Flip-chips are aligned by making a fiducial in the "top" chip that is
translucent/transparent to light of a wavelength shorter than infrared,
and at least one corresponding fiducial in the "bottom" chip. The
top-chip fiducial may be made of a transparent or translucent material,
its shape may be outlined by an opaque material, or it may be formed by
etching through the top chip. The bottom-chip fiducial may be reflective
of the light which is transparent/translucent to the fiducial in the top
chip, in which case alignment can be achieved by employing at least one
video camera which is located above the top chip. Alternatively, the
fiducial in the bottom chip may also be transparent/translucent to the
light, in which case alignment can be achieved by having the video camera
located below the bottom chip. The chips are aligned by aligning the
fiducials as seen by the video camera.