JP2520482B2 - Method for manufacturing lead frame for semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a lead frame for a semiconductor device.

[Prior Art] As a method of manufacturing a lead frame for a semiconductor device, a method of pressing is well known. In this press working method, an undesired portion of the rolled sheet metal material is sequentially punched out using a well-known progressive die to form a lead frame having a predetermined shape in a continuous body or a strip shape.

In recent years, with the diversification of functions of semiconductor devices using lead frames and the tendency toward lower pin count, the tips of the inner leads of the lead frames are becoming finer, and the lead width and spacing tend to be narrower. However, in the press working, the fine leads are punched apart from each other in terms of the strength of the punching blade. That is, the process of punching between the leads on both sides of the lead is performed in separate steps. For this reason, the inner lead is twisted and processing stress remains inside the lead frame. This internal stress is released by heating during the semiconductor device assembly process, leading to lead tip deviation, overlap, ups and downs, etc., leading to poor wire bonding connections and short circuits in the semiconductor device assembly process, leading to lower lead frame quality. It was a factor to make.

As a conventional technique for preventing such a factor, there is known a technique in which a connecting piece for connecting the ends of the leads is provided and the ends of the leads are fixedly held by tape or resin in a state where the ends of the leads are connected. . As still another known technique, there is proposed a method in which annealing is performed to remove the internal stress of the lead frame, and then the strip-shaped lead frame or the continuous body of the lead frame in which the tips of the leads are formed is heat-treated.

[Problems to be Solved by the Invention]

However, in the above technique, when the strip-shaped lead frame is arranged on the heat treatment jig, it is a manual work, which lacks workability and increases the number of steps. Further, there is a drawback that incidental equipment such as a vacuum device becomes expensive.

Further, in the technology for annealing the continuous body of the lead frame, deformation of the shape due to heating and slow cooling, deformation of the reference hole for positioning, and the size of the reference hole pitch change, and the semiconductor positioning in the subsequent process becomes unstable. There was a drawback that caused

Furthermore, because the tip of the lead is connected with a thin connecting piece,
When the continuous body of the lead frame is continuously or intermittently conveyed and subjected to the annealing treatment, there is a defect that the lead tip portion is deformed by the tensile force or the extra coining thickness is deformed.

The present invention eliminates the above drawbacks, to accurately create the wire bonding area of the inner lead tip in a required shape, and to impart a mechanical strength that can withstand the tension applied when performing annealing, Another object is to fix the tape by holding the tips of the inner leads in an accurate position. Another object of the present invention is to provide a manufacturing method for obtaining a lead frame having good workability, high quality, and required functional conditions.

[Means for solving the problem]

In order to achieve the above object, the present invention sequentially removes unnecessary portions of a strip-shaped thin metal sheet material, and a semiconductor element mounting stage held as a part of the thin metal sheet material by a support bar, and a stage of the stage. A plurality of inner leads radially arranged from the outer peripheral edge, and outer leads are formed continuously in the outer side of these inner leads, in a manufacturing method for forming a required lead frame by performing heat treatment in the middle of these forming steps, The inner lead and the stage are integrally formed with the end portion of the inner lead that is a joint portion with the stage as an intermediate piece, and a region near the inner lead including the tip and the intermediate portion. Forming a thin portion up to a portion including a part of the piece and wire-bonding the thin portion at the tip of the inner lead A strip-shaped lead frame is configured as a rear, a predetermined tension is uniformly applied to the strip-shaped lead frame, and the strip-shaped lead frame is continuously or intermittently conveyed for a required length to sequentially perform residual heat, annealing and slow cooling, After continuous annealing to remove residual stress, plating,
The lead frame required processing such as taping is applied,
Further, a cavity is formed between the outer peripheral edge of the stage and the cut end of the inner lead by punching out the intermediate piece and the intermediate piece side of the thin portion at the tip of the inner lead. Is characterized by.

[Action]

According to the method of the present invention, an intermediate piece is provided at the tip of each inner lead, and the inner lead is connected to the periphery of the stage part through the intermediate piece to be integrally formed, so that the lead frame can withstand the pulling force and tension of conveyance. So as to give mechanical strength. In addition, by forming an escape area for excess thickness when accurately forming a thin portion having a wire bonding area at the tip with this intermediate piece, deformation of the inner lead is minimized and a strip-shaped lead frame is processed. To do.

Thereafter, a predetermined tension is uniformly applied to the strip-shaped lead frame, the frame is continuously or intermittently conveyed for a required length, and preheating, annealing, and gradual cooling are sequentially performed to perform annealing for removing residual stress inside. Do it continuously. Then, plating is applied to a predetermined area of the lead frame, and thereafter, necessary processing for the lead frame such as taping or resin fixing for fixing the inner lead at a predetermined position is performed. And further,
The element mounting stage and the cavities are formed into a predetermined shape, and the intermediate piece is removed to obtain a required lead frame.

〔Example〕

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

FIG. 1 is a plan view showing a situation in an intermediate step of a lead frame manufactured by the method of the present invention, and FIGS. 2 (a) and 2 (b) are enlarged plan views showing details of an element mounting stage (of FIG. 1). It is the part enclosed with the circle A) and an expanded sectional view. 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 FIG. 1 and FIG. 2, 42ALLOY (Fe-Ni alloy) strip-shaped metal thin plate material slit into a predetermined dimension width is sequentially punched and removed using a progressive die. An outer lead 1, an inner lead 2 and a stage portion 3 for mounting a semiconductor element, and a support bar 6 for supporting the stage portion 3 are formed.

In the step of molding the inner lead 2, as shown in FIG. 2, the inner lead 2 is extended and punched so that the tip 8 of the inner lead 2 is provided with the intermediate piece 4 in the region shown by the diagonal lines in the figure. It is connected to the stage unit 3 via 4 and integrated. Further, coining for forming a thin portion of the wire bonding area 5 having a predetermined shape is applied to the tip portion of the inner lead 2 to form a continuous body of strip-shaped lead frames as shown in FIG.

In the above, the outer lead 1 and the inner lead 2 are formed, but when the number of lead pins increases and the lead width becomes narrower, the lead frame is provided with mechanical strength so as to withstand the tensile force and tension of conveyance. As shown in FIGS. 4 and 5, a strip-shaped lead frame continuous body may be formed except for the outer leads 1. However, the outer lead 1 is punched and removed after the annealing process of the next step is performed. Note that FIG. 5 (a) is an enlarged plan view of a portion surrounded by a circle A in FIG. 4, and FIG. 5 (b) is an enlarged vertical sectional view.

Next, the strip-shaped lead frame formed in the above step is continuously conveyed to the annealing treatment furnace while applying uniform tension. In the annealing furnace, the strip-shaped lead frame is sequentially preheated, annealed and gradually cooled, and further annealed to remove the internal residual stress of the strip-shaped lead frame. The annealing temperature is preferably 400 to 500 ° C, which is lower than the transformation point. However, depending on the required conditions of the lead frame or the shape and material such as the number and width of the lead pins, the treatment may be limited to the reduction of internal stress due to low temperature annealing. In addition, the atmospheric conditions in the furnace are
Bright annealing in a neutral atmosphere may be performed in consideration of oxidation prevention. Further, tension is applied by using a general tension applying device, and a tension detecting sensor is arranged at an appropriate position to automatically control to give a uniform tension.

Next, the strip-shaped lead frame is conveyed to a plating device and subjected to a required treatment, and the wire bonding area 5 and the stage portion 3 are plated with a noble metal. Further, after fixing the inner leads 2 with an insulating resin tape or resin while holding the lead tips, the stage part 3 and the cavitation part 10 are formed to a desired size and the intermediate piece 4 is removed to obtain the desired shape shown in FIG. Lead frame can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the intermediate lead piece is provided at the tip of the inner lead, and the inner lead lead is integrated around the semiconductor element mounting stage part. Therefore, the present invention withstands tensile force and additional tension in the annealing step. Mechanical strength can be imparted to the leadframe. Therefore, a highly accurate product can be obtained without deformation, cutting, or change in pitch dimension in the annealing process.

Further, the intermediate piece can be used for escape of mismatch and escape of excess thickness when forming the thin portion of the lead tip into an accurate shape, and the accuracy is further enhanced.

Furthermore, continuous processing that passes through the line as a strip-shaped lead frame is possible, and unlike the strip-shaped lead frame, there is no need for manual lamination on a heat treatment jig, rusting due to breathing, sweat, etc. is prevented, and workability is good. Become. In addition, since the inner lead is fixed to the resin table or the resin to form the stage and the cavitation with high positional accuracy, wire bonding is stabilized.

Further, since the internal stress can be reduced, it is possible to provide a high quality lead frame without the positional change of the tips of the inner leads even after the heating process of the semiconductor device assembling process.

[Brief description of drawings]

FIG. 1 is a plan view showing a situation in an intermediate step of a lead frame manufactured by the method of the present invention, FIG. 2 (a) is a plan view showing details of an element mounting stage portion, and FIG. 2 (b) is its plan view. FIG. 3 is a vertical sectional view, 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 step showing another example, and FIGS. )
FIG. 3 is an enlarged plan view and an enlarged vertical sectional view of a main part. 1: Outer lead, 2: Inner lead 3: Stage part, 4: Intermediate piece 5: Wire bonding area 6: Support bar, 7: Resin tape or resin 8: Tip, 10: Cavitation part

Claims (1)

(57) [Claims] 1. A semiconductor element mounting stage held as a part of the metal thin plate member by a support bar, in which unnecessary portions of the strip-shaped metal thin plate member are sequentially removed, and radially arranged from the outer peripheral edge of the stage. Multiple inner leads,
In a manufacturing method in which outer leads are formed continuously with the outer sides of these inner leads, and a heat treatment is performed in the middle of these forming steps to form a required lead frame, the tip portion of the inner leads and the stage The inner lead and the stage are integrally formed with the joining portion as an intermediate piece, and a thin portion is formed up to a portion including a portion of the inner piece and its vicinity including the tip of the inner lead. A band-shaped lead frame is formed by molding and using the thin portion at the tip of the inner lead as a wire bonding area, and the band-shaped lead frame is evenly applied to a predetermined tension, and the band-shaped lead frame is continuously or intermittently formed for a required length. After carrying and sequentially performing residual heat, annealing, and slow cooling to remove internal residual stress, The lead frame is subjected to necessary processing such as plating and taping, and further, the intermediate piece and the thin piece portion of the tip of the inner lead, including the intermediate piece side, are cut out by punching, and the outer peripheral edge of the stage and A method of manufacturing a lead frame for a semiconductor device, which comprises forming a cavitation between the inner lead and a cut end.