Under bump metallurgy, also known as pad limiting metallurgy (PLM).

(Under-Bump-Metallurgy) The metal stack that is deposited under the bump as part of the solder bumping process. It has the combined features of adhesion layer, diffusion barrier, wetting layer and oxidation protection layer. FlipChip uses NiV/Cu, Al/NiV/Cu, or Al/NiV/Cu/Ti/NiV/Cu as the UBM.

Ultrasonic BioMicroscope

A high frequency ultrasound that displays an image of the anterior (front) part of the eye. UBM is highly effective in the detection and monitoring of tumors that can not be seen with other imaging devices.