Principal Thermal Engineer, Liquid Cooling

At Juniper, we believe the network is the single greatest vehicle for knowledge, understanding, and human advancement the world has ever known.
To achieve real outcomes, we know that experience is the most important requirement for networking teams and the people they serve. Delivering an experience-first, AI-Native Network pivots on the creativity and commitment of our people. It requires a consistent and committed practice, something we call the Juniper Way.

Principal Thermal Engineer - Liquid Cooling Expert
Location: Sunnyvale, CA, USA
Department: Systems Technology, Thermal Engineering

At Juniper Networks, we're reimagining what's possible in networking. We go beyond building networks customers expect - we build the networks they deserve. Innovation, transformation, and excellence define our path forward. As our industry accelerates, we're looking for bold thinkers and trailblazers to help us build the future of networking.

If you're ready to work on breakthrough technologies and shape the future of thermal design in high-performance networking hardware, we want to talk to you.

About the Role

Juniper has an immediate opening for a Principal Thermal Engineer to join our Cooling Analysis and Testing group in Sunnyvale, CA. This highly visible role demands deep expertise in liquid cooling technologies (including cold plate and immersion cooling) applied to compute and network class hardware systems. You will be instrumental in solving challenging thermal issues across our product portfolio, influencing early architecture decisions, and driving next-generation cooling strategies to meet aggressive system-level goals.

Key Responsibilities

• Serve as a technical leader within the Thermal Engineering team, with a focus on liquid-cooled system design for networking and compute platforms.
• Lead the thermal architecture and analysis of complex electronic systems throughout the product lifecycle - from concept to mass production.
• Design and specify thermal solutions including cold plates, heat exchangers, immersion cooling setups, heat sinks, fans, TIMs, and related subsystems.
• Conduct CFD simulations (using FloEFD, FloTHERM, Macroflow) for Liquid cooling and heat transfer analysis. Interpret results to recommend actionable design changes.
• Collaborate with mechanical, electrical, and system architects to ensure thermal requirements are met across all levels.
• Evaluate feasibility studies and drive architecture trade-offs for advanced cooling methods and thermal innovations.
• Develop and oversee validation plans; guide technicians and engineers during test setup and data collection.
• Present findings and proposals clearly to cross-functional teams and executive leadership.
• Support the definition and evaluation of thermal requirements for high-power ASICs, optics, and densely packed modules.

Required Qualifications

• 15+ years of experience in electronics thermal engineering, including 10+ years in liquid and hybrid-cooled system design.
• Proven track record supporting 5-7+ NPI (New Product Introduction) cycles, ideally in high-density compute or networking environments.
• Expertise in both air and liquid cooling strategies, including design of cold plates, manifolds, immersion tanks, and cooling loops.
• Familiarity with regulatory and safety aspects of liquid cooling deployments.
• Hands-on experience with CFD tools - FloEFD, FloTHERM, Macroflow or equivalent. Proficiency in model setup, calibration, and post-processing.
• Familiarity with CAD tools like SolidWorks for thermal and mechanical integration tasks.
• Strong knowledge of thermal interface materials, heat pipe technologies, and high-power ASIC thermal packaging.
• Excellent communication and documentation skills; ability to work effectively across disciplines and drive thermal strategy at the system level.

Preferred Qualifications

• MS or PhD in Mechanical Engineering, Thermal Sciences, or related field.
• Background in high-performance computing, data centers, or telecom hardware.
• Experience with emerging cooling technologies (e.g., two-phase immersion, dielectric fluids).

Minimum Salary: $231,200.00

Maximum Salary:$332,350.00

The pay range for this position is expected to be between $231,200.00 and $332,350.00/year; however, the base pay offered may vary depending on multiple individualized factors, including market location, job-related knowledge, skills, and experience. The total compensation package for this position also includes medical benefits, 401(k) eligibility, vacation, sick time, and parental leave. Additional details of participation in these benefit plans will be provided if an employee receives an offer of employment.

If hired, employee will be in an "at-will position" and the Company reserves the right to modify base salary (as well as any other payment or compensation program) at any time, including for reasons related to individual performance, Company or individual department/team performance, and market factors.

Juniper's pay range data is provided in accordance with local state pay transparency regulations. Juniper may post different minimum wage ranges for permanent residency petitions pursuant to US Department of Labor requirements.

ABOUT JUNIPER NETWORKS

Juniper Networks challenges the inherent complexity that comes with networking and security in the multicloud era. We do this with products, solutions and services that transform the way people connect, work and live. We simplify the process of transitioning to a secure and automated multicloud environment to enable secure, AI-driven networks that connect the world. Additional information can be found at Juniper Networks ( or connect with Juniper on Twitter, LinkedIn and Facebook.

WHERE WILL YOU DO YOUR BEST WORK?

Wherever you are in the world, whether it's downtown Sunnyvale or London, Westford or Bengaluru, Juniper is a place that was founded on disruptive thinking - where colleague innovation is not only valued, but expected. We believe that the great task of delivering a new network for the next decade is delivered through the creativity and commitment of our people. The Juniper Way is the commitment to all our colleagues that the culture and company inspire their best work-their life's work. At Juniper we believe this is more than a job - it's an opportunity to help change the world.

At Juniper Networks, we are committed to elevating talent by creating a trust-based environment where we can all thrive together. If you think you have what it takes, but do not necessarily check every single box, please consider applying. We'd love to speak with you.

Additional Information for United States jobs:

ELIGIBILITY TO WORK AND E-VERIFY

In compliance with federal law, all persons hired will be required to verify identity and eligibility to work in the United States and to complete the required employment eligibility verification form upon hire.

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Information for applicants about E-Verify / E-Verify Informacin en espaol: This Company Participates in E-Verify / Este Empleador Participa en E-Verify
Immigrant and Employee Rights Section (IER) - The Right to Work / El Derecho a Trabajar

E-Verify is a registered trademark of the U.S. Department of Homeland Security.

Juniper is an Equal Opportunity workplace. We do not discriminate in employment decisions on the basis of race, color, religion, gender (including pregnancy), national origin, political affiliation, sexual orientation, gender identity or expression, marital status, disability, genetic information, age, veteran status, or any other applicable legally protected characteristic. All employment decisions are made on the basis of individual qualifications, merit, and business need.