This paper describes a package design and associated manufacturing assembly process that stack a module on top of another module using a frame board. The module on the top could be in molded or open frame form. In addition, this manufacturing process is compatible with the conformal shielding process important in RF applications. The complete module-on-module can be coated seamlessly and connected to the ground planes of the two substrates.
The module may be a part of product line that requires more functionality over the same foot print. There is the need to houses more components than its predecessor. Such example includes the standard memory package-on-package. However, if the module on top is not of commodity type, or when the volume is not big enough to develop a standard package, this module-on-module architecture and process could be a good solution. Alternatively, one could fix the design of bottom module , and design multiple choices of the top module. When stacked together, the two modules form various different configurations in order to serve different functionalities.
The structure of the module on module is shown in figure 1 below:
Figure 1 Structure of the Module on Module
On the frame board, there are vertical via where vertical electrical and power connection can be made. The frame board is mounted on the main board-II by surface mount process with underfill option. In the figure, a molded module on the top is shown, and an overall coating is applied to the whole module-on-module.
Figure 2 Manufacturing Process of the Module-on-module
The assembly process of the module-on-module is shown in Figure 2. First, the bottom module is manufactured by a one side SMT process and sawed, with the frame board soldered and underfilled. Then, the top module is SMT and molded in a panel form on the one side, and the bottom module is SMT and underfilled on the other side. Last, the complete module is sawed and conformal shielded by the sputtering process. The design of the ground plans of the substrates, together with that of the frame board, makes it such that the coating is connected to the ground planes of the boards.
It is important to study the warpage of such a module-on-module to make sure that it meets the JDEC standards. It is important to assure that the signal integrity of the electrical connections, including RF connections, inside of the frame board meets the requirement. Both simulation and measurement are made to test vehicles of the module-on-module. It is found that the simulation matches the measurement nicely. This module structure can be used for a variety of applications.