Advanced 3d Stacked Die Packaging Technology And Reliability Study

Since the 1990s, Ball Grid Array (BGA) has gradually replaced the traditional leaded package and become more and more popular. This has caused some advantages such as reduction of the package size, an increase in the number of the input and output ports, and enhancement of the function and performance. However, with the development of advanced packaging technology, the 2-dimensional (2-D) package has reached its limit. In order to overcome the bottleneck of the 2-D package technology, a three-dimensional (3-D) package technology has been proposed. The successful thinning of wafer by back-grinding has made the thickness of the 3-D multi-chip stacked die package similar to that of BGA (about 1.2 mm). Therefore, the 3-D stacked chip package can effectively increase the function of electronic devices, and has already become a very popular packaging method for semiconductor industry.In my thesis, the key difficulties for the 3-D stacked chip package were analyzed firstly, including wafer back-grinding, die attach, low radian wire bonding and chip MSL etc, and the corresponding solutions were proposed. Then, a stacked chip package qualification experiment was done by using epoxy resin film at the die attachment stage, instead of the traditional blue film. Both X-ray and C-SEM inspections did not reveal any delamination on chips, pins and lead frames, and any defect for the soldering wires etc. Further, the reliability of the package was evaluated, including TH, UHAST, TCT and HTSL measurements. The results indicated that all the samples passed this reliability experiment, no sample failed. Finally, the process of USB four layer stacked chips was investigated, and the influence of the process parameters on the performance of wire bonding was explored. It is found that although there was little cross line migration, in general the wire bonding was in good condition. Based on the ball shear and wire pull test experiments, it is found that the average wire pull force was between 8g and 13g, and the average ball shear force was between 22g and 28g. These data are higher than its technical standard, i.e.,5g for the wire pull force and 13g for the ball shear force. In conclusion, the experimental work in my thesis let us have deep understanding on the knowledge of the 3D stacked die package process, and contributed a lot to improve the yield of products.