Board level reliabiltiy assessment of chip scale packages

摘要

A large program had been initiated to study the board level reliabiltiy of various types of chip scale package (CSP). The reults on six different packages are reported here, whcih cover flex interposer CSP, rigid interposer CSP, wafer level assembly CSP, and lead frqme CSP. The packages were assembled on the pattern of electrical resistance change. The cycles to failure were analyzed using Weibull distribution function for each type of package. Selected packages were tested in the temperature/humidity chamber under 85degC/85RH for 1000 h. Some assembled packages were tested in vibration condition as well. In all there also cross-sectrical resistance of each package under testing was monitored continuously. Test samples were also cross-sectioned and analyzed under a Scanning Electronic Microscope (SEM). Different failure mechanisms were identified for various packages. It was noted that some packages failed at the solder joints while others failed inside the package, which was packaging design and process related.