Method for coplanarity inspection of package or substrate warpage for ball grid arrays, column arrays, and similar structures

A method for determining coplanarity of substrates for ball grid array, column grid array, and similar surface mount integrated circuit chips, using 3-D optical sensing means, comprising the steps of:

• providing opaque fiducials as index pads where the heights of said index pads are correlated with signal pad heights in a neighborhood about said index pads;
• said index pads being opaque to incident radiation from said 3-D optical sensing means;
• reflecting by said index pads sufficient radiation allow height measurement by said 3-D optical sensing means;
• disposing said index pads in a prearranged pattern over a domain of array signal pads;
• restricting said index pads to a predetermined range of heights;
• measuring the heights of each of at least three said index pads at said index pad coordinate locations;
• suitably fitting a preselected surface shape to the index pad height and coordinate location data;
• and calculating the difference in height between each index pad and the preselected surface shape evaluated at the index pad location.