Mechanical Design

Physical dimensions and mechanical considerations for PCB layout and enclosure design.

Every component on this page lives on Board B — the synth power conversion board carries all the tall parts. Board A (USB-PD core) is all-SMD small-signal apart from its USB-C receptacle and the JST XH interface connector.

Component Heights

Physical height reference for PCB layout and enclosure design.

Power Components

Height Profile

PCB Design Implications

• Tallest components: 470uF 25V / 35V electrolytic caps (10.5mm)

• Second tallest: C9, the 100uF 50V bridging cap (10.2mm)

• Third tallest: FASTON terminals J6-J9 (8.89mm)

• Then: 470uF 10V electrolytics & inductors (7.7mm / ~6-7mm)

• Total board height: ~12mm including PCB thickness (1.6mm)

• Clearance: Keep space around TO-263 packages for thermal dissipation

• CJ7912 advantage: Lower profile (2.3mm) allows flexible placement

• FASTON placement: Position at board edge for cable access

• Capacitor placement: Consider grouping tall caps for enclosure fit

PCB Dimensions

To be determined based on component placement.

Heatsink Design

Aluminum PCB Heatsink Concept

A cost-effective heatsink solution using JLCPCB's aluminum PCB service. The aluminum PCB acts as a custom-fit heatsink that sits on top of the voltage regulators (U6, U7, U8) and DC-DC converters (U2, U3, U4).

Design Approach

Cross-section view:

    Aluminum PCB (heatsink)
    ┌─────────────────────────────────────────────────────┐
    │░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░│
    └──┬──────────┬─────────────────┬─────────────────┬───┘
       │ Thermal  │                 │                 │
       │ Pad      │    (cutout)     │    (cutout)     │
    ┌──┴──┐    ┌──┴──┐           ┌──┴──┐           ┌──┴──┐
    │ IC  │    │ IC  │           │Cap  │           │Cap  │
    │ U6  │    │ U7  │           │     │           │     │
    └─────┘    └─────┘           └─────┘           └─────┘
    ════════════════════════════════════════════════════════
                        Main PCB

Key features:

1. Same outline as the Board B PCB - Easy alignment and mounting

2. Cutouts for tall components - Electrolytics (up to 10.5mm), inductors (6-7mm), FASTON terminals

3. Solid areas over ICs - TO-263 (4.5mm) and TO-252 (2.3mm) packages for heat transfer

4. Thermal gap pads - Fill the gap between IC top surface and aluminum PCB

Target Components for Cooling

Gap Calculation for Thermal Pads

The gap between IC package top and aluminum PCB bottom depends on:

• Aluminum PCB thickness: ~1.6mm

• Standoff/spacer height: TBD

• IC package height: 2.3mm (TO-252) to 4.5mm (TO-263)

Recommended thermal pad thickness: 1mm - 2mm (get multi-thickness pack to test)

Thermal Gap Pad Selection

Thermal gap pads (サーマルパッド) provide thermal interface between ICs and the aluminum heatsink.

Required Specifications

Recommended Products

AliExpress (Budget, 2-4 week shipping):

Amazon Japan (Fast delivery, 1-2 days):

Application Tips

1. Clean surfaces - Remove dust and oil from IC and aluminum PCB

2. Cut to size - Match IC package footprint (TO-263: ~10×9mm, TO-252: ~6.5×6mm)

3. Slight compression - Pads should be 10-20% compressed for optimal contact

4. No air gaps - Ensure pad fully covers IC thermal surface

Ordering Aluminum PCB from JLCPCB

1. Create edge cuts in KiCad matching the Board B PCB outline

2. Add cutouts for tall components (capacitors, inductors, FASTON terminals)

3. Export Gerber files with edge cuts only (no circuit needed)

4. Order as aluminum PCB from JLCPCB

5. Select thickness based on thermal mass requirements

Detailed KiCad procedure to be added after prototype testing.

Enclosure Considerations

To be added.