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.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.