Structural PCB Layout, Prototyping & DFM Support for Capacitive Touch Audio Device

We are looking for an experienced hardware/PCB engineer to execute a highly mechanical PCB layout and deliver working prototypes for a tactile electronic audio instrument. The electrical schematic and component logic are already complete. Your primary challenge is 3D spatial layout and structural PCB design. The device does not use a traditional plastic or metal enclosure; the entire chassis is constructed out of interlocking, puzzle-pieced FR4 PCBs. The Hardware & Structural Architecture: 1. The Enclosure (FR4 Puzzle-Piece Stack-Up): You will design the main motherboard, the top control board, the bottom mounting plate, and the interlocking side walls. The side walls must utilize locking PCB tabs to snap/solder together into a rigid frame. 2. Top Control Board: A board featuring 11 ENIG gold capacitive touch pads and unmasked "windows" for LED light bleed. 3. Carrier Motherboard: Houses a Raspberry Pi Pico (surface mounted), an MPR121 touch IC, 15 surface-mount LEDs, a 5V buck converter, integrated battery clips for dual 18650 batteries, and header footprints to receive two pre-assembled modules (a GY-PCM5102 DAC and a TPA3118 Amp). 4. The Connection: A low-profile pin header bridging the touch signals from the top board down to the motherboard. Key Mechanical & Layout Challenges: Transducer Clearance & Mounting: The bottom PCB must bolt directly into a central acoustic surface transducer, with a slight mechanical offset from the main enclosure walls to allow uninhibited kinetic vibration. The motherboard must be routed to wrap around or clear this central transducer. Battery Integration: You must find the optimal placement for dual 18650 through-hole battery clips within the motherboard footprint while maintaining a strict, low-profile total device height. Strict X/Y Alignment: The 15 LEDs on the carrier motherboard must perfectly align with the unmasked windows on the top control board. Deliverables & Responsibilities: Electro-Mechanical PCB Layout: Route the system based on our provided schematic and ensure the locking FR4 enclosure fits perfectly around the batteries and transducer. Prototyping: Order the initial batch (e.g., via JLCPCB or PCBWay), assemble the prototypes, and verify the hardware and structural integrity. Final Handover: Deliver the finalized Gerbers, BOM, Pick & Place (CPL) files, and 3D STEP files. DFM Support: Act as the technical point of contact to answer any Design for Manufacturing (DFM) questions from our fabrication partner. Payment Milestones ($1,500 Fixed Price): Milestone 1 (30% - $450): PCB Layout & 3D Structural Verification. Delivery of the routed PCB files and a complete 3D STEP file proving the puzzle-pieced boards lock together, the LEDs align perfectly, and the transducer/batteries clear the chassis. Milestone 2 (40% - $600): Prototype Delivery. You order, assemble, and power on the physical prototype, providing video proof of structural integrity, audio output, LED illumination, and touch response. Milestone 3 (30% - $450): Final Files & DFM Sign-off. Handover of all production-ready files and availability to answer technical questions from the assembly house during the first mass-production run. Requirements: Expertise in KiCad or Altium. Proven experience designing structural PCBs (interlocking tabs, enclosures made of FR4). Prior experience routing capacitive touch interfaces and I2S/analog audio. Please include the word "Ablaze" at the top of your proposal so we know you read the full description.