Sr. Staff Thermal Engineer

Job Title

Sr. Staff Thermal Engineer

Role Summary

Lead thermal analysis and thermal-management solutions for advanced semiconductor packaging and system designs used in AI and HPC data centers. Work on package technology team to define thermal requirements, simulate and validate designs, and deliver solutions that meet power, reliability, and assembly constraints.

Collaborate with hardware designers, suppliers, and test teams to drive thermal performance from concept through validation.

Experience Level

Senior-level. Role expects proven experience; posting specifies ~5 years of relevant package or system thermal analysis experience.

Responsibilities

Primary responsibilities include simulation, modeling, validation, and cross-functional technical communication.

• Perform steady-state and transient thermal simulations to guide package and system design decisions.
• Develop and validate thermal models for packaging designs, modeling heat transfer, airflow, and thermal interactions in complex electronics.
• Propose and evaluate thermal management solutions (heat sinks, TIMs, heat pipes, vapor chambers, TECs, liquid cooling, immersion, etc.).
• Use CFD results to drive design iterations and improve thermal performance.
• Drive lab-scale characterization and validation through prototypes and vendor experiments.
• Create analytical or semi-empirical quick-turn models for new concepts and product trade-offs.
• Develop and maintain CFD tools, templates, and best practices to improve simulation efficiency.
• Automate modeling and analysis workflows using Python or MATLAB; write technical reports and document methodologies.
• Communicate findings to stakeholders, suppliers, and customers as required.

Requirements

Must-have technical skills and experience; preferred items listed separately.

• Minimum ~5 years of experience in package or system thermal analysis.
• Deep understanding of thermal conduction and convective heat transfer.
• Hands-on experience with CFD and thermal tools such as ANSYS Icepak, ANSYS Fluent, and/or Flotherm.
• Experience setting up and interpreting CFD for complex geometries and boundary conditions.
• Experience designing, modeling, testing, sourcing, and deploying thermal technologies (TECs, heat pipes, vapor chambers, TIMs, phase change materials, liquid and air cooling systems).
• Working knowledge of lab-scale validation and characterization techniques for thermal designs.
• Ability to develop automation scripts (Python or MATLAB) to improve modeling throughput.
• Strong technical communication and ability to work in cross-functional teams.
• Ability to comply with U.S. export control requirements when applicable.

Nice-to-have:

• Knowledge of fluid dynamics and assembly/process modeling for 2D/3D packaging technologies.
• Experience with two-phase immersion cooling and single- or two-phase liquid flow.
• Familiarity with thermal technologies in HPC and data centers and with thermal control algorithms.
• Experience with statistical analysis, DOE, or JMP.

Education Requirements

M.S. or Ph.D. in Mechanical Engineering, Materials Science, Chemical Engineering, or a related engineering field (degree explicitly required in posting).

About the Company

Company: Lightmatter

Headquarters: Boston, Massachusetts, USA

Lightmatter develops photonic AI data-center infrastructure and optical chips for extreme-scale AI and HPC. The company invented the Passage 3D‑stacked photonics engine to provide high-bandwidth, low-latency interconnects across large-scale processors and raised $400M in Series D financing at a reported $4.4B valuation.