Yes, you must consider SMT passive components during design for:
- Functional performance
- Manufacturability
- Reliability
- Cost
- Repair ability
1. Board Space and Layout Planning
- Passive components (resistors, capacitors, inductors) take up real estate on your PCB.
- If you don’t plan their quantity, size, and spacing, your layout may become too dense or un-routable.
- Choosing smaller parts (0402 vs. 0805) can save space but may sacrifice ease of handling or reliability.
2. Cost Optimization
- Passive parts seem cheap, but hundreds or thousands per board add up.
- Smaller parts may cost more to assemble (e.g. 0201), and harder to repair.
- Selecting common sizes (e.g. 0603 resistors) lowers component, assembly, and rework costs.
3. Manufacturability (DFM)
- Design decisions directly affect how easily your board can be assembled:
- Too many different part sizes? → Slower setup
- Hard-to-place parts? → More defects
- Standardizing passive sizes (like using all 0603) makes assembly faster and cheaper.
4. Electrical Performance
- Capacitance and inductance values affect signal filtering, timing, and stability.
- Wrong size or placement of passives (e.g., decoupling capacitors too far from ICs) can cause:
- Power noise
| Component | Primary Role | Best Package |
| MLCC (0.1–1 µF) | High-frequency decoupling | 0402, 0603 |
| MLCC (10–100 µF) | Bulk power smoothing | 0805–1210 |
| Ferrite Bead | High-frequency noise suppression | 0603, 0805 |
| Tantalum/Polymer | Mid-frequency ripple control (optional) | 1206+ |
- Signal distortion
| Component | Purpose | Best Use Case | Size |
| Series Resistor | Reduce ringing/overshoot | Clock lines, SPI, GPIO | 0402–0603 |
| MLCC Capacitor | Stable power = stable signal | All ICs, especially digital | 0402–0805 |
| RC Filter | Filter analog noise / soft edges | ADCs, audio, sensors | 0603+ |
| Ferrite Bead | Block RF noise | Audio, analog, low-speed signals | 0603–0805 |
| Termination Resistor | Match impedance, reduce reflection | USB, CAN, HDMI, LVDS | 0402–0603 |
- EMI issues
| Component | Function | Best for EMI Use | Size |
| Ferrite Beads | Block high-frequency noise | Power lines, signal filters | 0603–1206 |
| MLCC Capacitors | Decouple noise to ground | Power decoupling, bypass | 0402–0603 |
| Series Resistors | Damping signal edges | High-speed digital lines | 0402–0603 |
| Common Mode Chokes | Block differential line noise | USB, CAN, Ethernet | 0805–custom |
| Inductors | Form filters with capacitors | Custom filter designs | 0805–1812 |
5. Repair and Rework
- 0603 and 0805 are easiest to manually rework.
- 0402 is okay with skilled techs.
- 0201 and smaller: High chance of damage during rework, expensive microscopes needed.
Large sizes (1210, etc.): Easy to handle but not common on dense modern boards
Best Overall for Cost Efficiency:
- 0603 (both resistor and capacitor):
- Widely used, low cost, reliable for assembly, not too small to rework.
- Strong supply chain support.