Fluidic Self-Assembly and Interconnection Processes: Fundamental Research, Scaling Limits, and Applications
Synthesis and Properties of Functional Materials
Microsystems
Production Automation and Assembly Technology
Final Report Abstract
The research focused on the following goals: (1) demonstrate working self-assembly principles, (2) establish a fluidic selfassembly platform that enables reel to reel like assembly of chips in a massively parallel manner, (3) and apply the process to enable the assembly of “Solid State Lighting Panels”. Good progress was made on these goals and a total of 5 journal papers have been published. • The first paper entitled “A First Implementation of an Automated Reel-to-Reel Fluidic Self-Assembly Machine” was published in Advanced Materials in 2014. The research was featured on the cover. This was the realization of the system that we originally proposed. The reported assembly process was no longer a discontinuous small-batch hand-operated process but resembled for the first time an automated machine like process involving a conveyer belt and a reel-to-reel (RTR) type assembly approach with automated agitation. • In 2015 we studied operational parameters to improve the originally low assembly yield. Many questions remain. However, the new level of understanding was critically important to reach a sufficiently high assembly yield (exceeding 99%). This metric is important for the work to be recognized as relevant. A low assembly yield would disqualify the process. • The gained assembly yield was sufficiently high to demonstrate an application. Specifically, the process was applied to fabricate solid state lighting modules (only small panels). This “potential” test bed application is exactly what we proposed at the outset of the program. • We were also able to make a contribution to the field of stretchable electronics; this was originally not proposed/anticipated. Stretchable electronics requires the assembly of devices on elastomeric substrates. This has been challenging using established robotic pick and place methods – our own robotic assembly attempts fail due to registration and alignment issues on the elastomeric substrates; moreover damage of the interconnects has been an issue on these substrates. We studied surface functionalization schemes and were able to demonstrate fluidic self-assembly of electronic chips on stretchable elastomeric substrates. • In 2016 we published an article entitled "Surface Tension Directed Fluidic Self-Assembly of Semiconductor Chips across Length Scales and Material Boundaries" to describe some of the scaling laws and challenges going forward. The ability to assemble truly microscopic chips was identified as the most important research and focus going forward. • In the last stage of the research we studied an originally proposed solder stack idea, now referred to as “Core-Shell Transformation Imprinted Solder Bumps”. The bumps use the high surface free energy of the liquid shell during the selfassembly to capture freely suspended Si-dies inside a heated (80 °C) water bath leading to wellordered defect free chip arrays; the molten liquid shell wets the metal contact (binding site) on the chips and yields self-aligned and electrically connected devices. The solid core provides the anchor point to the substrate. After the completion of the assembly, a short reflow raises the melting point yielding a solid electrical connection. The tuning of the material ratios leads to tailored transformation imprinted solders with high melting points (160 °C to 206 °C) in the final structure.
Publications
- “A First Implementation of an Automated Reel-to-Reel Fluidic Self-Assembly Machine,” Advanced Materials 26 5942–5949 (2014)
Se‐Chul Park, Jun Fang, Shantonu Biswas, Mahsa Mozafari, Thomas Stauden, Heiko O. Jacobs
(See online at https://doi.org/10.1002/adma.201401573) - “Method of and apparatus for self-assembly of components on a substrate”, EU Patent: EP2688093 A1, 22/01/2014
H. O. Jacobs
- “Approaching Roll-to-Roll Fluidic Self-assembly: Relevant Parameters, Machine Design, and Applications”, IEEE Micro PP (99) (2015)
Se-Chul Park, Jun Fang, Shantonu Biswas, Mahsa Mozafari, Thomas Stauden, and Heiko O. Jacobs
(See online at https://doi.org/10.1109/JMEMS.2015.2452772) - “Method of self-assembly of components on a substrate”, EU Patent EP 2790212 B1, 09/16/2015
H. O. Jacobs
- “Millimeter Thin and Rubber-Like Solid-State Lighting Modules Fabricated Using Roll-to-Roll Fluidic Self-Assembly and Lamination,”Advanced Materials 27: 3661– 3668 (2015)
Se-Chul Park, Shantonu Biswas, Jun Fang, Mahsa Mozafari, Thomas Stauden, and Heiko O. Jacobs
(See online at https://doi.org/10.1002/adma.201500839) - "Deformable printed circuit boards that enable metamorphic electronics" NPG Asia Materials 8 (2016)
Shantonu Biswas, Andreas Schöberl, Mahsa Mozafari, Jörg Pezoldt, Thomas Stauden and Heiko O. Jacobs
(See online at https://doi.org/10.1038/am.2016.186) - "Surface Tension Directed Fluidic Self-Assembly of Semiconductor Chips across Length Scales and Material Boundaries" Micromachines 7(4) 54 (2016)
Shantonu Biswas, Mahsa Mozafari, Thomas Stauden, and Heiko O. Jacobs
(See online at https://doi.org/10.3390/mi7040054)
