Precise, High-Throughput Dispensing of Thermal Interface Material in BGA Package Applications

摘要

In a flip chip BGA package, thermal interface materials (TIMs) are applied for thermal management between the die and the heat spreader or between the heat spreader and the heat sink to conduct the heat generated in the die during component operation. Without a thermal interface, the die will overheat and the components will not function properly. Advanced microelectronics packaging demands high and dynamic standards of its supplier industries in relation to speed, precision and flexibility. For example, the demands on functionality, power density, and performance of the components within a die are largely enhanced along with TIM requirements for higher heat resistance. Manufacturers are being asked to apply TIMs on more dies in more complicated geometries and to dispense them during any packaging process. This brings increased challenges for TIM dispensing equipment, such as the ability to handle abrasive and dry TIMs at a high throughput while maintaining precision and repeatability. A high-precision, high-throughput TIM dispensing process has been developed to fill the gap between the traditional slower dispensing of simple patterns and the challenges from emerging package designs. This process is being used in flip chip BGA production lines in package applications from consumer electronics to automotive products. These production lines are in full 24/7 operation with each dispensing system running at 240 units per hour (uph) for audio-video consumer electronics, 360 uph for CPUs/GPUs on smart phones, and 750 uph for automobile alternative power control panels and computation servers. In this new dispensing system, the valve can be tightly controlled to achieve high dispensing accuracy at fast speeds. The dispense pattern and route can be modified at no cost, in minutes, and during any step in the design or the assembly stage. Shapes that can be dispensed include dots, lines, boxes and circles with fine height and edge definitions of 25μm and 45μm. The process can cover a wide range of pattern dimensions between 0.5mm and 100mm at flow rates of 30-370 mg/ sec at a repeatability of 3-15% three sigma. Even TIM that has viscosity as high as 1500kcPs with a heavy load of large and coarse particles such as metals, ceramic, and glass beads can be dispensed using this equipment and process. New equipment and processes are under development to further push the limit on higher throughput and precision, increased flexibility, and material dispensability.