Double through-transmission ultrasonic inspection of plastic IC packages

A double through transmission ultrasonic technique for IC package inspection is presented. The technique makes use of a smooth plate under the IC package to reflect the ultrasound that has passed through the package. The reflected ultrasound goes through the package again and is received for signal and image processing to detect internal defects in the IC package. The technique overcomes the difficulties of the traditional pulse-echo SAM methods. It also offers advantages over the through transmission setup in the market. The technique was successfully applied to reveal the internal defects such as delamination and package crack in thin packages