JPH07326697A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To manufacture a high-quality lead frame which can be easily handled and easily worked at a low cost through a simple process so that the delivery date and quality of the lead frame can be easily controlled by using ordinary strips and making the lead frame to be able to be worked and formed in one die. CONSTITUTION:A strip 21 which is used for the base of a lead frame and another strip 22 used for the heat sink section of the lead frame are simultaneously fed into one die. In the die, the two strips 21 and 22 are united into one body by punching the strips 21 and 22 to a prescribed shape while the strips 21 and 22 are fed forward in a state where they are put together. Then the union of the two punched strips 21 and 22 is further intensified by forming closed-in formed parts 28 and 30 by closing in prescribed parts of the strips 21 and 22. Thereafter, a lead frame provided with a heat sink section 20 is manufacture by forming and bending the punched strips 21 and 22. It is desirable to constitute the strip 21 of a high-strength material and the strip 22 of a good heat conductor.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Demand for IC and transistor lead frames is increasing year by year, and the tendency is particularly remarkable in lead frames for power transistors, which require large heat dissipation. The lead frame used for such an application has a unique cross-sectional shape in which a heat sink portion and a lead portion are integrated.

Conventionally, there are the following two methods for processing such a power transistor lead frame.

First, there is a method of using a special-shaped strip having a heat-sink portion, which has a special shape, and putting it into one progressive die to complete the forming process such as punching and bending. As shown in FIG. 6, the profiled strip 1 used in this process has different plate thickness portions with the same cross section, the center is a thick plate portion and both sides are thin plate portions. Further, in the processing process, as shown in FIG. 7, the profiled strip 1 is sent out from the delivery device 2, the profiled strip 1 is smoothed by the leveler 3, and the press machine 4 is used.
Then, the strip-shaped lead frame 5 is formed by punching, molding, bending, cutting, etc., and the strip-shaped lead frame 5 is aligned by the aligning machine 6. An example of a general lead frame for a power transistor completed by such processing is shown in FIG. This type is called TO220. The cross-sectional shape is such that the die bonding portion 7 serving as the chip mounting portion and the header portion 14 having the center hole 13 have a large plate thickness and the lead portion 8 has a thin shape.

Next, two flat strips are processed separately, one part is processed as a heat sink part with a die for a heat sink part, and the other one is processed as a lead part as a lead part. It is a method of processing with a metal mold, and after processing, caulking both to integrate. As shown in FIG. 9, one of the two flat strips uses a thick flat strip 9 for the heat sink portion, and the other flat strip is
For the sheet, a flat strip 10 having a thin plate is used for the lead portion. Usually, one having a thickness of about 1/3 is used for the lead portion. Each processing process of the two flat strips is the same as that of FIG. 7 using the modified strip, but as shown in FIG. 10, the first heat sink portion 11 has a standard shape (see FIG. 8). ) Is the image of the upper half. Similar to this,
As shown in FIG. 1, the shape of the second lead portion 12 is an image of a standard lower half. A lead frame is obtained by caulking and integrating these two parts. The shape of the finished product after caulking is the same level as in FIG.

[0006]

However, the above-mentioned conventional device has the following drawbacks.

In the processing process using the deformed strip, (1) one die can be used for the press working, but since the deformed strip is formed by special rolling, the cost is much higher than that of a general rolled strip. It is expensive and usually doubles.

(2) Due to the deformed processing, a difference occurs in the processing strain balance between the thick plate portion and the thin plate portion, which easily causes a problem in quality.

(3) Since the deformed strip is generally thin on both sides, it is likely to be deformed or distorted during transportation, handling, etc. after completion of the strip.

On the other hand, in the case of the caulking process using two flat strips, (1) an inexpensive general flat strip may be used as the raw strip, but the two flat strips are separately pressed. Since it requires a machine, it requires two lines and two dies, and since it also requires caulking, the process is complicated and the processing cost is high.

(2) Due to the complexity of the process, delivery date management and quality control become difficult.

(3) Unlike the general press, there are many technical difficulties in the caulking process. The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art,
By using ordinary flat strips and allowing them to be processed and formed with one mold, the raw strips are easy to handle, high quality, easy to process, low in processing cost, and simple in process. It is to provide a method of manufacturing a lead frame that is easy to manage.

[0013]

According to the method of manufacturing a lead frame of the present invention, a flat strip serving as a base and a flat strip serving as a heat sink portion are simultaneously supplied into one mold, and two strips are formed in the mold.
The two flat strips are piled up in order and punched into a predetermined shape, and the two punched flat strips are crushed to integrate the two flat strips into a lead frame having a heat sink. It is something that is done.

[0014]

[Operation] Two flat strips, a flat strip serving as a base and a flat strip serving as a heat sink portion, are simultaneously supplied into the mold. As for the two flat strips, a part integrally formed by a punching burr by simultaneous punching in a mold and a part integrated by a crushing process by progressive feeding occur. This makes 2
The two flat strips are integrated. Therefore, the lead frame having the heat sink can be manufactured by one process and one mold.

[0015]

EXAMPLES Examples of the present invention will be described below. In this embodiment, a flat strip is used, and two types of flat strips having different thicknesses are simultaneously fed into one die, and punched and crushed by press working in the process of being sequentially fed in the die, A power transistor or IC having a heat sink portion of a predetermined shape by imparting processing such as molding or bending.
It manufactures lead frames for semiconductors for applications.

As shown in FIG. 2, two types of flat strips 21 and 22 matched to a predetermined final shape plate thickness are combined into one press die 23.
Supply at the same time. For example, the plate thickness of the first flat strip 21 serving as the base is determined, and then the second flat strip obtained by subtracting the plate thickness of the base flat strip from the plate thickness of the heat sink portion is selected. The width of the second flat strip is about 1 of the base flat strip.
/ 2. When these are overlapped with their center lines aligned, they have the same shape and cross section as the profiled strip.

These two flat strips 21 and 22 are respectively leveled to maintain the flatness and supplied to the mold 23 with the base down and the heat sink part up. The mold 23 is an ordinary progressive die. It is sufficient that the crushing function is added to the function of. That is, it may be the same as a precision progressive die that is generally provided for precision machining, and two flat strips 21 and 22 that are still stacked in a die 23 are simultaneously guided, punched, crushed, and molded into a predetermined shape. , It will be bent.

For punching in the die 23, two flat strips 2 are used.
In order to integrally guide 1 and 22, the mold 23
It is preferable to form a pilot hole for guide at a position common to both of them near the entrance of the. In FIG. 2, 24 is a lower mold, 25 is a stripper, and 26 is an upper mold.

As shown in FIG. 3, the two flat strips 21 and 22 are punched at the same time in the mold 23. However, a portion integrally formed by a punching burr by this simultaneous punching and generally a moisture resistance (after packaging). A portion integrally formed by a crushing process provided for improvement (due to invasion from the outside). By these portions, the mating portion of the lead frame composed of two flat strips is integrated to a level with no gap. That is, the holes are punched out, and the periphery is integrally formed by punching and various crushing processes to seal the entire mating portion.

Next, a method of manufacturing a standard lead frame for a power transistor called a TO220 type will be specifically described. Supply strips are 2 as shown in Fig. 4.
Select the type of flat strip, and the size of the base strip is 0.4
mm thickness x 64 mm width, and the dimensions of the flat strip to be the heat sink portion to be superposed thereon are 0.86 mm thickness x 36 mm width. The material of these flat strips is a copper alloy such as deoxidized copper, oxygen-free copper, 42 alloy, phosphor bronze, etc., and its shape is mainly that which has been processed by rolling.

Both flat strips may be made of the same material, or any combination of the above materials may be used. In particular, since the flat strip serving as the base is provided with the die pad portion and the lead portion serving as the functional surface, It is preferable that a high-strength alloy material such as 42 alloy is used so that there is no problem in strength, and the flat strip serving as the heat sink is made of oxygen-free copper having good thermal conductivity.

These are inserted into the mold 23, and integrally molded by stamping punching, crushing molding or the like at each stage. The part that becomes the press punch itself, that is, the entire periphery, is punched out together so that it is integrated with almost no gap due to punch burrs and the like. Further, as shown in FIG. 1 showing an example of the lead frame after molding, the recess 18 and the groove 19 formed in the die pad portion 29, the two crushed molding portions 28 around the center hole portion 27 by punching, and the heat sink portion. 20 to the die pad portion 29 at the four crush-molded portions 30 further improve the strength of integration.
Two types of flat strips 21 and 2 are integrated by these processes.
2 has the same shape and cross section as the profiled strip.

FIG. 5 shows an example of a lead frame for a large power transistor of a class called TO3P. The base forming the lead portion 49 has a thickness of 0.6 mm and is 9
In this example, the heat sink 50 has a width of 0 mm and the heat sink 50 has a thickness of 1.4 mm and a width of 45 mm. Crushing portions 54, 55, 56 are provided at four places around the center hole 51, two head portions of the header 52, and two places on both sides of the die pad 53, and both flat strips are securely caulked at these portions. It is integrally molded in one mold.

Therefore, as a die for simultaneously pressing two flat strips, it is possible to use a die substantially the same as a conventional die using a deformed strip. In other words, two flat strips are supplied to the die instead of the irregular strip, but the difference in the strips changes the guide shape at the inlet of the die or considers the drawing order ( This can be easily dealt with, for example, by first making a hole for overlapping the two flat strips, etc., and almost the conventional mold can be used as it is.

Further, since the bare strip can be dealt with by using two general and inexpensive rolled flat strips, it can be easily obtained and the cost can be reduced to half or less as compared with the special profile strip. . Also, by selecting the dimensions of the two flat strips, various types of lead frames can be dealt with, and by combining flat strips of different materials, the characteristics can be improved over modified strips of the same material. Lead frames can also be supplied.

[0026]

EFFECTS OF THE INVENTION According to the present invention, since a general flat strip is used, it can be easily handled, has no problem in quality, and can be manufactured at a low cost as compared with the case of a modified strip. In addition, since two types of flat strips are punched together by one die, crushed, and integrated, the processing is easier and the processing cost is lower than the case where they are separately processed and caulked. Further, since the lead frame having the heat sink portion is manufactured by one mold, the process is simple and the delivery date control and the quality control are easy.

[Brief description of drawings]

FIG. 1 is a power transistor lead frame (T) for explaining an embodiment of a lead frame manufacturing method of the present invention.
The top view which shows the example of shaping | molding of O220 type.

FIG. 2 is a diagram showing a state of insertion of a die inlet portion and two flat strips of the present embodiment.

FIG. 3 is a sectional view illustrating simultaneous press punching according to the present embodiment.

FIG. 4 is an explanatory diagram showing an example of selecting two flat strips according to the present embodiment.

FIG. 5 is a plan view showing a molding example of another power transistor lead frame (TO3P type) of the present embodiment.

FIG. 6 is a perspective view showing a profile strip used for a conventional power transistor lead frame.

FIG. 7 is a configuration diagram showing a conventional lead frame stamping process.

FIG. 8 Conventional power transistor lead frame (T
The top view which shows the example of molding of (O220).

FIG. 9 is a perspective view of two thick strips and thin strips which are materials for forming a power transistor lead frame by caulking two conventional molded parts.

10 is a plan view showing an example of the shape of a heat sink portion formed from the thick strip shown in FIG.

11 is a plan view showing an example of the shape of a lead portion formed from the thin strip shown in FIG.

[Explanation of symbols]

 20 Heat Sink Part 21 Flat Strip as Base 22 Flat Strip as Heat Sink Section 27 Center Hole 28 Center Hole Crush Formed Area 29 Die Pad Section 30 Die Pad Section Crush Formed Section 31 Lead Section

Claims (2)

[Claims] 1. A flat strip serving as a base and a flat strip serving as a heat sink portion are simultaneously supplied into one mold, and two strips are supplied in the mold.
The two flat strips are piled up in order and punched into a predetermined shape, and the two punched flat strips are crushed to integrate the two flat strips into a lead frame having a heat sink. A method for manufacturing a lead frame, comprising: 2. The method of manufacturing a lead frame according to claim 1, wherein the flat strip serving as the base is made of a high-strength material, and the flat strip serving as the heat sink is made of a good heat conductive material.