Sr. Staff Thermo-Mechanical Engineer

Lightmatter is leading the revolution in AI data center infrastructure, enabling the next giant leaps in human progress. The company invented the world’s first 3D-stacked photonics engine, Passage™, capable of connecting thousands to millions of processors at the speed of light in extreme-scale data centers for the most advanced AI and HPC workloads. Lightmatter raised $400 million in its Series D round, reaching a valuation of $4.4 billion. We will continue to accelerate the development of data center photonics and grow every department at Lightmatter! If you're passionate about tackling complex challenges, making an impact, and being an expert in your craft, join our team of brilliant scientists, engineers, and accomplished industry leaders. Lightmatter is (re)inventing the future of computing with light! In this role, you will work on leading-edge packaging technologies to enable AI architectures that will set new industry standards regarding compute power, performance, and efficiency. You will collaborate with the packaging team to carry out the required structural analysis for packaging technologies under consideration, identify key failure modes under product use conditions, and run appropriate parametric studies to influence product and package design upstream. You will focus on thermo-mechanical analysis and characterization of advanced photonics packaging technologies, including 3D stack development, heterogeneous integration of lasers and novel fiber attach methods, to define design, material, and process solutions that successfully meet assembly and reliability requirements. The results of your work will lead to advanced package designs that meet power dissipation, optical, assembly, and reliability requirements while delivering a system-level solution for leading-edge products in the AI market. Responsibilities: • Serve as the technical authority for thermo-mechanical simulation within the packaging organization, setting standards for model fidelity, validation methodology, and documentation practices adopted across the team. • Identify capability gaps in simulation tooling, characterization methods, or material databases and champion fundamental investigations that strengthen the team's long-term technical foundation. • Develop finite element stress, warpage, and assembly process models for wafer-level and unit-level photonic packaging, identifying design, process, and material parameters to mitigate failure modes and optimize yield. • Perform analysis to identify key reliability risks under product use conditions and drive appropriate design and material solutions to improve product mechanical integrity. • Conduct multi-physics simulations including solder collapse modeling for bump architecture definition and thermal-structural analysis for packaging stress to meet thermal, electrical, and optical requirements. • Develop analytical or semi-empirical models for quick turn assessments for new product concepts. • Drive characterization and validation of mechanical designs and electronic assemblies through lab-scale prototyping and vendor-initiated experiments, closing the loop between simulation predictions and physical hardware. • Develop Python and MATLAB automation frameworks to scale simulation throughput and establish repeatable, high-efficiency modeling workflows. • Summarize and communicate findings and recommendations with authority to key stakeholders across Lightmatter, suppliers, and customers. • Write reports and document methodologies that serve as the technical foundation for the packaging team. Required Qualifications: • MS or PhD in Mechanical Engineering, Material Science, or a related engineering field. • Deep expertise in finite element analysis using commercial tools such as Ansys, Abaqus, or equivalent, with demonstrated ability to develop and validate models for complex multi-material assemblies. • Hands-on experience with multi-physics simulation including thermal-structural coupling, solder joint fatigue modeling, and warpage analysis. • Strong understanding of semiconductor packaging failure modes including solder fatigue, delamination, CTE mismatch-driven stress, and underfill cracking under thermal cycling conditions. • Experience with wafer-level and unit-level assembly processes including flip-chip, BGA, and advanced 3D packaging architectures. • Proficiency in Python and/or MATLAB for simulation automation, data analysis, and scripting. • Demonstrated ability to develop analytical or semi-empirical models for first-order engineering assessments. • Experience driving characterization and validation programs through internal prototyping and external vendor collaboration. Preferred Qualifications: • Proven track record of communicating complex technical findings to cross-functional audiences including design, process, and product engineering teams. • Strong technical writing skills with experience producing simulation reports, design guidelines, and methodology documentation. • Experience with photonic packaging technologies including silicon photonics, co-packaged optics, fiber attach, or heterogeneous integration of laser devices. • Familiarity with optical packaging reliability requirements and the intersection of thermo-mechanical performance with optical alignment stability. • Ability to work independently and manage multiple projects with minimal supervision. • Experience with statistical analysis tools and techniques such as DOE and JMP. • Strong creative thinking skills with the ability to solve problems quickly. We offer competitive compensation. The base salary range for this role determined based on location, experience, educational background, and market data.Salary Range: total compensation goes beyond base salary, it also includes a new hire equity grant, annual performance-based equity, and other rewards that recognize your impact and contribution.$169,000—$244,000 USD Benefits • Comprehensive Health Care Plan (Medical, Dental & Vision) • Retirement Savings Matching Program • Life Insurance (Basic, Voluntary & AD&D) • Generous Time Off (Vacation, Sick & Public Holidays) • Paid Family Leave • Short Term & Long Term Disability • Training & Development • Commuter Benefits • Flexible, hybrid workplace model • Equity grants (applicable to full-time employees) Benefits eligibility may vary depending on your employment status and location. Lightmatter recruits, employs, trains, compensates, and promotes regardless of race, religion, color, national origin, sex, disability, age, veteran status, and other protected status as required by applicable law. Export Control Candidates should have capacity to comply with the federally mandated requirements of U.S. export control laws.