Handling ultra thin die for bonding: Pulse Vacuum Reverse Multi Step (PV-RMS)
The thickness of multilayered NAND flash memories has been reduced to less than 30 um including an adhesive layer. Although silicon is a relatively hard material, it will bend readily and break easily at this thickness. In making a device, a die pickup technique is necessary, but it is extremely difficult to remove an ultra thin die attached to the wafer tape. You may have experienced that peeling off a bandage quickly caused pain. Alleviating this pain is compared to the function of Pulse Vacuum-Reverse Multi Step (PV-RMS) that picks up thin dies from wafer tape. By pulsing vacuum from the outside of wafer tape, the PV-RMS promotes peeling of the die while reducing the adhesive force – corresponding to the reduced pain that would result from a similar method of bandage removal. It is effective not only for thin dies but also for dies with a fragile TSV structure. This is a key technique for future electronic device packaging.
Connect efficiently: Flip-chip Collective-bonding
As dies become larger, thinner and more densely populated with interconnects, reduced die warpage and increased die placement precision are required during flip chip bonding. To address this issue, the thermal-compression bonding (TCB) process has been proposed. It has been used in the latest memories manufactured by the through-silicon-via (TSV) process such as high bandwidth memory (HBM) and hybrid memory cube (HMC). Thermocompression bonding enables simultaneous solder bonding of interconnects and curing of underfill. However, the thermocompression bonding process requires a cycle time of about 10 seconds, which limits the improvement of productivity. Shinkawa conducts basic research and develops sub-system technologies applicable to various methods for collective bonding of multiple dies such as gang-bonding. We reported at the Electronic Components and Technology Conference (ECTC) 2017 that productivity can be improved up to 20 times by a combination of optimized sub-system technologies and usage of the high-speed TCB bonder FPB series.
