Introduction
In applications such as new energy systems, rail transit, and automotive engine compartments, fuse holders often face temperature cycles from –40 °C to +150 °C or even higher. High-temperature environments not only accelerate material aging but also cause differential thermal expansion that can loosen mating parts and raise contact resistance, thus undermining circuit protection and overall system reliability. Based on years of experience in developing electronic switches and protection components, this article focuses on two core topics—thermal-expansion matching and heat-dissipation design—and, through representative case studies and key design points, delves into material selection, structural optimization, and thermal-management schemes for fuse holders in high-temperature environments.

I. Key Challenges for Fuse Holders in High-Temperature Environments

1. Material Degradation

• Engineering plastics tend to crack under stress and distort dimensionally when exposed long-term to temperatures above 125 °C.

• Springs creep at elevated temperatures, reducing preload force over time.

2. Thermal-Cycle–Induced Contact Failure

• Repeated temperature swings (±50 °C or more) cause relative displacement between components with different CTEs (coefficients of thermal expansion), leading to loosened pins, springs, and housing interfaces.

3. Local Hot Spots and Heat Accumulation

• Under heavy currents or poor ambient cooling, temperatures around the fuse can spike above 200 °C during melting, exacerbating nearby material degradation.

4. Mechanical Reliability and Safety Requirements

• Sectors like rail and automotive impose strict vibration, shock, and fire-resistance standards, so heat-dissipation and sealing designs must also satisfy flame-retardance and structural-strength criteria.

II. Thermal-Expansion Matching Design

1. Comparison of Material CTEs

2. CTE-Matching Strategies for Pins, Springs, and Housing

1. Housing vs. Spring

• Choose PPS or LCP for the housing (CTE ≈12–15 ×10⁻⁶/K) to match stainless-steel springs (CTE ≈12 ×10⁻⁶/K), keeping thermal-cycle displacement under 20 µm.

2. Pins vs. Housing

• For copper-alloy pins (CTE ≈17 ×10⁻⁶/K) paired with PA66-GF30 housing (CTE ≈15 ×10⁻⁶/K), introduce a soft-transition buffer—such as an annular micro-wall or multi-wedge compression zone—at each pin hole to absorb about 5 µm per 10 K of differential expansion.

3. Ceramic Insert Application

• In ultra-high-temperature scenarios (>150 °C), embed low-CTE ceramic inserts in critical conductive paths. The metal-ceramic composite structure can reduce surrounding differential expansion to under 2 µm per 10 K.

3. Structural Buffers and Stress-Relief Features

• Micro-corrugated-tube transition: Machine tiny corrugations at the pin–spring interface to provide both conductivity and displacement absorption.

• Annular soft pad: Insert high-temperature silicone or rubber pads at the pin base or spring seat–housing interfaces for added thermal-cycle cushioning.

• Segmented snap-fit design: Divide the housing into inner and outer layers, linked by metal clips or locking rings that allow the inner layer to slide along guiding slots during thermal expansion, eliminating stress concentration.

III. Heat-Dissipation Design and Thermal Management

1. Base Heat-Sink Fin Design

• Material selection: Use high-thermal-conductivity aluminum alloys (7075 or 6063) for the base (CTE ≈23 ×10⁻⁶/K), constrained by design features to mate reliably with a PPS or LCP housing.

• Fin dimensions and spacing: For 100 A-class applications, fins should be ≥1.5 mm thick, 15 mm tall, with 8 mm spacing—boosting convective area and reducing local temperature by 5–10 °C.

• Assembly method: Employ cold-riveting or insert casting so the aluminum fins form a monolithic structure with the plastic base, ensuring minimal and stable thermal paths.

2. Metal-Insert Heat-Sink Solutions

• Copper-alloy heat-sink inserts: Mold cavities near the fuse-contact region, then insert C1100 copper pieces that are welded or mechanically locked to the pins and springs, swiftly channeling melting-event heat away.

• Thermal pads and conductive grease: In multi-way fuse-holder modules, place 0.5 mm thermal-pad layers or conductive grease between the metal inserts and fins to cut interface thermal resistance by at least 30%.

• Embedded thermal pillars: Bury multiple Φ2 mm×20 mm copper pillars in the plastic base to connect to the finned cover, forming a three-dimensional thermal path that uniformizes temperature distribution.

3. Thermal Simulation and Validation for Typical Applications

• Case Study A: Diesel Engine Control Box Fuse Holder

• Ambient: –40 °C to +130 °C, confined enclosure.

• Design highlights: PPS housing + copper inserts + aluminum base fins. Thermal simulation shows a maximum surface temperature of <95 °C under 50 A continuous current.

• Case Study B: 1500 V DC Inverter High-Voltage Circuit

• Ambient: –20 °C to +85 °C, high-altitude conditions.

• Innovations: Embedded ceramic composite thermal pillars, annular cooling channels, and integrated base fins. Measured temperature rise <40 °C after an 80 A short-circuit melt (500 ms), well below material deformation thresholds.

IV. Other Critical Design Elements

1. Arc Isolation and Fire-Resistance

• During high-temperature melts, arcs occur. Introduce ceramic partition plates or metalized quartz shards to form an arc chamber, isolating arc energy locally and using nearby fins to dissipate it rapidly.

2. Flame-Retardance and Aging-Life Control

• Select UL 94 V-0 (or higher) flame-retardant materials. Conduct accelerated-aging tests (150 °C, 500 h; 1 000 thermal cycles) on plastics and springs to ensure contact resistance remains <10 mΩ after 100 000 insertions.

3. Dust-Proofing, Water-Proofing, and Sealing

• Silicone O-rings between housing and base.

• Replaceable post-melt cover that allows “hot-swap” maintenance without power shutdown.

• High-temperature environments often involve dust or humidity. Design to IP 67:

V. Conclusion and Future Outlook

Under high-temperature conditions, fuse-holder reliability and service life hinge on both CTE matching and heat-dissipation design. By:

1. Precisely matching the thermal-expansion coefficients of pins, springs, and housings with structural buffers;

2. Employing base fins, metal-inserts, and three-dimensional thermal paths;

3. Integrating arc isolation, flame-retardance, accelerated-aging, and sealing features—

one can markedly enhance fuse-holder stability across –40 °C to +150 °C cycles or beyond. Looking forward, the maturation of low-CTE composites and graphene-based thermal materials, together with digital-twin thermal simulations and online monitoring, will further boost high-temperature adaptability of fuse holders—laying a stronger protection foundation for electric vehicles, high-speed rail traction, and avionics.