Surface Modeling
Mathematical method calculates a smooth coordinate transformation based on a set of discrete control points. Inspection software uses thin plate spline interpolation to compensate for the natural warpage of a circuit board during the assembly process. The algorithm treats the board as a thin metal sheet that resists bending, resulting in a realistic map of the surface height.
Computational Model
Control points are typically found by measuring the z height of specific fiducials or corners of the panel. By calculating the deformation between these points, the thin plate spline interpolation can predict the height of every pad on the board. This allows the placement nozzle to adjust its landing position for every component.
Warpage Compensation
Efficiency is a key advantage of this method because it uses a small number of data points to generate a complex surface. If the board has local distortions from heat, the spline adapts to those changes without requiring a high density scan. Using this technique improves the yield of fine pitch components by ensuring the leads always make contact with the solder paste.
High speed processors allow the machine to perform these calculations in milliseconds as the board enters the work cell.
