The longevity of solar photovoltaic modules depends on the durability and reliability of their components, one of which is the solder bonds in interconnect ribbons. The solder joints experience stresses from thermal cycling and constant elevated temperatures (40 °C–70 °C) in regular field operation leading to thermo-mechanical fatigue and intermetallic compound formation. To study the end-of-life wear-out mechanisms and to obtain activation energy of solder bond degradation, two field-aged modules from Arizona—a 21-year-old Solarex MSX60 module (with Sn62Pb36Ag2 at the solder joints) and an 18-year-old Siemens M55 module (with Sn60Pb40 at the solder joints)—underwent 800 and 400 modified thermal cycles, respectively. Using three heating blankets, each module had three temperature zones maintained at 85, 95, and 105 °C during the 15-min hot dwell time of the thermal cycle. Cell-level series resistance data obtained from three temperature zones enabled the calculation of activation energy for solder bond degradation for the MSX60 and the M55 modules to be 0.12 eV and 0.35 eV, respectively. From each temperature zone in both modules, busbar-solder samples were obtained, imaged through SEM, and analyzed with energy-dispersive X-ray spectroscopy. In the MSX60 module with traces of Ag in the solder material, phase segregation and growth were primarily observed at high temperatures. For M55 modules without Ag in the solder material, major phase segregation was observed in all temperature zones. The IMC thickness for both modules increased with increasing module temperature. The beneficial effect of Ag in solder material on mitigating solder bond degradation is presented.

中文翻译：

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寿命终止焊锡键降解的活化能：现场老化光伏组件的热循环

太阳能光伏模块的寿命取决于其组件的耐用性和可靠性，其中之一是互连带中的焊点。焊点在常规现场操作中承受来自热循环和恒定高温 (40 °C–70 °C) 的应力，导致热机械疲劳和金属间化合物的形成。为了研究寿命终止的磨损机制并获得焊点退化的活化能，来自亚利桑那州的两个现场老化模块 - 一个 21 岁的 Solarex MSX60 模块（焊点处有 Sn62Pb36Ag2）和一个 18年历史的 Siemens M55 模块（在焊点处使用 Sn60Pb40）——分别经历了 800 次和 400 次改进的热循环。使用三个加热毯，每个模块具有三个温度区，分别保持在 85、95、在热循环的 15 分钟热停留时间内，温度为 105 °C。从三个温度区获得的电池级串联电阻数据使 MSX60 和 M55 模块的焊点退化的活化能计算分别为 0.12 eV 和 0.35 eV。从两个模块的每个温度区，获取母线焊料样品，通过 SEM 成像，并用能量色散 X 射线光谱分析。在焊料中含有痕量 Ag 的 MSX60 模块中，主要在高温下观察到相分离和生长。对于焊接材料中不含 Ag 的 M55 模块，在所有温度区都观察到主要的相分离。两种模块的 IMC 厚度都随着模块温度的升高而增加。