A submount is used to mount a diode between two metal areas on the upper surface of a substrate. One of the areas is connected to a metal plate at the lower surface of the substrate through a via. The submount is clamped between two metal sheets. The top metal sheet has a through-hole for anchoring and self-aligning the diode. The electrodes of the diode are each coupled to one of the clamping metal sheets. Clamping metals provide pressure contact without soldering to the contact. But soldering can be alternatively used to enhance product reliability. Either the top metal sheet or the bottom metal sheet can be fully or selectively coating of solder for batch soldering at the contact point upon heating. The large metal plates and the large metal clamping sheets provide good heat sink and speedy soldering.