Analysis of interfacial peeling in IC chip pick-up process

Abstract

The IC chip–ejecting and pick-up process plays a critical role in advanced packages since the success ratio and productivity are determined by the delamination of the chip-on-substrate structure. The paper investigates analytically the interfacial peeling mechanism of a chip-on-substrate structure subjected to a transverse concentrated load resulting from ejecting needle from the fracture mechanics point of view. The effects of key factors, including chip size, initial crack length, and substrate material, are uncovered. Finite element calculations are performed to obtain the interfacial peeling energy-release rate by using virtual crack-closure technique with dummy nodes. Analytical formulas and numerical results match fairly well for the entire range of the chip length and the crack length. It is shown that the greater the ratio of length to thickness of the chip is, the smaller the energy-release rate is, and length is the more important factor than thickness to affect the peeling. It implies the interfacial peeling gets tougher for thin or big chips during the pick-up process. Second, as the crack grows, the peeling energy-release rate increases. Third, the softer the substrate is, the greater the peeling energy-release rate is under the action of a constant transverse load. For the pick-up of thin or big chips, in order to achieve high success rate and suppress damage to the chip, it is suggested that more compliant and thinner substrate be adopted, weaker adhesive strength be chosen, and multiple needles be used.

An analytical mechanics model for the island-bridge structure of stretchable electronics

“…Appendix: derivation of eqn (17) The characteristic equation of the eigenvalue problem (16b) with the roots denoted by x gives D(x 2 + m 2 ) 2 + k ¼ 0, which yields…”

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Programmable and scalable transfer printing with high reliability and efficiency for flexible inorganic electronics

“…A crucial step in manufacturing these unconventional electronic systems relies heavily on heterogeneous integration of inorganic materials with soft polymeric substrates, which requires the transfer of tiny, ultrathin, and delicate functional components (i.e., inks) from their fabricated rigid wafers to target soft polymeric substrates. However, the well-established pick-andplace techniques (i.e., single-ejector needle or vacuum nozzles) are unable to meet this stringent requirement (8,9). As an emerging manufacturing technique, transfer printing enables the assembly of multiscale and classes of materials on demand using a soft stamp and has been demonstrated to be a promising solution (10)(11)(12)(13)(14)(15)(16)(17).…”

Laser Transfer, Printing, and Assembly Techniques for Flexible Electronics

“…Distinctive assembly techniques based on stress‐induced interface fracture have been invented to be adaptive to the diversity of material properties and geometric sizes that lead to tremendous differences in mechanical properties. For those conventional rigid electronic components like IC chips, they are transferred by standard single‐ejector needle pick‐and‐place technique . With the increasing of the ratio of size to thickness, improved multiple‐ejector needles are developed to overcome the increasing flexibility of chips .…”