Article pubs.acs.org/cm
Polycyclic Aromatic Hydrocarbons as Sublimable Adhesives Haydn T. Mitchell,† Merry K. Smith,† Nicholas D. Blelloch,† Douglas W. Van Citters,‡ and Katherine A. Mirica*,† †
Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, United States
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S Supporting Information *
ABSTRACT: Polycyclic aromatic hydrocarbons (PAHs) are used as adhesives that can be removed on-demand by sublimation without application of solvent or mechanical force. These adhesives are polycrystalline solids that enable bonding of glass, metal, and plastic with lap shear forces ranging from 5 to 50 N cm−2. Systematic examination of factors governing bonding suggests that favorable chemical interactions between bonded surfaces and PAHs, and structural features at the surface of the substrate influence both the lap shear force and the mechanism of failure. Utilizing sublimable PAHs enables sequential bonding and release of substrates, as well as control of actuation of electronic systems through mechanical work.
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INTRODUCTION Temporary adhesives are used in construction,1 robotics,2 and electronics.3,4 Temporary adhesives are particularly important in the miniaturization of (3D) microelectronic devices, integrated circuits patterned on 2D silicon wafers stacked in 3D assemblies, but designing adhesives with the required strength and capacity for debonding remains a practical challenge.3,5,6 While reduction of planar features through decades of innovation in lithographic patterning has progressed on pace with Moore’s Law,7−10 reduction of bulk thickness in stacked semiconductors beyond the microscale is limited by the current selection of temporary adhesives that can bond thin structures during 3D electronics assembly without causing damage during debonding.11−13 As lithography and planar features approach their physical limit,10,14−17 it is increasingly important that silicon wafers reach submicron thicknesses to remain on pace with Moore’s Law in the future. Previous research on wafer thinning has focused on two aspects: (i) improving existing equipment and techniques for processing,12,13,18,19 and (ii) studying the mechanics of crack propagation to avoid fracturing.18−21 While these efforts have led to improvements, the typical method for processing silicon wafers has remained relatively constant for the past six decades.5,12,13 This process involves bonding the silicon wafers to a rigid carrier for mechanical stability before thinning to a thickness of
