Method for coplanarity inspection of package or substrate warpage for ball grid arrays, column arrays, and similar structures
First Claim
1. 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.
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Abstract
A method for determining coplanarity with 3-D sensing means of substrates for ball grid array, column grid array, and similar surface mount integrated circuit chips, in which opaque fiducials are provided as index pads. Heights of the index pads are correlated with signal pad heights in a neighborhood about the index pads. The index pads are opaque to incident radiation from the 3-D sensor. The index pads reflect sufficient radiation to be detected easily by the 3-D sensor. The index pads are disposed in a prearranged pattern over a domain of ball grid array signal pads. The index pads are restricted to a predetermined range of heights.
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Citations
12 Claims
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1. 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- 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;
Specification