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).