The push for size reduction is reaching the segment of vertical interconnects. Current technology has a lower limit of approximately 0.150mm (0.006”) with pump and materials being the limiting factor. GPD Global through cooperation with MicroCoat Technologies have developed a process to dispense vertical interconnects at line widths from 0.075 to 0.100mm. A combination of fluid formulation and pump development has resulted in the ability to dispense these line widths.
Many companies that are manufacturing stacked flash devices have gone to very fine line dispensed conductive adhesive instead of wirebonding to make the connections from layer to layer. MCT has developed a a low resistivity – high thermal conductivity die-stacking interconnect conductive adhesive that can be dispensed with almost any dispense head and the material can be applied at <70µm wide with no sag or slump to 16+ flash layers with a 5-6 day room temperature working life. Besides the cost and space savings compared to wirebonding, the conductive paths provide a ground-breaking method for helping to cool the device(s) with the high thermal conductivity of the epoxy acting as cooling fins.
Dispensing vertically requires precise control of the dispensing tip. Angling the nozzle towards the product ensures strong tacking of the fluid to the stack. Precise alignment of the dispense tip through calibration and vision algorithms ensures consistent results. The resultant lines were 75 to 100µm in width and were achieved with a 50µm nozzle. For more information visit the MCT website.