High throughput and fine pitch Cu-Cu interconnection technology for multichip chip-last embedding

Abstract

Ultra-thin packages with embedded actives for high functional density have become strategically important with fast growing market for portable electronics. 3D Packaging Research Center at Georgia Tech is pioneering a chip-last approach for die embedding using adhesively bonded copper bumps to enable ultra-fine pitch chip-to-package interconnections. This paper presents three advancements over the adhesive bonding technology demonstrated previously-1) A novel method to perform chip-last at panellevel, leading to 10-15x reduction in assembly time per die, 2) Improved 2-step assembly process to achieve simultaneous die embedding and cavity planarization, and 3) Adhesive bonding of high I/O die. To demonstrate high throughput assembly, x-ray and electrical yield results for an 8-10 dies, simultaneously bonded on a 3" x 3" panel with high accuracy have been discussed. The assembly process modification yielded planarization of the gap between the die and cavity wall to <1µm. Electrical yield of adhesively bonded large die with ~800 I/Os has also been discussed. These technology advancements aim to address some of the key limitations of conventional adhesive based assemblies, thus making chiplast adhesive bonding with low profile copper-to-copper interconnections a robust chip embedding solution for nextgeneration of highly integrated heterogeneous subsystems.