JP2501046B2 - 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.

[0007]

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 of the present invention is to provide a lead frame having good dimensional accuracy and high reliability.

[0009]

Therefore, in the present invention, taping is performed after releasing the distortion due to coining by removing the cavity or before removing the cavity so that the distortion due to the coining does not occur. It is a feature. In the first aspect of the present invention, the side edges of the inner leads are punched out so as to form a shape in which the tip portions of the inner leads and the semiconductor element mounting portion are connected, the lead frame is shaped, and then heat treatment is performed (annealing step ), After that, the cavity region between the tip portion of the inner lead and the semiconductor element mounting portion is punched, the inner lead is separated from each other, and the coining step for widening the inner lead tip,
After the precious metal plating process, the tape is attached so as to fix the inner leads that are finally separated from each other.

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.

In the second aspect of the present invention, in the first aspect, the coining step is performed before the cavity removal step. That is, the heat treatment step, the coining step, the cavity region punching, and the taping are performed in this order.

[0012]

According to the above method, since taping is performed after punching the cavity area, it is possible to obtain the lead frame with good dimensional accuracy because the distortion that occurs during punching can be fixed in a released state. Is possible.

According to the first method, the inner lead tips are annealed integrally with each other by a connecting piece or the like, then annealed, and then the cavity region is punched to release the connecting portion, coining, precious metal plating process. As described above, since the fixing by taping is performed in a state in which the strain generated at the time of punching is released, the accuracy can be further improved. In addition, when processing the shape,
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 the second method, since coining is performed before punching the cavity region, the strain due to coining is satisfactorily released by the punching of the cavity region, and the dimensional accuracy is improved as in the first method. Can be measured.

[0015]

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), using a strip-shaped material 1 called alloy 42,
The side edges of the inner leads 2 and the outer leads 3 are sequentially formed using a progressive die, and stamping is performed so that the tips of the inner leads and the pads 4 are continuous. 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. And FIG.
As shown in FIG. 5, punching is performed between the tip of the inner lead and the periphery of the pad, that is, the so-called cavity region, and the tip of the inner lead is separated.

Further, as shown in FIG. 3, the inner lead 2
Coin the tip to secure the flat width required for wire bonding. Here, if necessary, flat striking is performed to forcibly twist the inner leads.

Then, as shown in FIG. 4, a noble metal plating layer M such as Pt is formed on the tips of the inner leads and the pads.

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 to remove distortion, and then punched, coined and plated 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 tip of the inner lead is separated from the die pad before the coining, the tip of the inner lead is coined in a state where it is once released, and no residual strain remains. In this way, a good fixed state can be obtained without distortion during taping, and the accuracy can be further improved.

The same effect can be obtained by performing the coining step before the cavity removal step. In this case, although there is residual strain due to coining, the same effect can be obtained because it is released in the cavity removal process.

[0023]

As described above, according to the method of the present invention, the inner leads are fixed by taping after releasing the residual strain, so that the dimensional accuracy is good and the reliability is high. It is possible to obtain a high lead frame.

[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. In 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, a tip portion of the inner lead and the semiconductor element mounting portion are connected. A side edge of the inner lead is punched to form a shape, and a first shape processing step of shape processing of the lead frame and an annealing step of heat treatment; The second shape processing step of punching out the cavity area between the inner leads and the inner leads, the coining step for widening the inner lead tips, and the noble metal plating on the inner lead tips or the semiconductor element mounting portion. Attach an insulating tape to fix the plating process and the inner leads that are separated from each other. Method for fabricating a lead frame, characterized in that it has to include a taping process. 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. 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 second shape processing step of 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 and a precious metal plating on the tip of the inner lead or the semiconductor element mounting portion. Attach an insulating tape to fix the plating process and the inner leads that are separated from each other. Method for fabricating a lead frame, characterized in that it has to include a taping process.