Registration Vector Analysis in Sequential High Density Core Lamination
Sequential core lamination registration requires X-ray target vector mapping and dynamic affine drill scaling to maintain zero breakout microvia alignment.
Laser Drill Offset
Target Deviation
Measurement of the distance between the center of a laser ablated hole and the center of its landing pad defines the accuracy of the microvia formation process. Because high density boards use very small features, laser drill offset must be kept within a few microns to ensure a solid connection. The laser system identifies fiducials on the panel surface to orient itself before firing the beam at the programmed coordinates.
Any error in this orientation or in the mechanical movement of the mirrors leads to a misplaced hole. Software offsets are applied based on the measured position of the underlying copper.
Optical Calibration
The galvo mirrors that direct the laser pulse must be calibrated to compensate for thermal drift in the machine frame. Even a small amount of laser drill offset can prevent the microvia from fully landing on the copper target.
Via Integrity
Quality control teams cut and polish samples of the board to view the vertical alignment of the vias under a microscope. If the laser drill offset is too large, the plating in the hole will not form a continuous bond with the underlying copper. This failure often appears as a corner crack or an interfacial separation during thermal cycling tests.
The boundary of acceptance is defined by the minimum amount of pad area that must remain covered by the via.