Heterogeneous Interconnect Stitching Technology With Compressible MicroInterconnects for Dense Multi-Die Integration

In this letter, a heterogeneous interconnect stitching technology is proposed. Stitch chips with high-density fine pitch wires are placed between the substrate and the active chips. Fine-pitch microbumps are used to bond the chips and provide high density and low-energy signaling. Compressible microinterconnects (CMIs) are used to compensate for package non-planarity and enable chip-package interconnection. A testbed with two passive chips and one stitch chip was fabricated and assembled. The post-assembly electrical resistance values of the microbumps and CMIs, as well as the mechanical compliance of the CMIs, are measured. The resistance of the microbumps ranges from 77.8 to 188.3 μΩ and the resistance of the CMIs ranges from 141.2 to 252.9 mQ. The mechanical compliance of the CMI is approximately 13.7 mm/N with a vertical elastic deformation of up to 30 μm.