One of the most common questions in DC-DC converter design is whether to use a shielded or unshielded power inductor. The choice affects EMI, size, cost, PCB layout and thermal performance. Get it wrong and you either waste board space or end up with noise that interferes with sensitive circuits.
This guide compares shielded and unshielded inductors, explains when to use each, and covers PCB layout considerations.
Shaanxi SiRui Technology Co., Ltd. manufactures both shielded molded inductors and unshielded toroidal / drum-core inductors for DC-DC and POL applications. Contact: sales@sirui-tech.com | Web: www.sirui-tech.com
1. Unshielded vs Shielded Inductors
Unshielded: the core is open (drum core or toroid without cover). Magnetic field extends outside the component. Smaller, cheaper, but radiates EMI and requires PCB keep-out area.
Shielded: a magnetic shell or molded powder coating surrounds the winding, containing most of the field. Lower EMI, minimal keep-out, but larger and more expensive.
2. Comparison Table
| Parameter | Unshielded | Shielded |
|---|---|---|
| Radiated EMI | High | Low |
| Size (same L) | Smaller | Larger (20–40%) |
| Cost | Lower | Higher |
| PCB keep-out | 5–10 mm required | Minimal |
| Heat dissipation | Better (open) | Worse (enclosed) |
| Typical height | 2–5 mm | 3–8 mm |
3. When to Use Unshielded
- Cost-sensitive consumer electronics
- Space-constrained designs where size matters more than EMI
- Inductor placed far from sensitive analog/RF circuits
- High-frequency operation (>2 MHz) where shielded core loss is worse
- High current where open core runs cooler
4. When to Use Shielded
- EMI-sensitive environments near ADCs, audio, RF receivers
- Dense PCB layouts with limited keep-out space
- Automotive / industrial with strict EMI compliance
- Multiple inductors on one board (crosstalk)
- Portable devices with audio/camera noise complaints
5. PCB Layout Tips
For unshielded inductors: maintain 5–10 mm from sensitive circuits, use ground plane under the inductor to contain the field, orient inductors to minimize coupling between them.
For shielded inductors: can be placed closer, but still maintain clean ground for thermal reasons.
6. Sirui-Tech Inductor Products
- Shielded molded inductors: SMD, 1–100 μH, up to 30 A
- Unshielded drum-core: through-hole and SMD, low cost
- Toroidal inductors: custom wound on ferrite or powder cores
Conclusion
Choose unshielded when cost and size matter with available keep-out space. Choose shielded when EMI compliance, dense layouts or sensitive circuits are the priority. When in doubt, start with shielded and switch to unshielded after verifying EMI performance.
Need a power inductor? Contact Sirui-Tech at sales@sirui-tech.com with your inductance, current rating and frequency.