Overview
IEC TR 62878-2-7:2019 is a Technical Report that provides guidelines for accelerated stress testing of passive embedded circuit boards. It is focused on screening finished multilayer and high-density interconnection (HDI) embedded boards - particularly those used in mobile devices - to assess reliability under combined thermal, environmental and mechanical stresses.
Key topics and technical requirements
- Combined-stress test method: simultaneous thermal heating, humidity control and mechanical bending/vibration to better simulate real-world conditions.
- Thermal conditions: target circuit temperatures are controlled electrically; a typical test uses 325 °C for 1 hour for materials with high decomposition temperature (Td > 350 °C). An alternative setting of 305 °C for 1.5 hours is given for lower-Td materials.
- Environmental conditions: chamber set to 85 °C / 85 % RH (Dewpoint control with DI water recommended).
- Mechanical stress: dynamic bending (typical 2 mm deflection for standard MLCC; 1 mm for MLCC thinner than 150 µm) with vibration; test coupons are mounted in a validated bending tester placed inside the temperature-humidity chamber.
- Test coupons and stack-up: sample coupon size 35 × 5 mm; design rules include 100 µm line width, 350 µm via pad, and layer stack-up totaling 540 ± 54 µm. Test coupons incorporate heating circuits tied to embedded passives.
- Monitoring and failure criterion: real-time voltage monitoring across the heated circuit; failure defined as >20% increase in output voltage (indicative of resistance increase). Failed samples are cross-sectioned (via area) for root-cause analysis.
- Reporting: record and store time-history voltage data and cross-section images. The TR also includes coupon design rules and bending tester setup (Annex A and B).
Practical applications and users
Who benefits:
- PCB designers and layout engineers designing passive-embedded multilayer or HDI boards for mobile products.
- Reliability and test engineers developing screening plans for embedded passive PCBs.
- Manufacturing and quality teams in PCB fabrication and assembly houses performing lot screening.
- Independent test laboratories conducting accelerated reliability qualification.
Practical uses:
- Pre-production screening to detect via cracking, interconnect weakness, or early-life failures.
- Comparative assessment of material/process changes (e.g., new prepregs, lamination).
- Validating assembly processes and embedded passive integration for mobile device PCBs.
Related standards
- Normative reference: IEC 60194 (printed board design/terms and definitions).
- IEC TR 62878 is part of the broader Device embedding assembly technology series - refer to the IEC webstore for other parts and updates.
Keywords: IEC TR 62878-2-7:2019, accelerated stress testing, passive embedded circuit boards, HDI, multilayer PCB, bending tester, 85°C/85% RH, via cracking, mobile device PCB reliability.