The liquid discharge apparatus includes a head having liquid dischargers capable of deflecting the trajectories of discharged droplets in a plurality of directions. The upper metal line includes a diffusion barrier, which is made of a stack of a first WNx layer, a WCyNx layer and a second WNx layer. The diode has a box sign depth factor of less than about 1. The workpiece is then certified weld-enabled within a bandwidth range of the test wavelength.