Correlation between material selection and moisture sensitivity levels of quad flat no-lead (QFN) packages

Moisture sensitivity level (MSL) test is the well-known industrial standard to classify the level of moisture sensitivity of plastic packages. However, except for the classification, MSL test provides no suggestion for improving package MSL performance from the package design point of view. In order to achieve an expected MSL performance, further investigation of the correlation between package MSL and material selection is required. Based on this major objective, four kinds of molding compounds and two types of die attach materials were studied in this paper. Commercial 4times4 quad flat no-lead (QFN) packages were fabricated as the test vehicle. The stress ratio criterion was employed to evaluate the failure of 4times4 QFNs under MSL-1 tests. In addition, MSL-1 tests and related failure analysis were implemented to provide the experimental results. From the comparison between the stress ratio analysis and the experimental results, it is concluded that the molding compound with lower adhesion strength and higher Young´s modulus may lead to higher risk of delamination.