Nondestructive Monitoring of Die Warpage in Encapsulated Chip Packages

We describe an X-ray diffraction imaging technique for nondestructive, in situ measurement of die warpage in encapsulated chip packages at acquisition speeds approaching real time. The results were validated on a series of samples with known inbuilt convex die warpage, and the measurement of wafer bow was compared with the results obtained by optical profilometry. We use the technique to demonstrate the impact of elevated temperature on a commercially sourced micro quad flat nonlead chip package and show that the strain becomes locked in at a temperature between 94 °C and 120 °C. Using synchrotron radiation at the Diamond Light Source, warpage maps for the entire $2.2~\textrm {mm} \times 2.4~\textrm {mm} \times 150$ - $\mu \text{m}$ Si die were acquired in 50 s, and individual line scans in times as short as 500 ms.