5-sided Sealing Protection WLCSP Technology

The progress of electronic products could not be separated from the progress of semiconductor packaging technology. Semiconductor packaging plays a more and more important role in electronic products system, which integrates more functional devices in a more compact body. Wafer-level chip size packaging (WLCSP) not only significantly reduces the size of package, but also meets the high-density requirements of portable electronic products. On the other hand, WLCSP improves the speed and stability of data transmission in terms of performance. With the widespread use of WLCSP in electronic products, the reliability of WLCSP is also facing a huge challenge. Although the reliability of common WLCSP chips can be improved by backside lamination, the sidewall crack and chipping issue cannot be improved. In order to avoid the damage in the bare silicon of WLCSP, the development of 5-sided Epoxy Molding Compound (EMC) sealing protection WLCSP technology is an innovative idea. It can solve the defect of current WLCSP products and improve the package reliability. At present, the industry also has Fan-in five-sided protection WLCSP solution. The process is to complete the entire wafer-level packaging firstly, then adopt plasma dry etch method to open the scribe line from the backside of the wafer, and then the dry film material is squeezed into the gap to achieve the die sidewall protection. Fan in five-sided protection WLCSP is suitable for the product with low-profile bumps. Temporary wafer bonding process used in the process limits the bump height. Compared with two methods above, 5sided EMC sealing protection WLCSP (5SP-WLCSP) developed in this work has the following advantages: Firstly, the die shift issue can be avoided because no need for wafer reconstruction. Secondly, the wafer molding process after ball mount can avoid the ball misalignment issue caused by die shift, and the molding compound material provides protection for the solder ball. Thirdly, after molding process, the wafer still has Si as the overall support, and the warpage of the wafer is relatively low. This paper mainly studies the WLCSP process with 5-sided EMC sealing protection, optimizes the main process parameters and finds the best process window. In this paper, a 5x5mm daisy chain chip is used as the test vehicle to develop 5SP-WLCSP process. The overall package thickness is less than 0.5mm and the sidewall EMC thickness is thicker than 10um. 5SP-WLCSP meets the following reliability test requirements, including moisture sensitivity level MSL3, temperature cycle rest up to 500 times, high temperature storage test up to 500 hours, board level drop test and board level temperature cycle test. Promoting 5SP-WLCSP can effectively solve the issue of die chipping and sidewall crack. It will expand the application scenario of WLCSP products.