Authored By:
J. Kress, R. Park, A. Bruderer, and N. Galster
Atotech Deutschland GmbH
Basle, Switzerland
SH Cho
Dongyang Mirae University
Seoul, Korea
Summary
Embedding of actives and passives is a quickly growing field which is being investigated by many companies and institutes. Reasons for this increasing interest are to reduce the complexity of the packages, achievement of higher degree of miniaturization, shorter electrical connections, and a reduction of layer count.
Among other technical challenges, warpage is a major concern. The inherent different thermomechanical properties of the different materials involved cause internal stresses. Those stresses show up as warpage which makes handling during production more difficult, reduces the overall yield, and imparts reliability.
Presented in this paper is a composite type material which can be used as dielectric for the embedding of actives and passives. It combines the advantages of the mechanical stability of prepregs and the good encapsulation properties and ease of handling of resin coated copper foils (RCC). Also described is a concept for simulating the warpage of packages using such composite build-up materials taking into account different resin properties.
Conclusions
New material types can help to overcome some of the challenges of embedding technologies. We presented a type of composite resin material consisting of two distinct dielectric layers which are attached to a carrier foil. In a solvent free manufacturing, ultrathin glass fabrics can be easily employed and relatively thick resin layers for embedding can be created. Such a material combines the advantages of a prepreg (mechanical stability) with the advantages of an RCC (encapsulation properties). The thickness distribution above the dies is excellent which is important for reliable laser drilling processes.
A study was initiated in which the warpage is to be predicted for a defined chip layout and a defined set of material properties. The results of this investigation might allow to minimize warpage for a given layout by adjusting the material properties of the individual layers of the composite.
Initially Published in the SMTA Proceedings
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