Sr. Thermal Systems Engineer

Company:

Flex Location:

Littleton, MA Career Level:

Mid-Senior Level Industries:

Technology, Software, IT, Electronics Description Job Posting Start Date 03-09-2026 Job Posting End Date 05-08-2026 At JetCool, a Flex company, we're at the forefront of liquid cooling innovation, delivering advanced solutions that empower our partners in AI and high-performance computing. United by a shared purpose, our teams are pushing the limits of what's possible and tackling complex challenges. A career at JetCool offers the opportunity to make a real impact by helping build smarter, more sustainable data centers. Together, we're not just advancing technology — we're redefining cooling standards to create a more sustainable tomorrow. Job Summary To support our extraordinary teams who build great products and contribute to our growth, we're looking to add a Senior Thermal Systems Engineer located in Littleton, MA. Reporting to the Product Manager the Senior Thermal Systems Engineer will own the end-to-end architecture, analysis, validation, and deployment of direct-to-chip (D2C) cooling systems used to cool high-TDP CPUs/GPUs/accelerators. They will be the technical leader partnering with Product Management, Mechanical/Electrical Engineering, Manufacturing, Quality, Reliability, and key customers to deliver robust, scalable products that meet performance, reliability, and cost targets. What a typical day looks like: Own thermal architecture & modeling Define system-level thermal requirements (TDP range, ΔT, coolant temperature, flow rate, pressure drop, acoustic & power budgets). Apply first principles in fluid dynamics and heat transfer to analyze design concept thermal performance Build and validate 1D/3D models (e.g., FloEFD, Icepak, MacroFlow, ANSYS Fluent, COMSOL) for cold plates, manifolds, quick-disconnects (QDs), pumps, and CDUs. Perform sensitivity trade-offs (flow distribution, fin geometry, microchannel optimization, TIM selection, manifold topology). Design liquid cooling subsystems Specify and refine cold plates, CDUs, manifolds, hoses/QDs, reservoirs, filters, sensors, and controls. Collaborate with ME/EE on mechanical stack-up, materials, corrosion mitigation (galvanic compatibility), and leak risk reduction. Define DFX (DFM/DFA/DFT) and lead

EVT/DVT/PVT

from prototypes to mass production. Validate and qualify Develop test plans for thermal performance, pressure integrity, leak detection, long-term reliability (HALT/HASS), and contamination control (particulates, biogrowth). Execute lab and rack-scale testing (pump curves, flow balance, ΔP mapping, heat load emulation, transient behavior). Drive failure analysis and corrective actions (FMEAs, 8D/PPS). Partner across the business Work with Product Management on PRDs, roadmaps, and business cases. Support manufacturing process development (leak/pressure test stations, purge and fill, cleanliness criteria) and supplier selection/qualification.

Engage with customers:

define requirements, run pilots, analyze fleet telemetry, and support deployment at scale. The experience we're looking to add to our team: BS/MS in Mechanical Engineering or Aerospace Engineering or related field (PhD a plus). 5+ years experience in thermal design/validation for high-power electronics (preferably data center/server/HPC). Excellent first principles knowledge in fluid dynamics, thermodynamics, and heat transfer Proven expertise in liquid cooling, including CFD, pressure drop/flow modeling, and thermal metrology. Hands-on with lab instrumentation (flow meters, pressure transducers, thermocouples/RTDs, DAQ, leak detectors) and test automation (Python, LabVIEW, or similar). Experience bringing products from EVT → DVT → PVT → ramp, including DFX and supplier engagement. Excellent technical communication and documentation skills. BO18 What you'll receive for the great work you provide: Full range of medical, dental, and vision plans Life Insurance Short-term and Long-term Disability Matching 401(k) Contributions Vacation and Paid Sick Time Tuition Reimbursement Pay Range (Applicable to Massachusetts) $123,500.00 USD - $169,800.00 USD Annual Job Category Design, Process & Technology Engineering Is Sponsorship Available? No JetCool is an Equal Opportunity Employer and employment selection decisions are based on merit, qualifications, and abilities. We do not discriminate based on: age, race, religion, color, sex, national origin, marital status, sexual orientation, gender identity, veteran status, disability, pregnancy status, or any other status protected by law. We're happy to provide reasonable accommodations to those with a disability for assistance in the application process. Please email accessibility@flex.com and we'll discuss your specific situation and next steps (

NOTE:

this email does not accept or consider resumes or applications. This is only for disability assistance. To be considered for a position at JetCool, you must complete the application process first).