Evaluation of Leakage Currents of Semiconductor Packages Due to High-Voltage Stress Under an Immersion Cooling Environment  
[PERSON]  
1 Department of Mechanical and Automotive Engineering, Kongju National University,  
Cheonan-daero 1223-24, Seobuk-gu, Cheonan-si 31080, Chungnam, Republic of Korea; [EMAIL_ADDRESS]  
[PERSON]  
2 Department of Mechanical Engineering, Kongju National University,  
Cheonan-daero 1223-24, Seobuk-gu, Cheonan-si 31080, Chungnam, Republic of Korea; rkkows@[EMAIL_ADDRESS]  
[PERSON]  
3 Department of Mechanical Engineering, The University of Wunsong 18323, Cyconggi, Republic of Korea 3*  
memory devices should maintain their integrity even under this cooling environment in order to guarantee the stability of data storage. Evaluating the impact of the dielectric coolant used in immersion cooling on the reliability of memory packages is essential. However, previous research has primarily focused on thermal management and heat transfer performance. A study on the heat distribution and heat transfer characteristics of a CPU in a single-phase immersion cooling system revealed that increasing the coolant flow rate reduced the temperature stabilization time, while the heat sink material had no effect on cooling performance [5]. In water-cooled immersion cooling experiments involving individual GaN transistors and PCB substrates, water and water ethylene glycol mixtures exhibited higher heat flux than dielectric fluids. However, the devices failed before reaching the critical heat flux (CHF), whereas dielectric fluids successfully reached the CHF and demonstrated greater thermal stability [6]. Meanwhile, there was research on the reliability of package substrate under immersion cooling environments, but it primarily focused on the impact of coolant absorption on mechanical behavior. The absorption of dielectric fluid EC 100 reduced the stiffness of PCBs and mitigated the warpage phenomenon [7], while mineral oil increased the stiffness of PCBs and passive components but had no significant impact on the reliability [8]. I-V curve analysis has been employed to assess internal degradation mechanisms. Typically, semiconductor packages are tested under high-temperature and high-humidity conditions, as well as under voltage stress condition exceeding standard operating levels, to detect defects and ensure their reliability [9; 10]. DRAM, a volatile memory, is composed of capacitors and metal-oxide-semiconductor field-effect transistors (MOSFETs). Applying DC voltage stress to MOSFETs accelerates degradation due to electrical and thermal stress, leading to increased leakage current and additional heat generation [11]. If this phenomenon persists, it can cause permanent damage to the semiconductor chip [12]. Therefore, it is necessary to investigate the effects of voltage stress on the reliability of semiconductor packages, even under immersion cooling environment. This study evaluated the effects of DC voltage stress on heat generation and electrical degradation in air and single-phase immersion cooling environments for commercial DRAM packages, analyzing the acceleration mechanisms of the degradation. Heat generation characteristics were measured using an infrared camera in an air environment and a contact-based thermometer in an immersion environment. The experimental results showed that the immersion cooling environment allowed a stable temperature of the packages via its cooling performance. In contrast, heat generation continued to increase in the air environment, resulting in more rapid degradation at relatively high voltages (3.0 V and 3.1 V). The electrical characteristics were measured using a probe station and a current-voltage analyzer to evaluate the package's I-V curves. The analysis confirmed that heat generation is a critical factor in accelerating electrical degradation. In air, accumulated heat accelerated degradation, leading to a substantial increase in leakage current.