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Overmolded connectors combine cables and connectors in a molded polymer housing to boost durability and sealing. They relieve strain, prevent disconnections, and protect against dust, moisture, and mechanical stress.
Engineers often incorporate metal foil or mesh shields into overmolds to block electromagnetic interference. This hybrid design creates cable assemblies that withstand harsh industrial and telecom environments.
For context, copper foil offers the highest shielding but is relatively expensive. Aluminum foil is lighter and less costly, while tinplate (tin-plated steel) is the most cost-effective option. The following sections examine each material in turn.
Copper Foil
Copper foil is the go-to material for EMI shielding due to its high electrical conductivity. It remains flexible and corrosion-resistant, and can be soldered for easy grounding. The downside is cost: copper is relatively expensive compared to aluminum or steel.
Copper foil tape is sold in rolls for 100% coverage over complex shapes. It conforms to connectors and withstands flexing or vibration well. Thin copper foil (0.02–0.05 mm) provides near-ideal conductivity with minimal bulk. It bonds reliably when soldered, giving low-resistance grounding paths for high-frequency currents.
Aluminum Foil
Aluminum foil is lighter and cheaper than copper, but it is only about 60% as practical for EMI shielding. It bends easily, and its adhesive tape is known for strong adhesion. A drawback is that aluminum foil cannot be soldered (its oxide layer must be treated).
Aluminum foil tape is thinner and more flexible than copper, allowing it to conform to tight bends with ease. Its thermal conductivity can help dissipate heat from components. Because aluminum oxide prevents the foil from being soldered, conductive adhesives or contact paints are used to bond the foil to the metal chassis.
Aluminum foil is often chosen for low-weight designs: it has about 30% the density of copper. Ultra-thin aluminum tape (≈0.01–0.02 mm) is standard in laptop and smartphone connectors to trim every gram.
However, aluminum is relatively soft and may tear on sharp bends, and its oxide layer allows moisture to increase contact resistance over time. Many engineers accept these drawbacks in exchange for the cost and weight savings, without compromising performance.
Tinplate (Tin-Plated Steel)
Tinplate (tin-plated steel) is the cheapest. Its steel core yields weaker shielding than copper or aluminum. However, the tin plating not only resists corrosion but also makes the material solderable. Tinplate is strong, but it’s heavy and inflexible.
Tinplate is used for stamped EMI cans and connector shells. Its steel core attenuates low-frequency fields (unlike copper or aluminum), and the tin plating prevents corrosion while allowing for soldering. However, steel is stiff, so tinplate is best for rigid shields.
Tinplate is commonly used in automotive and industrial connectors where mechanical robustness is required. A stamped tinplate shell provides both structural support and EMI shielding in one part, simplifying assembly and ensuring good continuity.
The table below compares the shielding effectiveness, solderability, flexibility, and cost characteristics of each material.
| Material | Shielding Effectiveness | Solderability | Flexibility | Cost |
|---|---|---|---|---|
| Copper foil | Very high (highest) | Yes (easy) | High (flexible) | High |
| Aluminum foil | Moderate (~60% of copper) | No (oxide barrier) | Very high | Low |
| Tinplate (tin-plated steel) | Low (steel core) | Yes (tin-coated) | Low (stiff) | Lowest |
Material Selection Tips
- Copper foil: Use when maximum EMI shielding is required (for high-speed or RF signals) and soldering is necessary.
- Aluminum foil: Choose for lightweight, low-cost assemblies with strong adhesion; avoid if soldering is required.
- Tinplate: Ideal for budget or rugged applications (provides magnetic shielding) and is solderable; expect heavier, less flexible parts.
Ultimately, the best shield material depends on a connector’s EMI requirements, mechanical needs, and budget. If shielding demands are low and weight or cost is critical, aluminum or tinplate may suffice; copper is usually preferred if maximum attenuation is required.
In high-vibration or repeated-flex applications, adhesive aluminum tape can fatigue or peel away, whereas soldered copper foil or rigid tinplate shields stay intact. Copper foil and tinplate enclosures can be soldered or welded directly to connector shells for secure grounding, whereas aluminum foil relies on strong adhesive backing or clamps. These practical assembly considerations often influence the choice of shield material.
Why Romtronic
Romtronic is an ISO-certified OEM manufacturer with its own factory. With 28 years of ODM/OEM experience, we specialize in custom cable assemblies and connectors for automotive, medical, and industrial sectors, providing end-to-end solutions. Romtronic’s engineering team can advise on optimal shielding materials and handle precise overmolding of custom connector designs.
All manufacturing is conducted under ISO-certified quality systems (ISO 9001, 13485, and IATF 16949), providing customers with confidence in consistent quality and compliance.
With Romtronic, customers get robust overmolded connectors with optimized shielding solutions for any application. Romtronic offers one-stop solutions from prototyping to mass production.
Sam Wu is the Marketing Manager at Romtronic, holding a degree in Mechatronics. With 12 years of experience in sales within the electronic wiring harness industry, he manages marketing efforts across Europe. An expert in cable assembly, wiring harnesses, and advanced connectivity solutions, Sam simplifies complex technologies, offering clear, actionable advice to help you confidently navigate your electrical projects.
