JP2501047B2 - Manufacturing method of lead frame - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame manufacturing method, and more particularly to a lead frame manufacturing method using a punching method.

[0002]

2. Description of the Related Art With the high integration and miniaturization of semiconductor devices, the demand for lead frames has become strict. In particular, due to the increase in the number of leads and miniaturization, the lead spacing becomes narrower, and even minute strains in the leads cause positional displacement, and are therefore not allowed.

Therefore, a method has been proposed in which the tip of the inner lead and the pad are stamped into a continuous shape, and then heat treatment is performed to remove processing strain. According to this method, continuous operation is performed while applying tension in a reel state. Processing can be performed.

In addition, the tip of the inner lead is subjected to coining treatment in order to secure a flat width required for wire bonding, and a lead frame having a large number of leads is deformed due to handling in a semiconductor device manufacturing process. In order to prevent this, a taping process is performed in which an insulating tape or film connecting the inner leads is attached.

The coining process and the taping process are carried out with the tip of the inner lead and the pad being in a continuous state after the heat treatment, and it is considered that the extension of the inner lead due to the coining can be forcibly suppressed by the taping. It was being done. However, the elongation of the inner lead due to coining varies depending on the shape of the lead, and the strain is often considerably large.

By the way, the extension of the inner lead due to such coining is often released by so-called cavity removal for separating the tip of the inner lead and the pad. If you try to do this, if distortion occurs in the taping state, it will be contained without releasing the distortion.

This is a similar problem even when heat treatment is not performed.

[0008]

As described above, in the conventional method, since the taping is performed while the strain is still formed, the residual strain remains even after the inner lead tip and the pad are separated from each other. In a lead frame having a fine pattern shape, a positional deviation easily occurs due to a decrease in dimensional accuracy, which causes a decrease in reliability.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a lead frame having good dimensional accuracy and high reliability.

[0010]

Therefore, the present invention is characterized in that after the coining and the plating, taping is performed after releasing the strain due to the coining by removing the cavity.

In the first aspect of the present invention, the side edges of the inner lead are punched out so that the tip of the inner lead and the semiconductor element mounting portion are connected, the lead frame is shaped, and then the heat treatment is performed. (Annealing step), then punching the cavity area between the tip of the inner lead and the semiconductor element mounting part, separating the inner leads from each other, and a coining step for widening the tip of the inner lead, precious metal plating After the process, the cavity area between the tip of the inner leads and the semiconductor element mounting part is punched out, the inner leads are separated from each other, and finally the inner leads which are separated from each other are fixed to each other with tape. Is attached. Here, it is desirable that when the lead frame for punching out the side edge of the inner lead is processed, flat punching is performed to such an extent that the twist of the lead is corrected.

The second aspect of the present invention is a method in which the heat treatment is omitted from the first method, and is otherwise the same as the first method.

[0013]

According to the above method, the cavity region is punched out after the coining and plating steps, and taping is performed after that, so that the strain generated during coining is fixed in a released state. Therefore, it is possible to obtain a lead frame having good dimensional accuracy.

That is, according to the first aspect of the present invention, the inner lead tips are integrally molded with each other by a connecting piece or the like, annealed, subjected to a coining step, a noble metal plating step, etc., and then punched out in the cavity region to be connected. Since the part is released and the strain generated during punching is released, taping is performed,
Further, the accuracy can be improved. Further, in the shape processing, if the flattening is performed to such an extent that the twist of the lead is corrected, the residual strain can be further reduced.

According to a second aspect of the present invention, the inner lead tips are integrally molded with each other by a connecting piece or the like, and after a coining process, a precious metal plating process, etc., the cavity region is punched out to release the connecting portion and punch out. Since the fixing by taping is performed with the strain generated at the time of being released, the accuracy can be improved.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

1 to 5 are views showing a manufacturing process of a lead frame according to an embodiment of the present invention.

First, as shown in FIG. 1, a band-shaped material 1 called an alloy 42 is used, and the side edges of the inner leads 2 and the outer leads 3 are sequentially formed by using a progressive die, and the inner lead tip and Stamping is performed so that the pad 4 has a continuous shape.

After the side edges of the inner leads and the outer leads are formed in this manner, heat treatment is performed at 400 ° C. for 30 minutes with the tips of the inner leads and the pads being continuous. Then, as shown in FIG. 2, coining is performed on the tips of the inner leads 2 to secure a flat width required for wire bonding. Here, if necessary, flat striking is performed to forcibly twist the inner leads.

Further, as shown in FIG. 3, a noble metal plating layer M of Pt or the like is formed on the tips of the inner leads and the pads.

Then, as shown in FIG. 4, punching is performed between the tip of the inner lead and the periphery of the pad, that is, a so-called cavity region, the tip of the inner lead is individually separated, and the shape processing of the lead frame is completed.

Finally, as shown in FIG. 5, a polyimide tape T is attached to connect and fix the inner leads to each other to complete the lead frame.

The lead frame thus obtained is punched in a state in which the leading end of the inner lead is connected to the die pad, heat-treated for strain relief, and then coined, plated, and punched in the cavity region. Since the taping is performed after performing, the strain generated during punching is released and then fixed, so that the dimensional accuracy is good and the reliability is high.

Further, since the tips of the inner leads are integrally formed with the die pad, they are not deformed even after the punching process, the annealing process or the precious metal plating process.
Further, after such a processing step, since the inner lead tip and the die pad are separated from each other, residual strain is released here, and it is possible to obtain a good fixing state without strain when taping, It is possible to further improve the accuracy. Although the heat treatment conditions for annealing were set to 400 ° C. for 30 minutes in the above-mentioned examples, the temperature and time can be appropriately changed depending on the material, size and the like.

Further, in the above embodiment, the case where the annealing process is included has been described, but the present invention can be applied to the case where the annealing process is not included.

[0026]

As described above, according to the method of the present invention, after the coining and plating, the cavity region is punched out to release the residual strain and then the inner leads are fixed to each other by taping. Therefore, it is possible to obtain a lead frame having good dimensional accuracy and high reliability.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a lead frame according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a lead frame according to an embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of a lead frame according to an embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of a lead frame according to an embodiment of the present invention.

FIG. 5 is a manufacturing process diagram of the lead frame according to the embodiment of the present invention.

[Explanation of symbols]

 1 band-shaped material 2 inner lead 3 outer lead 4 pad C cavities area M plating layer

Claims (3)

(57) [Claims] 1. A method of manufacturing a lead frame comprising a semiconductor element mounting portion and inner leads arranged around the semiconductor element mounting portion at a predetermined interval, wherein the tip end portion of the inner lead is connected to the semiconductor element mounting portion. Punching the side edge of the inner lead so as to form a shape, a first shaping step of performing a lead frame shaping step, an annealing step of performing a heat treatment, and a coining step for widening the inner lead tip, A plating step of plating the tip of the inner lead or the semiconductor element mounting portion with a noble metal, and punching out a cavity region between the tip portion of the inner lead and the semiconductor element mounting portion to separate the inner leads from each other. Tapes are attached so that the inner leads that are separated from each other's shape processing process are fixed Method for fabricating a lead frame, characterized in that it has to include a grayed step. 2. The first shape processing step punches out a side edge of the inner lead so that a tip portion of the inner lead and the semiconductor element mounting portion are connected to each other,
The lead frame manufacturing method according to claim 1, further comprising: a step of shaping the lead frame; and a flat hammering step for correcting the twist of the lead. 3. A method of manufacturing a lead frame comprising a semiconductor element mounting portion and inner leads arranged around the semiconductor element mounting portion at a predetermined interval, wherein the tip portion of the inner lead and the semiconductor element mounting portion are connected to each other. Forming a shape, the side edge of the inner lead is punched to shape the lead frame, a first shaping process, a coining process for widening the inner lead tip, and the inner lead tip or the semiconductor. A plating step of plating the element mounting portion with a noble metal, and punching out a cavity region between the tip of the inner lead and the semiconductor element mounting portion to separate the inner leads from each other.
And a taping step of attaching a tape so as to fix the inner leads separated from each other.