Development of low-K encapsulating film for stacked packages

In recent years, semiconductor packages have become more compact and more highly integrated, as electronic devices have become thinner, lighter, faster, and have provided higher degree of performance to keep up with market demand. Stacked packages are progressing as one of the technologies that meet the said demand. We have developed a novel thermosetting resin that has a low dielectric constant. Using this material, we have developed an encapsulating film that could be used for stacked packages ([1],[2]). We propose a simple stacked-packages manufacturing process using the encapsulating film: First, a semiconductor element is mounted on a substrate, and it is encapsulated by the encapsulating film with circuits. Then another semiconductor element is mounted on the circuits on the encapsulating film. By repeating the process of encapsulating and mounting the semiconductor elements, the stacked package is achieved. The semiconductor elements in this stacked package could be connected to each other easily by using the vias that were formed in the film. Our low-K encapsulating film would provide good high-frequency characteristics. The physical properties, processability and encapsulating condition of the film, and some package reliabilities, will be discussed in this paper.