In 2007 Lead Free Package POP(Package on Package)will be a major new device to hit the streets this year and will challenge many to re-evaluate their soldering and rework products/processes. The implementation of lead-free in the commercial world and is well on the way in assembly plants worldwide and particularly in Asia. This represents a major logistics risk to commercial and aerospace community，while some are currently exempt from Lead Free legislation，they will be impacted by the use of Commercial off-The Shelf components finished with Lead Free component finishes. All POP is Lead free that I have seen. So if new POP memory devices are to be used in military equipments they will be lead free.Lead Free soldered electronics hardware requires higher processing temperatures than for traditional Tin Lead soldered hardware.The higher Lead Free soldering processing temperatures，coupled with faster production requirements increases the risk of board and component damage therefore requiring greater process control. The POP is another example of increased complexity especially in rework.Component manufacturers are all looking for new innovative ways to gain market share particularly in memory and products that reduce space on PCB are one way forward. There are two ways to reduce space one is reduce the pitch of the part to get more solder connections in the same array in the same space. Reducing space has been a constant theme for years now BGA/CSP have reduced the pitches for years down to mainstream BGA being 1.27mm and 1.00mm pitch. CSP have reduced to .8mm and.5 mm mainstream Future trends will go even lower to .8mm BGA and .4mm CSP.These are the assembly limits for current high volume assembly of electronic PCB Mainstream today.The next way to increase component density and performance is to go vertically. This is called POP Package on package，this is a Bga mounted on top of the other one. In some cases，component manufacturers are manufacturing up to four parts vertically for memory modules. The POP is being used in pitches of 1.0mm and 1.27mm for BGA with csp packages using 5.mm and .4mm pitch parts stacked vertically.The third way for component manufactures to increase sales is to mix DDR Ram and logic in one device i.e. POP.Alternatively designers can mix manufactures of Sram and Dram,or flash ram，and create their own specific package by making a custom POP from two different sources.This is sometimes a cost effect solution.