Probeless DfT Scheme for Testing 20k I/Os of an Automotive Micro-LED Headlamp Driver IC

Display driver ICs traditionally feature high I/O counts to drive the many signals required for a high-resolution display. If LEDs are placed in a crosspoint matrix the driver IC only needs to drive the rows and the columns. But the recent advent of high-resolution micro-LEDs for adaptive automotive headlighting poses a new test challenge. The micro-LED chip is bonded on top of the silicon driver IC making connection via 20,000 I/Os, one per pixel. The driver IC becomes a backplane to the micro-LED array. Due to the I/O pitch of just $40\mu \mathrm{m}$ and the sheer number of I/Os traditional probe card technologies become unviable. The paper describes a DfT concept that allows a self-test of the device on ATE, eliminating the need for any probing of the LED driver I/Os. Furthermore it delivers the necessary test infra-structure to prove the successful bonding between the driver IC and the micro-LED chip, allowing exact localization of assembly faults. During the mission life of the component the same DfT structures are used to monitor the health status of the headlight pixels, enabling the functional safety concept of the headlight system.