JP2000077597A - Lead frame for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent contacting between a lead which is not provided with insulating bond and a semiconductor chip by allowing the thickness of a part which is not provided with insulating bond provides to be smaller than the thickness of the lead of a part which the insulating bond of an inner lead provides. SOLUTION: An insulating bond 4 is applied near the tip end of an inner lead 2. The thickness of an inner lead at a tip end part 7 where an insulating bond 4 is applied is identical with that on an outer lead side. However for a range A, which overlaps with a semiconductor chip 5 of other inner lead 2 except for the tip end part 7, thickness is reduced by about 15 μm as compared to the tip end part 7 for providing a thin-wall part 3, forming a recessed part 8. Thus, even if slight inclination of the semiconductor chip 5 or a slight dispersion in thickness direction of a lead frame of the inner lead 2 occurs at bonding of the semiconductor chip, the inner lead 2 which is not provided with insulating bond 4 does not make contact with the semiconductor chip 5, and this results in the fixed and stable semiconductor chip 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for a semiconductor device, and more particularly to a lead frame for a semiconductor device used for a semiconductor device having a LOC structure and a mold package.

[0002]

2. Description of the Related Art LOC (Lead On Ch
ip) A tape with an adhesive having a thermoplastic or thermosetting adhesive layer formed on one or both surfaces thereof as a lead frame used for a semiconductor device having a structure or the like (a high heat-resistant insulating film having a thickness of about 50 μm, There is a lead frame (a pre-tape LOC lead frame) in which a semiconductor chip is mounted by heating and pressing on the surface of the tape with the adhesive by using an adhesive applied to a thickness of about 25 μm on both surfaces. .

In the case of this type of lead frame, a polyimide-based film is usually used as the high heat-resistant insulating film of the tape with an adhesive. As a method of attaching to a lead frame, a punching and attaching method using a die is adopted. Specifically, a film wound in a reel shape is punched into a predetermined shape by a mold, and the film is attached to a lead frame by heating and pressing.

[0004] The problem with this method is that the shape of the film to be pasted is determined by punching out the film with a mold, so that there is a surplus of punching out of the film, waste of material is large, and there is no waste. It is economic.

To solve this problem, as a method of efficiently using the material, a varnish-like insulating adhesive is applied to a mounting area of the semiconductor chip (the tip of the inner lead or the like) with a dispenser or the like to secure insulation. A lead frame (coating LOC lead frame) for fixing a semiconductor chip while fixing the semiconductor chip has been developed. In particular, when an adhesive is applied to the tip of the lead, a spot application method is used. In this method, since only the required amount is applied on the lead frame, no excess material is generated, and an expensive mold is not required. Therefore, the method is highly effective in reducing the manufacturing cost. .

[0006] The application of a varnish-like insulating adhesive (for example, a solution obtained by dissolving an adhesive resin in a solvent) is performed by moving a thin tubular needle (or nozzle) onto a lead frame while removing the adhesive from the needle. This is performed by discharging air to a predetermined portion of the frame by air pressure.

As the varnish-shaped insulating adhesive actually used for fixing the semiconductor chip, a varnish-shaped insulating adhesive used for a conventionally used semiconductor chip fixing film is used. This insulating adhesive is mainly thermoplastic.

[0008]

However, thermoplastic insulating adhesives are generally difficult to dissolve in a solvent and tend to have high viscosity even with a relatively small amount of dissolution. Therefore, in order to apply the varnish-like insulating adhesive on the lead frame with a dispenser, the varnish-like insulating adhesive must be made to have a relatively low viscosity with a small amount of dissolution in consideration of its workability. Therefore, it is difficult to obtain a thick and uniform insulating adhesive layer on the lead.

A conventional adhesive tape (consisting of a high heat-resistant insulating film having a thickness of about 50 μm and an adhesive applied to both sides thereof with a thickness of about 25 μm) is attached to a lead frame to mount a semiconductor chip. In the case of the structure (pre-tape LOC), the film with adhesive has a thickness of about 100μ.
m, the thickness variation is about ± 3 μm. Therefore, there is a necessary and sufficient space between the lead and the semiconductor chip.

On the other hand, in the case of a structure in which a varnish-like insulating adhesive is applied to a lead frame to mount a semiconductor chip (coating LOC), the applied thickness of the varnish-like insulating adhesive is about 20 μm. The thickness variation is about ± 5 μm. Therefore, in the case of the LOC lead frame coated with the adhesive, the distance between the lead and the semiconductor chip is much smaller than that in the case of the pre-tape LOC lead frame.
The ratio of the variation in the thickness is also very large as compared with the entire coating thickness.

Therefore, when a slight inclination of the semiconductor chip or a slight variation in the thickness of the inner lead in the thickness direction of the lead occurs when the semiconductor chip is bonded to the semiconductor chip, the inner lead without the insulating adhesive is brought into contact with the semiconductor chip. As a result, the function of the semiconductor chip may be degraded.

Accordingly, an object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to reduce the insulating property even if a slight inclination occurs in the semiconductor chip or a slight variation in the thickness of the inner leads occurs in the thickness direction. An object of the present invention is to provide a semiconductor device lead frame suitable for a low-cost and thin package, in which an inner lead without an adhesive is not in contact with a semiconductor chip and, therefore, the semiconductor chip can be stably fixed. It is in.

[0013]

In order to achieve the above object, a semiconductor device lead frame according to the present invention comprises an insulating material for fixing the semiconductor chip to a part of an inner lead in a semiconductor chip mounting area. In the lead frame to which the adhesive is applied, the thickness of the lead at the portion where the insulating adhesive is not provided is smaller than the thickness of the lead at the portion where the insulating adhesive is provided of the inner lead.

In the lead frame for a semiconductor device according to the present invention, the range in which the thickness of the inner lead is reduced is as follows.
It is desirable to set the area to overlap with the semiconductor chip except the tip of the inner lead.

Here, the range overlapping with the semiconductor chip excluding the tip of the inner lead means not only the range coinciding with the area in the chip outline line, but also the adjacent outer peripheral area continuous outside the area. This includes the case where it indicates the range including the area.

The gist of the present invention is to provide a lead frame for use in a semiconductor device in which an insulating adhesive is provided on inner leads of a lead frame and a semiconductor chip is fixed to the lead frame via the insulating adhesive. A low-cost lead frame that can stably fix a semiconductor chip by reducing the thickness of a lead in a portion where the insulating adhesive for semiconductor chip fixing is not provided, compared to a lead in a portion where the insulating adhesive for fixing is provided. Is to manufacture.

In the case of a LOC lead frame coated with an adhesive, the distance between the lead and the semiconductor chip is much smaller than in the case of the pre-tape LOC lead frame, and the ratio of the thickness variation is also reduced. It is larger than the coating thickness. Therefore, at the time of bonding to the semiconductor chip, the semiconductor chip is likely to come into contact with the lead on which the insulating adhesive is not provided due to a slight inclination of the semiconductor chip and a slight variation in the lead frame thickness direction of the lead frame.

However, in the present invention, the thickness of the lead at the portion where the insulating adhesive is not provided is smaller than the thickness of the lead at the portion where the insulating adhesive is provided on the inner lead. In this case, the gap between the lead and the semiconductor chip becomes large. Therefore, even if the semiconductor chip is slightly tilted or a slight variation occurs in the thickness direction of the lead frame, since the gap exists in the thin portion of the inner lead, the insulating adhesive is provided. The unread leads and the semiconductor chip are not in contact.

Therefore, by adopting the coated LOC lead frame, even if the distance between the inner lead and the semiconductor chip is reduced by the thickness of the insulating adhesive and becomes smaller than before, the change is not affected. It is possible to easily and stably fix the semiconductor chip by eliminating the influence, and it is also suitable for thinning the package.

Further, in the structure in which the lead thickness of the portion where the insulating adhesive is not provided is made thinner than that of the portion where the insulating adhesive is provided on the inner lead, a half-etching method is used for an etching frame. In the case of a stamping frame, there is an advantage that the coining method can be implemented at a very low cost.

Furthermore, if the distance between the semiconductor chip and the lead frame is too short, there is a possibility that the resin will not flow in between the resin and the cavity, resulting in a cavity. However, such a disadvantage can be avoided.

Further, since the above-mentioned problems such as the inclination of the semiconductor chip become more remarkable as the semiconductor chip becomes larger, the effect of the present invention can be obtained as the semiconductor chip accommodated in the semiconductor device becomes larger. Further, the effect is larger as the difference between the thickness of the part where the insulating adhesive is provided and the part where the insulating adhesive is not provided is larger.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the appearance of a LOC lead frame according to the present invention. The lead frame 10 mainly includes an inner lead 2 and an outer lead 1. The inner leads 2 are processed so that the tips are disposed within a chip outline line 6 which is a mounting area for the semiconductor chip 5 (FIG. 2), and are disposed so as to face each other from both directions. This chip outline line 6 is shown as a case where a larger semiconductor chip is mounted.

The outer leads 1 are connected to each of the inner leads 2 (two inner leads 2 are connected in parallel depending on the leads) and are formed so as to be parallel to each other. The outer lead 1 is provided with a tie bar 9 so as to connect between the leads to a portion exposed after resin sealing. Further, wide frame portions 11 are provided on both sides to support the tie bar 9.

An insulating adhesive 4 is applied to the tip of the inner lead 2 on the lead frame 10 having such a structure. The insulating adhesive 4 is made of a resin material, and is obtained by dissolving a thermoplastic insulating adhesive having a glass transition temperature of 220 ° C. in a varnish shape with a solvent. The varnish viscosity and solid content were as follows: varnish viscosity = 10,000 cp, solid content = 2
0%.

To apply this, a dispenser is used. That is, a varnish-melted insulating adhesive is stored in a container to which air can be supplied from the outside, and the adhesive in this container is guided to a needle and discharged onto a lead.

The method of applying the insulating adhesive 4 to the lead frame 10 is to apply a varnish-like insulating adhesive with a dispenser. The dispenser is a container for storing a varnish-like insulating adhesive, a pressurizing unit for feeding air to the container, a needle connected to the tip of the container, and a driving unit for moving the needle on the lead frame in the coating direction. It is composed of By injecting air into the container containing the varnish-like insulating adhesive, the insulating adhesive is discharged from the needle onto the inner lead 2 and the needle is sequentially moved in the direction adjacent to the lead, thereby obtaining the insulating property. Adhesive 4
Is applied.

The position where the insulating adhesive 4 is applied is near the tip of the inner lead 2. As shown in FIG.
The thickness of the inner lead 2 is the same as the thickness of the outer lead 1 at the tip 7 where the insulating adhesive 4 is applied. However, except for this tip 7,
The other portion of the inner lead 2 in the range A overlapping with the semiconductor chip 5 is formed as a thin portion 3 in which the thickness of the lead is reduced by about 15 μm from the tip 7.
8 is a concave portion formed by this.

Here, the inner lead 2 excluding the tip 7
The range A overlapping with the semiconductor chip 5 is a rough expression. This expression includes a case where the range A coincides with the region a in the chip outline line 6 and a range adjacent to the region a. This includes both cases where the range includes the outer peripheral region b. This embodiment shows the latter example.

As described above, the inner lead 2 has a portion A in a range A overlapping with the semiconductor chip 5 except for the tip portion 7 thereof.
The thickness of the lead is reduced by about 15 μm. As a method for reducing the thickness, a half etching method is used for an etching frame, and a coining method is used for a stamping frame.

As described above, the portion of the inner lead 2 in the range A overlapping with the semiconductor chip 5 excluding the tip 7 is
By forming the recess 8 by reducing the thickness of the lead by about 15 μm, a slight inclination of the semiconductor chip 5 and a slight variation in the thickness of the inner lead 2 in the thickness direction of the lead frame can be obtained at the time of bonding with the semiconductor chip 5. When the semiconductor chip 5 does not contact the inner lead 2 provided with no insulating adhesive, the semiconductor chip 5 can be stably fixed.

[0033]

As described above, according to the present invention, the thickness of the lead at the portion where the insulating adhesive is not provided is made smaller than the thickness of the lead at the portion where the insulating adhesive is provided on the inner lead. Therefore, in this portion, the gap between the lead and the semiconductor chip becomes large. For this reason, even if the semiconductor chip is slightly tilted or a slight variation occurs in the thickness direction of the lead frame, contact between the lead without the insulating adhesive and the semiconductor chip does not occur.

Therefore, the semiconductor chip can be fixed easily and stably.
Employing a C lead frame is advantageous in reducing the thickness of the package, and enables a large semiconductor chip to be stably mounted.

[Brief description of the drawings]

FIG. 1 is an external view showing a coated LOC lead frame according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a coated LOC lead frame according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional coated LOC lead frame.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer lead 2 Inner lead 3 Thin part 4 Insulating adhesive 5 Semiconductor chip 6 Chip outline line 7 Tip 8 Recess 9 Tie bar 10 Lead frame 11 Frame part

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ryuji Yonemoto 3550 Kida Yomachi, Tsuchiura-shi, Ibaraki F-term in the System Materials Research Laboratory, Hitachi Cable, Ltd. 5F067 AA01 AB02 BA06 BB04 BE10 CC02 CC07 DA14 DA18 DF02

Claims (2)

[Claims] 1. A lead frame in which an insulating adhesive for fixing the semiconductor chip is applied to a part of an inner lead in a mounting area of the semiconductor chip, wherein the insulating adhesive for the inner lead is provided. A lead frame for a semiconductor device, wherein the thickness of the lead at a portion where the insulating adhesive is not provided is smaller than the thickness of the lead at the portion. 2. The semiconductor device lead frame according to claim 1, wherein the range in which the thickness of the inner lead is reduced is a range overlapping with the semiconductor chip excluding the tip of the inner lead. For lead frame.