CSP Delamination - Application Note 540
Sample & Method
In this CSP the die is mounted to an elastomer material, which is then attached to a flex substrate with solder balls. The interconnections between the die and substrate are done with TAB (Tape Automated Bond) like connections. This part is flipped over and viewed through the solder ball/flex substrate side.
In the acoustic image, the traces run from chip, but seem to disappear when they encounter the large red area. This area is a massive delamination within the polyimide. Since the delamination reflects all the ultrasound to the transducer, there is no reflection from the traces behind the delamination.