JPH01133340A - Lead frame and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent a short circuit between adjacent leads, by making the width of each inner lead small at the point end. CONSTITUTION:Gap parts C between inner leads are punched by a punching machine P 1. Then the points of the inner leads are cut off by performing punching works by using a punch PN having a U shaped part K where its opening end A 2 is slightly smaller than a gap A 1 of a punch hole at an inner lead side section and a die pad 11 is formed. After that, a lead frame is completed by performing a plating process. In this way, the suppression of contact at the point prevents short circuits and makes it possible to obtain easily a highly reliable lead frame.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead frame and its method, and particularly to the shape of the tip of an inner lead and its manufacturing method.

[Prior art and its problems]

1c, the lead frame used for mounting the half-and-half LSI cap device is made of iron-based or copper-based gold m)c4 diagonal formed into a desired pattern by press working or etching.

Usually, as shown in FIG. 5, a lead frame includes a die pad 11 on which a semiconductor integrated circuit chip 1 (hereinafter referred to as a semiconductor chip) is mounted, a plurality of inner leads 12 arranged so as to surround the die pad, and an inner lead. A tie bar 13 integrally connects the die pad 12, an outer lead 14 extending outward from the tie bar connected to each inner lead, side bars 15 and 16 supporting the tie bar 13 from both sides, and supporting the die pad 11. It consists of 17 support pars.

During mounting, as shown in FIG. 6, C mounts the semiconductor chip 2 on the lead pad 11 of the lead frame 1, and connects the bonding pad of the semiconductor chip and the inner leads 12 of the lead frame with gold wire or aluminum wire. After connecting these wires with bonding wires 3 and sealing them with a sealing material 4 such as resin, the tie bars and side bars are cut and the outer leads are bent into a desired shape to complete the process.

As shown in an enlarged view of the main part of one example of such a lead frame in FIG. 7, the tip of the inner lead 12 is
It is in a straight line. As shown in FIG. 8, this usually involves a first punching step using a first punch P1 that punches out the gap between the leads, and a die pad 11 along with cutting the tips of the inner leads lTlft'J. It is formed by a second punching step using a second punch P2 to form.

In recent years, as semiconductor devices have become more highly integrated, lead frames have also become more dense, their plate thicknesses have become thinner, and the intervals between leads have become narrower. As a result, the lead becomes easily deformed, and the
As shown in the figure, the problem of easy occurrence of short circuits and misbonding between leads is becoming more and more serious.

The present invention has been made in view of the above-mentioned circumstances, and aims to prevent short circuits between adjacent leads and provide a highly reliable lead frame.

[Means for solving problems]

Therefore, in the present invention, the lead width of the inner lead is made smaller at the tip.

Further, the method for manufacturing a lead frame of the present invention includes a first punching step of punching out gaps between the plurality of leads extending toward the aa region on which the semiconductor element chip is mounted, and disassembling the leads individually. In order to achieve this, in a lead frame manufacturing method that includes a second punching step of cutting off the leading end of the lead, the second punching step has a lead width that is smaller than the lead width determined by the first punch used in the first punching step. Also, using a second punch having a U-shaped recess with a narrow opening width on the side surface at a position corresponding to each lead,
I try to separate each lead.

[Effect]

According to the lead frame having the above structure, since the lead width is narrowed at the tip of the inner lead, if the degree of deformation is small, contact at the tip is suppressed and short circuits are prevented.

Further, according to the above method, in the second punching step of cutting off the tips of the leads in order to separate them into individual leads without adding any process, the lead width is wider than the lead width formed in the first punching step. By using a second punch that has a small open U-shaped portion at a position corresponding to each lead, it is easy to form a narrow lead frame with the tips of the inner leads forming a step. Therefore, it is possible to easily obtain a highly reliable lead frame.

〔Example〕

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

FIG. 1 is a diagram showing a part of a lead frame according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the tip of an inner lead of the lead frame.

This lead frame is similar to the conventional lead frame shown in FIG. 7, but the width 1 at the tip of the inner lead 12 is 0.02 to 0.03z wider than the width 2 of the other parts.
The lead frame is characterized in that it is formed with steps so that it becomes narrower by m, and is otherwise completely the same as the conventional lead frame. Identical members are given the same reference numerals.

Next, the Va method for this lead frame will be explained.

First, a gap (hole) C between the inner leads is punched out using a first punch P1 such as 1J shown in FIG. 3 (first punching step).

Next, punching is performed using a second punch PN having a =1-shaped portion K on the inner lead side cross section with an opening width A2 that is slightly smaller than the hole interval A1 of the first punch, and the tip of the inner lead is punched out. The die pad 11 is formed together with the cutter tUt (second punching step).

In this way, a step is formed at the tip of the inner lead as shown in Figures 1 and 2, and the width of the tip (1) is 0.02 to 0.03 ttrtr smaller than the width of the other part (2). ing. Here, the interval A1 between the holes of the first punch corresponds to the (width 2 in the middle part) of the inner lead, and the opening width A2 in the U-shaped part of the second punch corresponds to the width 1-1 of the tip. handle.

After this, the lead frame is completed through the usual plating process.

Further, during mounting, the semiconductor chip is bonded to the die pad 11, a wire bonding process is performed, and sealing is performed.Finally, the tie bars and night bars are cut off and the outer leads are bent into a desired shape to complete the semiconductor device.

In this way, a highly reliable lead frame can be formed very easily.

When bonding, as shown in Figure 2, taking into account the precision and safety of the wire bonder, the bonding wire 3 is fixed so that the bonding point BP is located at a position slightly set back from the leading edge of the inner lead. .

Figure 4 does not show the deformed state of the inner lead, but even if the tip is displaced more greatly than in the case of the conventional lead frame shown in Figure 9, there will be no contact between adjacent leads, resulting in a short circuit. It can be seen that there is no occurrence of

〔Effect of the invention〕

As explained above, according to the lead frame of the present invention, since the lead width is reduced at the tip, short circuits between adjacent leads due to deformation are prevented, and reliability can be improved. .

In addition, when manufacturing the above-mentioned lead frame, in the process of cutting off the tips of the inner leads, a punch with a U-shaped part slightly smaller than 1 width to 1 degree width is used in the cross section of the punch. By doing so, it can be easily formed without requiring any additional steps.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a lead frame according to an embodiment of the present invention, Fig. 2 is an enlarged view showing the tip of the inner lead of the same lead frame, and Fig. 3 is a diagram showing the lead frame used in ¥J construction. Figure 4 shows a punch, Figure 4 shows a deformed state of the inner lead of the lead frame, Figure 5 shows a normal lead frame, and Figure 6 shows a semiconductor device using the lead frame. 7 is an enlarged view of the main parts of a conventional lead frame, FIG. 8 is a dimensional view of a punch used to punch out the lead frame of FIG. 7, and FIG. FIG. 2 is a diagram showing an example of a short circuit caused by deformation of a conventional lead frame. 1... Semiconductor chip, 2... Lead frame, 3...
... Die pad, 4... Bonding wire, 5...
- Sealing resin, 10... Inner lead, 11...
Outer lead, 12...Lead frame, 13...
・Semiconductor chip (tC chip for memory), 14... Insulating film, 15... Bonding wire, 16...
・Pounding pad, 17... Sealing package,
78... Tie bar, Pl... First punch, P2.
PN...Second punch. Figure 1 Figure 2 Figure 4 Figure 6 Figure 7 Figure 8

Claims (3)

[Claims] (1) In a lead frame equipped with a plurality of inner leads, an outer lead connected to each inner lead, and a tie bar connecting each inner lead, the lead width at the tip of the inner lead is set wider than at other parts. A lead frame characterized by its small size. (2) The lead frame according to claim (1), wherein the inner lead has notches formed on both sides at the leading edge thereof. (3) When forming a lead frame by a punching method, it includes a first punching step to form a gap between the inner leads, and a second punching step to cut off the tips of the inner leads to separate the leads. In the second punching step, a U-shaped recess with an opening width smaller than the lead width determined by the first punch used in the first punching step is provided on the side surface at a position corresponding to each lead. A method for manufacturing a lead frame, characterized in that a second punch is used.