R J Hegler Technologies, LLC
Team Member of Five Design and Development, LLC

Design Guidelines

Practical engineering principles for building reliable, manufacturable electronic systems.

Resistors: Thin‑Film vs. Thick‑Film

Choosing the correct resistor technology affects precision, noise, and stability.

  • Thin‑Film: 0.1–1% tolerance, 5–25 ppm/°C tempco, low noise — ideal for precision analog.
  • Thick‑Film: 1–5% tolerance, 100–250 ppm/°C tempco — ideal for cost‑sensitive general use.

Capacitor Selection

Dielectric choice determines stability, DC bias behavior, and suitability for analog or power applications.

  • C0G/NP0: Zero DC bias distortion — best for timing and precision analog.
  • X7R/X5R: General‑purpose decoupling; DC bias reduces effective capacitance.
  • Tantalum: Stable, but requires 50% voltage derating. CAUTION: failure mode is a short circuit!
  • Electrolytic: High bulk capacitance for power filtering.

Connector Selection

Connector choice impacts reliability, assembly cost, and long‑term serviceability.

  • High‑Reliability: Gold plating, latching, vibration‑resistant.
  • Cost‑Optimized: Tin contacts, friction‑fit for low‑cycle consumer applications.

Component Derating Philosophy

Derating improves reliability and prevents marginal designs from becoming field failures.

  • Voltage: operate at ≤50–70% of rating
  • Current: operate at ≤50–80% of rating
  • Temperature: keep junctions 20–30°C below max

ESD/EMI‑Conscious Layout

Good layout prevents emissions, susceptibility, and intermittent failures.

  • Minimize high di/dt loops
  • Use solid ground planes
  • Place TVS diodes at connector entry points
  • Keep analog and digital domains isolated

MCU Selection Criteria

  • ESP32: Connectivity‑focused IoT applications.
  • ARM Cortex‑M: Industrial, medical, and professional embedded systems.
  • Others: PIC/AVR, RP2040, MSP430 for niche or legacy needs.

Test Points & DFT

DFT improves manufacturability and reduces debugging time.

  • Power rail test pads
  • UART/SWD/JTAG access
  • Analog node access
  • Pogo‑pin fixture support

DFM Considerations

Small design choices can dramatically affect manufacturing cost.

  • Standardize component values
  • Minimize BOM line count
  • Use panel‑friendly board shapes
  • Provide fiducials for automated assembly