Packaging Engineer- Materials

We’re looking for a hands-on process and materials engineer to own wafer level molding and underfill processes, material qualification, and assembly integration across development and manufacturing. Summary: Seeking an experienced engineer to lead wafer level mold and underfill process development for advanced semiconductor packages (fan-out wafer level packaging, 2.5D/3D, chiplet). This role spans mold compound and underfill material selection and qualification, wafer level molding and encapsulation processes, underfill dispense and cure, reliability, failure analysis, and cross-functional support through package and system productization. Core Responsibilities: • Develop and optimize wafer level molding processes including compression molding, transfer molding, and mold underfill (MUF) for fan-out and advanced heterogeneous packages. • Own mold compound and underfill material selection and qualification, including evaluation of filler content, CTE, modulus, Tg, viscosity, and moisture uptake to meet thermo-mechanical and reliability requirements. • Drive underfill process development including capillary underfill (CUF) dispense strategies, flow and void optimization, and cure profile development for high-density flip chip and chiplet assemblies. • Evaluate and mitigate assembly risks including warpage, delamination, void formation, bleed-out, mold flash, and filler settling; define process windows and controls to ensure repeatable yield across wafer and panel formats. • Collaborate with OSATs and material suppliers to qualify mold and underfill materials, define dispense and cure equipment requirements, and manage process transfers into production. • Lead characterization of mold and underfill material properties (viscosity, gel time, cure kinetics, adhesion, CTE, modulus) and correlate material behavior to process outcomes and package reliability. • Work closely with thermal mechanical modeling teams to model solder joint reliability of bump interconnects with various underfills and predict warpage with various mold compouds. • Support reliability qualification including thermal cycling, drop, mechanical shock, and power cycling. • Work cross-functionally with design, reliability, thermal, and manufacturing teams to ensure robust package performance from concept through high-volume production. Required Technical Skills: • Strong experience in wafer level molding and underfill processes for advanced semiconductor packages including fan-out wafer level packaging (FOWLP), 2.5D, and chiplet architectures. • Deep understanding of mold compound and underfill material science including epoxy resin systems, filler particle size and loading, cure chemistry, and how material properties drive thermo-mechanical package behavior. • Experience with underfill dispense techniques (capillary, no-flow, mold underfill), flow and void characterization, bleed-out control, and cure process optimization including staged and snap cure profiles. • Understanding of thermo-mechanical behavior driven by mold and underfill materials including CTE mismatch, warpage evolution through cure and reflow, delamination driving forces, and material-induced reliability risks. • Hands-on experience with failure analysis of mold and underfill failures including cross-sections, SEM/EDS, CSAM, TGA, DSC, and DMA for material characterization and thermal cycling reliability evaluation. • Ability to work with OSATs and material suppliers to develop, qualify, and transfer mold and underfill processes into production, including equipment setup and process control plans. • Strong problem-solving skills with ability to debug mold and underfill yield and reliability issues in manufacturing environments, including DOE-driven process optimization. Preferred / Differentiating Skills: • Experience underfill materials for III-V or photonics packaging including optically clear encapsulants and low-modulus underfills. • Experience with mold and underfill integration in advanced packaging architectures including 2.5D interposers, 3D stacking, chiplet assemblies, and CoWoS-like structures where material interactions and warpage are critical constraints. • Familiarity with a broad bill of materials for advanced packaging encapsulation including clear adhesives and underfills for photonics, high-filler, low-CTE mold compounds for 2.5D interposer assemblies. • Experience developing mold and underfill solutions for high-power or high-TDP devices where material thermal conductivity, warpage stability, and coefficient of thermal expansion are tightly constrained. • Exposure to thermo-mechanical modeling or collaboration with simulation teams for warpage prediction, delamination risk assessment, and material property sensitivity analysis for mold and underfill optimization. • Understanding of system-level interactions (TIM application and cold plate interaction with wafer level molded wafer).