JPH10275889A - Lead frame for semiconductor device - Google Patents

Abstract

(57) Abstract: A lead frame for a semiconductor device capable of preventing leakage of a sealing resin at a package corner portion and preventing an increase in an assembly yield of a mold package by preventing peeling or dropping at an end portion of a resin dam bar. I will provide a. SOLUTION: A slit 7 is provided in a suspension lead holding portion 4 of a lead frame 1 for a semiconductor device so as to partially overlap a portion in contact with a resin dam bar 8. As a result, the adhesion between the resin dam bar 8 and the lead frame 1 can be improved, so that peeling or dropping at the end of the resin dam bar can be prevented. Since the slit has a shape closed toward the inside of the package, the sealing resin does not flow into the slit, which falls in the finishing step and does not cause a problem such as damage to the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure of a lead frame used for a semiconductor device.

[0002]

2. Description of the Related Art Generally, a lead frame for a semiconductor device is provided with a dam bar in order to prevent a sealing resin from leaking between outer leads during resin sealing. This dam bar is made of a metal integral with the lead frame, and after resin sealing, the dam bar between the leads is cut by a mold or the like in order to make each lead electrically independent. However, in recent years, as the number of pins and the pitch of a mold package have been reduced, it has become difficult to cut a dam bar between leads with a mold or the like. From such a background, a lead frame in which a dam bar is made of an insulating resin has been devised instead of a conventional dam bar made of metal integral with a lead frame. By forming the dam bar with an insulating resin (hereinafter, a dam bar formed of an insulating resin is referred to as a resin dam bar), it is not necessary to cut the dam bar with a mold after resin sealing. This is effective in reducing the pitch and simplification of the process.

[0003] Although many techniques relating to such resin dam bars have been introduced so far,
297338 points out a problem that occurs when a lead frame of resin dam bar specification is actually manufactured, and proposes a countermeasure. Hereinafter, the contents will be specifically described with reference to FIG.

First, an insulating resin for a dam bar is applied to a predetermined position of a lead frame and heated at a high temperature of 100 ° C. or more to dry a solvent in the resin. Due to the difference, the lead frame is warped. In order to prevent this, dummy leads are provided at the corners of the package, and the resin dam bar is extended from the outermost outer lead to the dummy leads, and the dummy leads and the package corners of the lead frame are not connected by an insulating resin. Such a lead frame has been proposed. That is, the structure is such that a slit is provided between the insulating resin and the corner portion. By doing so, the thermal shrinkage of the insulating resin is absorbed by the deformation of the dummy leads, and the warpage of the entire lead frame can be eliminated.

However, at present, the use of a kind of insulating resin, for example, a low-elasticity resin or an ultraviolet-curable epoxy resin containing a filler, hardly causes warpage of the lead frame due to heat shrinkage. know.

Further, when assembling is performed using such a lead frame having a resin dam bar specification, the following problems occur.

In other words, the resin that has flowed into the slit falls into the mold during the finishing process, causing damage to the mold, and the resin dam bar at the corner part being peeled off from the lead frame during the assembling process, or missing. This causes a problem that the sealing resin leaks out between the leads at the package corners in the resin sealing step.

[0008]

The first problem is that when a semiconductor device is assembled using a conventional lead frame, leakage of sealing resin occurs at a corner of a package, and the assembly yield is reduced. That is.

The reason is that the lead frame shown in FIG. 5 has a structure in which an end of a resin dam bar is bonded and fixed to an end of a dummy lead provided at a corner portion. Since the resin is simply adhered on the dummy lead, the resin may be peeled off or cut off in the worst case due to vibration or impact until the resin sealing process.
There is a risk of falling off. When such a resin dam bar is peeled or dropped, the sealing resin leaks between the outer leads at the package corners in the resin sealing step,
This is because the assembly will be defective.

After all, a fundamental measure is required to improve the adhesiveness at the end of the resin dam bar.

A second problem is that when a lead frame according to the prior art is assembled, there is a risk that the finishing mold may be damaged by the sealing resin flowing between the slits.

The reason is that, in the lead frame structure shown in FIG. 5, since the end of the slit is open toward the inside of the package, the resin easily flows into the slit in the resin sealing step. Would. Even if the slit width is reduced to about 0.1 mm, it is difficult to avoid the inflow of the sealing resin. As described above, there is a risk that the resin accumulated between the slits may fall off due to vibration or impact during transportation or when placed on the mold, and when the dropped resin gets into the mold, the mold is easily removed. This is because they will be damaged.

After all, such a problem cannot be solved without preventing the resin from flowing into the corners of the lead frame.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to prevent the resin from flowing out which causes damage to the finishing mold and to prevent the resin dam bar from peeling or falling off. Accordingly, it is an object of the present invention to provide a technique for completely preventing resin leakage between outer leads in a package corner portion and improving the yield of a mold package.

[0015]

According to a first aspect of the present invention, there is provided a semiconductor device lead frame in a suspension lead holding portion (4 in FIG. 1) adjacent to an outermost end. A slit (7 in FIG. 1) is provided in the portion, and the lead frame structure is such that at least a part of the slit is in contact with the resin dam bar (8 in FIG. 1).

The lead frame structure employs a through hole (7a in FIG. 2) as the shape of the slit.

Further, as the shape of the slit, a notch (FIG. 3) opened toward the outer lead (6 in FIG. 3).
7b) is adopted as the lead frame structure.

Also, instead of the slit, half-etching thinner than the thickness of the lead frame (7c in FIG. 4)
However, there is a lead frame structure provided at a portion of the suspension lead holding portion (4 in FIG. 4) that comes into contact with the resin dam bar (8 in FIG. 4).

According to the present invention, a through hole is formed as a slit at a corner of the lead frame, that is, at a portion where the suspension lead holding portion and the resin dam bar are in contact with each other. Is provided, the adhesion of the resin dam bar to the lead frame at the corner is improved. In particular, in the case of a through hole or a cut, the resin dam bar is buried in the inside of the through hole, so that adhesiveness equal to or higher than that of the other portions can be obtained. Also, in the case of half-etching, by increasing the bonding area, it is possible to obtain adhesiveness equal to or higher than other portions. This prevents the end of the resin dam bar from peeling or dropping during the assembling process, thereby preventing the sealing resin from leaking between the outer leads at the package corner in the resin sealing process. It is possible to suppress.

Further, by making the shape of the slit closed relative to the inside of the package, it is possible to prevent the sealing resin from flowing into the slit. This makes it possible to take drastic measures such as eliminating the generation of the resin itself.

Also, as described above, the problem of warpage of the lead frame due to the difference in linear expansion coefficient between the resin dam bar and the lead frame material is prevented by using an ultraviolet curable epoxy resin containing a low elastic resin and a filler. It is possible to

[0022]

Next, embodiments and examples of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view of a lead frame for a semiconductor device according to the present invention, and FIG. 2 is an enlarged plan view of a package corner.
FIGS. 3 and 4 are enlarged plan views showing another application example of the invention.

In the lead frame 1 for a semiconductor device according to the present invention shown in FIGS. 1 and 2, a suspension lead 3 extending from four corners of a rectangular die pad 2, a suspension lead holding portion 4 for holding the same, and a die pad In the boundary between the inner lead 5 and the outer lead 6 and the boundary between the inner lead 5 and the outer lead 6,
A resin dam bar 8 for connecting each lead and the suspension lead holding section 4 is formed, and a slit 7 is provided in the suspension lead holding section 4 at a portion adjacent to the outermost outer lead. The end portion and at least a part of the slit 7 are in contact with each other.

As the material of the lead frame 1, for example, 42 alloy or copper is used, and the thickness is, for example, 0.1.
Those having a size of 25 mm or 0.15 mm are used.

Although the four corners of the die pad 2 are held only by the suspension leads 3, it may be connected to a specific lead such as a GND lead. In addition to the structure shown, the die pad 2 is separated from the suspension lead 3, and instead, a plate material having a larger area than a region formed by connecting the tips of the inner leads 5 is formed on one of the inner leads 5. It may be of a heat spreader type adhered to the surface.

The suspension leads 3 are processed, if necessary, to provide a step of, for example, 0.15 mm or 0.175 mm between the die pad surface and the inner lead surface.

The thickness of the resin dam bar 8 is the same as that of the lead frame 1.
And the material is, for example, a low-elasticity polyimide resin or an ultraviolet-curable epoxy resin containing a filler.

As a method of forming the resin dam bar 8, a method of applying a dam bar resin to a desired position by a dispense method or a screen printing method and solidifying the resin by ultraviolet light or heat is used. Further, by pressing the resin portion with a mold or the like before the resin is completely solidified, the thickness of the resin dam bar 8 can be made substantially the same as the thickness of the lead frame 1.

The slit 7 is of the through-hole 7a type shown in FIGS. 1 and 2 and, for example, as shown in FIG. 3, a portion where the resin dam bar 8 and the suspension lead holding portion 4 overlap with each other. It may be of a type provided with a notch 7b partly open toward. The shape of the cut may be any shape as long as the shape is closed with respect to the inside direction of the package. FIG.
As shown in (1), half etching 7c provided so that a part thereof overlaps with the resin dam bar 8 may be used. The shape of the half-etching may be any shape other than the illustrated one as long as a part thereof overlaps the resin dam bar 8. Further, a part of the resin dam bar 8 is buried in a part of these slits by the method described above.

In the lead frame for a semiconductor device according to the present invention, a through hole (7a in FIG. 2), a cut (7b in FIG. 3) or a half etching (FIG. 3) is formed at a portion where the suspension lead holding portion 4 and the resin dam bar 8 overlap. 4 7c) is provided to improve the adhesiveness between the resin dam bar 8 and the lead frame 1. For example, in the case of a through hole or a cut, the resin is buried in the inside thereof, so that the adhesive force between the end of the resin dam bar and the lead frame 1 is greatly improved as compared with other portions. In the case of half-etching, hemispherical half-etching is simply added to about 50% of the contact area between the resin dam bar 8 and the lead frame 1,
It is possible to increase the adhesive strength about 1.5 times.

Next, how the introduction of such a slit has an effect on sealing resin leakage in the resin sealing step will be described.

In general, when assembling a semiconductor device, various heat histories and vibrations / shocks are applied to a semiconductor device lead frame. The case of assembling using the semiconductor device lead frame of the present invention is no exception, and various loads are applied in each process.

First, when a semiconductor element is mounted on a die pad in a die bonding step, a silver paste made of, for example, an epoxy-based resin is used to adhere and fix the element to the die pad.
Heating of about 250C to 250C is required. In the wire bonding step, for example, about 240
° C heat is applied to the leadframe. Due to such heat, a distortion occurs between the resin dam bar and the lead frame due to a difference in linear expansion coefficient of each material, and particularly at an end portion of the resin dam bar or the like, the adhesive force with the lead frame is weakened, Peeling may occur.

Furthermore, the lead frame is constantly exposed to vibrations and shocks during each process and during transport in each device. Due to such vibrations and shocks and the above-mentioned heat history, the exfoliation of the end portion of the resin dam bar is further increased, and in the worst case, it may be lost.

If such a resin dam bar is peeled or dropped off at the corner of the package, the sealing resin leaks from the peeled or dropped portion in the next resin sealing step, making subsequent assembly difficult. turn into. This tendency is particularly noticeable in the lead frame having the conventional structure shown in FIG.

That is, by introducing the slit proposed by the present invention, the resin dam bar can be prevented from peeling and missing, and as a result, such a problem can be suppressed.

Further, since such a slit has a closed shape with respect to the interior direction of the package, the finish metal due to the falling off of the sealing resin leaked into the slit, which is a problem in the lead frame of the conventional structure, is problematic. There is no inconvenience such as mold breakage.

[0038]

By using the semiconductor device lead frame of the present invention, leakage of the sealing resin at the package corner can be prevented, and the assembly yield can be improved.

The reason is that a through hole as a slit is provided at a portion where the suspension lead holding portion and the resin dam bar are in contact with each other, a cutout part of which is open toward the outer lead side, or a half-etching is provided. In the portion, the adhesion of the resin dam bar to the lead frame is improved. As a result, heat history, vibration,
This is because it is possible to prevent the end of the resin dam bar from peeling off or falling off due to the impact.

Further, by using the lead frame for a semiconductor device of the present invention, it is possible to prevent a problem such as damage to the finishing mold caused by falling of the resin flowing between the slits.

The reason is that the shape of the slit provided in the suspension lead holding portion has a structure closed toward the inside of the package, so that the sealing resin flows into the slit in the resin sealing step. This is because it can be prevented from being performed.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a lead frame for a semiconductor device of the present invention.

FIG. 2 is an enlarged plan view of the semiconductor device lead frame shown in FIG. 1;

FIG. 3 is an enlarged plan view showing an application example of the lead frame for a semiconductor device of the present invention.

FIG. 4 is an enlarged plan view showing an application example of the lead frame for a semiconductor device of the present invention.

FIG. 5 is a plan view of a conventional lead frame for a semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead frame 2 Die pad 3 Suspended lead 4 Suspended lead holding part 5 Inner lead 6 Outer lead 7 Slit 7a Through hole 7b Cut 7c Half etching 8 Resin dam bar

Claims (4)

[Claims] 1. A die pad on which a semiconductor element is mounted, a suspension lead portion and a suspension lead holding portion extending from four corners of the die pad, an inner lead and an outer lead radially arranged around the die pad, In a semiconductor device lead frame having a dam bar made of an insulating resin near a boundary between the inner lead and the outer lead, a slit is provided in a portion adjacent to the outermost end in the suspension lead holding portion. A lead frame for a semiconductor device, wherein the slit and at least a part of a dam bar made of the insulating resin are in contact with each other. 2. The lead frame for a semiconductor device according to claim 1, wherein said slit is a through hole. 3. The lead frame for a semiconductor device according to claim 1, wherein the shape of the slit is open toward the outer lead. 4. The lead frame for a semiconductor device according to claim 1, wherein half etching is provided at a contact portion between said suspension lead holding portion and said dam bar.