Chip attach for silicon hybrid multi-chip modules

The author describes the requirements of chip attachment techniques for silicon hybrid circuits, compares flip-chip, tape automated bonding (TAB), and wire bonding, and discusses the significance of assembly yield and test. Although area array flip-chip technology provides perhaps the ultimate electrical interconnection density, TAB can also be applied in very-high-density format. Silicon devices can be bonded face down with short beam leads and equal inner and outer lead-bonding (OLB) pitches. Assembly of high-lead-count TAB test chips onto fine-line aluminum-polyimide and copper-polyimide connections on silicon substrates has been evaluated in the RISH (Research Initiative into Silicon Hybrids) program. A range of bonding experiments was completed. Solder assembly was achieved with box thermode reflow down to OLB pitches of 175 mu m, with possible extension to bonding at 125 mu m or less. Single-point gold-gold OLB was achieved at 100- mu m bond pitches.<>