An electronics housing passes EMI testing as a prototype. Production begins, and small changes in wall thickness, warpage, or fastening pressure create gaps at the seams. Shielding performance varies between units, forcing redesign, tooling changes, or delayed certification after the budget has already been committed.
The lowest material quote does not predict the final cost. The full cost depends on how the housing material, shielding method, and enclosure design perform together.
Two Ways to Shield a Housing, Two Different Cost Curves
EMI shielding comes from one of two approaches. Either conductive fillers are compounded into the resin, or a standard resin gets coated afterward through vacuum metallization, electroless plating, or conductive paint.
A coating adds a secondary process, with the risk of scratches, uneven coverage, or delamination during use. Conductive fillers remove that stage, but they affect impact resistance and wear tooling faster.
Shielding effectiveness also depends on enclosure design, including seam continuity, vents, and grounding points, as much as it depends on the material. A conductive resin cannot compensate for a housing that lets interference through a gap.
Wanox recommends conductive fillers in five recurring situations:
- High-reliability products such as industrial and telecom equipment, where coating delamination risk is unacceptable over a long service life
- Complex geometries, where spray coating struggles to cover the shape evenly
- Small and medium production runs, where coating equipment and masking fixtures only pay off above roughly one million units
- Projects that need a simpler supply chain, since fillers remove a secondary process
- Thin-wall housings exposed to thermal cycling, where a coating can crack as the coating and the plastic expand at different rates and break electrical continuity
Coatings remain the right call when geometry allows even coverage and volume is high enough to spread the equipment cost.
Heat Resistance and Flame Retardancy Work Against Each Other
Heat deflection temperature shows how a material holds up under load as temperature rises. Unfilled ABS reaches roughly 94°C. Standard polycarbonate reaches 110°C to 120°C. PC/PBT(polycarbonate/polybutylene terephthalate) blends go higher still.
Flame retardant additives needed for UL94 compliance typically lower that heat performance even as they cut flammability risk. A resin data sheet reports these properties under controlled conditions, but the finished formulation has to meet every requirement at once.
Wanox sees four conflicts recur most often:
- Flame retardants lowering heat resistance, the most common conflict. Flame-retardant ABS needs special formulation to hold above 90°C while meeting the top UL94 rating.
- Halogen-free systems, now common as regulations move away from halogenated chemistry, degrade more after long-term thermal aging.
- Thinner housings need higher flame retardant loading to meet the same rating, which lowers heat resistance further and keeps pushing thinner designs to lose ground.
- Thermally conductive fillers interfere with flame retardant dispersion, while flame retardants reduce thermal conductivity in return.
Some housings also need to move heat away from internal components rather than just resist it. Thermally conductive compounds based on nylon, PBT, or PC serve that purpose, and their fit depends on thermal conductivity, mechanical strength, and flame performance together.
Stacking Requirements Multiplies the Trade-offs
Shielding fillers, thermal fillers, and flame retardants each affect strength, flow, and cost on their own. Combined in one formulation, those effects compound. A formulation can meet each requirement in separate tests and still fail when all three apply together, which is why requirements added late are a common source of rework.
Wanox sets minimum values before formulation begins: shielding effectiveness, heat resistance, flame rating, and the mechanical properties the housing must retain.
Formulation is then matched to the application:
- Low-end consumer electronics prioritize flame retardancy and basic heat resistance, with shielding handled through structural design
- Mid-range IoT devices balance fillers against flame retardants, choosing filler types that limit the impact on flame retardancy
- High-end industrial and telecom housings start from specialty high-temperature resins, then get modified for shielding and thermal performance
Cost gets assessed as total cost of ownership, since fillers cost more per kilogram but remove a process step, while coatings cost less but add one. Wanox validates the formulation through joint sample production, tuning filler loadings without over-engineering the part.
Real Housing Cost Includes What Happens After Molding
Plastic housings generally cost less than machined or die-cast metal, but the shielding and thermal method chosen changes that comparison, and resin price per kilogram alone misses the downstream costs.
Wanox prices housings against seven factors:
- Mold costs, including wear-resistant coatings where fillers accelerate mold wear
- Secondary processing costs for spray equipment, masking, and curing ovens, which fillers eliminate
- Scrap and yield costs from coating adhesion or filler uniformity
- Supply chain costs from coordinating multiple suppliers
- Certification costs for flame safety and shielding effectiveness
- Grounding costs, since fillers simplify grounding while coatings need continuous conductivity engineered to the grounding point
- Lifecycle costs, since coating wear can cause shielding failure years into a product’s life while filler-based shielding does not degrade
Material selection handled this way holds up past the first shipment. Shielding, heat resistance, and flame retardancy get weighed against each other before the mold is cut, not discovered against each other in the field.
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Material selection made this way holds up after launch, not just in the lab. Contact Wanox to talk through your housing requirements before the mold is cut.
