JPH02156661A - Lead frame - Google Patents

Abstract

PURPOSE:To prevent leads from being short-circuited mutually and to prevent bonding wires from being short-circuited by a method wherein, when a plurality of lead frames are laminated, one part of an inner lead is fixed via an insulating layer and an outer lead is arranged in such a way that it is situated on an identical face from an end part of at least a package. CONSTITUTION:A first lead frame and a second lead frame 1a, 1b are laminated via a polyimide film 10; inner leads 4a, 4b of the frame 1a are extended alternately from different planes and are arranged three-dimensionally. Outer leads 12a, 12b which are situated in a direction opposite to them are extended alternately from an identical plane. A square pad 2 used to mount a semiconductor element and a support bar 13, used to support the pad 2, which is stretched in a diagonal direction from a corner part are formed on the first frame 1a; tie bars 11a, 11b used to maintain an interval of the individual leads are formed at the frames 1a and 1b. Thereby, the frames 1a, 1b are insulated by the film 10; the leads 12a, 12b are made at a uniform height at their tip parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a lead frame, and particularly to a lead frame having a laminated structure including GI layers of leads.

(Prior Art) For example, in a normal IC, as shown in FIG. 7, a semiconductor element 3 is fixed to a die pad of a lead frame 1, and a bonding pad of this semiconductor element 3 and an inner lead 4 of the lead frame are connected. It is manufactured by connecting with gold or aluminum bonding wires 5 and sealing them with resin 6.

The lead frame used here has a die pad 2 for mounting a semiconductor element, and a tip extending so as to surround the die pad, as shown in FIGS. 8(a) and 8(b). An inner lead 4, a tie bar 11 extending in a direction substantially perpendicular to the inner leads and integrally supporting these inner leads, and an outer lead 12 disposed on the outside of the tie bar so as to be connected to each of the inner leads. and a support par 13 that supports the die pad 2.

The tips of the inner leads are arranged parallel to the outer periphery of the die pad 2 at a predetermined interval so as to surround the die pad 2.

Incidentally, as semiconductor devices become more dense and highly integrated, the number of lead pins increases, but packages tend to remain the same or become smaller.

As the number of inner leads increases within the same area, the width of the inner leads and the distance between adjacent inner leads naturally become narrower. Therefore, deformation of the inner leads due to a decrease in strength may cause a short circuit between the inner leads.

Furthermore, when wire bonding is used to connect the bonding pad and inner lead of a semiconductor element with a bonding wire, the bonding area becomes narrow due to the small lead width, and the deformation of the tip causes
Bonding errors are more likely to occur.

Furthermore, since there are a large number of leads, the tips of the leads cannot be extended very close to the die pad, and the bonding wire must be made longer. This not only wastes the bonding wire, but also poses many problems, including the risk of short-circuiting between wires or between wires and leads even after wire bonding has been successfully performed.

In order to solve this problem, the present applicant has made every other inner lead 4 extending around the die pad 2 close to the die pad 2, and formed a wide part r at the tip of the inner lead to serve as a bonding area. We are proposing one with staggered tips. This lead frame is completely the same as the lead frame shown in FIG. 8(b) except for the tip of the inner lead.

This has made bonding easier, but the lead strength has decreased due to the small lead width.
Problems such as deformation of leads and short circuits between leads due to the deformation are still factors that reduce the reliability of semiconductor devices.

A method has also been proposed in which the number of leads is increased within the same area by joining two lead frames via an insulating material (Japanese Patent Laid-Open No. 63-66959).
Publication No.).

This method has problems in that it is difficult to handle, requires a special sealing mold, and requires a large investment in equipment. For example, since the bending position of the outer lead is displaced from the end of the package in a staggered manner,
It is also necessary to prepare a special lead bending tool in the outer lead molding process after resin sealing. Further, there was a problem in that the mounting process on a printed circuit board was difficult because the lead positions were displaced in a staggered manner.

(Problem to be Solved by the Invention) As described above, even in the method of increasing the number of leads within the same area by joining two lead frames via an insulating material, the outer leads are not connected to the package. Because they are displaced from the ends in a staggered manner, assembly is extremely difficult, and in terms of equipment investment, etc., they are practically unusable.

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 for a semiconductor device that is easy to mount and has high reliability even when increasing density.

(Structure of the Invention) <Means for Solving the Problems> Therefore, in the present invention, in a lead frame made of a laminate of a plurality of lead frames, a part of the inner lead is fixed via an insulating layer, and , the outer leads are arranged on the same plane from at least the end of the package.

Preferably, the first one has about half the total number of reads.
This lead frame and a second lead frame which similarly has about half the total number of leads are laminated via an insulating adhesive, and the second lead frame is placed between the outer leads of the first lead frame. The outer lead is arranged so that the

(Function) According to the above configuration, since the tip of the inner lead is three-dimensionally configured, the width or interval of the inner lead can be made sufficiently large without increasing the size of the package, and the outer lead Since the leads are arranged so as to be on the same plane from the end of the package, the resin sealing process, the mounting process on the printed circuit board, etc. can be performed in the same way as before using conventional equipment.

(Example) Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the lead frame 1 according to the embodiment of the present invention includes a first lead frame 1a and a second lead frame 1.
The inner leads 4a of the first lead frame and the inner leads 4b of the second lead frame alternately extend from different surfaces to form a three-dimensional structure. 7 outer leads 12a of the first lead frame and outer leads 12b of the second lead frame.
and are configured to extend alternately from the same plane.

This first lead frame includes a rectangular die pad 2 for mounting a semiconductor element, a support par 13 that extends diagonally outward from a corner of the die pad 2 and supports the die pad 2, and a tip that surrounds the die pad. The inner lead 4a extends in a direction substantially perpendicular to the inner lead 4a, and engages with the tie bar of the second lead frame to integrally support these inner leads. The tie bar 118 is composed of a first tie bar 11a that extends to a length of 2, and an outer lead 12a that extends from each inner lead to the outside of the first tie bar 118.

Further, the second lead frame is similar to the first lead frame, except that there is no die band 2 and the inner leads have a step near the tie bar. An inner lead 4b extending to surround the die pad 2 of the lead frame, and the inner lead 4
a second tie bar extending in a direction substantially perpendicular to b and extending half the length of the lead spacing so as to engage with the tie bar of the first lead frame and integrally support these inner leads; 11b, and an outer lead 1 extending from each inner lead to the outside of the second tie bar 11b.
2b.

Furthermore, in the engaging portions of the tie bars of these first and second lead frames, one of the tie bars has a full part in the shape of a 7, and the other has a convex part, so that these are fitted and fixed. It has become.

Next, a method for manufacturing this lead frame will be explained.

First, as shown in FIG. 2(a), a die pad 2 (not shown) is provided with an interval 2p that is twice the predetermined lead pitch p.
, the first one having a number of reads that is half the predetermined number of reads.
Processing the shape of the lead frame.

Thereafter, as shown in FIG. 2(b), the bonding area 8a is plated.

Thereafter, as shown in FIG. 2(C), a polyimide tape F is attached to the package area excluding the bonding area Ba to integrally fix the inner lead 4a.

Furthermore, as shown in FIG. 2(d), the tie bar between each lead is cut to make it half the lead spacing.
A first lead frame is formed.

Note that a notch is formed in the side rail (not shown) of the first lead frame to make it easier to break, and a pilot hole is formed for alignment with the second lead frame.

On the other hand, the second lead frame is also formed in substantially the same manner as the first lead frame, although the details are different.

That is, first, as shown in FIG. 3(a), there is no die pad, and like the first lead frame, the interval 2p is twice the predetermined lead pitch p, and the predetermined number of leads is 1/2/1). The shape of the second lead frame having the number of leads is processed.

Thereafter, as shown in FIG. 3(b), the bonding area Ba is plated as in the case of the first lead frame, and a step is formed near the tie bar using a mold. This step is made to have a size equal to the thickness of the lead frame plus the thickness of the polyimide film.

After that, as shown in FIG. 3(C), polyimide tape F is similarly attached to the package area except the bonding area Ba, and the inner leads 4a are integrally fixed.
Furthermore, as shown in FIG. 3 fd), the tie bars between the leads are cut to make the lead spacing 1/2, thereby forming a second lead frame.

A polyimide film 10 is pasted on the surface of the first lead frame 1a thus formed, and the second lead frame 1b is laminated thereon while aligning with the pilot holes, and the tie bars are engaged. After fitting the joints K, the two are heated at low temperature and fixed with a polyimide film, and then a lead fixing tape 1 is placed on top of this.
0a is adhered and fixed, and a lead frame as shown in FIG. 1 is completed.

Then, when implementing it, as in the past, as shown in Fig.
As shown in FIG. 4, a desired semiconductor chip 3 is fixed onto the die pad 2, wire bonding is performed as shown in FIG. 4 fb), and resin sealing is performed as shown in FIG. 4 fc). , sealed in a resin package.

Finally, the outer leads are bent into a desired shape and the tie bars are cut out, completing the mounting as shown in FIG. 4(d).

When the semiconductor device thus formed is mounted on a printed circuit board, since the outer leads extend from the same plane, it can be mounted in exactly the same way as a conventional planar lead frame.

As an additional advantage, according to this lead frame, the tip of the inner lead 4 is connected to the support bar 1 at both ends.
Since it is fixed with the insulating polyimide tape F attached to 3, it is reinforced by the polyimide tape, and the support bar prevents the insulating film from shrinking, and the support bar and inner lead are not aligned with each other. It is meant to be retained. Therefore, the positional relationship with the tip of the support banner lead is always maintained correctly, and no positional deviation occurs during bonding, resulting in extremely high bonding accuracy.

Needless to say, short circuits between the leads and the bonding wires are also prevented.

In addition, since the inner leads of the first and second lead frames have a three-dimensional structure, they can be arranged in high density without narrowing the lead width at the tip, and are further reinforced with insulating tape. Therefore, the positional relationship between the die pad and the tip of each inner lead can always be maintained correctly. As a result, the tips of the inner leads can be brought closer to the die pad, the amount of bonding wire used can be reduced, and manufacturing costs can be reduced.

In the above embodiment, the inner leads were formed so as to extend alternately from between the inner leads of the other lead frame, but as shown in FIG. Good too.

Further, in the above embodiment, the distance between the tip of the inner lead and the die pad was set constant, but as shown in FIG. It may be formed to have a shape.

By forming the bonding wires in a staggered manner in this way, the bonding wires can be shortened and short circuits can be prevented.In addition, since there is an insulating film under the long bonding wires, short circuits can be prevented even if the wires are slack. The risk of this is extremely small.

In this way, the tip of each inner lead is fixed with an insulating film, the end is fixed with a tie bar, and there is an insulating tape under the long wire, so
Short-circuit accidents in the resin encapsulation process are also significantly reduced, and extremely reliable semiconductor devices can be formed at a high yield.

Further, in the embodiment described above, the die pad is provided only on one of the two lead frames, but a die pad may be provided on each of the lead frames, and the die pads may be used in an overlapping manner. In this case, the heat capacity of the die pad increases and the surface area also increases, resulting in good heat growth properties.

In addition, in the above embodiment, the two lead frames are W4.
Although the explanation has been given on a layered structure, it goes without saying that two or more layers are also effective.

〔Effect of the invention〕

As explained above, according to the present invention, the tips of the inner leads are three-dimensionally configured, while the outer leads are configured to extend from the same plane at the end of the package. The width or spacing of the inner leads can be made sufficiently large without increasing the size of the package, and the resin sealing process and mounting on the printed circuit board can be performed in the same way as with conventional equipment (#iVR equipment). Therefore, a highly reliable semiconductor device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a lead frame for a semiconductor device according to an embodiment of the present invention, and FIGS. 2(a) to 2(d) are manufacturing process diagrams of a first lead frame of the lead frame for a semiconductor device. , FIGS. 3(a) to 3(d) are manufacturing process diagrams of the second lead frame of the lead frame for the same semiconductor device, and FIGS. 4(a) to 4(d) are manufacturing process diagrams of the second lead frame of the lead frame for the semiconductor device. 5 and 6 are diagrams showing a modification of the lead frame; FIG. 7 is a diagram showing a conventional semiconductor device; FIG. 8(a) and FIG. 8 fb) is a diagram showing a lead frame of the same semiconductor device. DESCRIPTION OF SYMBOLS 1... Lead frame, 1a... 1st lead frame, 1b... 2nd lead frame, 2... Die pad, 3... Semiconductor element, 4.4a, 4b... Inner lead , 5... bonding wire, 6...
Resin, f... wide part, F... polyimide tape, 1
0... Polyimide film, 11... Tie bar 1
2.12a. 12b... Outer lead, 13... Support bar Fig. 1 Fig. 2 (C) Fig. 2 (d) Fig. 4 (G) Fig. 4 (b) Fig. 4 (C) Fig. 4 ( d) Figure 3 (0) Figure 3 (b) Figure 3 (C) Figure 3 (d) Figure 5Lζ; Figure 6 Figure 7

Claims (2)

[Claims] (1) In a lead frame consisting of a stack of multiple lead frames, part of the inner leads are fixed via an insulating layer, and the outer leads are at least flush with the end of the package. A lead frame characterized by being arranged in. (2) Consisting of a first lead frame having approximately half the total number of leads and a die pad, and a second lead frame having approximately half the total number of leads and having a step on the inner lead, A second lead frame is laminated on the first lead frame via an insulating adhesive layer, and the outer leads of the second lead frame are arranged between the outer leads of the first lead frame. A lead frame characterized by: