JPH04337658A - Lead frame and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a lead frame which fits to a conventional semiconductor device assembly line with a sufficient wire bond reliability and a lead strength even if a pattern is fine in a lead frame which is equipped with electrical wiring between an element and the outside, mounting a semiconductor element. CONSTITUTION:A lead frame which has a first lead frame 1a consisting of a metal plate whose plate thickness is thick and a second lead frame 1b which consists of a metal plate whose plate thickness is thin, and adhered to the first lead frame 1a through an insulator 23, and then a lead 2b is extended in a direction for mounting a semiconductor and where the first lead frame 1a and a die pad 3 support the second lead frame.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame and a method for manufacturing the same, and more particularly to a lead frame for a semiconductor device and a method for manufacturing the same.

0002

2. Description of the Related Art Conventionally, most semiconductor devices have been of the resin-sealed type. FIG. 11 is a side sectional view of a conventional semiconductor device. In FIG. 11, 11 is a semiconductor element, 12 is a die pad on which the semiconductor element 11 is placed, 13 is a bonding wire made of a thin metal wire, 14 is an inner lead made of a metal strip, 15 is an outer lead also made of a metal strip, and 16 is a bonding wire made of a thin metal wire. It is mold resin.

Electrical signals are transmitted between the semiconductor element 11 and the outside via bonding wires 13, inner leads 14, and outer leads 15. The die pad 12, inner leads 14, and outer leads 15 are collectively referred to as a lead frame, and are processed from a plate-shaped material of copper alloy or iron alloy by punching with a press or chemically dissolving with etching.

A general method for manufacturing lead frames by etching is to selectively harden or decompose a dry film or liquid photosensitive resin on the surface of the metal plate to form a desired corrosion-resistant film, and then apply an etching solution. The process consisted of spraying to melt the metal plate material and peeling off the corrosion-resistant film.

[0005] Lead frames for semiconductor devices are also used to reduce the size of semiconductor device packages and to meet the demands for miniaturization and higher performance of electronic equipment as semiconductor and related peripheral technologies improve. The miniaturization of semiconductor elements and the increase in the number of pins of semiconductor devices are progressing year by year. As a result, the patterns of lead frames used in semiconductor devices have become extremely fine, and the number of lead frames that are difficult to manufacture by press processing is increasing. Therefore, lead frames having such fine patterns are currently manufactured by etching processing, which allows finer processing than press processing.

[0006]

However, as the number of pins in semiconductor devices in recent years has increased significantly, especially in gate arrays, there have been some cases where lead frames with conventional structures cannot be used. That is, due to the increase in the number of pins, the pitch of the tips of the inner leads 14 became narrower, making processing extremely difficult. A method of fine-machining by thinning the plate thickness has also been adopted, but there are problems with the strength of the pins, and they are difficult to mount because they bend easily.

Therefore, such multi-pin semiconductor devices mainly use TAB (Tape Automated Bondi).
ng) method is used, but in the TAB method, the TAB tape itself is expensive, it lacks versatility depending on the semiconductor device model, and furthermore, the manufacturing line must be changed significantly, so it is very expensive in terms of cost. There was a problem that it was disadvantageous.

The present invention was made to solve the above-mentioned problems, and has dramatically improved strength and pattern density compared to conventional multi-pin lead frames.
In addition, it is possible to assemble semiconductor devices with a very large number of pins in the same way as before, and mounting on the board does not require any special technology.Furthermore, since it uses wire bonding method, only one model can be assembled. The purpose of this lead frame is to have the versatility to be compatible with several types of semiconductor devices with different dimensions and electrode positions.

That is, the objective is to obtain a semiconductor device that is cheaper than the TAB method, which requires a dedicated assembly line and is not versatile.

0010

[Means for Solving the Problems] Accordingly, in claim 1 of the present invention, there is provided a lead frame on which a semiconductor element is mounted, a die pad on which the semiconductor element is mounted,
A first lead frame made of a thick metal plate and a thin metal plate are bonded to the first lead frame with an insulator interposed therebetween, and the leads extend in the mounting direction of the semiconductor element. The above object is achieved by a lead frame having a second lead frame, the first lead frame and the die pad supporting the second lead frame. .

According to a second aspect of the present invention, a first processing step of press-working or etching a metal plate having sufficient strength as a lead frame on which a semiconductor element is mounted; an adhesion step of adhering a metal plate thinner than the lead frame to one side of the lead frame through an insulator;
The above object is achieved by a lead frame manufacturing method according to claim 1, further comprising a second processing step of etching only the thin metal plate.

[0012] According to a third aspect of the present invention, a first processing step of press-working or etching a metal having sufficient strength as a lead frame on which a semiconductor element is mounted, and a lead frame manufactured by the first processing step. an adhesion step of applying an insulating adhesive to one side of the lead frame and adhering a metal plate thinner than the lead frame; and a second step of etching only the thin metal plate.
The above object is achieved by a lead frame manufacturing method according to claim 1, which comprises a processing step.

[0013]

[Operation] The lead frame according to claim 1 of the present invention is electrically insulated by the insulator interposed between the first lead frame and the second lead frame, and the support means by the first lead frame and the die pad. supports the second lead frame.

[0014] Furthermore, in the method for manufacturing a lead frame according to claim 2 of the present invention, in the first processing step, a metal plate having sufficient strength as a lead frame on which a semiconductor element is mounted is pressed or etched, and in the bonding step, A metal plate thinner than the lead frame is adhered to one side of the lead frame via an insulator, and in a second processing step, only the thin metal plate is etched.

Further, in the method for manufacturing a lead frame according to claim 3 of the present invention, in the first processing step, a metal plate having sufficient strength as a lead frame on which a semiconductor element is mounted is pressed or etched, and in the bonding step, the metal plate is pressed or etched. Apply an insulating adhesive to one side of the lead frame,
A metal plate thinner than the lead frame is bonded, and only the thin metal plate is etched in a second processing step.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. First, a lead frame which is an embodiment of the present invention will be explained using FIGS. 1 to 6.

FIG. 1 is a partially enlarged view of a lead frame according to an embodiment of the present invention, FIG. 2 is a plan view showing the entire lead frame according to this embodiment, and FIG. 3 is a diagram showing semiconductor elements mounted on the lead frame according to this embodiment. 4 is a perspective view of the back side of FIG. 2, FIG. 5 is a side sectional view of a semiconductor device using the lead frame in this embodiment, and FIG.
1 is a side sectional view of a semiconductor device using a lead frame in this example.

In FIGS. 1 to 6, reference numeral 1 denotes a lead frame (FIG. 1) on which a semiconductor element is mounted, and is a multilayer lead frame in which two metal plates of different thickness are bonded together with an insulator interposed therebetween. The plate has a thin structure.

Reference numeral 1a designates the first lead frame having a thicker plate on the bonding surface side (FIG. 4). 1b is a second lead frame, which is the thinner of the lead frames (FIG. 3). This second lead frame 1b has leads 2b extending in the mounting direction of the semiconductor element 11 for electrical wiring, and the leads 2a of the first lead frame 1a and the semiconductor element 11 (FIG. 5) are mounted thereon. It is supported by the die pad 3.

The leads 2a of the first lead frame 1a are not involved in electrical wiring, but support the leads 2b of the second lead frame 1b, and have the function of transmitting heat generated from the semiconductor element 11 to the outside. There is.

Next, two methods of manufacturing the lead frame of this embodiment will be explained with reference to FIGS. 7 to 10. Fig. 7 is a process diagram showing the manufacturing process of this embodiment, Fig. 8 is an enlarged view showing the tip of the inner lead, Fig. 9 is a partially enlarged view of the first lead frame, and Fig. 10 is a diagram of the lead frame during the second processing step. FIG.

In FIG. 7, reference numeral 71 indicates a first processing step, in which a metal plate having sufficient strength as a lead frame on which a semiconductor element is mounted is pressed or etched. 72 is an adhesion step, which is a step of adhering a metal plate thinner than the lead frame to one side of the lead frame manufactured in the first step via an insulator, or having an insulating property on one side of the lead frame. This is a step of applying an adhesive and bonding a metal plate that is thinner than the lead frame. 73 is the second processing step,
This is a step of etching only the thin metal plate. Details of each of the above steps will be described later.

This manufacturing method will be explained in detail below. First, a VQFP lead frame 4 was prototyped by etching, assuming that a semiconductor element with an outer size of 10 mm x 10 mm and 400 electrodes would be mounted thereon. FIG. 8 shows an enlarged view of the tip portion of the inner lead 5b of the thinner lead frame 4b among the two lead frames constituting the lead frame 4. As shown in FIG. The length of the tips of the inner leads 5b is changed for every other lead in order to secure the area of the bonding portion 6, and the width of the bonding portion 6 is 100 μm.
The pitch was 200 μm, the minimum width of the inner leads 5b was 40 μm, and the minimum interval was 35 μm.

The material is Sn2%-Ni0.2%-P0.
06% - Select a copper alloy plate material with the balance being Cu, and for the thicker lead frame 4a (Figure 9), the dimension is 300 m.
m x 450 mm, plate thickness 150 μm standard length material, dimensions 300 mm x 400 mm for lead frame 4b (Figure 8)
A regular length material with a plate thickness of 30 μm was used. The lead frame 4 had dimensions of 240 mm x 60 mm, and was designed so that six lead frames were arranged on the above-mentioned regular length material.

[0025] First, the above-mentioned plate material having a thickness of 150 μm is coated with a liquid photocurable resin by electrodeposition, and this is sandwiched between glass masks having the pattern of the lead frame 4a prepared in advance, and ultraviolet rays are irradiated from both sides. The sample was irradiated to harden the portion to be formed into a corrosion-resistant film, and developed to obtain a sample having a desired shape of a corrosion-resistant film. Subsequently, a ferric chloride solution was sprayed onto both sides of the sample for etching, and the corrosion-resistant film was peeled off to complete the lead frame 4a. This enlarged plan view is shown in FIG. Die pad 7 on which semiconductor elements are mounted
The dimensions were 30 mm x 30 mm, and a slit 8 with a width of 0.3 mm was provided on the outer periphery of the mounting portion of the semiconductor element. The distance between the tip of the inner lead 5a and the die pad 7 is 150 μm
The pitch of the inner leads 5a was set to a minimum of 300 μm.

The lead frame 4a obtained in this manner is not separated individually, but is attached to a support frame, and a polyimide resin sheet 9 is pasted on the bonding surface (FIG. 10), and a copper sheet for the lead frame 4b is further placed on top of the polyimide resin sheet 9. Alloy plate material was attached. Next, in the same way as when processing the lead frame 4a, liquid photocurable resin 17 is coated by electrodeposition, and positioning pins 19 are provided on the glass mask 18 of the pattern (bonding surface side) of the lead frame 4b. The holes for positioning provided in the support frame of the lead frame 4a are fitted into the lead frame 4a, and ultraviolet rays 20 are irradiated from both sides with the cross section as shown in FIG. A sample was obtained in which the bonding surface had the pattern of the lead frame 4b and the back surface had a solid corrosion-resistant film. Next, the sample was etched by spraying ferric chloride solution,
The lead frame 4 was completed by peeling off the corrosion-resistant film. As a result of measuring this lead frame 4, the dimensional error was 10 μm.
It was within

In this embodiment, a polyimide resin sheet 9 is used as an insulator between the lead frame 4a and the lead frame 4b, but if insulation can be guaranteed, a liquid adhesive may also be used between the lead frames. It is possible. Further, the material of the lead frame is not limited to the copper alloy used in this embodiment, and various metal materials such as other copper alloys and iron alloys can be used. However, since it is possible that the difference in thermal expansion coefficient may have an adverse effect such as distortion or internal stress, it is preferable to use materials with the same thermal expansion coefficient for the two materials having different thicknesses.

[0028]

As explained above, the lead frame of claim 1 manufactured by the manufacturing method of claim 2 or claim 3 of the present invention has higher strength and strength than the conventional multi-pin lead frame. There has been a dramatic improvement in pattern density. Furthermore, this lead frame allows semiconductor devices with a very large number of pins to be assembled in the same manner as before, and mounting on a board does not require any special technology.

Furthermore, since the wire bonding method is adopted, one type of lead frame has the versatility to be compatible with several types of semiconductor elements having different sizes and electrode positions. That is, it is necessary to newly establish a dedicated assembly line, and compared to the TAB method which does not have general versatility, it is possible to obtain a cheaper semiconductor device.

[Brief explanation of drawings]

[Fig. 1] A partially enlarged view of a lead frame in an embodiment of the present invention.

[Fig. 2] A plan view showing the entire lead frame of this example.

[Fig. 3] Partially enlarged perspective view of the semiconductor element mounting surface of the lead frame of this example.

[Figure 4] Perspective view of the back side of Figure 2

[Figure 5] Side sectional view of a semiconductor device using a lead frame in this example

[Figure 6] Side sectional view of a semiconductor device using a lead frame in this example

[Figure 7] Process diagram showing the manufacturing process of this example

[Figure 8] Enlarged view showing the tip of the inner lead

[Figure 9] Partially enlarged view of the first lead frame

[Figure 10] Side sectional view of the lead frame during the second processing step

[FIG. 11] Side sectional view of a conventional semiconductor device

[Explanation of symbols]

1 Lead frame 1a First lead frame 1b Second lead frame 2a 1a lead 2b 1b lead 3 Die pad 11 Semiconductor element 23 Insulator 71 First processing process 72 Adhesion process 73 Second processing process Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (3)

[Claims] 1. A lead frame on which a semiconductor element is mounted, the lead frame comprising a die pad on which the semiconductor element is mounted, a first lead frame made of a thick metal plate, and a first lead frame made of a thin metal plate, which are insulated. a second lead frame that is adhered to the first lead frame with an object interposed therebetween, and whose leads extend in the mounting direction of the semiconductor element;
The lead frame is characterized in that the first lead frame and the die pad support the second lead frame. 2. A first processing step of pressing or etching a metal plate having sufficient strength as a lead frame on which a semiconductor element is mounted; and an insulating layer on one side of the lead frame manufactured by the first processing step. The lead frame according to claim 1, further comprising an adhesion step of adhering a metal plate thinner than the lead frame via an object, and a second processing step of etching only the thin metal plate. manufacturing method. 3. A first processing step of pressing or etching a metal having sufficient strength as a lead frame on which a semiconductor element is mounted, and a lead frame manufactured by the first processing step having an insulating property on one side. 2. The method according to claim 1, further comprising a bonding step of applying an adhesive and bonding a metal plate thinner than the lead frame, and a second processing step of etching only the thin metal plate. Lead frame manufacturing method.