A Flexible Manufacturing Method for Wafer Level Packages

Abstract

The demand for Wafer Level Chip Scale Packages (WLCSP) has experienced tremendous growth due to the surge in demand for advanced mobile products. The increased demand is seen for both 200mm wafers and 300mm wafers, however a significant segment of the market continues to be driven by 200mm designs. The infrastructure capacity supporting 200mm WLCSP has been stressed as a result of the mature status of 200mm technology and the rate of conversion of alternative package formats to WLCSP. This creates a dilemma for WLP service providers because adding 200mm capacity continues to require a significant amount of capital. Since 200mm volumes will most likely decline within the next 5 years, it is difficult to justify the use of capital when the depreciation term is longer than the anticipated life cycle of the product. Conventional methods of manufacturing wafer level packages require the use of equipment specifically sized to a given silicon wafer diameter although there is no technical requirement to maintain the round silicon format. The conventional method has been beneficial since it leveraged equipment and processes developed for the IC industry, however the equipment is very expensive for larger wafer diameters and the fine geometries required in advanced node IC products are not required for wafer level packaging. The problem is serious for 200mm and 300mm wafer bump lines, however the capital equipment cost for a future 450mm bumping line may well be prohibitive for wafer level packaging. A new manufacturing method has been developed to produce a wafer level package that severs the link between wafer diameter and wafer level packaging methods. The new manufacturing method is wafer size agnostic, so one manufacturing module can produce fan-in, fan-out, and 3D fan-out products regardless of the incoming wafer size. The same bill of materials, manufacturing methods and manufacturing location can produce wafer level packages from any size silicon wafer. In this method the wafer is diced prior to processing and then the die are recombined into a uniform panel size. Once recombined into a panel format, the product is processed with conventional wafer level packing techniques, including dielectric deposition, metal plating and solder ball drop. Since the manufacturing module is wafer size agnostic, there is no risk of capital for investment in the manufacturing infrastructure. A change in loading between 200mm, 300mm, and 450mm wafers does not adversely affect the utilization of the manufacturing module. The process also enables new advanced wafer level packages otherwise unattainable with conventional manufacturing methods. This presentation will describe the new manufacturing module approach and the results of process characterization for products produced in the module.