There is a huge industry developed around the demand to drill multiple, spaced holes (through or non-through) in substrates such as electronic wafers, thin film electronics, organic packaging substrates, glass, silicon wafers, sapphires or the like. These holes or patterned drillings may be used for electrical connections, filtration, cytology, bioassays, chemotaxis, or particle monitoring and have diameters that commonly lie in the micron range. Not only must the holes be identical to each other in diameter but also must be placed at precise locations and with the right geometry with respect to the substrate or adjacent holes.
Generally, such drilling machines see movement in all three axes simultaneously although this can be accomplished in different ways. Generally, the substrate is positionally moved in the horizontal X axis beneath a drill that plunges in the Z vertical axis after the drill has been positionally moved in the Y horizontal axis atop the substrate by a gantry unit. (The gantry unit is comprised of a motor driven stiffened beam to which the drill is affixed along with the necessary electrical, air and water supplies.) Optionally, the gantry Y axis positioning remains as above, but the drill unit may be positionally moved in the X axis along the face of the beam while the substrate is held motionless below the gantry unit. In either system drilling is initiated once the drill is in the proper position with respect to the substrate as indicated by a set of metrology positioning sensors on the machine. Optionally, at least one pressure foot may be used to secure the PCB substrate to the z axis drill unit. This positioning prior to drilling occurs extremely rapidly by computer control, cycling up to thousands of times per minute. Pursuant to Newton's third law of motion, each of these three positioning movements creates a reactionary force in the structure of the PCB substrate drilling machine. Since it is this machine that metrology positioning sensors are coupled to, the settling time or lag for the PCB substrate to be positioned within the acceptable ranges of the feedback sensors (prior to the initiation of drilling) is slowed by the effects of the reactionary forces, thus slowing the positioning process and adding slight inaccuracies in the positioning and eventual placement of the holes in the PCB.
Prior art PCB substrate drilling systems rely on the use of a massive, heavy machine base to minimize these reactionary forces coupled with light moving masses of the gantry and attached components as well as an extremely stiff beam, however, these reactionary forces still inherently reside in the machine and serve to limit the speed and precision of positioning at which the machine can function.
In the prior art, the Y axis positioning of the beam is accomplished by a central linear drive motor that positions the rigid beam on feedback from centrally mounted positioning sensors. The outermost right and left ends of the beam are assumed to be in line with the center of the beam with respect to the Y axis by virtue of the beam's stiffness. This is correct, but within measurable spatial limitations as the beam still has some flex. This flex causes the settling time at the end of each positioning to become longer thus cancelling out any move time reduction gained by the improved acceleration of the lighter moving masses. Generally, the sensors operate with moderately large settling windows (in the 0.2 micron range) in the Y axis. These prior art solutions that increase the mass of the machine base (reaction mass) and make the moving masses lighter do not completely address the root cause of the problem—that all parts of the gantry (and beam) are not completely aligned in the Y axis as indicated by the metrology system. For the PCB drilling machine to address this causes additional Y axis positional settling time.
Henceforth, a PCB substrate drilling machine with a faster and more precise way to position and settle in the Y axis would fulfill a long felt need in the substrate drilling and surface patterning industry. If such an invention accomplished this by enhancing the positioning of the Y axis beam, it would be compatible with either of the current styles of PCB drilling machines. This new invention utilizes and combines known and new technologies in a unique and novel configuration to overcome the aforementioned problems and accomplish this.
USPTO Backgrounds
USPTO Backgrounds