Innovative solutions to enhance the legacy equipments towards "one generation ahead" in flip chip BGA 0.8mm ball pitch technology

Abstract

VAI ball attach has been the legacy ball placement equipment for flip chip ball grid array (FCBGA) technology for the past 4 years. The rapid advances of integrated circuit (IC) fabrication technology and the accelerated growth of the market for faster, smaller, yet less expensive products continue to challenge IC packaging technology. Hence, the package size is getting smaller with higher IO count, smaller ball pitch and size. Current requirements call for a ball pitch reduction from the industry standard of 1.27 mm or 1 mm to 0.8 mm (with a potential to go down further to 0.65 mm or even 0.5 mm). Ball size is also not an exception to the rule. It has been reduced from 30 mil or 24 mil to 20 mil (diameter). The fact that semiconductor industries utilize high capital and incur intensive equipment costs has prompted us to enable and reuse the existing legacy equipments to extend the capability to be generation ahead. The legacy equipments faced serious technical road blocks to achieve the high ball placement accuracy in term of yield and machine run-rate to stay competitive. Using current gravitational ball drop technology, the lightness of the solder balls has created a lot of ball placement issues such as solder balls were not dropped per expected timing. This was largely due to the equipment's ability to precisely control the timing and location of ball placement. Therefore, the tighter the ball pitch and ball size, the lower the yield would be. Besides, new packages with 2 mm keep-out-zone (KOZ) design requirements were also one of key challenges for the existing tooling design to handle in term of package rest platforms and also the gripping mechanisms. Failure of reusing the legacy equipments would mean scraping our fleet of 21 equipments and replacing them with next generation equipments at a cost of USD$420K per tool, which translates to USD$20.5M over the next 4 years. The team took up the challenge to explore various opportunities to extend the lifespan of legacy equipments without having to revert to purchasing new equipment in order to meet the future flip-chip BGA chipset requirements through year 2008