Sea-of-leads MEMS I/O interconnects for low-k IC packaging

Technology feasibility of MEMS-type chip I/O interconnects (namely Sea-of-Leads or SoL) is demonstrated. Acting like a spring, a MEMS lead can provide high mechanical compliance to compensate for mismatch of coefficient of thermal expansion (CTE) between a Si chip and a composite substrate. The comp...

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Bibliographic Details
Published in:Journal of microelectromechanical systems 2006-06, Vol.15 (3), p.523-530
Main Authors: Dang, B., Bakir, M.S., Patel, C.S., Thacker, H.D., Meindl, J.D.
Format: Article
Language:English
Subjects:
Assembly
Chips
Circuit boards
Dielectric substrates
Exact sciences and technology
Failure analysis
Instruments, apparatus, components and techniques common to several branches of physics and astronomy
Integrated circuit packaging
Integrated circuits
Interconnections
Lead
Low-k interlayer dielectrics
Mechanical instruments, equipment and techniques
Microelectromechanical systems
microelectromechanical systems (MEMS) I/O interconnects
Micromechanical devices
Micromechanical devices and systems
Packaging
Physics
Printed circuits
Semiconductors
Silicon substrates
solder joints
Soldering
Solders
Springs
Thermal expansion
underfill
Wafer scale integration
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Summary:Technology feasibility of MEMS-type chip I/O interconnects (namely Sea-of-Leads or SoL) is demonstrated. Acting like a spring, a MEMS lead can provide high mechanical compliance to compensate for mismatch of coefficient of thermal expansion (CTE) between a Si chip and a composite substrate. The compliant interconnects can provide low-stress connection between a chip and a PWB substrate, and, therefore, are promising to enable wafer-level packaging of IC chips with mechanically weak low-k interlayer dielectrics (ILD). The compliant interconnection also eliminates the need for an expensive underfilling process, which is one of the key challenges for scaling of conventional controlled collapse chip connection (C4) solder bumps in organic flip-chip packages. For the first time, SoL MEMS interconnects were investigated through the whole procedure of process integration, assembly, as well as reliability assessment. Without underfill, the SoL MEMS interconnects survived more than 500 thermal cycles indicating a promising improvement over a regular C4 solder joint. Failure analysis suggests that the MEMS leads do not fracture while failure occurs close to solder-Cu pad interface due to a nonreliable joining. Full reliability potential of the SoL MEMS interconnects may be demonstrated upon optimization of PWB metallurgy, soldermask design and lead compliance.
ISSN:1057-7157
1941-0158
DOI:10.1109/JMEMS.2006.876792