US20100031727A1

US20100031727A1 - Production method of multi-gauge strips

Info

Publication number: US20100031727A1
Application number: US12/514,583
Authority: US
Inventors: Choong Yeol Kim
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-11-20
Filing date: 2007-11-20
Publication date: 2010-02-11
Also published as: WO2008062992A1; JP2010510066A

Abstract

The present invention provides a method of producing a multi-gauge strip which has a thick portion and a thin portion which are continuously disposed along its length. The method of producing multi-gauge strips consisting of a relatively thick portion and a relatively thin portion formed along the widthwise direction while continuously transferring a strip material, is characterized by comprising the steps of: primarily forming a strip material by pressing the upper side thereof so as to make a groove in the lower side of the part where a thin portion is to be formed; and secondly forming the resulted strip by pressing the upper side of the primarily formed strip so as to form the part having a groove into a thin portion and the other part into a thick portion.

Description

TECHNICAL FIELD

The present invention relates to a method for production of multi-gauge strips (MGS) which are mainly used as materials for lead frames of semiconductors. Multi-gauge strips refer to a band-shaped member consisting of a thick portion and a thin portion which are continuously disposed along the lengthwise direction. The present invention relates to a method of producing multi-gauge strips by using a general purpose roller or a press.

BACKGROUND ART

Multi-gauge strip is a member having a use in a lead frame which supplies electricity to semiconductor parts requiring great electric capacitance or to electric or electronic parts, while supporting them. For example, it is used to supply electricity to heat generating parts, such as a power transistor or a connector, as well as to smoothly radiate heat generated from such parts. Multi-gauge strip is generally produced by forming a thick portion and a thin portion in a strip made of copper and a copper alloy, wherein the thin portion is used as a lead and the thick portion as a heat radiator.
Conventional multi-gauge strips are formed to have a thin portion of which thickness is around 30% of that of a thick portion. However, it cannot be formed by a conventional rolling method, since such rolling work makes the length of a thin portion more elongated. Therefore, various approaches which stretch a material to the widthwise direction have been developed so as to form a thin portion.
In conventional methods for producing a multi-gauge strip, scalping of a part of a certain material so as to form a thin portion, or welding a material for a thin portion to each end of a thick portion or the like have been used for a time. However, these methods are not currently used owing to the poor competitiveness. In recent years, a mode of straining a material to the widthwise direction is mainly used.
Among the methods of producing multi-gauge strips, one of the most commonly used methods is a V-Mill-employing method as shown in FIG. 1. The method processes a strip material (2) which includes the formation of a groove (
) (1 b) in the upper side at the center of a dice (1), and then of slopes (1 c) in each right and left side of the groove (1 b), wherein the slopes (1 c) broadens from the acute angle part (1 a) so as to form a shape of V.
As approaching the strip material (2) to the dice (1), the center portion of the strip material (2) inserted into the groove (1 b) is formed into a thick portion (2 a) shown in FIG. 2, and each side of the lower part of the thick portion (2 a) is cut by a right angled part (1 d) and an acute angled part (1 a) in the upper part of the groove in the dice (1), forming a cut part (2 b) having a slanted surface (2 c) and a linear surface (2 d). When further advancing the strip material (2) at this state, the dimension of the cut part (2 b) becomes increased owing to the gradually expanded slanted surface (1 c), and the cut part (2 b) is formed to a thin portion (2 e) by a flat part (1 e) of the dice (1). Then a multi-gauge strip (2) having the thick portion (2 a) and the thin portion (2 e) is formed. At this time, for forming the strip material (2) on the dice (1), a roll (not shown) moves in a back-and-forth motion in the feeding direction of a material or moves in a left-and-right motion at a right angle to the feeding direction of a material. Further, hammering of the upper side of the material at high speed is employed, or the dice (1) can be modified to have the shape of a roll for the formation.

DISCLOSURE OF INVENTION

Technical Problem

However, in the above method, a roll should moves back-and-forth while applying pressure, and one of the reciprocal movement should be unloaded state, therefore the production rate is low owing to the limitation in speed and pressurization. Further, since the shape of a dice is structured to comprise a V-shaped slope, the fabrication, maintenance and repair thereof are difficult, and the shape of the acute angle part is weak against the applied pressure.
Particularly, for a W-shaped multi-gauge strip having two thick portions, the pressure should be increased as much as the volume of a protrusion (2 f) in the groove, and this necessitate a high ejecting power, thereby causing limitation in formation itself as well as a material transfer.
There is another method called MGR (Multi Grooved Roll), wherein a pair of the upper and the lower roll each of which has depression and prominence (3 a,3 b), respectively, and a pair of the upper and the lower roll having a flat surface (4 a,4 b) are placed alternately at multiple stages in tandem, as shown in FIG. 3. In this method, the upper and the lower roll (3 a,3 b) pressurize both sides of a material (5) to form a bended part and a thin portion, then the upper and the lower roll having a flat surface (4 a,4 b) correct the depression and prominence of the formed material to a flat plane by repeated rolling. In other words, the thin portion is formed by being gradually widened in both left and right side directions.
In the method, when the width of a thin portion formed by a single movement of rolling is set to be wide, wave forms are produced in the thin portion, and when the width is set to be narrow, the number of a pair of the upper and the lower roll having depression and prominence respectively should be increased, increasing cost of tools in total production cost. Therefore, through the correction using the upper and the lower roll having a flat surface, the length of the thick portion is formed to be same with the length of the thin portion.
As another embodiment of aforementioned MGR method, multiple stages of the upper and the lower roll are placed in tandem for formation. This method uses the upper roll (6) where a groove (6 a), flat surfaces (6 b) in each side of the groove, and a slope (6 c) are formed, and the lower roll (not shown) having a flat surface with the upper roll, as shown in FIG. 4. The upper roll (6) forms a thick portion (7 a) by making the center portion of a material (7) be inserted into the groove (6 a), and at the same time the flat surfaces (6 b) and the slope (6 c) form a thin portion (7 b) and slopes (7 c) at both ends of the thin portion. The above procedure is repeated so as to gradually increase the width of the thin portion.
At this time, when the width of a thin portion is set to be wide in order to reduce the number of rolls, the same result as obtained from the MGR method of FIG. 3 will be obtained. Therefore, it is made to have the slopes formed in each end of the thin portion in widthwise direction, and a correction procedure should be carried out by using the upper and the lower roll having a flat surface as in the above-described MGR method of FIG. 3.
For the method shown in FIG. 3, the strip material forms into a multi-gauge strip, via the shape A, B and then C, as shown in the cross-sectional view of FIG. 5. In other words, by repeating the formation of the material from the sides to the center in the widthwise direction, the width of the thin portion becomes increased while reducing the width of the thick portion. Further, in the method shown in FIG. 4, the strip material is formed into a multi-gauge strip via the shape D, E and then F. In other words, formation is carried out in a way that a thick portion is formed first at the center portion of the material and then the width of the thin portion is increased in each side of the center portion of the material.
In the meantime, for the methods represented in FIGS. 4 to 6, a large number of rolls are required for the formation, which makes the cost of tools increased, and when a material passes through each formation roll, the speed would be limited because the position of a thick portion in the widthwise direction should be maintained constantly. Further, since dust is generated during the repeated pressurization of each side of the thick portion, defective rate is increased.
Moreover, in the above method, each roll arranged in tandem requires a speed-increasing function, since the thicknesses of both of the thick portion and the thin portion are decreased as the material passes through each upper and lower roll, wherein the decrement contributes to an increase in length. Further, the material becomes hardened during the repeated formation procedure, thereby requiring large scale equipment for exclusive use.
Also, the methods described above have common problems that, when forming the thin portion through repeated formation process of a material, the position of the material during formation is not fixed. Accordingly, the formation of a shape having a multiple number of the thick and the thin portions is structurally restricted.

Technical Solution

The present invention has been designed to dissolve the problems of conventional arts. The object of the present invention is to provide a method of producing multi-gauge strips in which the formation of a thick portion and a thin portion can be conducted simultaneously as the elongation rate in the lengthwise direction of the thick portion becomes synchronized with that of the thin portion, by firstly forming the thin portion having a groove in the lower side of the strip material, thereby making a certain space between the groove and a lower roll, wherein the space makes the elongation rate in the widthwise direction high when the thick portion and the thin portion in the upper side are formed.
For achieving the aforementioned object, the method of producing multi-gauge st rips of the present invention characteristically comprises the following steps in a method of producing a multi-gauge strip consisting of a relatively thick portion and a relatively thin portion formed along the widthwise direction while continuously transferring a strip material: primarily forming a strip material by pressing the upper side thereof so as to make a groove in the lower side of the part where a thin portion is to be formed; and secondly forming the resulted strip by pressing the upper side of the primarily formed strip so as to form the part having a groove into a thin portion and the other part into a thick portion.
Further, according to the method of producing multi-gauge strips of the present invention, the groove formed in the primary forming step is in the shape of a trapezoid or curved surface.
Still further, according to the method of producing multi-gauge strips of the present invention, the primary forming step comprises formation of the strip material into a processed strip which has a thick portion formed at the center in the widthwise direction of the strip, and a groove (
) formed in each end of the lower side; and the second forming step comprises formation of the processed strip into a multi-gauge strip consisting of a thick portion in the center and a thin portion at each end of the thick portion.
Moreover, according to the method of producing multi-gauge strips of the present invention, the second forming step comprises formation of a W-shaped multi-gauge strip by forming a square-shaped depressed area at the center in the upper part of the thick portion.
Further, according to the method of producing multi-gauge strips of the present invention, the primary forming step comprises formation of a strip material into a processed strip which has a multiple number of grooves in the lower side thereof and a thick portion between said grooves; and second forming step comprises formation of the processed strip into a multi-gauge strip consisting of a multiple number of thick portions and thin portions therebetween, by forming the grooves in the inner part of the processed strip into a thin portion and then forming the grooves at each end part simultaneously into a thin portion.
Still further, according to the method of producing multi-gauge strips of the present invention, the formation of the grooves in the inner part into a thin portion in the second forming step, is conducted subsequently in order of grooves in the center and outward grooves.
Still further, according to the method of producing multi-gauge strips of the present invention, the primary forming step comprises formation of a strip material into a processed strip having grooves formed in each side of the protrusion at the center of the lower side, and a thick portion formed outside of the grooves; and a second forming step comprises formation of the processed strip into a multi-gauge strip consisting of thick portions at each end thereof and a thin portion between the thick portions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are reference figures showing a method of producing a multi-gauge strip by using a conventional V-Mill.

FIGS. 3 to 6 are reference figures showing a method of producing a multi-gauge strip by using a conventional MGR method.

FIG. 7 is a conceptual plan view of the equipment for describing a method of producing a multi-gauge strip according to the present invention.

FIG. 8 is a cross-sectional view showing a forming procedure according to a first embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a forming procedure according to a second embodiment of the present invention.

FIG. 10 is a cross-sectional view showing a forming procedure according to a third embodiment of the present invention.

FIG. 11 is a cross-sectional view showing a forming procedure according to a fourth embodiment of the present invention.

NUMERALS USED IN THE MAJOR PART OF THE DRAWINGS

10: strip material
20, 40, 45, 60: processed strip
21, 41, 61: thick portion (of the processed strip)
22, 42, 62: groove
30, 50, 70: multi-gauge strip
31, 51, 71: thick portion (of the multi-gauge strip)
32, 52, 72: thin portion (of the multi-gauge strip)
33: square-shaped depressed area (33)

MODE FOR THE INVENTION

Hereinafter, the method of producing multi-gauge strips according to the present invention is described by referring to the attached drawings as follows:
According to the present invention, a method of producing multi-gauge strips of the present invention comprises the following steps in a method of producing a multi-gauge strip consisting of a relatively thick portion and a relatively thin portion formed along the widthwise direction while continuously transferring a strip material: primarily forming a strip material by pressing the upper side thereof so as to make a groove in the lower side of the part where a thin portion is to be formed; and secondly forming the resulted strip by pressing the upper side of the primarily formed strip so as to form the part having a groove into a thin portion and the other part into a thick portion. Specific examples according to the present method are described in the below.

EXAMPLE 1

The first embodiment of a method of producing a multi-gauge strip according to the present invention comprises the steps of: forming a strip material (10) into a processed strip (20) in which a thick portion (21) is formed at the center portion in the widthwise direction, and grooves (
) (22) are formed in each end of the lower side; and forming the processed strip (20) into a multi-gauge strip (30) having thin portions (32) formed on each side of the thick portion (31) in the center, as shown in FIGS. 7 and 8.
At this time, the shape of the grooves (22) is not particularly limited, and may include curved groove such as circular or elliptical type, or trapezoid.
The processed strip (20) is formed by a first lower roller (101) having at least one protrusions (101) at each side end in the widthwise direction, and a first upper roller having a flat surface (not shown), and the multi-gauge strip (30) is continuously formed by a second lower roller (not shown) having a flat surface, and a second upper roller (102) having a groove (102) corresponding to the thick portion in the center.
The strip material (10) on the protrusion (101) of the first lower roll (101) is pressurized by the first upper roller. By the pressurization, a groove (22) having a shape of the corresponding to the protrusion is formed on the lower side of the strip, while forming a processed strip (20) which is elongated to the widthwise direction as well as the lengthwise direction. The groove (22) formed on the lower part of the processed strip (20) forms a space over the second lower roller having a flat surface. With respect to the space formed in the above, while the upper side of the processed strip (20) is being inserted into a groove (102) of the second upper roller (102) to form a thick portion (31), the flat portion of the second upper roller (102) makes the slanted area of the groove in the processed strip (20) gradually come into contact with the upper side of the second lower roller, making the thickness of the slanted area of the groove reduced so that ends of the groove is elongated to the widthwise and the lengthwise direction, forming a thin portion (32). Accordingly, a multi-gauge strip (30) is finally, formed which consists of the thick portion (31) at the center and the thin portions (32) at each side of the thick portion.
The thickness of the thin portion in said processed strip (20) is formed to be larger than the required thickness of the thin portion of the resulting multi-gauge strip (30), since the upper side of the processed strip (20) is to be stretched and elongated when contacting with the groove (102) of the second upper roller (102). In other words, while formation of the thick portion by the groove (102) of the second upper roller (102), the flat portion pressurizes the upper side of the groove part of the processed strip (20) to stretch it in the widthwise direction, thereby forming a thin portion. Simultaneously with that, nearly the same volume in each thick portion and thin portion is elongated in the lengthwise direction, too, thereby synchronizing the elongation rate in the lengthwise direction of the thick portion with that of the thin portion. This is due to the cross-sectional shape of the processed strip (20) having a groove.
In the above, even if there is no extra volume to be elongated (stretched) in the thick portion and the thin portion, the formation process is carried out as same as above described, except for eliminating the rolling work for the corresponding volume reduction. Further, in the case that a multi-gauge strip should have a thin portion with a large width, the slanted part of the groove in the processed strip (20) which forms a space, is allowed to have an acute angle in order to extend the length of the slanted part. In the case that a multi-gauge strip should have a thin portion with a relatively narrow width, the length of the slanted part of the groove is allowed to be shortened. Like these, the shape or dimension of the groove is optionally adjusted depending on the standard required.
The formation process as described so far can be applied same to other examples, therefore further description on this is eliminated in other examples.
Instead of using rollers, a press and a cast, i.e. punch and die or the like can be used for formation. The processed strip (20) is formed by using a lower punch (110) having at least one protrusions (111) at each end in the widthwise direction and a flat upper die (120). The multi-gauge strip (30) is formed by using an upper punch (140) having a groove (141) corresponding to the thick portion (31) over the center of a flat lower die (130).

EXAMPLE 2

This example 2 of the present invention demonstrates a method in which, when forming a processed strip (20) into a multi-gauge strip (30) in the above example 1, a square-shaped depressed area (33) is formed on the upper side at the center of the thick portion (31), resulting in W-shaped multi-gauge strip (30), as shown in FIG. 9.
In this method, as an upper punch (240) for forming a W-shaped multi-gauge strip (30), one having a groove (241) with the square-shaped depressed area (242) formed in the center of the lower side is used. In this method, the pressure inside the groove (241) is increased as much as the volume of the square-shaped depressed area (242) as compared to the case in which a groove (241) is only formed in the upper punch (240), however the space formed in the lower side of the processed strip (20) increases the flexibility of the material. Hence, it does not necessitate high pressure and it is possible to carry out formation without restriction on ejection and transfer of a material.

EXAMPLE 3

This example 3 of the present invention demonstrates a method which comprises: a step of forming a strip material into a processed strip (40) having a multiple number of grooves (42) in the lower side thereof and a thick portion (41) therebetween; and a step of forming the processed strip (40) into a multi-gauge strip (50) consisting of a multiple number of thick portions (51) and thin portions (52) therebetween, by forming the grooves in the inner part of the processed strip (40) into a thin portion and then forming the grooves at each end simultaneously into a thin portion, as shown in FIG. 10.
In this method, when forming the processed strip (40) into a multi-gauge strip (50), it is preferred that the formation is conducted subsequently in order of grooves in the center of the processed strip (40) and outward grooves, and then finally the grooves in the edge of the processed strip (40) is formed into a thin portion. In this case, the groove can be formed as a trapezoid or curved groove.
Specifically, a strip material is formed into a first processed strip (40) having a multiple number of grooves in the lower side, by using a lower punch (310) having a multiple number of protrusions and a flat upper die (320); then the first processed strip (40) is formed into a second processed strip (45) in which the inner groove part is formed into a thin portion, by using a flat lower die (330) and a first upper punch (340) having protrusions corresponding to the inner grooves of the first processed strip (40); and finally the second processed strip (45) is formed into a multi-gauge strip (50) having a multiple number of thick portions (51) and thin portions (52) formed therebetween by using a flat lower die (330) and a second punch (350) having protrusions (351) corresponding to the grooves (42) of the first processed strip (40).
Instead of using a cast and a press of a punch and a die, rollers can be used for forming a multi-gauge strip (50).

EXAMPLE 4

This example 4 of the present invention demonstrates a method which comprises: a step of forming a strip material into a processed strip (60) having grooves (62) formed in each side of a protrusion (63) at the center of the lower side, and thick portions (61) which are formed on each side of the grooves; and a step of forming the processed strip (60) into a multi-gauge strip (70) consisting of thick portions (71) at each end and a thin portion (72) therebetween, as shown in FIG. 11.
In this method, the protrusion (63) of the processed strip (60) is preferably formed to be a curved shape, and the grooves (62) can suitably have either of a trapezoid or a curved shape.
Specifically, the strip material is formed into a processed strip (60) having a protrusion (63) at the center of the lower side of the strip, grooves (62) formed therebetween, and thick portions (61) formed on each side of the grooves (62), by using a lower punch (410) having a protrusion (411) where a groove (412) is formed in the center and a flat upper die (420); and then the processed strip (60) is formed into a multi-gauge strip (70) consisting of thick portions (71) at each end thereof and a thin portion (72) between the thick portions, by using a flat lower die (430) and an upper punch (440) having a protrusion (441) corresponding to the groove (62) of the processed strip (60).
In this method, since the inner protrusion (411) has a wire-like curved shape, the elongation rate in the widthwise direction is higher than that in the lengthwise direction. In the other hand, in the slanted part of the groove, the elongation rate in the widthwise direction is higher that that in the lengthwise direction, as aforementioned. Accordingly, it is possible to form rather wider thin portion in the center of the multi-gauge strip (70). Further, in this example also, rollers can be used, instead of using a die and a cast of a punch and a die.
In the above, the present invention has been described through the preferred embodiments. However, the scope of the present invention is not limited to such specific examples, and can be further modified by an ordinarily skilled person in the art, without departing from the spirit of the present invention by referring to the claims attached hereto.

INDUSTRIAL APPLICABILITY

According to the method of producing multi-gauge strips of the present invention, it is possible to reduce investment cost by being capable of forming a multi-gauge strip with a general low-price equipment; to decrease production cost by using a reduced number of process tools owing to the simplified forming process; to minimize the dust generation, thereby decreasing defective proportion while improving productivity at the same time; and to result in multi-gauge strips in various shapes by allowing formation of a thick portion and a thin portion in optional location of a material. Therefore, the present invention may contribute to the development in industries related to semiconductor parts and electric or electronic parts where such multi-gauge strips are used.

Claims

1. A method of producing multi-gauge strips consisting of a relatively thick portion and a relatively thin portion formed along the widthwise direction while continuously transferring a strip material, characterized by comprising the steps of:

primarily forming a strip material by pressing the upper side thereof so as to make a groove in the lower side of the part where a thin portion is to be formed; and secondly

forming the resulted strip by pressing the upper side of the primarily formed strip so as to form the part having a groove into a thin portion and the other part to a thick portion.

2. The method of producing multi-gauge strips according to claim 1, wherein the groove formed in the primary forming step is in the shape of a trapezoid or curved surface.

3. The method of producing multi-gauge strips according to claim 1, wherein the primary forming step comprises formation of the strip material into a processed strip which has a thick portion formed at the center in the widthwise direction of the strip, and a groove formed in each end of the lower side; and the second forming step comprises formation of the processed strip into a multi-gauge strip consisting of a thick portion in the center and a thin portion at each end of the thick portion.

4. The method of producing multi-gauge strips according to claim 3, wherein the second forming step comprises formation of a W-shaped multi-gauge strip by forming a square-shaped depressed area at the center in the upper part of the thick portion.

5. The method of producing multi-gauge strips according to claim 1, wherein the primary forming step comprises formation of a strip material into a processed strip which has a multiple number of grooves in the lower side thereof and a thick portion between said grooves; and second forming step comprises formation of the processed strip into a multi-gauge strip consisting of a multiple number of thick portions and thin portions therebetween, by forming the grooves in the inner part of the processed strip into a thin portion and then simultaneously forming the grooves at each end part into a thin portion.

6. The method of producing multi-gauge strips according to claim 5, wherein the formation of the grooves in the inner part into a thin portion in the second forming step, is conducted subsequently in order of grooves in the center and outward grooves.

7. The method of producing multi-gauge strips according to claim 1, wherein the primary forming step comprises formation of a strip material into a processed strip having grooves formed in each side of the protrusion at the center of the lower side, and a thick portion formed outside of the grooves; and a second forming step comprises formation of the processed strip into a multi-gauge strip consisting of thick portions at each end thereof and a thin portion between the thick portions.