10.1.2 RTK Package—High CTE Mold Compound

The RTK package uses a mold compound with a high coefficient of thermal expansion (CTE) of 12 ppm/°C. This mold compound allows for the CTE of the packaged IC to more closely match the CTE of a conventional FR4 PCB (~14 ppm/°C to 17 ppm/°C). This CTE match is important when considering the effects that temperature swings can induce on a board with large differences in CTE values. Package and board combinations with widely dissimilar CTEs can experience mechanical cracking or fracturing of the solder joints caused by frequent changes in temperature and the corresponding differences in expansion. Devices with normal mold compounds in similar packages typically have CTE values that are 25% lower than values found with the RTK package.