Senior Hardware Engineer: High-Speed Actuator Driver (Single-Sided PCBA & Thermal Math Trial)

Project Context: We are upgrading the hardware architecture for a high-speed electromagnetic actuator driver used in industrial test rigs. The legacy design utilized an overly expensive GaN architecture. We are pivoting to a highly robust, cost-effective Silicon MOSFET design housed in a highly restricted mechanical cavity. Before awarding the full PCB routing contract, we require a Phase 1 Paid Trial (Desktop Research & Math Proof) to validate your DFM and thermal analysis capabilities. The Phase 1 Trial Scope ($50 - $100 Fixed Price) 1. The DFM & Cost Pivot (Silicon over GaN): - Requirement: Select standard, cost-effective Silicon MOSFETs (and drivers if needed) to replace the legacy GaN switching stage. - Pulse Spec: Must comfortably drive a continuous 10Hz to 50Hz square wave with a 3A peak pulse, maintaining a sharp rising edge. - Cost & Z-Axis Red Line: Total switching stage BOM must be strictly under $5 USD. Package thickness must be strictly under 1.2mm (e.g., low-profile DFN/QFN). 2. The "Flat-Back" Mechanical Constraint (Single-Sided PCBA): - Requirement: Due to strict puncture-prevention mechanical guidelines, the new PCBA must be 100% single-sided (Bottom placement only). - Confirmation: You must confirm that your selected BOM and layout strategy can accommodate routing and placing ALL components exclusively on the bottom layer, leaving the top layer as bare FR-4. 3. The Thermal Trapping Math (Tj Calculation): - Requirement: The PCBA will be hermetically sealed inside a PC/ABS plastic carrier and fully potted with RTV silicone (zero airflow). - The Math: Provide the formulas and your calculation proving the maximum Junction Temperature (Tj) of your selected FETs will remain safely below max ratings during continuous 50Hz / 3A operation. Your thermal resistance model (R_theta_JA) MUST account for the RTV silicone encapsulation and plastic housing. To Apply: Start your proposal with the word "PHYSICS". Briefly explain how you would approach the thermal math for an RTV-encapsulated board. If your logic aligns, we will fund the Phase 1 milestone immediately. Successful completion of Phase 1 leads directly to the Phase 2 full PCB redesign contract.