JPS61234061A - Manufacture of lead frame of semiconductor device - Google Patents

Abstract

PURPOSE:To readily form a lead frame with many fingers with bumps by forming bumps at the ends of the fingers by pressing the frame formed on a substrate together with the substrate by electroforming, and then separating the lead frame from the substrate to obtain the lead frame. CONSTITUTION:A resist layer 9 of the desired pattern is formed on a substrate 8 made of a conductive metal, and the shape of a nonresist portion 8a is formed in a lead frame shape of the desired pattern. A metal layer is formed only on the nonresist portion 8a except the layer 9 by electroforming. Thus, part of a laminate of the substrate 8 and the metal layer 10 formed in one plate shape is pressed, bent, and the layer 10 is separated from the substrate 8 to obtain fingers 4. The ends of many fingers 4 extended inward from the frame portion 5a of the lead frame 7 are bend downward, and are formed in circular bumps 4b through a neck 4a. The ends are formed in circular shape to allow the bonding position of a semiconductor chip 1 with recessed electrode to displace laterally of the fingers 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a lead frame used for fixing semiconductor chips such as ICs and LSIs.

[Background technology]

2. Description of the Related Art Conventionally, metal lead frames have been used to assemble semiconductor devices in which semiconductor chips are integrated with a resin mold and have a plurality of protruding pins. 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. , a plurality of fingers 4 whose inner ends face the periphery of the tab 2, a frame 5 that supports these fingers 4 and the outer ends of the tab lead 3, and a plurality of fingers 4 provided at regular intervals along both side edges of the frame 5 It consists of a sprocket hole 6.

To assemble a semiconductor device using such a lead frame 7, first attach the semiconductor chip 1 onto the tab 2, and then connect each electrode of the semiconductor chip l and the corresponding inner end of the finger 4 with a wire or a wire. After that, the inner region of the rectangular frame portion 5 is molded with synthetic resin to cover the semiconductor chip 1, and then the frame portion 5 is cut out to obtain a flat lead or in-line type semiconductor device.

Incidentally, a bump is formed at the tip of the finger 4 of the lead frame 7 to connect to the electrode of the semiconductor chip 1. However, in recent years, as semiconductor devices with a large number of pins have been required, the width of the finger has become extremely large. As the lead frame becomes smaller, it becomes very difficult to connect the lead frame including the fingers, and it is even more difficult to integrally form a bump at the tip of the finger.

Conventionally, methods such as photoetching have been used to perform extremely fine processing as described above, but etching requires expensive manufacturing equipment and is difficult to reduce costs.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing a lead frame that can easily form a lead frame having a large number of bumped fingers.

[Summary of the invention]

As a means for achieving the above object, the present invention involves press-molding a lead frame formed on a substrate by electroforming together with the substrate to form a bump at the tip of the finger, and then peeling the lead frame from the substrate to lead the lead frame. It is characterized by having a frame body.

〔Example〕

FIG. 1 explains the manufacturing process of a lead frame in an embodiment of the present invention.

First, as shown in FIG. 1(a), a resist layer 9 having a desired pattern is formed on a substrate 8 made of a conductive metal such as stainless steel. This resist layer 9 is laminated only at positions where the lead frame 7 is not formed, and the shape of the non-resist portion 8a is the shape of the lead frame of a desired pattern.

Next, the substrate 8 on which this resist layer 9 has been formed is subjected to an M-release treatment using caustic soda if the resist is an alkaline developing type, or a solvent such as methylene chloride if the resist is a solvent type, and then copper and nickel are formed by electroforming. , layering conductive metals such as gold.

As a result, the metal layer is formed only on the non-resist portion 8a excluding the resist layer 9, as shown in FIG. Furthermore, the resist 9 is removed by washing with a solvent such as methyl isobutyl ketone (
A laminate like C) is obtained.

A part of the laminate of the substrate 8 and the metal layer 10 thus formed into a single plate is bent by press molding so as to protrude toward the substrate 8 as shown in FIG. This molded part is the tip of the fingers of the lead frame 7, and the figure shows a pair of fingers 4 extending oppositely toward the tab 2. In this case, by press-forming with the resist layer left in place, the resist layer surrounding the finger tips can act to prevent the fingers from shifting laterally, and can also have a buffering function against excessive pressing force. Note that tab 2 is not particularly required.

Next, the metal layer 10 is peeled off from the substrate 8 to obtain the finger 4 having a cross-sectional shape as shown in FIG.

Figure 2 shows a lead frame 7 obtained by the above method.
FIG. 4 is an enlarged perspective view of the finger 4 portion of FIG. As is clear from the figure, the tips of the many fingers 4 extending inward from the frame 5 of the lead frame 7 are curved downward, and the tips form circular bumps 4b through the neck 4a. There is.

By making the tip shape circular, the bonding position of the semiconductor chip 1 with the recessed electrode can be tolerated against lateral displacement of the fingers 4, and ease of assembly can be improved, but it is not limited to a circular shape. It can be changed into various shapes such as a rectangle or a polygon.

Figure 3 shows a state in which a semiconductor chip is attached to a wiring board using a lead frame.
is mounted and fixed on the upper surface of the printed wiring board 11, and a device hole 11a is provided in the printed wiring board 11 at a portion where the fingers 4 of the lead frame 7 extend.

The semiconductor chip 1 is placed in the device hole 1a, and the bumps 4b at the tips of the fingers 4 are fixed to electrodes provided on the top surface of the semiconductor chip 1 with solder.

As the substrate 8 for electroforming, in the above embodiment, a thin stainless steel plate, which itself is conductive, is used, and by press-working the substrate 8 and the fingers 4 at the same time when press-forming the tips of the fingers 4, it is possible to prevent the fingers 4 from breaking. Although unnecessary deformation was avoided, the substrate 8 is made of a material that itself does not have conductivity or has a high resistance value, such as a synthetic resin film such as polyester or polyimide resin, or a thin aluminum plate whose surface does not have conductivity. In the case of a synthetic resin film, conductivity may be imparted to the surface by vapor deposition, sputtering, electroless plating, etc., and in the case of an aluminum thin plate, the surface may be coated with zinc or the like. It is sufficient to impart conductivity through a substitution reaction.

In particular, in the case of such synthetic resins and aluminum thin plates, the materials themselves are flexible, malleable, and ductile, so the finger 4
It is possible to absorb variations in working pressure during press working, and it is possible to easily manage the dimensions of the bump portion.

〔Effect of the invention〕

As described above, according to the manufacturing method of the present invention, the lead frame main body is formed by electroforming, so even if it has a large number of narrow fingers, it can be manufactured with high precision. Manufacturing costs can be kept low compared to

Further, since the bending process of the bump at the tip of the finger is performed together with the substrate, even a finger with a small width and a narrow diameter can be sufficiently press-formed, and manufacturing becomes easy.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the manufacturing process of a lead frame according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view showing a finger portion of a lead frame manufactured according to the present invention, and FIG. FIG. 4, which shows a state in which the chip is attached to a wiring board, is a plan view of a general lead frame. DESCRIPTION OF SYMBOLS 1...Semiconductor chip, 1a...Electrode, 2...Tab, 4...Finger, 4b...Bump, 7...Lead frame, 8...Metal substrate, 8a...Non resist section. Figure 1 θ Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A method for manufacturing a lead frame in which fingers to be connected to electrodes of a semiconductor chip are formed of conductive metal foil, the method comprising forming a resist layer in a desired pattern on a substrate whose surface is made conductive at least, and forming a resist layer on a non-resist part. A semiconductor product that consists of a process of laminating metal by electroforming to form fingers, a process of press-molding a substrate with laminated metal layers to form a bump at the tip of the finger, and a process of peeling the metal layer from the substrate. A method for manufacturing lead frames for equipment.