Warpage
The primary goal of warpage evaluation is to measure the deviation from planarity after deformation of a flat surface. However, this feature can also be applied to surfaces of arbitrary shapes.
•
First a rigid body rotation of the surface is computed as a best fit in a least squares sense.
•
From that rotated average surface, the deformation in the normal direction is computed.
The original (material frame) coordinates of the surface, which can consist of several boundaries, are given as
X
. After deformation, corresponding points are located at
x
, where
x
=
X
+
u
.
The total displacement
u
is decomposed into an average displacement and a warping displacement, so that
