Packaging Engineer- Materials

Volantis Semiconductor · San Francisco

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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).

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