Abstract: Additional “auxiliary” bumps are used to stabilize alignment and reduce slippage of dense arrays of interconnect bumps on opposing die during a bonding process. One example of auxiliary bumps are interdigitated bumps. Interdigitated bumps are more self-aligning and laterally stable because bumps do not meet head-to-head. Rather, the head of a bump on one die falls into the space between bumps on the other die. Another example of auxiliary bumps are nail bumps. In nail bumps, one bump is harder (the nail) and “drives” into the opposing softer bump during bonding. This constrains the lateral movement of the two bumps relative to each other and reduces lateral slippage. In some embodiments, the auxiliary bumps and interconnect bumps are formed in the same process, and also bonded in the same process.

Abstract: An etching step is performed on an LED/substrate wafer to etch through the LED epitaxial layers entirely around each LED on the substrate wafer to form a gap between each LED on the wafer. The substrate is not etched. When the LEDs/substrates are singulated, edges of each substrate extend beyond edges of the LED die. The LEDs are flip-chips and are mounted on a submount with the LED die between the submount and the substrate. An insulating underfill material is injected under the LED die and also covers the sides of the LED die and “enlarged” substrate. The substrate is then removed by laser lift-off. The raised walls of the underfill that were along the edges of the enlarged substrate are laterally spaced from the edges of the LED die so that a phosphor plate can be easily positioned on top to the LED die with a relaxed positioning tolerance.

Abstract: An etching step is performed on an LED/substrate wafer to etch through the LED epitaxial layers entirely around each LED on the substrate wafer to form a gap between each LED on the wafer. The substrate is not etched. When the LEDs/substrates are singulated, edges of each substrate extend beyond edges of the LED die. The LEDs are flip-chips and are mounted on a submount with the LED die between the submount and the substrate. An insulating underfill material is injected under the LED die and also covers the sides of the LED die and “enlarged” substrate. The substrate is then removed by laser lift-off. The raised walls of the underfill that were along the edges of the enlarged substrate are laterally spaced from the edges of the LED die so that a phosphor plate can be easily positioned on top to the LED die with a relaxed positioning tolerance.