JP2666696B2 - Lead frame for resin-sealed semiconductor device, method of manufacturing the same, and resin-sealed semiconductor device - Google Patents

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 resin-sealed semiconductor device, a method for manufacturing the same, and a resin-sealed semiconductor device.

[0002]

2. Description of the Related Art In a most commonly used lead frame for a resin-encapsulated semiconductor device (hereinafter simply referred to as a lead frame), an element mounting portion is usually formed of a lead frame material. (Hereinafter, an element mounting portion formed of a lead frame material is referred to as an island). However, in such a general lead frame island, the island size must be changed in accordance with the size and aspect ratio of the semiconductor element due to the limitation of the wire bonding technology and the like. Types of lead frames must be prepared. Further, if the island size is too large with respect to the size of the resin sealing portion of the package, the inner lead length existing inside the resin sealing portion of the package becomes short, and the lead pull-out strength is extremely reduced. Furthermore,
It is known that an increase in the size of the island increases an area to be peeled off from the sealing resin at the time of heating during mounting, so that the resistance to package cracks is significantly reduced.

In order to solve the former problem that a plurality of types of lead frames having different island dimensions must be prepared in accordance with the dimensions and the aspect ratio of the semiconductor element, a lead frame having no island is prepared and an acrylic-based lead frame is prepared. The polyimide insulating resin film coated with the resin thermosetting adhesive layer is cut to a required size, and the polyimide film 7 is fixed on the inner lead 3C of the lead frame with the adhesive 6 as shown in FIG. There is known a technology in which a single type of lead frame can be used for a variety of semiconductor element dimensions by using the same as an element mounting portion to enhance the versatility of the lead frame.

As a technique for mounting a semiconductor element having a size larger than the package size, as shown in FIG. 6, a filler having a fixed particle size formed on inner leads 3D of a lead frame having no island is used. A technique in which a semiconductor element and a lead frame are fixed by an insulating resin 8 containing, for example, is disclosed in Japanese Patent Application Laid-Open No. 64-33939. In this method, when a thermoplastic resin is used as the insulating resin, the semiconductor element is fused and then fixed by cooling after the resin supplied on the lead frame is heated to the melting point or higher. When the resin is used, the resin is heated on a lead frame to form a semi-cured B stage, and is pressed and heated to be fixed.

The package structure of the two conventional resin-encapsulated semiconductor devices described above is a so-called COL (c
This is called a “hip on lead” structure.

[0006]

However, in the above-mentioned prior art, the insulating resin film must be cut with a die in view of the requirement for accuracy, and even in the bonding step, high precision with the lead frame is required. In addition to the need for accurate positioning, there are difficulties such as not being able to obtain sufficient adhesive strength unless heat and pressure is applied while maintaining strict parallelism between the lead frame and the insulating resin film. Although the versatility is certainly improved, the process of providing the semiconductor element mounting portion on the lead frame becomes very complicated and expensive. In addition, the thickness of the polyimide film used as the insulating film must be 75 μm or more due to workability problems (mainly problems in transportation).
Since the thickness of the insulating film including the adhesive layer becomes 100 μm or more, it has a drawback that it is difficult to apply to a thin package.

Further, polyimide used as a material of an insulating resin film has low adhesiveness and adhesion to an epoxy resin used as a sealing resin, and the package crack which is the latter problem mentioned above is a problem. It also has the drawback of lowering the withstand capacity.

In the latter conventional technique, the bonding process of the semiconductor element to the lead frame must be performed under heating in either case of using the resin. There is a problem in that a sufficient adhesive strength cannot be obtained unless pressure bonding is performed while maintaining strict parallelism with the resin film.

The conventional resin-encapsulated semiconductor device package adopting the COL structure and the lead frame used therein have the following three main problems.

First, the manufacturing process is complicated. In particular, it is difficult to form an element mounting portion on a lead frame and to fix a semiconductor element to the lead frame. The compatibility with the manufacturing process of the resin-encapsulated semiconductor device to be used is also very low. Therefore, the productivity is extremely low and the production cost is high.

Second, when the material formed as the element mounting portion on the lead frame is a thermoplastic organic resin such as polyphenylene sulfide or polyimide,
Poor adhesion / adhesion with the silver-based epoxy resin used as an adhesive for semiconductor elements and the epoxy resin used as an encapsulation resin, resulting in reduced package crack resistance and reduced moisture resistance. . Therefore, when these materials are used as the element mounting portion, a decrease in reliability cannot be avoided.

Third, in the lead frame of these COL structures, the thickness of the element mounting portion cannot be inevitably increased by 50 to 150 μm in addition to the thickness of the lead frame itself. Since the filling property of the resin at the time of sealing is deteriorated, it becomes an obstacle to thinning the package.

[0013]

According to a first aspect of the present invention, there is provided a lead frame for a resin-encapsulated semiconductor device, wherein the lead frame is provided to cover a part of the lead frame and contains silicon dioxide powder as a filler. And at least one element mounting portion made of a thermosetting resin film.

According to a second aspect of the invention, there is provided a method of manufacturing a lead frame for a resin-encapsulated semiconductor device, wherein an insulating thermosetting resin film is printed on a part of the surface of the lead frame by using a screen printing method, and a semiconductor element is mounted. It forms a part.

A resin-encapsulated semiconductor device according to a third aspect of the present invention is provided so as to cover a part of a lead frame and is provided with a diacid as a filler.
At least one device mounting portion made of an insulating thermosetting resin film containing silicon oxide powder, and an adhesive is interposed on the device mounting portion.
And a resin for sealing the semiconductor element.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG.
1A and 1B are a top view and a cross-sectional view taken along line AA of a first embodiment of a resin-encapsulated semiconductor device lead frame according to the present invention.

1 (a) and 1 (b), a lead frame 1 has an island 2 having a minimum size within a processing limit of the manufacturing method. The surface of the inner lead 3 provided on the island 2 and its periphery is covered and connected and fixed by an insulating resin film 4 to form an element mounting portion.

The resin film 4 used in the first embodiment is a one-part epoxy resin containing 70% by weight or more of spherical fine powder of silicon dioxide (average particle size: 6 μm) as a filler. The resin thickness on the islands 2 and the inner leads 3 is 20 μm or less. This resin film 4 can be easily realized by a screen printing method. In the first embodiment, a screen frame having a size of 750 mm square as a screen is provided by Tokyo Process Service Co., Ltd.
An SX-230 screen provided by the company is attached, and a pattern of a required element mounting portion is formed (opened) by a photolithography technique with an emulsion thickness of 10 μm. The use of spherical silicon dioxide fine powder having an average particle diameter of 6 μm as a filler is based on the SX-230 described above.
This is for obtaining good printability using a screen. Further, the lead frame 1 is fixed by vacuum suction on a metal base plate coated with a fluorocarbon resin, which has extremely low adhesion to the epoxy resin, and is positioned with the screen. The screen printing is performed in a usual procedure using the one-part epoxy resin described above, and then the one-part epoxy resin is cured (hereinafter, referred to as “cure”) by heating together with an underlay plate. Is peeled off from the base plate together with the resin film 4.

In the resin-encapsulated semiconductor device using a lead frame according to the first embodiment, the semiconductor element 10 is formed on the insulating resin film 4 by a general method using an adhesive such as a silver paste. Then, the connection between the electrode on the semiconductor element and the inner lead 3 of the lead frame is made by a thin metal wire using an ultrasonic thermocompression bonding method, and thereafter, a general resin-sealed semiconductor device is manufactured. It is obtained through a process. Also, when the dimensions of the semiconductor elements to be mounted are changed, it can be easily dealt with only by changing the pattern of the screen. Therefore, it is not necessary to change the pattern of the lead frame. Can deal with elements.

FIG. 2 is a sectional view of a second embodiment of the present invention, which is the same as the first embodiment except that there is no island. Also in this case, the resin film 4A can be easily formed by the screen printing method.

Next, the body size (mold part) is 12 m.
9.8 in 88 pin QFP of mx12mmx2.7mm thickness
When a comparative study was conducted on the case where a semiconductor element having a square of mm was mounted, the inner lead length in the resin sealing portion could only be 0.5 m with a general lead frame.
It was found that the lead pull-out strength was very weak and not practical.

Next, as Comparative Example 1, about 75 μm thick polyimide film and acrylic thermosetting adhesive were applied to a lead frame having no islands and long inner leads for about 2 hours.
After cutting to a size of 10.6 mm square, the one coated with 0 μm was bonded to a lead frame to form an element mounting portion, and a semiconductor element was bonded with an epoxy-based silver paste to produce a semiconductor element. A 0.7 mm thick E pellet manufactured by Nitto Denko Corporation
Cut to 0.6 mm square, place on a lead frame, and further perform a predetermined cure on a Teflon plate with the semiconductor element mounted on it, and then peel off from the Teflon plate to make a product. 5.5 mm as shown in FIG.
10.55mm for lead frame with corner island
Semiconductor elements are bonded with epoxy-based silver paste on a resin film created by screen-printing an insulating epoxy resin on a screen with square opening dimensions, and semiconductor devices are created for these three types. Table 1 shows the results of evaluation of cracks. The lead frame used in this evaluation was made of a copper-based material having a thickness of 0.125 mm, and the plating specifications were nickel plating and palladium plating.

[0023]

[Table 1]

As shown in Table 1, in the resin-encapsulated semiconductor device using the lead frame of the first embodiment, the crack occurrence rate was as low as or more than that of Comparative Example 2. In addition, the compatibility with the assembly and manufacturing process of the conventional resin-encapsulated semiconductor device is very high, the reliability is high, and the thickness of the element mounting portion is thin, so that it is possible to easily cope with a thin package. It has the advantage that.

FIGS. 3A and 3B are a plan view and a sectional view taken along line BB of a third embodiment of the lead frame for a resin-sealed semiconductor device according to the present invention.

In the third embodiment, the lead frame 1A has the island supporting leads 5, and the element mounting surface of the lead frame 1A is the island supporting leads 5 and the insulating resin film thereon. 4B. The lead frame 1A has a required pattern of a one-pack epoxy resin containing 70% by weight or more of silicon dioxide spherical fine powder (average particle size: 6 μm) as a filler in the lead frame just like the first embodiment. It can be obtained by screen printing with an underlaying plate and peeling after curing.

The resin-encapsulated semiconductor device using the lead frame according to the third embodiment can be assembled similarly to the first embodiment. The semiconductor element is the resin film 4
A is fixed on A by a general method using an adhesive such as a silver paste, and between the electrode on the semiconductor element and the inner lead is wire-bonded with a thin metal wire using an ultrasonic thermocompression bonding method. Can be obtained through a general process of manufacturing a resin-sealed semiconductor device. The third
In the embodiment, since most of the element mounting surface is made of an epoxy resin, the adhesiveness between the epoxy mounting and the element mounting surface, which are frequently used for bonding semiconductor elements, and the element mounting surface and The adhesion between the back surface and the sealing resin is greatly improved.

Next, the body size is 14 mm × 20 mm.
Using an 80-pin QFP with a thickness of × 2.7 mm, an ordinary 7.
Comparative Example 3 assembled using a lead frame having an island of 4 mm × 8.7 mm, and a third example in which an element mounting portion made of a 7.4 mm × 8.4 mm insulating resin film was provided on a 3 mm square island. Table 2 shows the results of manufacturing a semiconductor device using the example of Example 1 and comparing the package crack resistance. The lead frame of this example is 0.15 m
It is a copper-based material with a thickness of m, and the plating specification is silver plating only at the tip of the inner lead. A common epoxy resin silver paste was used for bonding the semiconductor element to the island or the element mounting portion.

[0029]

[Table 2]

As shown in Table 2, also in the third embodiment, the crack occurrence rate was zero, and good results were obtained. In addition, the resin-encapsulated semiconductor device using this lead frame has the advantages that the compatibility with the conventional manufacturing process of the resin-encapsulated semiconductor device is very high, and that the package crack resistance is very high. I have. Also, as a secondary effect, the majority of the element mounting portion is made of an insulating resin film, so that the elastic modulus of the element mounting portion decreases, and the semiconductor element is fixed without using a low-stress silver paste. However, there is an advantage that the warpage is small.

FIG. 4 is a top view of a fourth embodiment of a lead frame for a tree-sealed semiconductor device according to the present invention.

In the fourth embodiment, the lead frame 1B has, in addition to the main island 2A, an element mounting portion formed by a plurality of insulating resin films 4C formed on the inner leads 3B. The lead frame of the fourth embodiment is a one-part epoxy resin containing, as in the first embodiment, 70% by weight or more of spherical fine powder of silicon dioxide (average particle size: 6 μm) as a filler on the lead frame. The resin can be obtained by screen-printing the resin together with the underlaying board using a screen having a required pattern, and peeling the lead frame 1B from the underlaying board together with the element mounting portion made of the insulating resin after curing.

The resin-encapsulated semiconductor device having a plurality of semiconductor elements mounted thereon using the lead frame according to the fourth embodiment is assembled in the same manner as a lead frame provided with islands according to a commonly used lead frame pattern. It can be carried out. The semiconductor element is fixed on the island 2A and the resin film 4C by a general method using an adhesive such as a silver paste, and a thin metal wire is formed between the electrode on the semiconductor element and the inner lead using an ultrasonic thermocompression bonding method. , And thereafter can be obtained through a general manufacturing process of a tree-sealed semiconductor device.

14 mm × 20 mm × 2.7 mm thick 80
Using a pin QFP, a 5.0 mm square 1
In the case of a multi-chip package (hereinafter referred to as MCP) in which four main semiconductor elements and four sub-semiconductor elements of 1.2 mm square are mounted in the same package, when a lead frame having five islands is used, lead The pattern design of the frame becomes very complicated. On the other hand, in the lead frame of the fourth embodiment, as shown in FIG. 4, a main semiconductor element of 5.0 mm square is mounted on a general island 2A, and four main semiconductor elements of 1.2 mm square are mounted. Since the semiconductor element may be mounted on the element mounting portion formed of the resin film 4C, the design is extremely easy.

As described above, the design of the lead frame for MCP according to the fourth embodiment is simpler, and in some cases, a lead frame designed for mounting one semiconductor element may be diverted for MCP. There is an advantage that it becomes possible. Further, there is an advantage that the design change of the semiconductor element mounting portion can be easily executed by changing the pattern of the screen.

The lead frame of the fourth embodiment uses, for example, a copper-based material having a thickness of 0.15 mm, and the plating specification can be nickel plating or palladium plating on the entire surface. Further, since a general epoxy-based silver paste can be used for bonding and fixing each semiconductor element to the island or the resin film, there is no particular problem in manufacturing.

[0037]

As described above, the lead frame for a resin-encapsulated semiconductor device and the resin-encapsulated semiconductor device using the same according to the present invention include the conventional leads for a resin-encapsulated semiconductor device. Compared to frames, by forming element mounting parts of insulating epoxy-based organic resin by screen printing method, semiconductors can be maintained with high consistency with general assembly and manufacturing processes of resin-encapsulated semiconductor devices. By improving the adhesiveness with the epoxy paste for element bonding and the adhesion with the sealing resin, it becomes possible to mount a large semiconductor element without lowering the package crack resistance.

Further, in a conventional lead frame for a resin-encapsulated semiconductor device having a COL structure, the thickness of the element mounting portion is
50-150μ in addition to the thickness of the lead frame itself
m-thickness deteriorates the filling property of the sealing resin during resin sealing by the transfer molding method.
Although it was difficult to apply to a thin package such as P, in the lead frame for a resin-encapsulated semiconductor device according to the present invention, the increase in the thickness of the element mounting portion was about 20 μm, so that The adverse effect on the filling property is very small, and it can be applied to a thin package.

Further, since the step of forming the element mounting portion on the lead frame can be performed independently of the manufacturing process of the lead frame, the element mounting portion can be changed only by changing the screen printing pattern. Compared with the case where a lead frame having a general island is used, there is also an advantage that the versatility of the lead frame can be greatly increased.

[Brief description of the drawings]

FIG. 1 is a top view and a cross-sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a top view and a cross-sectional view of a third embodiment of the present invention.

FIG. 4 is a top view of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a conventional lead frame for a resin-encapsulated semiconductor device.

FIG. 6 is a cross-sectional view of a conventional lead frame for a resin-encapsulated semiconductor device.

[Explanation of symbols]

 1, 1A, 1B Lead frame 2, 2A Island 3.3A-3D Inner lead 4, 4A-4C Resin film 5 Support lead 6 Adhesive 7 Polyimide film 8 Insulating resin 10 Semiconductor element

Claims (3)

(57) [Claims] 1. A semiconductor device comprising: a lead frame; and at least one element mounting portion provided over a part of the lead frame and made of an insulating thermosetting resin film containing silicon dioxide powder as a filler. Characteristic lead frame for resin-encapsulated semiconductor device. 2. A lead for a resin-encapsulated semiconductor device, wherein a semiconductor element mounting portion is formed by printing an insulating thermosetting resin film on a part of the surface of a lead frame using a screen printing method. The method of manufacturing the frame. 3. A device provided over a part of the lead frame.
At least one device mounting portion made of an insulating thermosetting resin film containing silicon dioxide powder as a filler, a semiconductor device fixed on the device mounting portion via an adhesive, and the semiconductor device And a resin for sealing the resin.