Novel Flip Chip Technologies for Ultra Thin Chip
Telecommunication equipment that supports high-level information networks is being made portable, small and lightweight. Thus, the miniaturization of semiconductor devices is necessary, and chip thinning and flip chip technologies are key in achieving it. The typical flip chip manufacturing steps for thin semiconductor devices are as follows. First, semiconductor elements are formed on a wafer. Surface protective tape is attached to the surface of the wafer and backside grinding is performed to make the wafer thin. Then, dicing tape is attached to the backside of the wafer and the wafer is diced from the surface side, using a diamond blade, and divided into chips. Then, the chips are picked up, using pick up needles and bumps are formed on the surface of the chip. Next, seal resin is attached to a substrate, then the surface of the chip is attached to the substrate with the seal resin and flip chip interconnection and sealing are performed to mount the chip. This manufacturing step has some problems. In this paper, a novel thin package manufacturing process is described.
A study on chip thinning process for ultra thin memory devices
Telecommunication equipment that supports high-level information networks is being made portable, small and lightweight. Thus, the miniaturization of semiconductor devices is necessary, and chip thinning technologies are important key technologies to achieve it. The manufacturing steps for semiconductor devices are generally classified into steps for patterning semiconductor elements in a wafer, steps for thinning a wafer, steps for dicing semiconductor elements into chips and sealing the chips in packages. Wafers are thinned by means of mechanical in-feed grinding using a grindstone containing diamond particles, resulting in spiral grinding saw marks on the backside of the wafers. Dicing wafers always causes surface chipping, dicing saw marks on the chip side and backside chipping. Such defects on chip faces become sources of cracks, decreasing chip strength. Therefore, the manufacturing process of thin chips must achieve the requirement of no damage on all chip faces. We already proposed a novel wafer thinning process namely a dicing before grinding (DBG) and DBG + mirror finish process on 56th ECTC, and also proposed a novel flip chip process for ultra thin chip on 57th ECTC. Incidentally, the thickness required for a semiconductor chip to work has not yet been determined. In this paper, the memory chip performance test results are described.
Heat Recovery Systems
Geothermal energy is recovered from an underground zone of relatively hot strata via a borehole into which is inserted a heat pipe system containing a working fluid, the heat pipe system comprising an assembly of two tubes in concentric relation, the inner tube being constituted by a relatively small diameter capillary for the return of working fluid to the vicinity of the zone of the relatively hot strata. The working fluid is preferably assisted in its return under gravity by means of a pump. The system includes heat exchange means operable to recover thermal energy from the working fluid. A third and outermost tube may be used to reduce heat losses, this third tube enclosing the two tubes over all but that part of their length which is in the zone of relatively hot strata.