Package Thermal Characterization

Effective heat removal from the IC chip, through the package, to the adjacent environment is crucial to maintain an allowable device junction temperature. The latter directly affects the electrical circuit performance both at the component and system levels. Aside from thermal enhancement of individual packages by the IC manufacturers, proper printed circuit board (PCB) layout and cabinet design by the end users can also substantially reduce the overall package thermal resistance. The fundamentals of various heat transfer modes can be found in any classic heat transfer textbook, and recent advances in heat transfer and fluid flow development can be referred from published technical papers. Thus, the intent of this application note is threefold: 1. provide practical aspects of package thermal resistance definition; 2. show how the data are generated; and, 3. discuss package mounting, board effect, and system effect on heat transfer. This application note first covers the basics of package thermal characterization to help the end user in interpreting the package thermal data. Subsequently, the package mounting effects, board effects, and system effects on package heat transfer are outlined, along with some critical dimensions. The last section is a summary of major guidelines for the end user to obtain a better thermal design at the board and system levels.