Strip.

Claims (1)

[Scope of utility model registration request] A lead frame protection sheet characterized by having plastic stripes bonded to both edges of one side of a thin long tape along the length of the tape.