Thermal Simulation Engineer

CspeedIO is a stealth startup backed by Sutter Hill Ventures and Atreides Capital - headquartered in Palo Alto, CA.  Our executive team has a demonstrated track record of building and scaling category-defining semiconductor and infrastructure businesses at companies like Broadcom, Lumentum, Tesla, Apple, Samsung, Intel, and VMware.

CspeedIO is developing next-generation optical semiconductor solutions for the AI infrastructure market, focused on enabling true “scale-up” architectures.  Our mission is to replace traditional copper interconnects with advanced fiber-optic technologies that overcome the limitations of existing optics solutions and architectures.

The Role

This position owns thermal modeling for CspeedIO optical engines, from die-level power maps through cooling boundary conditions, and the correlation of those models against measured hardware.

Thermal design here is a functional requirement rather than a reliability margin. Photonic device behavior is temperature-dependent, so wavelength and channel-to-channel uniformity shift with the temperature field across the photonic IC. The assembly also contains a small-footprint, high-flux die whose temperature must be held within a narrow window. The optical engine operates in a thermally shared environment. The deliverable is a defensible temperature field, not a junction temperature.

Responsibilities

Thermal modeling and architecture

• Build and maintain thermal models of the optical engine spanning die, package, interface materials, lid, and cold plate, for air- and liquid-cooled configurations.
• Establish the cooling boundary condition methodology and its validity limits, and quantify thermal crosstalk from adjacent high-power devices.
• Resolve the temperature field across the photonic IC to the resolution photonic design requires, and own the resulting gradient and uniformity specifications.

Materials and interfaces

• Define the heat extraction path for high-flux die within the assembly, die attach, and thermal interface material selection where footprint and power density are constraining.
• Quantify the sensitivity of engine temperature to material property tolerance and assembly variation.

Correlation and design influence

• Define the thermal characterization plan and lead simulation-to-hardware correlation to a stated and tracked accuracy tolerance.
• Provide thermal requirements and constraints to package layout, photonic design, and electrical design during architecture definition rather than after freeze.
• Generate reduced-order thermal models for system integrators and customers, and engage cold plate, heat sink, and thermal material suppliers.

Required Qualifications

• MS or PhD in Mechanical Engineering, Electrical Engineering, Physics, or equivalent practical background.
• 6+ years of thermal simulation for semiconductor packages or electronic systems, including one product carried from architecture through hardware correlation.
• Expert proficiency in a commercial thermal or CFD tool for electronics: Ansys Icepak or Fluent, Simcenter Flotherm, Cadence Celsius, or equivalent.
• Command of heat transfer fundamentals sufficient to defend a model rather than only to run one.
• Demonstrated correlation of thermal simulation against measured hardware, with methodology revised on that basis.

Preferred Qualifications

• Silicon photonics or optoelectronic thermal work, particularly thermo-optic sensitivity and wavelength stability.
• Thermal design for small-footprint, high-flux die.
• Direct-to-chip liquid cooling and cold plate design or specification.
• 2.5D/3D package thermal modeling, and coupled electrothermal or thermal-structural workflows.
• First-generation product experience where the thermal methodology had to be established rather than inherited.