A Tier-2 automotive supplier based in Gothenburg, Sweden, was developing a new generation of exhaust gas temperature sensors for a major Nordic heavy-duty truck platform. These sensors are mounted directly on the exhaust manifold and are subjected to extreme thermal cycling—from the frigid -40°C of a Scandinavian winter cold start to over +800°C at the sensing tip during full-load operation—plus continuous high-frequency engine vibration. The internal spring contact that connects the sensor's ceramic sensing element to the wiring harness was failing during accelerated life testing.
The Failure Mode
The original spring contact, made from a standard phosphor bronze alloy, was experiencing stress relaxation. After approximately 500 hours of combined thermal cycling and multi-axis vibration testing, the contact normal force had degraded below the critical threshold needed to maintain a stable, low-resistance electrical connection. This degradation resulted in intermittent sensor signal dropout, which would trigger an emissions-related diagnostic fault code on the vehicle's CAN bus.
Our Approach
The Swedish engineering team provided a comprehensive specification package, including the target force-deflection curve and the vibration profile derived from ISO 16750-3 (the international standard governing environmental testing of vehicle electrical equipment, widely adopted by Swedish OEMs). Our proposed solution centered on two critical modifications:
1.Material Upgrade: We recommended transitioning the part from standard phosphor bronze to Beryllium Copper C17200, heat-treated to TH02 condition after forming. BeCu is widely specified in Nordic automotive applications for its superior ability to retain spring force under sustained elevated temperatures and cyclic mechanical stress. Its fatigue endurance limit significantly exceeds that of phosphor bronze under these specific operating conditions.
2.Geometry Refinement: Using Finite Element Analysis (FEA) simulation, our engineering team identified a sharp internal bend radius in the original design that was functioning as an unintended stress concentrator. We proposed increasing this radius by 0.2mm. This subtle modification did not alter the part's external envelope or its fit within the sensor housing, but it reduced the peak forming stress in that critical zone by approximately 18%.
Manufacturing and Independent Validation
We manufactured a pilot batch of 2,500 pieces using a modular progressive die at our Shenzhen facility. Representative samples were shipped to an accredited independent test laboratory in Sweden for validation against the customer's full test protocol. The results confirmed that after 1,000 hours of exposure to 125°C ambient temperature with superimposed random vibration, the new BeCu spring contacts retained over 95% of their specified initial normal force. The contact resistance deviation across all test samples remained below 2 milliohms, well within the allowable drift margin.
Long-Term Outcome
The Swedish customer formally approved the redesigned spring contact and placed a follow-on production order for 25,000 pieces to support their initial manufacturing ramp for the new truck platform. This project demonstrated how a focused materials engineering intervention—specifically, the substitution of heat-treated beryllium copper for standard phosphor bronze—could resolve a persistent, field-relevant reliability challenge that threatened to delay the sensor's final qualification. For Tingfeng Hardware, this engagement reinforced our commitment to delivering engineering-driven solutions tailored to the exacting standards of the Nordic automotive supply chain.