The Research On Defect Inspection Of Flip Chip Using Active Thermograph And Ultrasonic Inspection

microelectronic packaging. The solder bumps develop towards ultra-fine pitch and high density. It brings great challenge for defect inspection method. Traditional nondestructive detection methods with their own disadvantages are insufficient for solder joint assessment. So it is indispensable to improve defect inspection method of flip chip solder joint, or to propose a new method.The primary works of the paper contain two parts, which both focus on non-contact, nondestructive defect inspection of flip chip solder joint. First, active thermograph is introduced into defect inspection of flip chip solder joint. Second, due to the variance of the skill levels of operators, the ultrasonic inspection method is unreliable and low efficiency sometimes. Pattern recognition method is introduced for ultrasonic inspection of flip chip solder joint. The main content of this paper comprises:The basic principle of active thermograph is investigated. According to the characteristics of flip chip, a defect inspection based on active thermograph is proposed. In this approach, the flip chip is heated by non-contact thermal source. A commercial infrared thermal imager is employed to capture the thermal distribution on the chip. The thermal distribution and evolution indicate defects inside flip-chip. Experimental investigation and stimulation is carried out. The results prove the ability of detecting defects inside flip chip. Ultrasonic inspection of flip chip based on pattern recognition is constituted by four consequent steps: image acquisition, segmentation, feature extraction and classification.The image of flip chip solder joint was captured by scanning acoustic microscopy and segmented using correlation coefficient. Then geometric features are extracted and fed to the neural network for classification and recognition. Experimental results validated the feasibility of the approach and demonstrated the high recognition rate. Therefore, this approach was proved to have high potentiality for solder joint defect inspection in flip chip packaging.A defect inspection system based on active thermograph and a algorithm for pattern recognition of solder joint are designed. The results prove that these methods have ability of detecting defects inside flip-chip, and can be applied in defects inspection and diagnosis of flip-chip.