Sr. Mechanical Development Engineer

Flex is the diversified manufacturing partner of choice that helps market‑leading brands design, build and deliver innovative products that improve the world. A career at Flex offers the opportunity to make a difference and invest in your growth in a respectful, inclusive, and collaborative environment. If you are excited about a role but don’t meet every bullet point, we encourage you to apply and join us to create the extraordinary.

To support our extraordinary teams who build great products and contribute to our growth, we’re looking to add a Mechanical Development engineer located in Littleton, MA
. Reporting to the Product Manager
, the Mechanical Development engineer will own the design, analysis, validation, and refinement of mechanical components and assemblies that enable reliable, high‑efficiency liquid cooling. They will work closely with Thermal, Electrical, Product Development, Manufacturing, and Quality teams to take products from concept through launch and into scalable production.

• Own mechanical design for liquid cooling components including cold plates, manifolds, quick‑disconnects, tubing assemblies, housings, and chassis interfaces.
• Create and manage detailed CAD models, 2D drawings, GD&T, and tolerance stack‑ups to ensure robust, manufacturable designs.
• Select materials and finishes to address corrosion, galvanic compatibility, cleanliness, pressure containment, and long‑term durability in liquid cooling environments.
• Drive sealing strategies using O‑rings, gaskets, welds, brazes, and adhesives matched to coolant chemistry and operating conditions.

• Perform engineering calculations and simulations related to mechanical stress, thermal expansion, fatigue, vibration, flow/pressure, and structural integrity.
• Collaborate with thermal engineers to optimize mechanical features influencing flow distribution, pressure drop, fin/channel geometry, and heat transfer efficiency.
• Conduct DFM reviews with suppliers to align machining, brazing, and fabrication methods with design requirements.

• Build and iterate on prototypes to evaluate fit, finish, assembly, and performance.
• Develop mechanical validation plans for pressure tests, leak testing, burst testing, vibration/shock, environmental exposure, thermal cycling, and dimensional inspection.
• Design test fixtures and support automated data collection where needed.
• Lead root cause analysis for failures (e.g., leaks, deformation, material incompatibility) and implement corrective design changes.

• Collaborate with manufacturing engineering and suppliers on fabrication, machining, brazing, plating, and sealing processes.
• Define critical‑to‑quality (CTQ) characteristics and participate in supplier qualification.
• Review and approve tooling, control plans, and inspection criteria for new mechanical parts.
• Support build events (EVT/DVT/PVT) and ensure mechanical components meet functionality, quality, and reliability targets.

• Work with Program Management and Product Development to translate product requirements into mechanical specifications.
• Partner with Thermal and Electrical teams to ensure system‑level integration of cooling hardware with processors, boards, and rack infrastructure.
• Provide input to serviceability, reliability, manufacturability, and cost trade‑off discussions.
• Support customer evaluations, pilot deployments, and field feedback analysis.

• BS/MS in Mechanical Engineering or equivalent experience.
• 7+ years developing complex mechanical components or assemblies for electro‑mechanical systems; experience with liquid cooling or fluid systems strongly preferred.
• Strong proficiency with CAD (Solid Works, Creo, NX), drawing generation, and GD&T (ASME Y14.5).
• Experience designing for precision machining, brazing, plating, elastomer sealing, and pressure‑rated components.
• Hands‑on experience with pressure/leak testing, dimensional inspection, materials evaluation, and mechanical validation testing.
• Familiarity with materials (copper, aluminum,…