Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-10-14
2002-08-13
Tsai, Jey (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S616000, C438S689000, C438S690000, C438S691000, C438S734000, C438S963000, C219S216000, C219S216000, C219S216000, C219S216000, C219S216000
Reexamination Certificate
active
06432806
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming bumps used for forming conductive bumps in electronic parts. Also, the present invention relates to a template used in the bump forming method and a method of manufacturing the template.
2. Description of the Related Art
A method of forming metallic bumps such as solder bumps on an electronic part such as an LSI and joining the electronic part to a printed circuit board by the metallic bumps has come into wide use. In one method of forming the metallic bumps, metallic balls are previously formed and stored in a metallic ball container, and then the metallic balls are taken out from the metallic ball container and attached to the electrodes of the electronic part so that the metallic balls can be used as metallic bumps of the electronic part. For example, Japanese Unexamined Patent publication No. 8-112671 discloses the above-described metallic bump forming apparatus.
In the conventional metallic bump forming apparatus, a suction head is used to take out the metallic balls from the metallic ball container and attach them to the electrodes of electronic part. A template (suction pad) for mounting metallic balls is attached to the suction head, the template having through-holes arranged in the same arrangement as that of the electrodes of the electronic part. Suction grooves are provided in the surface of the sucking head and connected to a vacuum source, and the through-holes of the template for mounting metallic balls are connected to the suction grooves of the suction head, so that the metallic balls can be attracted by vacuum suction.
When the template for mounting metallic balls comes into contact with the metallic balls accommodated in the metallic ball container, the metallic balls are respectively sucked by and attracted to the through-holes in the template. When the suction head is then moved above the electronic part, the metallic balls attracted to the through-holes in the template are respectively located on the electrodes of the electronic part. Then, the metallic balls are joined to the electrodes of the electronic part under heat and pressure, the metallic balls becoming the metallic bumps. After that, the suction head is separated from the electronic part, with the result that the metallic balls are transferred from the suction head to the electronic part.
The template for mounting metallic balls is usually made of inorganic material such as glass, which is resistant to distortion, and its charging level is low. Plastics are not suitable for the material for the template for mounting metallic balls, because plastics are easily distorted, and their charging level is high. If the template for mounting metallic balls is made of a plate which is easily distorted, the template is distorted and the positions of the through-holes are shifted from the positions of the electrodes of the electronic parts, when the metallic balls are bonded to the electrodes of the electronic part under heat and pressure by means of thermo-compression. When the template for mounting metallic balls has an electrification property, the metallic balls are attracted to the template at positions other than those of the through-holes by static electricity when the template is moved above and then into the metallic ball container to suck the metallic balls to the through-holes.
Through-holes in the template for mounting metallic balls are formed by etching. Alternatively, the through-holes can be formed by machining such as drilling or electric discharge machining. However, when the template for mounting metallic balls is made of inorganic material such as glass, the side walls of the through-holes become unsmooth, and there is a possibility of generation of burrs which is an irregularity of the side walls of the through-holes.
If the side walls of the through-holes are not smooth, the following problems may be caused. The metallic balls bite into the end portions of the through-holes in the template for mounting metallic balls when the template is pressed against the electronic part to join the metallic balls to the electrodes of the electronic part, and the metallic balls adhere to the template and the metallic balls are torn off from the electrodes of the electronic part, when the suction head is separated from the electronic part.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a. method of forming bumps, a template for mounting metallic balls capable of reliably joining the metallic balls to the electrode pads of an electronic part and a method of manufacturing the template.
A method of forming bumps onto a chip having electrodes, according to the present invention, comprises the steps of using a template having through-holes with smoothed side walls formed corresponding to the electrodes of the chip, to attract conductive balls to be formed into bumps by vacuum suction, positioning the conductive balls attracted by the template to the electrodes, pressing the conductive balls against the electrodes by the template, and releasing vacuum suction.
A method of manufacturing a template, according to the present invention comprises the steps of: forming through-holes in a plate for attracting and supporting conductive balls thereat, and smoothing the side walls of the through-holes formed in the through-hole forming step.
Preferably, the through-holes are formed by etching the template. Preferably, the side walls are smoothed by irradiating the template with laser beams. Also, preferably, the step of irradiating the template with laser beams comprising irradiating the side walls of the through-holes with laser beams via a mask having openings, the size of which is a little larger than the diameter of each through-hole.
A template, according to the present invention comprises through-holes for attracting and supporting conductive balls by vacuum suction, the through-holes having smoothed side walls.
In this structure, the side walls of the through-holes in the template are smoothed by irradiating the side walls with laser beams. Accordingly, the conductive balls do not bite into the end portions of the through-holes in the template, and, when the suction head is separated from the electronic part after the conductive balls have been joined to the electrode pads of the electronic part, the, conductive balls are surely separated from the template and the conductive balls are reliably joined to the electrode pads of the electronic part.
Further, the present invention provides a template comprising an inorganic material layer and an organic material layer laminated on each other, said template having through-holes formed through the inorganic and the organic material layer for attracting and supporting conductive balls.
In this structure, the inorganic material layer gives a sufficiently high mechanical strength to the template to resist distortion. The through-holes are provided through the inorganic and the organic layer, and the portion of the through-holes in the organic material layer can be more smoothly formed than the portion of the through-holes on the inorganic material layer. The conductive balls are sucked and attracted by the portion of the through-holes formed in the organic material layer. Accordingly, the conductive balls do not bite into the end portions of the through-holes in the template, and, when the suction head is separated from the electronic part after the conductive balls have been joined to the electrode pads of the electronic part, the conductive balls are surely separated from the template and the conductive balls are reliably joined to the electrode pads of the electronic part.
Further, the present invention provides a template comprising an air permeable material layer and a resin layer laminated on each other, said template having through-holes formed through the resin layer.
The air permeable material layer allows communication between the suction groove of the suction head and the through-holes in the resin layer, and the through-holes
Kitajima Masayuki
Muraoka Yoshitaka
Noda Yutaka
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Zarneke David A.
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