Electric heating – Metal heating – By arc
Reexamination Certificate
1999-01-14
2001-11-20
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121710, C219S121740
Reexamination Certificate
active
06320158
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 on electronic parts. Also, the present invention relates to a method and an apparatus of fabricating a perforated plate which can be used as a 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 are 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 are irregularities 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 onto a chip having electrodes, by which metallic balls can be reliably joined to the electrodes of the semiconductor chip.
Another object of the present invention is to provide a method and an apparatus of fabricating a perforated plate, which can be used as a template for forming metal bumps on the electrodes of the semiconductor chip.
A method of forming bumps onto a chip having electrodes, according to one aspect of the present invention, comprises the steps of: using a template having through-holes formed by a laser, said through-holes being arranged corresponding to the positions of the electrodes of the chip, to attract conductive balls to be formed into bumps to the template at the through-holes by vacuum suction; positioning the conductive balls attracted by the template to the electrodes; pressing the conductive balls against electrodes by the template; and releasing vacuum suction.
A method of fabricating a perforated plate, according to another aspect of the present invention, comprises the steps of: supporting a plate to be processed and including an inorganic material layer on a support table having at least one cavity; and irradiating the plate to be processed with laser beams at the position of said at least one cavity to form a through-hole.
Preferably, the plate to be processed is a glass plate. Preferably, the perforated plate is a template for forming metal bumps on the electrodes of the semiconductor chip.
Preferably, the laser beam is irradiated onto one side of the plate to be processed, the plate to be processed is then reversed, and the laser beam is irradiated onto the other side of the plate to be processed.
Preferably, the perforated plate has a mark such as a letter or a figure.
An apparatus of fabricating a perforated plate, according to another aspect of the present invention, comprises a support table having a surface on which a plate to be processed can be supported, and at least one cavity; and a laser irradiating means for irradiating a laser beam to the plate to be processed at the position of said at least one cavity to form a through-hole.
Preferably, the perforated plate is a template for forming metal bumps on the electrodes of the semiconductor chip.
Preferably, the laser irradiating means is one of an excimer laser and a harmonic YAG laser.
Preferably, the apparatus further comprises a material having a greater transmittance to the laser than that of the plate to be processed arranged in said at least one cavity.
REFERENCES:
patent: 4027137 (1977-05-01), Liedtke
patent: 4923608 (1990-05-01), Flottmann et al.
patent: 5861323 (1999-01-01), Hayes
patent: 2271308 (1994-04-01), None
patent: 2236973 (1991-04-01), None
patent: 62-25435 (1987-02-01), None
patent: 64-45150 (1989-02-01), None
patent: 64-73625 (1989-03-01), None
patent: 2-30390 (1990-01-01), None
patent: 2-182390 (1990-07-01), None
patent: 4-69945 (1992-03-01), None
patent: 4-65130 (1992-03-01), None
patent: 5-129374 (1993-05-01), None
patent: 5-299424 (1993-11-01), None
patent: 8-18209 (1996-01-01), None
patent: 8-67522 (1996-03-01), None
patent: 8-118005 (1996-05-01), None
patent: 8-112671 (1996-05-01), None
patent: 8-141765 (1996-06-01), None
patent: 9-64048 (1997-03-01), None
patent: 9-270429 (1997-10-01), None
patent: 9-298355 (1997-11-01), None
patent: 9-298356 (1997-11-01), None
patent: 63-154282 (1988-06-01), None
Office Action of Japanese Patent Appln. No. 10-110869 dated Jan. 5, 1999 with translation.
Kitajima Masayuki
Muraoka Yoshitaka
Noda Yutaka
Tokura Fumihiko
Armstrong Westerman Hattori McLeland & Naughton LLP
Evans Geoffrey S.
Fujitsu Limited
LandOfFree
Method and apparatus of fabricating perforated plate does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus of fabricating perforated plate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus of fabricating perforated plate will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2593990