There are three key industry trends that are driving the need for temperature-dependent warpage measurement: the trend toward finer-pitch devices,the emergence of lead-free processing,and changes in device form factors. Warpage measurement has become a key measurement for analysis; prevention and prediction of interconnect defects and has been employed in failure analysis labs and production sites worldwide.
Over the past decade,the shadow moiré technique has become the method of choice for temperature-dependent warpage measurement. It is estimated that there are over 200 such machines installed worldwide. However,as the above-mentioned industry trends began to emerge,certain limitations of shadow moiré became apparent,such as camera resolution restrictions,schematic limitations on heating/cooling mechanisms,and data processing techniques that can affect accuracy. As a result of recent developments in projection moiré technology,these issues have been addressed,and the technique is poised to meet the future requirements of the microelectronics industry.
In this paper we discuss projection moiré as a new technique for warpage measurement of advance packages,with applications in failure analysis,new product qualification and process control. Projection moiré addresses many shadow moiré limitations,including camera resolution,heating uniformity and noise.
Key words: warpage,failure analysis,interconnect defects,moiré,shadow moiré,projection moiré,coplanarity.