JPH04337661A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To obtain a lead frame with an improved dimension accuracy by enabling a distortion which is generated at the time of punching to be fixed in a released state by performing taping after punching a cavity region. CONSTITUTION:Side edges of an inner lead 2 or an outer lead 3 are formed in sequence using a band-shaped material called an alloy 42 and then a forward- feed mold and stamping is made so that an inner lead tip and a pad 4 are in continuous shape. After forming the side edges of the inner lead and the outer lead in this manner, heat treatment is performed while the inner lead tip and the pad are continuous. Then, an area between the inner lead tip and a pad peripheral, namely the cavity region, is punched, thus enabling the inner lead tip portion to be separated. Further, coining for securing a flat width which is needed for wire bonding is performed to the tip of the inner lead 2, where flattening is performed for correcting twisting of the inner lead as needed.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art As semiconductor devices become more highly integrated and smaller, demands on lead frames are becoming more severe. In particular, with the increase in the number of leads and their miniaturization, the lead spacing has become even narrower, and even minute distortions in the leads can no longer be tolerated because they can cause misalignment.

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 treated to remove processing distortion. processing can be performed.

[0004] Furthermore, coining processing is applied to the tips of the inner leads to ensure a flat width necessary for wire bonding, and lead frames with a large number of leads are more susceptible to deformation of the inner leads due to handling during the manufacturing process of semiconductor devices. To prevent this, a taping process is used in which an insulating tape or film is attached to connect the inner leads.

[0005] This coining process and taping process are performed while the inner lead tip and the pad remain continuous after heat treatment, and it is thought that the elongation of the inner lead due to coining can be forcibly suppressed by taping. It was getting worse. However, the elongation of the inner lead due to coining differs depending on the shape of the lead, and the strain often becomes quite large.

By the way, the extension of the inner lead due to such coining is often released by so-called cavity extraction, which separates the tip of the inner lead from the pad. If you try to do this, if there is distortion in the taping state, the distortion will be contained without being released.

[0007]

[Problems to be Solved by the Invention] In this way, in the conventional method, taping was performed with distortion still formed, so even after the inner lead tip and pad were separated, residual distortion remained. In a lead frame having a fine pattern shape, positional deviation is likely to occur due to a decrease in dimensional accuracy, which causes a decrease in reliability.

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

[0009]

[Means for Solving the Problems] Therefore, in the present invention, taping is performed after the distortion due to coining is released by cavity extraction or prior to coining, so that the distortion due to coining is not generated. This is a characteristic feature. In the first aspect of the present invention, the side edge of the inner lead is punched out so that the tip end of the inner lead and the semiconductor element mounting part are connected, the lead frame is shaped, and then heat treatment is performed (annealing process). ), then a coining process to punch out the cavity area between the tip of the inner lead and the semiconductor element mounting part, separate the inner leads from each other, and make the tip of the inner lead wider;
After going through a precious metal plating process, tape is attached to fix the separated inner leads.

[0010] Here, when shaping the lead frame by punching out the side edges of the inner leads, it is preferable to flatten the leads to such an extent that the twisting of the leads can be corrected.

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

0012

[Operation] According to the above method, since taping is performed after punching the cavity area, it is possible to fix the lead frame with good dimensional accuracy by releasing the distortion that occurs during punching. becomes possible.

According to the first method, the tips of the inner leads are integrally molded with each other using connecting pieces, etc., and then annealing is performed, and then the connecting portion is released by punching out the cavity area, and the coining and precious metal plating processes are performed. After the distortion that occurs during punching is released, the parts are fixed by taping, which further improves accuracy. Further, when shaping the lead, if the lead is flattened to the extent that the twist is corrected, the residual strain can be further reduced.

According to the second method, since coining is performed before punching the cavity region, the distortion caused by coining is effectively released by punching the cavity region, and dimensional accuracy is improved as in the first method. can be measured.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 to 5) are diagrams showing the manufacturing process of a lead frame according to an embodiment of the present invention. First, as shown in Fig. 1), using a band-shaped material 1 designated as alloy 42, the side edges of the inner lead 2 and outer lead 3 are sequentially formed using a progressive mold, and the inner lead tip and pad 4 are formed in sequence. stamping so that it forms a continuous shape. After forming the side edges of the inner leads and outer leads in this manner, heat treatment is performed at 400° C. for 30 minutes while the inner lead tips and pads remain continuous. and,
As shown in Figure 2, punching is performed between the tip of the inner lead and the periphery of the pad, that is, the so-called cavity area.
Separate the inner lead tips individually.

Furthermore, as shown in FIG.
Coining is performed at the tip to ensure the flat width required for wire bonding. Here, flat beating is performed to force twisting of the inner lead as necessary.

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 pad portions.

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

The lead frame thus obtained is punched with the leading edge of the inner lead connected to the die pad, heat treated to remove distortion, and then punched in the cavity area, coined, and plated. After that, taping is performed, which releases the distortion that occurs during punching, and then fixes it.
It has good dimensional accuracy and is highly reliable.

Furthermore, since the inner lead tip is separated from the die pad prior to coining, coining is performed with one end open, and no residual strain remains. In this way, it is possible to obtain a good fixed state without distortion during taping, and it is possible to further improve accuracy.

Note that the same effect can be obtained even if the coining process is performed before the cavity extraction process. In this case, although there is residual strain due to coining, it is released in the cavity extraction process, so the same effect can be obtained.

[0023]

[Effects of the Invention] As explained above, according to the method of the present invention, since the inner leads are fixed to each other by taping after releasing the residual strain, dimensional accuracy is good and reliability is achieved. It becomes possible to obtain a high lead frame.

[Brief explanation of drawings]

[Fig. 1] Manufacturing process diagram of a lead frame according to an embodiment of the present invention

[
Figure 2: Manufacturing process diagram of lead frame according to the embodiment of the present invention

[Fig. 3] Manufacturing process diagram of a lead frame according to an embodiment of the present invention

[Figure 4
] Manufacturing process diagram of a lead frame according to an embodiment of the present invention

[Figure 5]
Manufacturing process diagram of a lead frame according to an embodiment of the present invention

[Explanation of symbols]

1. Strip material 2 Inner lead 3 Outer lead 4 Pad C Cavity area M Plating layer

Claims (3)

[Claims] 1. A method for manufacturing a lead frame comprising a semiconductor element mounting part and inner leads arranged around the semiconductor element mounting part at predetermined intervals, wherein the tip of the inner lead and the semiconductor element mounting part are connected. a first shape processing step in which the side edges of the inner leads are punched out to form a shape of the lead frame, an annealing step in which heat treatment is performed, and the tips of the inner leads and the semiconductor element mounting portions are a second shape processing step of punching out the cavity region between the inner leads and separating the inner leads from each other; a coining step of making the inner lead tips wider; and plating precious metal on the inner lead tips or the semiconductor element mounting portions. A method for manufacturing a lead frame, comprising: a plating step; and a taping step, in which an insulating tape is attached to fix the inner leads separated from each other. 2. In the first shape processing step, a side edge of the inner lead is punched out so that the tip end of the inner lead and the semiconductor element mounting portion are connected to each other.
2. The method of manufacturing a lead frame according to claim 1, comprising a step of shaping the lead frame and a flattening step of correcting twisting of the lead. 3. A method for manufacturing a lead frame comprising a semiconductor element mounting part and inner leads arranged around the semiconductor element mounting part at predetermined intervals, wherein the tip of the inner lead and the semiconductor element mounting part are connected. a first shape processing step of punching out the side edge of the inner lead so as to form a shape and processing the shape of the lead frame; an annealing step of performing heat treatment; and a coining step of widening the tip of the inner lead; A second shape processing step of punching out a cavity region between the tip of the inner lead and the semiconductor element mounting part and separating the inner leads from each other, and plating the inner lead tip or the semiconductor element mounting part with a precious metal. A method for manufacturing a lead frame, comprising: a plating step; and a taping step, in which an insulating tape is attached to fix the inner leads separated from each other.