Printing – Stenciling – Traveling-inker machines
Patent
1998-11-06
2000-08-22
Funk, Stephen R.
Printing
Stenciling
Traveling-inker machines
101129, B41F 1546
Patent
active
06105495&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a screen printing apparatus and method for executing screen printing by applying printing paste such as cream solder to a circuit board such as a printed circuit board on which an electronic circuit is formed, through a screen having opening holes formed in a printed pattern.
BACKGROUND ART
In recent years, screen printing apparatuses and methods have been used for a cream solder printing process in a circuit mounting process for electronic components. The reduced size and weight of electronics and their improved functions, however, further urge the reduction of the size of electronic-components-mounted circuit boards and the improvement of their accuracy, thereby requiring very accurate printing. Thus, the use of both contact printing and snap-off-speed-controlled printing has become popular.
Contact printing eliminates the gap between a screen and a circuit board in order to minimize the distortion of the screen due to the gap. Snap-off-speed-controlled printing controls the snap-off speed to a low value (in recent years, a common value has been 1 mm/sec.) in order to stabilize printed that is, to minimize the disruption of printed shapes occurring when the screen is pulled due to the viscosity and adhesion of cream solder filled in the opening holes in the screen when the screen is released from the circuit board. Furthermore, in recent years, low-pressure printing is gathering the industry's attention and various attempts are being made to improve this technique. This printing method minimizes the spreading of cream solder to the rear surface of the screen caused by an unnecessarily high printing pressure (a pressure effected when squeegees press the screen) and misalignment caused when the squeegees pull the screen during printing.
An example of low-pressure printing is the screen printing apparatus described in Japanese Patent Application Laid-Open No. 7-205397.
An example of low-pressure printing in a conventional screen printing apparatus and method is generally described below with reference to the drawings.
FIG. 9 shows a schematic front view generally describing a low-pressure printing head section in a general conventional screen printing apparatus and method and also schematically shows a circuit diagram of part of a pneumatic circuit in the low-pressure printing head section.
In FIG. 9, 1 is a squeegee, 2 is a squeegee holder for gripping and holding the squeegee 1, 3 is a holder for holding the squeegee holder 2, 4 is an air cylinder for both rods that elevatorily drives the squeegee 1, 5 is an elevating guide used to elevatorily drive the squeegee 1, 6 is a slide bearing for the elevating guide 5, 7 is an upper piston rod of the air cylinder 4, 8 is a stopper for adjusting the elevating stroke of the air cylinder 4, 9 is a lower piston rod of the air cylinder 4, 10 is a base block secured to the tip of the lower piston rod 9, and 11 is a rotation-supporting shaft secured to the base block 10.
The holder 3 is fitted on the base block 10 in such a manner that it can be rotationally oscillated using the rotation-supporting shaft 11.
Reference numeral 12 designates a micrometer head secured to the base block 10 wherein the amount of the protrusion of its tip can be adjusted so that the tip abuts the holder 3. Reference numeral 13 denotes a spring mounted between the base block 10 and the holder 3, and the micrometer head 12 and the spring 13 are located at approximately symmetrical positions about the rotation-supporting shaft 11. Reference numeral 14 indicates a clamp lever that fixes the rotational oscillation of the holder 3.
Reference numeral 15 designates a manual regulator that transmits to a lower port 16 in the air cylinder 4 the pressure of air passing the regulator 15 when the squeegee 1 is elevated. The air pressure must be manually adjusted in advance using the manual regulator 15 so as to account for the weight of the squeegee 1 and associated components operating in response to the squeegee 1 as well as the resistance effected d
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Mitsushiro Koji
Naito Takao
Onishi Hiroaki
Sato Syoji
Takahashi Ken
Funk Stephen R.
Matsushita Electric - Industrial Co., Ltd.
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