BACKGROUND ART A lead frame has been conventionally manufactured by an etching process. The conventional etching process for forming a lead frame has limitation in that it should be performed for each lead frame because it employs a method based on metal corrosion. Such a lead frame has been manufactured in such a manner that a photoresist layer deposited with photoresist is formed and exposed to form an exposing portion and an etching process is performed for selective corrosion. The etching process causes corroded material to be necessarily removed and is accompanied with complicated processes such as photoresist and exposure processes. Also, the etching process has limitation in reducing pitch of the lead frame by corrosion. However, the present invention employs an electroforming process that can obtain a fine pitch by forming more precise pattern than a metal pattern obtained by the etching process. In the present invention, since only material required for a lead frame is used in an

electroforming tub, waste of material is avoided. The product of the present invention is formed in a lead frame master by performing an electroforming process in an electroforming tub without etching. This enables that the product can be manufactured simply in comparison with the conventional method undergoing complicated etching process.

For this reason, the production cost of the lead frame and error can be reduced.

The present invention is technically different from the conventional electroforming method in that a lead frame master including an insulating hetero-material having elasticity is used. That is, the present invention is characterized in that an insulating hetero-portion having elasticity is formed. The present invention is also characterized in that a root portion is formed below the insulating hetero-portion so as to fail to easily remove the insulating hetero-portion. The insulating hetero- portion facilitates detachment of the electroformed lead frame and enables repeated use of the lead frame master because it includes the root portion and the pin portion.

There has been a conventional method for forming an electroforming member by performing an electroforming process based on a register deposited on an electrode base and forming a pattern on the register. However, since the register does not have elasticity, the lead frame master cannot be repeatedly used. Also, since the register is simply attached onto the electrode plate, its removal is likely to occur.

In the lead frame master of the present invention, the insulating hetero-portion including silicon having elasticity as a main component is formed on the electrode base and includes the root portion that fails to readily remove the insulating hetero-portion from the master.

DISCLOSURE OF THE INVENTION Accordingly, the present invention is directed to a lead frame and its manufacturing method using electroforming that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide to a lead frame and its manufacturing method using electroforming that can obtain a fine pitch.

The lead frame includes a pattern having fine dimensions. It is general tendency that the pattern of the lead frame becomes sophisticated and its pitch becomes smaller. That is, a precise pattern having pitch of several microns or several tens of microns is required. In the present invention, such a fine pattern can be obtained by performing an electroforming process without corrosion.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the scheme particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a lead frame and its manufacturing method are characterized in that the lead frame is detachably formed on overlapped electrode bases having the same pattern as that of the lead frame by performing an electroforming process in a lead frame master in which the electrode bases are filled with an

insulating hetero-material, the lead frame master including a root portion formed by removing the upper one of the overlapped electrode bases and an insulating hetero-portion of a pin portion formed on the root portion, wherein the electrode bases are exposed in the insulating hetero-portion in a shape of the lead frame. The insulating hetero-portion includes a material having elasticity. An example of the insulating hetero-portion having elasticity includes silicon as a main component.

Silicon has elasticity in addition to excellent insulating and hetero characteristics. Also, metal plate of various materials may be used as the electrode bases. In the present invention, stainless steel is used as the electrode bases considering intensity and surface characteristics.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings: FIGs. 1,2, and 3 illustrate a method for manufacturing an electrode base having the same shape as that of a lead frame; FIGs. 4,5, and 6 illustrate a method for manufacturing an electroforming master that can form a

lead frame by an electroforming process; FIG. 7 illustrates the state that electroforming is implemented by digesting a lead frame master in an electroforming tub; FIG. 8 illustrates the state that a lead frame is filled at the height of an insulating hetero-portion of a pin portion; and FIG. 9 illustrates the state that a lead frame is detached from a lead frame master.

BEST MODE FOR CARRYING OUT THE INVENTION Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

A lead frame master of the present invention includes a base supporting its main body, a root portion formed on the base, an insulating hetero-portion of a pin portion formed on the root portion, and an electrode base formed in the insulating hetero-portion in a shape of a lead frame.

The insulating hetero-portion of the present invention includes a material having elasticity in addition to insulating and hetero characteristics. An example of such an insulating hetero-portion includes silicon as a main component.' FIGs. 1,2, and 3 illustrate a method for manufacturing an electrode base having the same shape as that of a lead frame. A lead frame master of the present invention is manufactured in such a manner that a reverse pattern having a shape opposite to the shape depicted in drawings is used to form an electrode base by an etching process. In the present invention, the pattern of the lead frame is defined as a reverse pattern in which its

transparent and opaque portions are reversed.

As shown in FIG. 1, a photoresist 2 is deposited at a predetermined thickness on an electrode base basic material 1 of plate shaped conductive metal that can facilitate detachment of a lead frame.

In FIG. 2, the photoresist is exposed using a reverse pattern film to form an exposing portion 3. The exposing portion 3 has the same shape as that of the lead frame.

In FIG. 3, an etching space portion is formed by an etching process in the electrode base basic material 1, in which the exposing portion 3 is formed. The electrode base basic material having the etching space portion 5 has the same pattern as that of the lead frame. The electrode base basic material having such a pattern is defined as an electrode base in the present invention. The etching process may be performed simultaneously in lower and upper portions of the electrode base basic material.

FIGs. 4,5, and 6 illustrate a method for manufacturing an electroforming master that can form a lead frame by an electroforming process.

As shown in FIG. 4, two electrode bases are formed and overlapped with each other. The upper electrode base 6 and the lower electrode base 4 may have the same thickness.

However, the thickness of the upper electrode base 6 is adjusted in response to the thickness of a lead frame, which will substantially be manufactured.

In FIG. 5, an insulating elastic material is filled in the overlapped electrode bases and a base is attached to the electrode bases so as to enhance intensity. A plate shaped base portion 9 is formed below the overlapped electrode bases 4 and 6 in a state that it is separated from the lower electrode base at a predetermined distance.

An insulating hetero-material having elasticity is filled between the base portion 9 and the overlapped electrode bases 4 and 6. The insulating hetero-material is then arranged horizontally around the height of the upper electrode base. At this time, the insulating hetero- material portion filled in the etching space portion of the electrode base is defined as an insulating hetero- portion 7 of a pin portion. Also, the insulating hetero- material portion filled between the base portion and the electrode base is defined as a root portion 8.

FIG. 6 illustrates a lead frame master of the present invention. In FIG. 6, the upper electrode base of FIG. 5 is removed. In the lead frame master of the present invention, the root portion 8 is formed on the base portion 9, and the insulating hetero-portion 7 of the pin portion is formed on the root portion 8. The insulating hetero-portion of the pin portion is protruded from the electrode base 4.

FIG. 7 illustrates the state that electroforming is implemented by digesting the lead frame master in an electroforming tub. Once an electroforming process is started in an electroforming tub by connecting a negative electrode (-) to the electrode base 4, ionized metal starts to be coupled with the electrode base 4, so that the lead frame 10 is formed. Conductive metal such as nickel and copper is used as an electroforming metal.

In FIG. 8, the lead frame 10 gradually becomes thick to have the height as high as the hetero-portion of the pin portion.

In FIG. 9, when the lead frame 10 is as high as the hetero-portion of the pin portion, it can be detached from the electroforming master. The lead frame has the same shape as that of the pattern.

In the present invention, the base portion serves to support the lead frame master to have durability. The electrode base and the insulating hetero-portion can be formed of various materials. As an example, stainless steel may be used as the electrode base. Stainless steel has excellent durability and serves to facilitate detachment of the lead frame. In this case, the hetero- material can thinly be deposited for detachment. In the present invention, an example of the insulating hetero- material includes silicon as a main component. If silicon is used as the insulating hetero-material, the hetero- portion of the pin portion is not damaged in spite of detachment of the lead frame because the hetero-portion of the pin portion has elasticity. Also, silicon serves to facilitate detachment of the lead frame. Therefore, the lead frame master provided with the insulating hetero- portion having elasticity can repeatedly be used. There has been a conventional method for forming a lead frame by an electroforming process based on a register. In the conventional method, stress occurs between the register and the electroforming member. The electroforming member affects the register and vice versa. In this case, if detachment of the electroforming member is performed, the electroforming member or the register is to be damaged. If a hardened material is used as the register, it is considered a temporary use or it is difficult for its repeated use even in case of undergoing special processes.

However, since the insulating hetero-portion having elasticity is used in the present invention, the electroforming member can repeatedly be formed without damaging the hetero-portion.

The lead frame master and its manufacturing method of the present invention have been described based on the

depicted pattern and its reverse pattern. Another lead frame master and its manufacturing method will now be described based on the fundamental conception of the present invention. That is, the lead frame master and its manufacturing method will be described using the existing product. In case of the existing product, the electrode base is not formed by the etching process using a reverse film pattern. That is, two lead frames are overlapped with each other and they are filled with the insulating hetero- material. Then, the same processes as described above are performed. In this case, material that is not suitable for detachment of the lead frame is likely to be used as the electrode base. Therefore, there is inconvenience in that the hetero-material should be deposited on the electrode base.

INDUSTRIAL APPLICABILITY The present invention is characterized in that the lead frame is manufactured by the electroforming process that can obtain more precise lead frame pattern than a metal pattern obtained by metal corrosion based on the conventional etching process. Unlike the etching process, waste of material is avoided in the present invention. If the insulating hetero-portion of the pin portion is damaged, the damaged portion can be repaired for its reuse.

The product of the present invention is manufactured by performing the electroforming process in the electroforming tub without undergoing etching and exposing processes. Therefore, a precise product can be obtained by more simple process than the conventional process.

While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled

in the art that. various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.