Staff Mechanical Engineer

Why This Role Exists

We're at a critical inflection point in the grid, where we have new sources and loads at a capacity that we couldn't have dreamed of. Traditional grid electronics, with their lack of control and DC based capabilities, just can't keep up. With real customer demand, we're closing the gap between the grid of today and the grid of the future by building innovative smart transformers and modular power electronics. We're excited to commercialize and deploy our technology across multiple customers for real world impact. We are growing the team and are looking for passionate, dedicated, ambitious hires who are excited by ownership and the modernization of our grid.

This role is critical to Expand's success- you will be working closely with the founders and first EE hires in the lab and in the field with real customers, reporting to the CEO. As our first ME hire, you will lead technical development of the mechanical design of our proprietary power electronics technology for immediate deployment. You will own the mechanical development of Expand's DC-DC module- architecture, design, testing, and customer pilots. You will have a critical role in shaping the core technology, product direction, and culture of a cross-functional and rapidly growing early stage company. You'll be one of the most valuable founding members of a company shaping the future of the electric grid. In doing so, you will push the limits of what's achievable with renewable technology. The successful candidate can drive their own projects today and grow with the company into senior leadership roles.

Your Day to Day and Key Responsibilities

You will be leading the mechanical design and development of Expand's power electronics products, from the cabinet down to the board level, and in doing so, defining how next-generation power conversion hardware is packaged, cooled, and protected in the real world. You'll own the mechanical development cycle, including requirements definition, thermal and structural modeling, CAD design, prototyping, testing, and design for manufacturing. You'll shape the company's mechanical roadmap while navigating environmental, safety, and regulatory requirements.

You'll also use creativity and innovation to:

• Design and develop enclosures, housings, and structural systems for medium-voltage power electronics, from first principles to test and validation to deployment for manufacturability and serviceability
• Conduct multi-physics simulations and optimizations to iterate on designs and validate them against demanding thermal, fluid, environmental, structural, and performance targets
• Build cost models and analyses to evaluate trade-offs and optimize manufacturability, from concept to production
• Own the design, modeling, and analysis of electro-mechanical hardware, including heat sinks, insulation, magnetics, and mechanical enclosures for custom PCBAs
• Solve packaging challenges, like thermal management, vibration, and EMI
• Own thermal management architecture, such as heat sinks, forced air, cold plates, and liquid cooling, for high-power-density converters and magnetics
• Simulate and model thermal, structural, and airflow behavior to maximize performance and reliability
• Design for ingress protection, outdoor deployment, vibration, seismic, and transport requirements
• Conduct lab testing, validation, and debugging of prototype hardware, including thermal characterization under load
• Collaborate closely with power electronics engineers on component placement, busbar and interconnect design, creepage/clearance, and EMI shielding
• Document technical specifications, architecture decisions, and validation reports
• Drive design for manufacturing and assembly, working with external vendors
• Mentor and guide more junior engineers
• Collaborate on IP generation

Requirements
Required Experience

You've done this before: you are a highly experienced mechanical engineer, a master of your craft. Enclosure design, thermal management, and packaging for power electronics is your bread and butter, but it still gives you excitement and fulfillment, especially with a mission you care deeply about. You have a proven track record of taking hardware from concept through production.

You also have experience in:

• Hands-on experience with multi-physics simulation tools (CFD, thermal, structural) with a track record of using them alongside cost analysis to navigate trade offs, optimize, and inform system architecture decisions
• Deep expertise in mechanical engineering fundamentals, such as GD&T, finite element analysis, and designing for long-term reliability
• Mechanical and thermal design for high-power electronics (heat sink design, airflow management, cold plates, and/or liquid cooling)
• Designing enclosures and housings for harsh or outdoor environments, including sealing, gasketing, corrosion resistance, and ingress protection
• Startups or fast-paced, early stage company environments
• Bringing a hardware product from concept to market through design, test, deployment, and manufacturing while meeting certification standards and regulations (UL, IEC, etc.)
• Fluency in typical mechanical engineering design tools, such as SolidWorks, Fusion 360, or Onshape, and simulation tools such as ANSYS, SimScale, or similar CFD/FEA packages
• Extensive hands-on time in the lab and shop - prototyping, instrumenting thermal tests, and iterating quickly on what the hardware tells you

Bonus Experience

• Packaging for medium-voltage power electronics
• Busbar, laminated bus, and high-current interconnect design
• Experience with EMI/EMC-driven mechanical design and shielding
• DER, inverter, EV charging, or utility equipment product development
• Knowledge of relevant industry standards (UL 1741, UL 50E, NEMA 250, IEC 60529, etc.)
• Managing fabricators and contract manufacturers, including quoting, DFM feedback loops, and quality processes
• Interacting and communicating with customers for development and deployment

You're described as a

• Fast moving, hands-on builder, taking responsibility for outcomes from design through deployment and hungry for ownership
• Independent, gritty problem solver, who thrives in uncertainty, loves a challenge, and responds to obstacles with the best of their abilities
• Strong and collaborative communicator, able to explain technical decisions to both engineers and non-technical stakeholders, and to share feedback openly and kindly
• Mission-driven, motivated by positive real-world impact and passionate about pushing the boundaries of power electronics and electrification
• Fearless and endlessly curious, energized by open questions and new possibilities, willing to bet on bold ideas and learn fast from what the hardware tells you, and taking intelligent risks with a sense of wonder and a drive to explore what's possible

Don't meet every requirement? Apply anyway-we value diverse backgrounds and potential over perfect checklists. We're more interested in what you can do than in every box being ticked.

Benefits

Come work on breakthrough technology in a collaborative, mission-driven culture with direct influence over company trajectory and room to grow as the team scales. This is an onsite position based in the San Francisco Bay Area. Minimum travel will be expected. We are open to supporting relocation for the right candidate.

We want you to stay for a while- you will receive $150,000 - $190,000 base with meaningful early employee equity, based on level and experience, as well as benefits:

• Health Insurance: We offer 100% coverage of employee premiums
• Dental & Vision Insurance: We offer 100% coverage of employee premiums
• Retirement Plan: We offer a 401(k) plan
• Unlimited PTO