Design for
Manufacturing Guide
Hardware guidelines for partners, OEMs, and developers building with QWR. Covers electronics, mechanical enclosures, XR optics, and material specifications — from prototype to production.
Layout rules, component clearances, signal integrity, and testability requirements. All PCBs must conform before fabrication. Deviations require written sign-off from QWR Engineering.
Board Specifications
| Parameter | Minimum | Recommended | Notes |
|---|---|---|---|
| Min trace width | 0.1 mm | 0.15 mm | Signal traces; power traces per IPC-2221 |
| Min trace spacing | 0.1 mm | 0.15 mm | Increase for high-voltage rails (>50 V) |
| Min via drill | 0.2 mm | 0.3 mm | Micro-vias require DFM review |
| Min annular ring | 0.125 mm | 0.15 mm | All drill classes |
| Board thickness | 0.6 mm | 1.0 mm | XR form-factor targets: 0.8 mm |
| Copper weight (outer) | 1 oz | 1 oz | 2 oz for power stages |
| Copper weight (inner) | 0.5 oz | 1 oz | — |
| Edge clearance | 0.3 mm | 0.5 mm | All copper from board edge |
| Min solder mask opening | 0.1 mm | +0.05 mm exp. | LPI solder mask preferred |
Component Placement
Keepout zones
Maintain a 3 mm component-free keepout on all board edges. Connectors are exempt only if deliberately edge-mounted.
Heatsink clearance
No components taller than 0.5 mm within 2 mm of any active heatsink or thermal pad footprint.
SMD orientation uniformity
Align passive components in consistent orientations to optimise the reflow profile and reduce tombstoning risk.
Decoupling placement
Place decoupling capacitors within 0.5 mm of IC power pins. Use a separate copper pour — not a shared power plane tap.
Test point coverage
Expose all key power rails and I²C/SPI/UART buses via labelled test points. Minimum pad diameter: 1 mm.
Fiducial markers
Include a minimum of 3 fiducials at board corners for SMT pick-and-place. 1 mm copper circle, 3 mm copper-free keepout.
Signal Integrity
USB 3.0, MIPI, and LVDS pairs must be length-matched within 2 mil. Route on the same layer. No vias mid-pair unless unavoidable; add compensating vias to both lines simultaneously.
Specify controlled impedance stackup in fab notes. 50 Ω single-ended, 90 Ω differential for USB. QWR standard 4-layer stackup: Signal / GND / Power / Signal.
Pre-Submission Checklist
- Design Rule Check (DRC) passes with zero errors in KiCad / Altium
- All component footprints verified against physical datasheet land patterns
- Schematic reviewed for power sequencing and inrush protection
- BOM exported with MPN, manufacturer, and approved alternatives flagged
- Gerber, drill, and IPC-D-356 netlist packaged for fab
- Assembly drawing includes polarity markers and reference designators
- Pick-and-place centroid file generated and validated
Wall thickness, draft angles, assembly strategy, and fastener standards for injection-moulded and CNC-machined enclosures across QWR product lines.
Injection Moulding
| Parameter | Value | Notes |
|---|---|---|
| Nominal wall thickness | 1.5 – 2.5 mm | Uniform wall preferred; avoid abrupt transitions |
| Min wall thickness | 0.8 mm | Structural ribs only; consult material datasheet |
| Min draft angle | 1° | 2° recommended for textured surfaces |
| Rib thickness | 50–60% of wall | Prevents sink marks on outer face |
| Boss outer diameter | 2× screw dia. | Gusset to adjacent wall if height > 3× OD |
| Min inside radius | 0.5 mm | At wall junctions; hard corners cause stress concentration |
| Snap-fit deflection | ≤ 2% | Of nominal beam length; verify with FEA for repeated cycles |
| Gate location | Non-cosmetic surface | Weld lines must not cross structural features |
CNC Machining (Aluminium)
Min feature size
Min pocket width 1.0 mm, min hole diameter 0.5 mm. Tolerances tighter than ±0.05 mm require QWR Engineering sign-off.
Chamfer vs fillet
Prefer chamfers on external edges; fillets on all internal corners. Min internal fillet R = 1/3 × cutter diameter in that pocket.
Thread specification
M-series metric threads only. Specify fit class on drawing. M2 minimum for structural fastening in aluminium enclosures.
Surface finish callout
Include Ra value on drawing. Bare aluminium default: Ra 1.6 µm. Hard-anodised: specify class 1 or class 2 per MIL-A-8625.
Design for top-down assembly where possible. Every additional axis of assembly adds handling time and increases defect risk. QWR targets single-axis assembly for all sub-assemblies.
Fastener Standards
Approved fasteners
- M2 / M2.5 / M3 socket head cap screws (ISO 4762)
- M2 / M2.5 self-tapping for plastic bosses
- Snap-fit for non-structural cosmetic panels
- Heat-set inserts (M2+) for thermoplastic boss reuse
Not permitted
- Imperial fasteners (UNC/UNF) — metric only
- Adhesive-only structural joints
- Countersunk screws in plastic under 2.5 mm wall
- Custom fastener profiles without DFM review
XR optics are the highest-precision component class in any QWR product. Tolerances are an order of magnitude tighter than standard mechanical parts. Any deviation must be validated through QWR's optical test bench before EVT build.
Display Panel Requirements
| Parameter | Specification | Status |
|---|---|---|
| Panel type | Micro-OLED / LCoS | ✓ Approved |
| Min PPI | 2000 PPI | ⚠ Verify per FOV target |
| Luminance (peak) | ≥ 5,000 nit | ✓ Required for outdoor AR |
| Colour gamut | ≥ 85% DCI-P3 | ✓ Minimum |
| Refresh rate | 90 Hz minimum | ✓ 120 Hz preferred |
| Pixel response time | ≤ 2 ms | ✓ Required to prevent ghosting |
| Panel flatness | ≤ 10 µm bow | ⚠ Critical — waveguide coupling |
| Operating temperature | 0°C to +50°C | ✓ Consumer operating range |
Waveguide Design Rules
Waveguide substrates are designed and validated entirely by QWR. Do not alter grating period, substrate index, or coupling angles. Mechanical drawings show keep-in zones only.
Incoupler position tolerance
In-coupling grating must be positioned within ±15 µm XY of nominal. Rotational tolerance: ±0.05°. Verified via autocollimation.
Waveguide-to-display gap
Air gap between display exit pupil and waveguide surface: 0.3 mm ± 0.05 mm. Contamination in this gap is a field-return trigger.
Stray light baffling
Include light-absorbing baffles (Acktar or equivalent) between illumination path and detector. Reflectance < 0.5% at design wavelength.
Waveguide handling
Handle only with clean-room gloves. No contact with grating surface. Ship in nitrogen-purged sealed bags to prevent particulate ingress.
Eye-Box & FOV Targets
| Parameter | Target | Minimum Acceptable |
|---|---|---|
| Horizontal FOV | 40° | 30° |
| Vertical FOV | 30° | 22° |
| Eye-box (horizontal) | 12 mm | 8 mm |
| Eye-box (vertical) | 8 mm | 6 mm |
| Eye relief | 18 mm | 14 mm |
| MTF @ 50 lp/mm | ≥ 0.3 | 0.2 |
| Uniformity (centre vs edge) | ≥ 70% | 60% |
All devices must pass QWR's optical qualification suite: MTF measurement, uniformity map, stray light scan, and eye-box cross-section. Test reports must be submitted with EVT build samples.
Material selection and tolerance callouts must be explicit on all engineering drawings submitted to QWR. Unspecified materials default to QWR's standard equivalents — this can cause schedule delays if design intent differs.
Approved Material Families
| Category | Approved Materials | Typical Use | Notes |
|---|---|---|---|
| Structural plastic | PC, PC/ABS, PA66-GF30 | Main enclosures, structural frames | UL94 V-0 required for all powered devices |
| Flexible / gasket | TPU 85A–95A, Silicone | Seals, nose pads, cable strain relief | Shore A specified on drawing |
| Optical plastic | PMMA (optical grade), Zeonex | Lens elements, light pipes, diffusers | Transmission ≥ 92% at design wavelength |
| Metal (structural) | Al 6061-T6, Al 7075-T6, Ti Gr.5 | Machined frames, hinges, optic mounts | 7075 for high-load; Ti for premium/medical |
| Metal (cosmetic) | Al 6063-T5, SS 316L | External covers, decorative elements | Anodising spec required |
| PCB substrate | FR-4, Rogers 4350B | Standard PCB, RF/mmWave boards | Rogers for >5 GHz designs |
| Adhesive | 3M 467MP, Loctite 603 | FPC bonding, lens seating | UV-cure only for optical bonding |
Dimensional Tolerance Classes
TOLERANCE CLASS REFERENCE ──────────────────────────────────────────── CLASS LINEAR TOLERANCE ANGULAR TYPICAL APPLICATION ────────────────────────────────────────────────────────────────────────── T1 — Coarse ± 0.5 mm ± 1.0° Non-mating cosmetic features T2 — Medium ± 0.2 mm ± 0.5° Standard mating enclosure faces T3 — Fine ± 0.05 mm ± 0.1° Precision mechanical interfaces T4 — Optic ± 0.01 mm (10 µm) ± 0.02° Waveguide & lens seats T5 — Ultra ± 0.002 mm (2 µm) ± 0.005° Active optical alignment only ────────────────────────────────────────────────────────────────────────── Default if unspecified: T2 | Optic mounts: T4 minimum
All T3, T4, and T5 features must carry explicit GD&T callouts per ASME Y14.5-2018. Drawings without GD&T on precision features will be returned for revision.
Surface Finish Standards
| Finish | Ra (µm) | Process | Use Case |
|---|---|---|---|
| Machined (as-cut) | Ra 3.2 | CNC milling / turning | Non-visible structural |
| Machined (fine) | Ra 1.6 | CNC + finishing pass | Mating faces, sealing surfaces |
| Anodised | Ra 0.8 – 1.2 | Type II or III | External aluminium; specify colour |
| Polished | Ra 0.2 – 0.4 | Mechanical + buff | Mirror / chrome cosmetics |
| Optical surface | Ra < 0.01 | Diamond turning / lapping | Lens surfaces, waveguide substrate faces |
| Moulded texture | SPI A1 – D3 | Tool texture per SPI standard | Call out SPI grade on drawing |
Compliance & Certification Requirements
Required — all hardware
- RoHS 3 (EU 2015/863) compliance across full BOM
- REACH SVHC declaration from material suppliers
- UL94 V-0 or V-2 flame rating for enclosure plastics
- Material Safety Data Sheets (MSDS/SDS) on file
Required — consumer products
- CE marking (RED Directive for wireless devices)
- FCC Part 15B / Part 15C (US market)
- BIS certification (India market)
- EN 62368-1 / IEC 62368-1 safety standard
Strictly prohibited in any QWR-manufactured product: hexavalent chromium, cadmium, lead (except exempted solder per RoHS Annex III), mercury, PBB, PBDE. Queries on exemptions must go to QWR Compliance before component selection is finalised.
Documentation Required at Design Freeze
- Complete BOM with MPN, manufacturer, material grade, and RoHS status
- Engineering drawings for all custom parts — GD&T per ASME Y14.5-2018
- 3D STEP or Parasolid files for all mechanical components
- Material certificates (CoC) from approved suppliers
- Surface finish callouts on all external and mating faces
- Tolerance analysis (worst-case or RSS) for all critical assemblies
- Compliance declarations: RoHS, REACH, UL94 flame class
- Optical prescription file (Zemax or CODE V) for all optical elements