Automatic apparatus and method for exposing, registering, and handling double-sided printed circuit boards

Apparatus for effecting precise positioning of a circuit board preparatory to exposure thereof, said circuit board having three slots therethrough, one of said slots extending in one direction, two of said slots extending in directions perpendicular to said one direction, each of said slots having generally parallel side walls, said apparatus comprising:

• (a) three positioning elements each having a portion adapted to be inserted into one of said slots,
• each such portion being noncircular in the plane at said board, each such portion being so shaped and sufficiently small, in the plane of said board, that when said positioning elements are in predetermined rotated positions about axes transverse to said board, said portions may be inserted freely into said respective slots, and when thus inserted will be relatively loose and non-binding in said respective slots, but will not be sufficiently loose that said portions may rotate more than a partial revolution about said axes,
• each such portion having two regions on opposite sides of its associated one of said axes,
• said regions being so shaped and positioned that when said positioning elements are rotated about said axes through angles as large as are permitted by the walls of said slots, said regions will engage and move said walls, and said board will be in a known position relative to said axes, and
• (b) means to effect said rotations of said elements about said axes through angles as large as are permitted by said walls of said slots.

In a system for exposing and handling double-sided printed circuit boards, apparatus for effecting highly precise positioning of such boards before each exposure, said apparatus comprising:

• (a) three slots formed in each board in predetermined positions, two of such slots being parallel to each other, one of such slots being perpendicular to said parallel slots, each slot having parallel walls,
• (b) three accurately-positioned locaters respectively adapted to be inserted into said slots,
• each locater being noncircular, and being cross-sectionally sized and shaped to be loosely received in an associated slot when said locaters are in predetermined rotated positions about the axes of said locaters,
• said axes being perpendicular to said board, each locater also being so cross-sectionally sized and shaped that the locater may not rotate more than a partial revolution about its axis, further rotation being prevented by engagement of two wall-engagement portions of the locater with opposed walls of the slot,
• said two wall engagement portions of each locater being disposed equal distances on opposite sides of a first plane containing the locater axis, and also being disposed equal distances on opposite sides of a second plane containing the locater axis, said second plane being perpendicular to said first plane,
• (c) means to shift said locaters in their axial directions and into said respective slots when said locaters are in said predetermined rotated positions, and
• (d) means to rotate said locaters about their respective axes to cause said two wall-engagement portions of each locater to engage regions of the opposite walls of the associated slot, said rotation means effecting locater rotation as far as permitted by said slot walls, and thus effecting accurate positioning of said circuit board relative to the axes of said locaters regardless of tolerance variations in the widths of said slots.

In a method of exposing and handling double-sided printed circuit boards of the type having non-parallel slots therein adapted to receive positioning elements, the steps of accurately positioning said circuit boards at exposure stations without enlarging said slots, without having the accuracy of the positioning diminished because of tolerance variations in the widths of said slots, and without effecting any scuffing of the surfaces of said circuit boards, said method comprising:

• (a) effecting air-floating of each circuit board at a position at which the slots thereof are above positioning-element locations,
• (b) effecting, while said floating of said board is continued, upward movement of positioning elements that are noncircular and fit loosely into said slots when said positioning elements are in predetermined rotated positions about their axes,
• (c) effecting rotation of said elements about their axes, as far as permitted by the walls of said slots, to cause binding of slot wall-engaging regions of said elements relative to the walls of their associated slots and thus cause accurate positioning of said board,
• (d) discontinuing said air-floating action,
• (e) drawing a vacuum beneath said board to suck said board down onto an exposure stage, and then
• (f) unrotating said elements and lowering them out of said slots.