# Cross Comparison Between Thermal Cycling and High Temperature Stress on I/O Connection Elements

## TL;DR

This paper compares how heat and temperature changes affect the reliability of FPGA I/O connections, revealing different degradation mechanisms.

## Contribution

The study introduces a method to distinguish between on-die and package-level aging in FPGAs using resistance monitoring.

## Key findings

- High-temperature dwell and thermal cycling both cause sub-linear resistance drift in FPGA I/O paths.
- High-temperature stress has a lower activation energy (0.62 eV) compared to thermal cycling (1.3 eV).
- Resistance monitoring can identify whether degradation is from on-die or package-level components.

## Abstract

This work examines resistance drift in FPGA I/O paths subjected to combined electrical and thermal stress, using a Xilinx Spartan-6 device as a representative platform. A multiplexed measurement approach was employed, in which multiple I/O pins were externally shorted and sequentially activated, enabling precise tracking of voltage, current, and effective series resistance over time, under controlled bias conditions. Two accelerated stress modes were investigated: high-temperature dwell in the range of 80–120 °C and thermal cycling between 80 and 140 °C. Both stress modes exhibited similar sub-linear (power-law) time dependence on resistance change, indicating cumulative degradation behavior. However, Arrhenius analysis revealed a strong contrast in effective activation energy: approximately 0.62 eV for high-temperature dwell and approximately 1.3 eV for thermal cycling. This divergence indicates that distinct physical mechanisms dominate under each stress regime. The lower activation energy is consistent with electrically and thermally driven on-die degradation within the FPGA I/O macro, including bias-related aging of output drivers and pad-level structures. In contrast, the higher activation energy observed under thermal cycling is characteristic of diffusion- and creep-dominated thermo-mechanical damage in package-level interconnects, such as solder joints. These findings demonstrate that resistance-based monitoring of FPGA I/O paths can discriminate between device-dominated and package-dominated aging mechanisms, providing a practical foundation for reliability assessment and self-monitoring methodologies in complex electronic systems.