Modelling Indium Interconnects for Ultra Fine-Pitch Focal Plane Arrays

Stoyanov, Stoyan; Bailey, C.; Waite, Rhys; Hicks, Christopher; Golding, T. D.

doi:10.1109/itherm45881.2020.9190397

Cited by 1 publication

(1 citation statement)

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“…The indium solder visco-plastic behavior is modelled using the Anand inelastic strain rate model. The material model constants for indium are taken from [31] and the model has been previously demonstrated in the modelling of the thermal fatigue performance of FPA interconnects under cycling thermal load at cryogenic condition [32,33]. The models for the dynamic behavior of liquid indium, related to selfalignment of flip-chip in the case of FPA assembly using reflow bonding process, require also the following additional properties of indium, sourced from [34,35]:…”

Section: Fpa: Bill Of Materials and Propertiesmentioning

confidence: 99%

Modeling Insights Into the Assembly Challenges of Focal Plane Arrays

Stoyanov

Bailey

2023

IEEE Access

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Ongoing technological advances in photodetector material growth and processing, readout integrated circuits, and robust hybridization (packaging) methods for assembling high-resolution and smallpitch size pixel arrays are the main enabling factors for pushing the frontiers of high-performance Focal Plane Array (FPA) technologies for imaging systems. This paper details the development of analytical and numerical models and demonstrates their use to generate insights into the feasibility of two flip-chip assembly processes for packaging infrared (IR) detector chips. The modelling studies focus on the challenges of forming the indium interconnection arrays in the case of the FPA technologies using Group III-V compound semiconductor materials and ultra-fine pitch pixel array layouts. The accurate alignment of the IR detector chip onto the readout chip in the case of high-density pixel architectures is a critical requirement for the packaging process. To gain better understanding of this requirement, which has a clear implication for the quality and subsequent reliability performance of the FPA, compression and reflow bonding process models are developed using suitable modeling approaches and methods and then demonstrated for two distinctive focal plane array design configurations. The novelty of this work is in the developed modeling capabilities utilizing different computational methods, from large deformation and contact analysis finite element to energy-based and harmonic motion mechanics, to characterize and optimize the mechanical and dynamic non-linear behavior of the indium solder joints and their formation during FPA packaging. The feasibility of bonding techniques for different resolution FPAs and under flip-chip misalignment conditions is assessed. The modeling results pointed to a very strict, sub-micrometer flip-chip placement accuracy requirement for the assembly of FPAs with ultra-fine indium bump array resolution.INDEX TERMS IR detectors, Focal Plane Array, compression bonding simulation, reflow self-alignment modeling, indium joints, ultra-fine pitch flip chip assembly, compound semiconductors.

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