JPH0366153A - Manufacture of lead frame for semiconductor device use - Google Patents

Abstract

PURPOSE:To give a lead frame a mechanical strength which is resistant to a tensile force and an added tension during an annealing process by a method wherein an intermediate piece is provided at the tip of an inner lead and the inner lead is united to a periphery of a semiconductor-element mounting stage. CONSTITUTION:Inner leads 2 are extended and stamped so as to form intermediate pieces 4 at tips 8 of the inner leads 2; they are connected and united to a stage part 3 via the intermediate pieces 4. In addition, a coining operation to form thin parts of a wire bonding area having a prescribed shape is executed on the tip parts of the inner leads 2; a continuous body of a belt-shaped lead frame is formed. While a uniform tension is being exerted on the belt-shaped lead frame, the lead frame is conveyed continuously to an annealing treatment furnace and is heated, annealed and cooled gradually one after another to remove an internal residual stress. Then, the belt-shaped lead frame in this state is conveyed to a plating apparatus; a required treatment is executed; the inner leads 2 are fixed by using an insulating resin tape or a resin in a state that the tips of the leads are held; after that, the stage part 3 and cavity parts are formed in required sizes; the intermediate pieces 4 are removed to obtain a desired lead frame.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a lead frame for a semiconductor device.

[Conventional technology]

A well-known method for manufacturing lead frames for semiconductor devices is press processing. This pressing method is
A well-known progressive die is used to sequentially punch out unnecessary parts of a rolled thin metal plate material, thereby forming a lead frame of a predetermined shape into a continuous body or strip.

In recent years, as the functions of semiconductor devices using lead frames have become more diversified and the number of pins has increased, the tips of inner leads of lead frames have become finer, and lead widths and intervals have become narrower. However, when working with a press, the punching between fine leads is performed at a distance from the viewpoint of the strength of the punching blade. That is, the process of punching out the space between the leads on both sides of the lead is performed in separate steps. As a result, the inner lead is twisted and machining stress remains inside the lead frame. This internal stress is released by heating during the semiconductor device assembly process, causing the lead tips to overlap, rise and fall, and deteriorate the quality of the lead frame, such as poor wire bonding connections and short circuits during the semiconductor device assembly process. This was a contributing factor.

As a conventional technique for preventing such factors, it is known to provide a connecting piece that connects the ends of the leads, and to fix and hold the ends of each lead with tape, resin, etc. while the ends of each lead are connected. . As another known technique, a method has been proposed in which a lead frame is annealed to remove internal stress, and then a strip-shaped lead frame or a continuous body of lead frames, in which lead tips are formed, is heat treated.

[Problem to be solved by the invention]

However, in the above technique, arranging the strip-shaped lead frames on a heat treatment jig requires manual work, which lacks workability and increases the number of steps. Furthermore, there is a drawback that the cost of ancillary equipment such as a vacuum device is high.

Furthermore, in the technology of annealing a continuous lead frame, heating and slow cooling cause deformation of the shape, deformation of the positioning reference holes, and changes in the pitch of the reference holes, making semiconductor positioning in the subsequent process unstable and causing problems. There was a drawback that caused this.

Furthermore, since the lead tips are connected with thin connecting pieces, when a continuous lead frame is continuously or intermittently conveyed and annealed, the lead tips may be deformed due to tensile force or deformation due to excess coining. There were also other drawbacks.

The present invention eliminates the above-mentioned drawbacks, creates a wire bonding area at the tip of an inner lead accurately in a desired shape, provides mechanical strength sufficient to withstand the tension applied during annealing, and The purpose is to align and hold the tips of the inner leads in accurate positions and fix them with tape. Furthermore, it is an object of the present invention to provide a manufacturing method for obtaining a lead frame that is easy to work with, has high quality, and has the required functional conditions.

[Means to solve the problem]

In order to achieve the above object, the present invention includes an intermediate piece at the tip of each inner lead, connects each inner lead to the periphery of the stage part via this intermediate piece, and integrates the inner lead and the stage. A strip-shaped lead frame is constructed by accurately forming and processing a thin part having a shape and having a wire bonding area at the tip with an intermediate piece. Then, a required tension is uniformly applied to this strip-shaped lead frame, and a continuous process of annealing is interposed in the middle of the manufacturing process of the strip-shaped lead frame, thereby obtaining a lead frame having the required structural function. shall be.

[Effect]

In the method of the present invention, an intermediate piece is provided at the tip of each inner lead, the inner lead is connected to the periphery of the stage part via this intermediate piece, and is integrally formed.
Provides mechanical strength to withstand tensile force and tension. In addition, this intermediate piece forms a relief part for excess thickness when accurately molding a thin part with a wire bonding area at the tip, making it possible to process a strip-shaped lead frame while minimizing deformation of the inner lead. do.

After this, a predetermined tension is uniformly applied to the strip-shaped lead frame, and the frame is continuously or intermittently conveyed for a required length, and preheating, annealing, and slow cooling are performed sequentially to remove internal residual stress. Do it continuously. Then, plating is applied to a predetermined area of the lead frame, and then the lead frame is subjected to necessary processing such as taping or resin fixing to fix the inner leads in a predetermined position. Furthermore, the element mounting stage and cavity are shaped into a predetermined shape,
The intermediate piece is removed to obtain the required lead frame.

〔Example〕

Hereinafter, features of the present invention will be specifically explained with reference to embodiments shown in the drawings.

FIG. 1 is a plan view showing the situation in an intermediate process of a lead frame manufactured by the method of the present invention, and FIG. FIG. 3 is a portion surrounded by A) and an enlarged cross-sectional view. Moreover, FIG. 3 is a plan view showing the final product of the lead frame obtained by the method of the present invention.

As shown in Figures 1 and 2, a metal thin plate material in the form of a band of 42ALLOY (Fe-Ni alloy), which has been slit to a predetermined width, is punched out and removed in sequence using a progressive die. Outer lead 1. A stage part 3 for mounting the inner lead 2 and the semiconductor element, and a support par 6 for supporting the stage part 3 are formed.

In the forming process of the inner lead 2, as shown in FIG. 2, the inner lead 2 is extended and punched so that the intermediate piece 4 in the area shown by diagonal lines in the figure is provided at the tip 8 of the inner lead 2. 4 and is connected to the stage section 3 and integrated. Furthermore, coining is applied to the tip of the inner lead 2 to form a thin part of the wire bonding area 5 having a predetermined shape, thereby forming a continuous band-shaped lead frame as shown in FIG.

The above is outer lead 1. Although the inner lead 2 has been formed, if the number of lead pins increases and the lead width becomes narrower, in order to give the lead frame mechanical strength to withstand the bending force and tension of conveyance, it is necessary to As shown in FIG. 5, a continuous band-shaped lead frame may be formed by excluding the outer lead 1. However, the outer lead 1 is punched out and removed after being subjected to the next annealing process. Note that FIG. 5(a) is an enlarged plan view of the portion surrounded by circle A in FIG. 4, and FIG. 5(b) is an enlarged longitudinal sectional view.

Next, the belt-shaped lead frame formed in the above process is continuously conveyed to an annealing treatment furnace while applying uniform tension. In the annealing furnace, the strip lead frame is preheated and
Annealing and slow cooling are sequentially performed, and further annealing is performed to remove internal residual stress in the band-shaped lead frame. The annealing temperature is preferably 400 to 500°C below the transformation point. However, depending on the required conditions of the lead frame, the shape and material such as the number and width of the lead pins, the process may be limited to reducing the internal stress by low-temperature annealing. In addition, bright annealing is preferably performed in a neutral atmosphere in consideration of oxidation prevention. Further, tension is applied using a general tension applying device, and a tension detection sensor is placed at an appropriate position to automatically apply uniform tension.

Next, the belt-shaped lead frame is transported to a plating apparatus and subjected to necessary processing, and the wire bonding area 5 and the stage section 3 are plated with a precious metal. Furthermore, after fixing the inner lead 2 with an insulating resin tape or resin while holding the lead tip, the stage part 3 and the cavity part 10 are formed to the required dimensions, and the intermediate piece 4 is removed, as shown in FIG. A desired lead frame can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, since the manufacturing method includes an intermediate piece at the tip of the inner lead and integrates the inner lead around the stage portion on which the semiconductor tray is mounted, it can withstand tensile force and additional tension in the annealing process. Mechanical strength can be imparted to the lead frame. Therefore, there is no deformation in the annealing process, no change in cutting or pitch dimensions, etc., and a highly accurate product can be obtained.

In addition, the intermediate piece can be used to escape mismatches and excess thickness when forming the thin part of the lead tip into an accurate shape.
The accuracy is even higher.

Furthermore, it can be processed continuously by passing the line as a strip-shaped lead frame, does not require manual lamination on a heat treatment jig unlike strip-shaped lead frames, prevents rusting due to breathing, sweat, etc., and has good workability. Become. Furthermore, since the stage and hiccup are formed by fixing the inner lead to a resin table or resin with high positional accuracy, wire bonding becomes stable.

Moreover, since the internal stress can be reduced, the position of the inner lead tip does not change even after the heating process in the semiconductor device assembly process, and a high-quality lead frame can be provided.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the intermediate process of a lead frame manufactured by the method of the present invention, FIG. 2(a) is a plan view showing details of the element mounting stage, and FIG. 3 is a plan view of a lead frame obtained by the method of the present invention, FIG. 4 is a plan view of a lead frame in an intermediate process showing another example, and FIGS. )
are an enlarged plan view and an enlarged longitudinal cross-sectional view of main parts. l: Outer lead 2: Inner lead 3: Stage section 4: Intermediate piece 5: Wire bonding area

Claims (1)

[Claims] 1. Sequentially remove unnecessary parts of the strip-shaped metal sheet material,
In a manufacturing method in which a lead frame for a semiconductor device is formed with a stage on which a semiconductor element is mounted and a plurality of inner leads and outer leads arranged radially from the stage, heat treatment is performed to form a required lead frame in the middle of the manufacturing process. The tip of each inner lead with
A thin-walled part that is integrally connected to the periphery of the stage part via this intermediate piece and has a wire bonding area at the tip thereof is molded to form a band-shaped lead frame, and the band-shaped lead frame After uniformly applying a predetermined tension to the lead frame, the strip lead frame is continuously or intermittently conveyed for the required length, and preheating, annealing, and slow cooling are performed sequentially to remove internal residual stress. 1. A method for manufacturing a lead frame for a semiconductor device, characterized in that the element mounting stage and cavity are formed into a predetermined shape by subjecting the lead frame to necessary processing such as plating, taping, etc.