NCP versus NCF for thermocompression MEMS bonding using gold stud bumps

Assembly tests for a high volume MEMS product where thermocompression bonding with gold stud bumps is considered to be employed are presented in this work. In order to avoid a time consuming capillary underfill process, the bonding will be performed in combination with a non-conductive paste (NCP) or a non-conductive film (NCF). The target of this work was to identify limitations with the use of these adhesives for this specific and similar applications. Bonding parameters were optimized and varied systematically individually for each adhesive. Two types of bumps (called Standard and AccuBumps™) were tested for the NCP whereas only AccuBumps™ were tested for the NCF. Results of visual inspection, shear testing and inspections of cross sections with scanning electron microscopy and energy dispersive X-ray spectroscopy were compared for the two types of adhesives. Satisfactory assembly results were achieved for both adhesives; based on these results a final selection of NCP or NCF seems to remain a question of cost efficiencies of the different process flows.