Using Active Thermography For Defects Inspection Of Flip Chip

With the development of electronics technology, flip-chip technology has been usedextensively in microelectronic packaging. However, different disadvantages occurred intraditional detection methods. Therefore, in this paper we investigated a novel approachfor solder joint inspection based on the active thermography. The main content is asfollowing:1. Main principles of infrared thermography were investigated and a flip chipinspection system based on active thermography was built. To testify the feasibility ofthis method, finite element software was adopted to simulate the whole system.2. One self-made test vehicle with the solder bumps of500μm in diameter wasdetected. Image and signal processing procedures were applied. With quantitativeanalysis, the positions of the missing bumps could be detected. Then, the test vehiclewith the solder bumps of135μm in diameter was detected. Since the diameter and thepitch were smaller, the disturbances caused by the noises were much more significant.Principle component thermography was introduced to distinguish the missing bumpsfrom the sound ones.3. Test vehicle with cracks in bumps were tested. Signal differences caused bycracks were minor and high frequency signals need to be analyzed, so wavelet analysiswas investigated to extract characteristics. Self-organized maps were applied to classifyvarious signals, and thus different bumps could be inspected.With series of methods in image and signal processing, defect inspection of flip chipbased on active thermography was proved to be efficient.