Three-dimensional integrated circuits (3D IC) based on TSV (Through Silicon Via) technology is the latest packaging technology with the smallest size and quality.
Finally, a complete test vehicle with a molded-underfilled interposer reported on an organic substrate has been achieved.
Cross-sections have highlighted cracks in solder joints leading to the development of an improved version of the compound. While the daisy chains resistances remained in specifications after molding and pre-conditioning, some electrical failures appeared after 250 thermal cycles. Electrical performances of the 35μm high Cu pillars interconnections have been measured on the interposer backside thanks to TSVs and rerouting. 170μm thick dice have been assembled on 120μm thin silicon interposers having 60μm diameter TSV via-last and encapsulated with optimized wafer-level MUF process. For this study, a molding-last approach using a dry-film lamination process has been chosen. A focus is made on void-less molding-underfilling process development and wafer level reliability evaluation of first level (die to wafer) interconnections and TSV subjected to thermal cycles. After a materials screening with regard to warpage issue, “molding last” was studied with the selected material, including compatibility with temporary bonding debonding, bumping, sawing and report on organic substrate. The developments were carried out in the frame of “silicon package” where the silicon interposer is either reported on P-BGA or directly assembled on board.
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Manufacturability issues are discussed together with the need for good reliability of the stretchable interconnections when stress is applied during stretching.This paper is dedicated to the full integration of a new silicone-based material for Molding-Underfilling (MUF) on silicon interposer wafers containing Through Silicon Vias (TSVs) and top dice. The reliability of the overall system is improved by varying the thickness of the embedding polymer, wherever the presence and type of components requires to. Embedding is done by moulding the electronic device in a stretchable polymer. This new developed technology is based on the combination of rigid standard SMD components which are connected with 2-D spring-shaped metallic interconnections. The process steps used are standard PCB fabrication processes, resulting in a fast technology transfer to the industry.
In this contribution a new low cost, elastic and stretchable electronic device technology will be presented, based on the use of a stretchable substrate. Conformable and elastic circuitry is an emerging topic in the electronics and packaging domain. Electronics for implantation on the other hand should ideally be soft and conformable in relation to the body tissue, in order to minimize the rejecting nature of the body to unknown implanted rigid objects. They should be soft, conformable and to a certain degree stretchable. Those devices should become invisible to the user, especially when they are embedded in clothes (e.g. Compared with the single copper or gold trace, the calculated stress was reduced up to 10 times.Ī growing need for ambient electronics in our daily life leads to higher demands from the user in the view of comfort of the electronic devices. In this way, each conductor track has been split in four parallel lines of 15 mum and 15 mum space in order to improve the mechanical performance without limiting the electrical characteristics. Moreover, the damage in the metal is significantly reduced by applying narrow metallization schemes. This design allows a large deformation with the minimum stress concentration. Different configurations were simulated and compared among them and based on these results, a horseshoe like shape was suggested. Common metal conductors used in the electronic industry have very limited elastic ranges therefore a metallization design is crucial to allow stretchability of the conductors going up to 100%. A silicone material was chosen as substrate because of its low stiffness and high elongation before break. These interconnections are done by embedding sinuous electroplated metallic wires in a stretchable substrate material.
In this work, the design of flexible and stretchable interconnections is presented.
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