JPH06252149A - Composite film for bump formation and forming method for transfer bump based thereon - Google Patents

Abstract

PURPOSE:To provide a recyclable composite film for bump formation with which bumps for connection or contact are accurately and easily formed on semiconductor elements, electric and electronic components and electric circuits, and a method for forming transfer bumps based on such a film. CONSTITUTION:Metallic bodies 3 for bump are attached to an insulating film 1 based on polyimide resin by plating filling; the metallic bodies 3 penetrate the film and are removable therefrom. On one side of the film the metallic bodies 3 are projected; on the other side a thermoplastic resin layer 2 is formed. After the metallic bodies 3 have been removed, forming a conductive layer on the thermoplastic resin layer 2 makes it is possible to fill new metallic bodies by plating. This makes the film recyclable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump forming composite which can easily form bumps used for connecting and mounting various parts such as semiconductor devices, printers, recording devices, display devices, electric parts and electric circuits. The present invention relates to a film and a transfer bump forming method using the film.

[0002]

2. Description of the Related Art With the development of the semiconductor industry in recent years, electronic devices have become thinner, smaller and lighter, and in devices and equipment that use a lot of semiconductor devices, semiconductor elements are densely mounted on a substrate of a fixed area. Is desired. In the technical field of semiconductor mounting, metal projections (bumps) are formed on a semiconductor element directly or by transfer to form connection terminals, which are used for mounting. The method of forming such bumps can be applied to various electric and electronic components other than semiconductor elements, which leads to improvement in mounting density in electronic devices.

However, it is generally difficult to directly form bumps on a semiconductor element and many other electronic components from the viewpoint of manufacturing technology (formation technology), which causes a reduction in manufacturing yield. On the other hand, although a so-called transfer bump forming method of forming bumps by a transfer method has been proposed, the method of forming bumps on ITO glass, which is currently being performed, has a manufacturing cost, a manufacturing method, a bump transfer method, and the like. There are various restrictions, and they are not yet satisfactory in terms of practical application.

Therefore, the inventors of the present invention proposed a practical transfer bump forming method in Japanese Patent Application No. 4-87942, which is a composite film in which a bump metal body is detachably held in an insulating film. However, since it is necessary to process the insulating film into a special shape, it cannot be said to be sufficient in terms of mass production.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of various problems in the conventional bump forming technique described above, and is highly accurate and easy for semiconductor elements, electric / electronic parts, electric circuits and the like. It is an object of the present invention to provide a film capable of forming a bump used for connection and contact and reusing a film after use, and a transfer bump forming method using this film.

[0006]

The inventors of the present invention have made extensive studies in order to achieve the above object, and as a result, penetrated the bump metal body in the thickness direction in the insulating film in a detachable state. It was found that the thermoplastic resin layer can be reused by forming a thermoplastic resin layer on one side so that the metal body can be refilled in the film after the bump transfer, and the above object can be achieved, thus completing the present invention. Came to do.

That is, according to the present invention, the bump metal body is held in a detachable manner so as to penetrate the front and back surfaces of the insulating film and project from at least one surface of the insulating film, and the other of the insulating films. The present invention provides a composite film for bump formation, which is characterized in that a thermoplastic resin layer is formed on its surface.

Further, according to the present invention, after the protruding portion of the metal body in the composite film for forming bumps is bonded onto the semiconductor element, the electric circuit, or the electric circuit component, the metal film is transferred to the bonding portion of the insulating film. And a method for forming a transfer bump, which comprises removing a composite film comprising a thermoplastic resin layer.

[0009]

EXAMPLES Examples of the bump forming composite film of the present invention and a transfer bump forming method using the same will be described below with reference to the drawings.

FIG. 1 is an enlarged cross-sectional view showing a state where the composite film for bump formation of the present invention is brought into contact with an electrode portion on an external substrate as an adherend, and FIG. 2 is for melting a bump metal body. FIG. 6 is an enlarged cross-sectional view showing a state in which bumps are formed by transferring to an electrode portion on an external circuit by.

As is apparent from FIG. 1, the composite film for bump formation of the present invention penetrates through the front and back surfaces of the insulating film 1 and is made of solder, gold, silver, copper, nickel, tin, lead, indium, or these. Metal body 3 for bumps made of alloys of
Are held, and the metal body 3 projects to one surface (lower side in the figure). Further, since the metal body 3 needs to be held in a detachable state, it is preferable that the metal body 3 has a taper as shown in the figure. Usually, the degree of taper depends on the thickness direction of the insulating film 1. Metal body 3
The angle with the taper direction is less than 20 degrees, preferably 5
It is about 15 degrees. Although the protruding shape of the bump metal body 3 is not particularly limited, it is possible to prevent the metal body 3 from dropping off before use, and to securely bond and transfer to an electric circuit or an electric circuit component or a semiconductor element as an adherend. In order to do so, it is preferable to have a mushroom shape as shown in the figure, and usually 1
It is formed to have a height of about 000 μm or less.

Further, although FIG. 2 shows a state in which the bump metal body 3 is separated from the insulating film 1 by heat fusion and transferred, solder or tin, or the like can be used as such a heat-meltable metal body. It is preferable to use a metal having a melting point of 450 ° C. or lower, such as lead or indium. In addition, in the present invention, the metal body 3 is not limited to the one in which the substantially spherical bumps 13 are formed by heat melting as shown in FIG. A melting point metal body may be used. In this case, a metal layer such as solder that easily heats and melts is formed on the surface of the electrode portion 4, and the electrode portion 4 and the bump metal body 3 are heat-bonded. After that, the insulating film 1 is forcibly peeled off by utilizing the difference in the coefficient of thermal expansion, the metal body 3 is separated and transferred, and the bump 1
3 can be formed.

In the present invention, the thermoplastic resin layer 2 is formed on the other surface of the insulating film 1, that is, on the side opposite to the protruding side of the bump metal body 3. The resin layer 2 is separated from the metal body 3 of the composite film of the present invention and transferred, and then thermally bonded to a conductive layer such as a metal foil by utilizing the thermal adhesive property of the resin layer 2 and electrolytically plated. The metal body can be filled in the insulating film again, and plays an important role in terms of reusability.

The insulating film 1 used in the present invention may be one having an electrical insulating property and also having an appropriate flexibility. Specifically, polyester resin,
Used regardless of thermosetting resin or thermoplastic resin such as epoxy resin, urethane resin, polystyrene resin, polyethylene resin, polyamide resin, polyimide resin, ABS resin, polycarbonate resin, silicone resin, fluorine resin be able to. Among these resins, a resin having transparency is preferable from the viewpoint of ease of alignment during transfer bump formation, and among them, a polyimide resin that exhibits excellent heat resistance and mechanical strength is used. Is preferred. Furthermore, the thickness of the insulating film 1 can be arbitrarily selected according to the amount (volume) of metal to be transferred and formed, but from the viewpoint of balance between mechanical strength and flexibility, it is usually about 5 to 500 μm. desirable.

On the other hand, the thermoplastic resin layer 2 formed on the other surface of the insulating film 1 has an electric insulating property and, as described above, exhibits plasticity by heating and exhibits thermal adhesiveness. A film having a melting temperature lower than that of the insulating film 1 is adopted. Specifically, polyester resin, urethane resin, polystyrene resin, polyethylene resin, polyamide resin, polyimide resin,
Examples thereof include ABS resin, polycarbonate resin, silicone resin, and fluorine resin. Among these resins, it is preferable to use a polyimide-based thermoplastic resin from the viewpoints of transparency, heat resistance, mechanical strength, etc., as in the case of the insulating film 1. Further, the thickness of these thermoplastic resin layers 2 is 1/2 of the diameter of the bump metal body 3 held in the insulating film 1 in view of the balance between the development of thermal adhesiveness and flexibility.
˜1 / 1000, preferably about 1/10 to 1/20.

FIG. 3 is an enlarged sectional view showing another embodiment of the bump forming composite film of the present invention.

In FIG. 3, the bump metal body 3 is held in a composite film obtained by heat-bonding two laminated films of an insulating film 1 and a thermoplastic resin layer 2. As described above, since the composite film of the present invention has the thermoplastic resin layer 2 formed on one surface thereof, a plurality of films can be laminated via the resin layer 2. Therefore, the amount (volume) of the metal body 3 to be held and the height of the bump 13 to be transferred and formed can be adjusted.

FIG. 4 is a sectional view showing each manufacturing step for obtaining the composite film for bump formation of the present invention.

First, as shown in FIG. 4 (A), a laminated film comprising an insulating film 1 and a thermoplastic resin layer 2 is prepared. The laminating method is not particularly limited, and any method such as a thermocompression bonding method, a coating laminating method, and a melt extrusion method can be used.

Next, a through hole of a desired size is formed at a predetermined position as shown in FIG. 4B by mechanical processing, laser processing, optical processing, chemical etching, or the like. The method of forming the through hole is arbitrary depending on the shape and size of the hole, but since it is simply forming the through hole, it is an NC drill (numerical control drill) that is a relatively inexpensive processing method that is generally used. ) It is advantageous that mechanical processing methods such as processing can be used.

Thereafter, as shown in FIG. 4C, a conductive layer 6 such as a copper foil or a copper plate is formed on the thermoplastic resin layer 2 side by thermocompression bonding, and the conductive layer 6 is used as a cathode for electrolytic plating. Then, a desired metal is plated and filled in the formed through hole to form the bump metal body 3. The electrolytic plating process is performed until the filled metal projects from the surface of the insulating film 1. When the cross section of the metal body 3 to be filled is circular,
In order to eliminate the variation in the protrusion height when a plurality of metal bodies are filled, it is preferable that the protrusion height is about 5 times the cross-sectional area. Since the conductive layer 6 is removed by etching in the next step, it is preferable to use a metal whose solubility in the etching liquid is different from the type of the metal body to be filled.

Finally, the conductive layer 6 is removed by a known etching process to obtain the bump-forming composite film of the present invention as shown in FIG. 4 (D). After that, alignment holes and jig holes for alignment can be provided by mechanical processing, laser processing, optical processing, chemical etching processing, or the like.

The composite film for forming bumps of the present invention has the above-mentioned structure. After the protruding portion of the bump metal body 3 is joined to the adherend as shown in FIG. 1, the metal body as shown in FIG. 3 is transferred to the adherend to form bumps 13. The composite film after the transfer of the bumps 13 is in the state shown in FIG. 4 (B).
By recycling in the step shown in (D), the metal body 3 can be refilled and held in the insulating film 1 and the thermoplastic resin layer 2, and thus can be reused.

[0024]

As described above, since the bump-forming composite film of the present invention holds the metal body for bumps in a desired size in a detachable manner, it can be accurately applied to high-density electric parts and electric circuits. Moreover, the bumps can be easily transferred and formed. Therefore, as compared with the conventional bump connector method in which bump electrodes are formed and connected to the semiconductor device itself, the manufacturing efficiency of the semiconductor device and the like is improved, and the product yield and productivity are improved.

Further, since the thermoplastic resin layer is formed on one surface, a conductive layer such as a copper foil is thermally adhered to the film even after the bump metal body is transferred to the adherend, and the metal body is subjected to electrolytic plating or the like. It can be refilled by means. Therefore, the film can be recycled, is economical, and can be mass-produced.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing a state in which a bump-forming composite film of the present invention is brought into contact with an electrode portion on an external substrate as an adherend.

FIG. 2 is an enlarged cross-sectional view showing a state where transfer bumps are formed on an adherend using the composite film shown in FIG.

FIG. 3 is an enlarged cross-sectional view showing another embodiment of the bump-forming composite film of the present invention.

4 (A) to (D) are cross-sectional views showing respective manufacturing steps for obtaining the bump-forming composite film of the present invention.

[Explanation of symbols]

 1 Insulating Film 2 Thermoplastic Resin Layer 3 Metal Body for Bump 4 Electrode Section 5 External Circuit 6 Conductive Layer 13 Bump

Claims (2)

[Claims] 1. A metal body for bumps is detachably held so as to penetrate the front and back surfaces of an insulating film and project from at least one surface of the insulating film, and the bump metal body is held on the other surface of the insulating film. Is a composite film for bump formation, wherein a thermoplastic resin layer is formed. 2. A semiconductor element, an electric circuit, or an electric circuit component is joined to the bump forming composite film according to claim 1 after the protruding portion of the metal body is bonded, and then the metal body is transferred to the bonding portion for insulation. A method of forming a transfer bump, which comprises removing a composite film comprising a film and a thermoplastic resin layer.