Screen printing method and apparatus therefor

A screen printing apparatus including a stage (3) by which a circuit board (1) is supported, moved, and positioned, driving means (9, 10, 11) for driving the stage (3) in an X, Y, and .theta. directions, a screen plate (4) to which the circuit board (1) that has been positioned is contacted, and a squeeze (13, 14) which is moved on the screen plate (4) in direct contact therewith for printing a pattern of printing paste (12) on the circuit board (1) that has been positioned, characterized by having:

• an imaging means (6) by which positions of board recognition marks (2, 2) on the circuit board (1) and positions of screen recognition marks (5, 5) on the screen plate (4) are recognized as well as positions of an aperture pattern (18) in the screen plate (4) and positions of a land pattern (19) in a specific portion of the circuit board (1) through the aperture pattern (18) in a state where the circuit board (1) is closely contacted with the screen plate (4) are recognized;
• an image processing unit (16) by which an amount of movement of the stage (3) in the X, Y, and .theta. directions required for making the positions of both recognition marks (2, 2, 5, 5) in register with each other is calculated, as well as an amount of movement of the stage (3) for positional correction required for making the positions of the aperture pattern (18) and the land pattern (19) is calculated based on the positions of the aperture pattern (18) and the land pattern (19) recognized through the aperture pattern (18);
• and a control unit (17) for controlling the driving means (9, 10, 11) on the basis of the calculated amount of movement of the stage (3) in the X, Y, and .theta. directions and the amount of movement:
• for positional correction so as to position the circuit board (1) in relation to the screen plate (4) such that the aperture pattern (18) corresponds to the land pattern (19).

In a circuit board screen printing system wherein indicia on a circuit board substrate and on a screen plate are recognized automatically and used to move the screen plate relative to the circuit board substrate for alignment prior to apply a pattern onto the circuit board substrate, the improvement comprising:

• imaging means for recognizing the position of an aperture on the screen plate and the position of a land pattern on the circuit board substrate;
• control unit means for calculating any discrepancy in alignment between the recognized aperture and the recognized position of a land pattern that corresponds to the aperture;
• and
• driving means for providing a relative movement of the screen plate and the circuit board substrate to minimize any discrepancy prior to enabling an application of a pattern onto the circuit board substrate.