Special characteristic of future flip chip underfill materials and the process

New materials and process for future flip chip packaging have been studied. Three types of new concept materials with suitable process are discussed in this paper. First is the preset underfill (PUF) process. A non-conductive underfill film is used in this process by a flip chip-bonding machine with lamination capability. Throughput and reliability are mainly studied for this process. Basic reliability requirements such as Thermal Shock Test -40 C to +125 C/1000 cycles, Pressure Cooker Test 121 C×2 atm/168 hrs, and Moisture Sensitivity Level/JEDEC Level 3, have been achieved with high throughput. Second is the transfer underfill (TUF) material. A modified transfer molding machine instead of a liquid underfill dispensing machine does underfill in this process. The required characteristics for the transfer underfill material are no volatiles in the material pellet and good flow ability with gap below 100 μm. New TUF material has successfully clears the requirements with newly developed clean tablet (CT) technology, and filler particle distribution control. Third is an underfill paste (UFP) material. This new material has high thermal stability at operating temperatures up to 80 C, and rapid curing characteristics such as 150 C×20 min or 175 C×5 min, due to the special reaction control of the epoxy and phenol curing system. This material can be used in a current dispensing process with a minor adjustment in the heating parameter. Coating or printing processes are also available options for this UFP material. In this paper, the future of flip chip packages is discussed with these three materials and processes