Mold flow analysis of molding process for a MEMS fingerprint sensor package

In the process of plastic packaging, void is a common defect, as the volume of semiconductor devices is becoming more and more smaller and thinner, the void problem has become the main factors influencing the reliability of product. In this study, A MEMS fingerprint sensor is taken as simulation carrier. Firstly, 3D mold flow simulation using Moldex3D is applied to the encapsulation of sensor. From the result, the distribution of the possible void in the transfer process is predicted. Secondly, under the constant condition of processing parameters, by changing the location and the amount of the gate, the flow simulation of the sensor was carried on, the purpose of finding out the influence of different gate project on the void problem for the sensor packaging. By comparing the mold flow analysis results of the different gate design project, the study reveals that the gate project has a great effect on the void problem for the sensor package. When the encapsulation model adopts one gate, the void amount of the gate in the middle of the sensor package is less than the gate in the two ends of the sensor package, due to the fact that the melt flow becomes more balanced. When the model adopts two gates, the melt flow of the model is more balance than one gate, hence the air is more easily pushed out, but the excessive pressure may be caused. Thus the gate design should be comprehensively considered with including the structure characteristics of the product and the transfer molding processes.