This work presents an experimental investigation of adhesive-based die attachment using the Drop-Attach technique, compared with the conventional pick-and-place method. Drop-Attach is a contactless process that eliminates the mechanical stresses inherent to force-assisted placement. In this method, dies are optically aligned and released—via a short air pulse—from a height of 100–300 μm above a substrate coated with a flat adhesive layer, enabling pressure-free, contactless placement. The process achieves smaller cycle times, potentially improving the throughput over conventional methods that require additional time for deceleration and bonding-force buildup. To assess feasibility and performance, a silver-filled bismaleimide/acrylate adhesive was printed on ENIG-finished pads, and dummy silicon dies with Au-, Ag-, and Cu-coated surfaces were assembled using both techniques. Bond quality was comprehensively analysed through measurements of bond line thickness, die tilt, void formation, die-shear strength, failure mechanisms, and electrical performance. Drop-Attach achieved minimal die tilt (≤0.1°) and uniform BLTs, though higher voiding and ∼9.55% increased electrical resistance were observed. The lower shear strength was primarily attributed to the absence of adhesive fillet formation rather than the lack of applied pressure. While trade-offs remain, this study demonstrates the feasibility of adhesive-based die attachment using the Drop-Attach method, which enables faster cycle times and higher throughput while significantly reducing mechanical stresses. These advantages position Drop-Attach as a promising technique for next-generation semiconductor packaging. ... Read more

Handling ultra-thin semiconductor dies during assembly remains challenging due to their mechanical fragility and sensitivity to placement forces. Contactless die transfer methods reduce mechanical loading and have potential to enable higher placement speeds and improved throughput but introduce challenges such as uncontrolled impact dynamics, die rebound, and misalignment during landing. This work investigates a liquid-assisted contactless adhesive bonding approach in which droplets deposited on stencil-printed conductive adhesive act as transient damping and alignment media during die landing. Dummy silicon dies with a gold (Au) surface finish were released from a short distance onto the adhesive. Four liquids with different physical and chemical properties—deionized (DI) water, isopropyl alcohol (IPA), acetone, and liquid flux—were investigated to evaluate the influence of key fluid parameters, including surface tension, viscosity, and density, on die impact dynamics, stabilization, and subsequent bonding quality. The results demonstrate that droplet material properties significantly influence die landing dynamics in liquid-assisted contactless assembly. Among the investigated liquids, deionized water enabled reliable die entrapment and damping. In contrast, for the lower-surface-tension solvents isopropyl alcohol (IPA) and acetone, the droplets were not sufficiently confined under the experimental conditions, and therefore no direct die entrapment was observed, although impact damping was still achieved. Die entrapment and stabilization behavior were analyzed using high-speed camera recordings and complementary two-dimensional simulations performed in COMSOL Multiphysics. Furthermore, the impact of the droplets on the resulting bond interface and joint quality was evaluated through post-bond characterization. The study provides insight into droplet-mediated die landing and offers guidelines for selecting liquids for reliable contactless micro-assembly. ... Read more