Flexible pillars for displacement compensation in optical chip assembly

Power delivery, signaling and cooling for 2D and 3D integrated systems

“…At distances of ±25 µm away from the center, the optical coupling improvement due to the pin exceeds 4 dB. The 4 dB coupling improvement is significantly larger than the 0.23 dB excess loss of the pins [33,34], which clearly demonstrates the benefits of the pins. Note that the profile of the relative intensity curve of the optical pin is almost flat across the entire endface of the pin and abruptly drops beyond the edges of the pin (X=±25 µm).…”

“…The height separation between the chip and the substrate has minimal effect on the optical power received at the photodetector (except for losses through the polymer pin) because the light is tightly confined within the crosssectional area of the pin. Although we consider using polymeric materials with relatively high optical absorption losses for the fabrication of the optical pins, due to their very short length (height), the optical transmission losses through the pins are small [33,34]. The optical pins are designed to be mechanically compliant (flexible).…”

“…The top of Figure 2.17 demonstrates that for a given loss budget of, e.g., 1 dB, the 50x150 µm flexible pins double the displacement tolerance from less than 15 µm to approximately 30 µm. The 4 dB pin-assisted loss reduction at the 30 µm displacement can decrease the BER by few orders of magnitude [33,34]. Thus, the optical pins provide a method of reducing optical coupling losses caused by thermomechanically induced misalignment between the CTE mismatched chip and substrate.…”

Deep Proton Writing: A Rapid Prototyping Tool for Polymer Micro-Optical and Micro-Mechanical Components

“…The most commonly used approach is the use of 45 • micro-mirrors, which are generally directly integrated in the PCB-embedded waveguides (Glebov et al, 2005;Hendrickx et al, 2007;a;Yoshimura et al, 1997). To enhance the coupling efficiency when using waveguide-integrated micro-mirrors, we investigated a pillar-assisted coupling scheme, in which an optical micro-pillar is placed between a surface-mounted laser/detector and an out-of-plane coupling micro-mirror to compensate for differences in thermal expansion of the materials (Glebov et al, 2006). Our optical simulations showed that the introduction of pillars in the coupling system increases the link efficiency by several dBs and that the tolerance for mechanical misalignments also strongly increases.…”

‘trimoda’ Wafer-Level Package: Fully Compatible Electrical, Optical, and Fluidic Chip I/O Interconnects

“…Moreover, due to the flexible nature of the polymer pins, it was also demonstrated that the optical polymer pins can maintain high coupling efficiency between the chip and substrate during misalignment, which may be induced due to the coefficient of thermal expansion (CTE) mismatch between the die and package substrate. It was shown that for a 30 ptm misalignment, a 50x150 ptm polymer pin maintains optical interconnection and incurs only a 1 dB loss [4,5].…”