Method and apparatus for screen printing

A screen printing method in which screen printing is effected on a board by using a mask after the position of the board has been adjusted by an image processor and an XY.theta. table to such an extent that the deviation of a recognition mark on the board from a reference point of the mask falls within a predetermined allowance range, said method comprising the steps of:

• placing the board on a board support of transportation means which includes said board support for attracting and supporting the board, a transportation table for attracting and supporting said board support and means for transporting said transportation table with a desired accuracy;
• conveying, by said transportation means, the board to a positioning station provided with said image processor, camera means, means for clamping said board support and being moveable in the vertical direction and said XY.theta. table on which said clamping means is mounted;
• at said positioning station, cancelling the attraction of said board support to said transportation table while clamping said board support by said clamping means;
• positioning the board by reading the recognition mark of the board by said camera means and by moving said XY.theta. table under the command by said image processor;
• after positioning, releasing said board support from the clamped state and attracting said board support to said transportation table to enable said board support to be transported by said table while maintaining the board in the positioned state;
• and
• conveying the board to said printing station in which screen printing is effected on the board while the distance between the mask and the board in the vertical direction alone is being adjusted to a predetermined value and while the positioned state of the board is maintained.

A screen printing apparatus comprising:

• transportation means for successively transporting a plurality of boards to be printed from a positioning station where each board is positioned to a printing station where printing is performed;
• a board support for attracting and supporting each board, said board support being attracted to and supported on said transportation means;
• means operative to attract successive board supports to said transportation means and to cancel the attraction;
• an actuator for operating said operative means at said positioning station to cancel the attraction of said board support to said transportation means;
• and
• image processor means and XY.theta. table means operative to move each board support in said positioning station to adjust a recognition mark on a board on the board support to a printing reference point;
• and
• said operative means again attracting and supporting the board support on said transportation means to enable said transportation means to transport the thus positioned board to said printing station while maintaining the board in the positioned state.

A screen printing apparatus in which a circular index table on which a board is placed is intermittently rotated so as to transport the board from a positioning station where the board is positioned by an image processor and an XY.theta. table to a printing station where screen printing is effected on the board so that elements of an electronic circuit are printed on the board at predetermined positions, said apparatus comprising:

• a board support for supporting the board in attracted state, said board support being attracted to and supported on said index table;
• means mounted on said index table and operative to attract and support said board support to and on said index table and to cancel the attraction;
• an actuator for operating said operative means at said positioning station to cancel the attraction of said board support to said index table;
• a support means disposed in said positioning station and operative to support said board support when said board support is released from the attraction to said index table;
• image processor means and XY.theta. table means disposed in said positioning station and being operative to move said support means relative to said index table so as to adjust a recognition mark on a board on said board support to a printing reference point;
• and
• said support means releasing said board support onto said index table and said operative means attracting and supporting said board support to and on said index table again so that the positioned board is conveyed to said printing station by said index table while the board is kept in the positioned state.

A screen printing apparatus in which screen printing is effected on a board by a mask after the board has been positioned by an image processor and an XY.theta. table such that the offset of a recognition mark on the board from a reference point of the mask falls within a predetermined allowance range, said apparatus comprising:

• transportation means including a board support on which the board is supported and attracted thereto, a transportation table on which said board support is supported and attracted thereto, a vacuum source with operating valve means for performing attracting operations, and means for guiding said transportation table with a desired accuracy;
• a supply/discharge station where an unprinted board is supplied to said transportation means while a printed board is discharged from said transportation means;
• a positioning station provided with an image processor and camera means disposed above a transportation surface of said transportation means, attraction means movable in the vertical direction and operative to attract and support a lower portion of said board support, and an XY.theta. table, said attraction means and said an XY.theta. table being disposed below said transportation surface at a position opposite to that of said camera means;
• and
• a printing station provided with a screen printing mechanism including a vertically movable means capable of positioning the mask at a predetermined distance to the board transported to and placed in said printing station.

A screen printing method in which a plurality of boards to be printed are successively transported by transportation means from a positioning station where positioning of each board is effected to a printing station where each board is printed, said method comprising the steps of:

• transporting each board to said positioning station while the board is fixed to said transportation means;
• at said positioning station, releasing fixation of the board to said transportation means and positioning the board relative to said transportation means to assure that the board is positioned in the correct printing position;
• again fixing the thus positioned board to said transportation means while the board is kept in the positioned state;
• transporting the fixed board to said printing station by said transportation means;
• and
• performing a screen printing on the board in the positioned state at said printing station.

A screen printing apparatus in which a plurality of boards to be printed are successively transported by transportation means from a positioning station where positioning of each board is effected to a printing station where each board is printed, said apparatus comprising:

• means for fixing each board to said transportation means;
• means for releasing fixation of the board to said transportation means at said positioning station;
• means provided in said positioning station to position, relative to said transportation means, the thus released board to assure that the board is positioned in the correct printing position;
• and
• means for again fixing the thus positioned board to said transportation means while the board is kept in the positioned state;
• the thus positioned board being transported by said transportation means to said printing station to effect a screen printing on the board.