Packaging technology by Liquid Mold-UnderFill (MUF) material for the advanced mobile devices
As one approach of advanced packaging technologies, high reliability Liquid Mold UnderFill (Liquid MUF) materials and unique process will be presented here. Liquid MUF materials have the features of high adhesion, low CTE and low modulus. It is possible to alleviate the stress of the solder of each device mounted in the package, and they have excellent reliability too. These materials are adjusted the workability depending on the application. Moreover, because of low viscosity, the Liquid MUF material could be mold-underfilled with relatively lower stress to large Flip Chip devices with small gap and narrow pitch compared to the conventional solid materials. As for the processes of the liquid materials, printing, dispensing and compression molding are applicable. In this paper, the printing process, especially vacuum printing encapsulation systems (VPES) and pressure curing systems, will be mainly discussed. In addition, module package structure that achieved by these material and process development will be also explained in detail.
Wafer level CSP process by VPES (vacuum printing encapsulation systems)
BGA and CSP markets are increasing, but these technologies use plastic or ceramic substrates as interposers, and the packaging size is really larger than chip size. Recently, wafer level CSP as extremity packaging has been introduced. This packaging method starts with the transfer molding method. However, transfer molding of epoxy resin can cause large warpage due to thermal expansion mismatch between wafer and insulating layer after molding, and reliability is poor. In this paper, we developed low cost and high reliability wafer level CSP packaging. We developed very low warpage, low expansion, high adhesive strength, and high purity encapsulating liquid epoxy resin. The coating method used VPES (vacuum printing encapsulation systems) to produce void-free packaging. VPES is very suitable for large scale production. We achieved low cost and high reliability wafer level CSPs as extremity packaging with a good combination of low warpage epoxy resin and VPES.
New packaging of a chip on a board by a unique printing method
Transfer molding is a typical method for packaging integrated circuits (ICs). Transfer molding is very difficult to do at heights less than 1 mm, and has a limited surface mounting area. Recent research of high density surface mounting for thinner and lighter weight packaging has progressed for both IC cards and liquid crystal displays (LCDs). However, the dispensing method has many problems, such as the height variations of the coating, difficulties of uniform spreading on large size ICs, and one-by-one encapsulation. A unique printing method is developed to solve such problems. Through this method it is possible to achieve a height less than 1 mm and a uniform thickness on an integrated system. On reaching these parameters, the surface mount ICs replace molded packaged devices that are manufactured using expensive equipment and molding dies. The method requires only a small amount of epoxy resin and is, therefore, more economical than the conventional transfer molding process. A one-component epoxy resin NPR-150 suitable for printing is developed. >