I. Application Issues of Ultra-Low ESR (≤3mΩ) in AI Server VRMs
Main Question 1: Our CPU power supply has a very poor transient response; measurements show a large voltage drop. Is the VRM ESR of the output capacitor too high? Are there any capacitors with an ESR below 4 milliohms recommended?
Q1:
Question: When debugging the VRM of the AI server CPU power supply, we encountered a problem of excessive core voltage transient drops. We have tried optimizing the PCB layout and increasing the number of output capacitors, but the discharge slope measured with an oscilloscope is still unsatisfactory, leading us to suspect that the capacitor’s ESR is too high. For this type of application, how can we accurately measure or evaluate the actual ESR of the capacitor in the circuit? Besides referring to the datasheet, what practical methods are there for on-board verification?
Answer: For such high-performance applications, we recommend using multilayer solid-state capacitors with ultra-low ESR characteristics, such as the YMIN MPS series, whose ESR can be as low as ≤3mΩ (@100kHz), consistent with the standards of high-end Japanese competitors. During on-board verification, the voltage recovery speed can be observed through load step tests, or the impedance curve can be measured using a network analyzer. After replacing these capacitors, it is usually not necessary to redesign the compensation loop, but transient response testing is recommended to confirm the improvement effect.
Q2:
Question: Our GPU power supply module experiences a significant voltage drop under high-temperature environmental testing. Thermal imaging shows that the capacitor area temperature exceeds 85°C. Research indicates that ESR has a positive temperature coefficient. When evaluating the high-temperature performance of capacitors, in addition to the room temperature ESR value in the datasheet, should we also pay attention to the ESR drift curve over the entire temperature range? Generally, which materials or structures result in less temperature drift for capacitors?
Answer: Your concern is crucial. It is indeed important to pay attention to the stability of the capacitor’s ESR over the entire temperature range (-55°C to 105°C). Multilayer polymer solid-state capacitors (such as the YMIN MPS series) excel in this regard, exhibiting a gradual change in ESR at high temperatures. For example, the increase in ESR at 85℃ compared to 25℃ can be controlled within 15%, thanks to their stable solid-state electrolyte and multilayer structure, making them ideal for high-temperature, high-reliability scenarios such as AI servers.
Q3:
Question: Due to extremely limited PCB layout space, we cannot reduce the overall ESR by connecting multiple capacitors in parallel. Currently, the ESR of a single capacitor is around 5mΩ, but the transient response is still substandard. We see single-capacity capacitors on the market claiming ESR below 3mΩ. What are the impedance characteristics of these multilayer solid-state capacitors at higher frequencies (e.g., above 1MHz)? Will their high-frequency filtering effect be compromised due to different structures?
Answer: This is a common concern. High-quality low-ESR multilayer solid-state capacitors (such as the YMIN MPS series) can achieve both low ESR and low ESL (equivalent series inductance) through optimized internal electrode structure. Therefore, it maintains very low impedance in the 1MHz to 10MHz high-frequency range, resulting in excellent high-frequency noise filtering. Its impedance-frequency curve typically overlaps with that of comparable products from leading international brands, without affecting power integrity (PI) design.
Q4:
Question: In a multi-phase VRM design, we detected current imbalances in each phase, suspecting a connection to the ESR parameter consistency of each phase’s output capacitors. Even using capacitors from the same batch, the improvement is limited. For AI server power supply designs aiming for extreme performance, what level of batch ESR consistency and dispersion should capacitors typically achieve? Do manufacturers provide relevant statistical distribution data?
Answer: Your question touches upon the core of mass production reliability. High-performance capacitor manufacturers should be able to strictly control ESR consistency. For example, ymin’s MPS series, through fully automated production processes, can control the batch-specification ESR dispersion within ±10% and provides detailed batch parameter statistical reports. This is crucial for high-power CPU/GPU power supply designs requiring multi-phase current sharing.
Q5:
Question: Besides using expensive network analyzers, are there simpler methods in the field to qualitatively or semi-quantitatively evaluate the ESR and discharge speed of capacitors? We tried using an electronic load for step testing, but how can we extract effective parameters from the measured voltage drop waveform to compare the performance of different capacitors?
Answer: Yes, load step testing is a good method. You can focus on two parameters: the maximum voltage drop (ΔV) and the time required for the voltage to recover to a stable value. A smaller ΔV and a shorter recovery time usually mean a lower equivalent ESR and faster response of the capacitor network. Some leading capacitor suppliers (such as ymin) provide detailed application notes to guide you on how to set up tests and interpret data, thereby quantifying the improvements brought by ultra-low ESR capacitors like the MPS series.
II. Thermal Management Issues Regarding High Ripple Current and High Temperature Stability
Main Question 2: After the machine runs for a long time, the capacitors get very hot, and the ambient temperature is also high. I’m worried that they will break down in the long run. Are there any 560μF capacitors with particularly high ripple current that can withstand temperatures up to 105℃? Capacity is also crucial
Q6:
Question: When our AI server is running at full load, the measured temperature of the capacitor area in the GPU power supply circuit reaches over 90°C. Calculations show a ripple current requirement of approximately 8.5A, but the rated ripple current of existing capacitors is significantly insufficient at high temperatures. How should we interpret the ripple current value in the datasheet when selecting capacitors? For example, for a capacitor labeled “10.2A @ 45°C”, how much will its actual usable current be dated at an ambient temperature of 85°C?
Answer: Ripple current derating is critical for high-temperature design. Datasheets typically provide temperature-ripple current derating curves. Taking the YMIN MPS series as an example, its nominal 10.2A ripple current (@45°C) still maintains an effective capacity of ≥8.2A after derating at an ambient temperature of 85°C, a reduction of approximately 20%, thanks to its low loss and excellent thermal design. Choosing this type of capacitor ensures stable operation in high-temperature environments.
Q7:
Question: We successfully reduced the capacitor temperature rise by increasing the PCB copper foil thickness from 1oz to 2oz, but the effect was still not as expected. For capacitors that need to withstand ripple currents of over 10A, besides copper thickness, what other PCB design factors significantly affect their final operating temperature? Are there any recommended layout and via design guidelines?
Answer: PCB design is crucial. In addition to thickening the copper foil, it is also important to ensure short and wide current paths and reduce loop impedance. For high ripple current capacitors like the YMIN MPS series, it is recommended to place an array of thermal vias around the capacitor pads (not directly below) and connect them to the internal ground plane for heat dissipation. Following these design guidelines, combined with the capacitor’s own low ESR of 3mΩ, the typical temperature rise can be controlled within 15°C, significantly improving reliability.
Q8:
Question: In a multiphase VRM, even with uniform capacitor placement, the capacitor temperature in the middle phase is still 5-8°C higher than on the sides, which may be due to airflow and layout asymmetry. In this case, are there any targeted capacitor layout or selection strategies to balance the thermal stress of each phase? Answer: This is a typical problem of uneven heat dissipation. One strategy is to use capacitors with higher ripple current ratings in the center phase or hot spots, or to connect two capacitors in parallel at those locations to distribute the heat load. For example, a specific high-Irip model from the YMIN MPS series can be selected for localized reinforcement without changing the overall capacitor capacity, thus optimizing the system’s heat distribution without over-design.
Q9:
Question: In our high-temperature durability tests, we found that the capacitance of some capacitors exhibited measurable degradation with increasing temperature and prolonged operation (e.g., a degradation exceeding 10% at 105°C). For AI server power supplies requiring long-term stability, how should the capacitance-temperature characteristics and long-term capacitance stability of capacitors be considered? Which type of capacitor performs better in this regard?
Answer: Capacitance stability is a core indicator of long-life reliability. Solid-state polymer capacitors, especially high-performance multilayer types, have an inherent advantage in this regard. For example, ymin’s MPS series uses a special polymer electrolyte, whose capacitance variation can be controlled within ±10% across the entire temperature range (-55℃ to 105℃). Furthermore, after 2000 hours of continuous operation at 105°C, the capacitance decay is typically less than 5%, far superior to ordinary liquid or solid-state capacitors.
Q10:
Question: To control capacitor temperature rise at the system level, we plan to introduce thermal simulation. What key parameters (e.g., thermal resistance Rth) do we need to obtain from the supplier to build an accurate capacitor thermal model? How are these parameters typically measured, and are they provided as standard in the datasheet?
Answer: Accurate thermal simulation requires the capacitor’s junction-to-ambient thermal resistance (Rth-j-a) parameter. Reputable capacitor manufacturers will provide this data. For example, ymin provides thermal resistance parameters based on JESD51 standard test conditions for its MPS series capacitors, and may include temperature rise reference curves for different PCB layouts. This greatly helps engineers predict and optimize system thermal performance in the early stages of design.
III. Verification Issues Regarding Long Lifespan and High Reliability
Main Question 3: Our equipment is designed for a lifespan of over 5 years, but the current capacitors are estimated to degrade in performance within 3 years. Are there any solid-state capacitors with a long lifespan that can guarantee over 2000 hours at 105°C?
Q11:
Question: Our AI server is designed for 5 years of uninterrupted operation. Assuming a server room ambient temperature of 35°C, the capacitor core temperature is expected to be around 85°C. How should the “2000 hours @ 105°C” lifespan test result commonly found in specifications be converted to the expected lifespan under actual operating conditions? Are there any universally accepted acceleration models and calculation formulas?
Answer: The Arrhenius model is typically used for lifespan conversion; for every 10°C decrease in temperature, the lifespan approximately doubles. However, actual calculations must also consider ripple current stress. Some vendors offer online lifespan calculation tools. Taking the YMIN MPS series as an example, its 2000-hour @105°C test was conducted under full load conditions. Converted to 85°C and considering the actual working stress after derating, its estimated lifespan far exceeds the 5-year requirement, and detailed calculations are provided.
Q12:
Question: In our self-conducted high-temperature aging baseline tests, we found that some capacitors experienced an ESR increase of over 30% after 1500 hours. For capacitors with a nominal long lifespan, what key performance degradation data (such as ESR increase and capacitance change) should be included in the lifespan test report? What degradation range can be considered acceptable?
Answer: A rigorous lifespan test report should clearly record the test conditions (temperature, voltage, ripple current) and periodically measured ESR and capacitance changes. For high-end applications, it is generally required that after 2000 hours of high-temperature full-load testing, the ESR increase should not exceed 10%, and the capacitance degradation should not exceed 5%. For example, the official lifespan test report for the YMIN MPS series uses this standard, providing transparent data and demonstrating its stability under harsh conditions.
Q13:
Question: Servers require various mechanical vibration tests. We’ve encountered issues with micro-cracks appearing on capacitor pin solder joints due to vibration. When selecting capacitors, what mechanical structures or testing certifications should be considered to improve vibration resistance?
Answer: Focus on whether the capacitor has passed vibration tests according to standards such as IEC 60068-2-6. Structurally, capacitors with resin-filled bottoms and reinforced pin designs offer superior vibration resistance. For example, ymin’s MPS series uses this reinforced structure and has passed rigorous vibration tests, ensuring connection reliability during server transportation and operation.
Q14:
Question: We want to build a more accurate capacitor reliability prediction model, which requires failure rate distribution data (e.g., the shape and scale parameters of the Weibull distribution). Do capacitor manufacturers typically provide this detailed reliability data to customers?
Answer: Yes, leading manufacturers provide in-depth reliability data. For example, Ymin can provide its MPS series with reports including failure rate (FIT) values, Weibull distribution parameters, and lifetime estimates at different confidence levels. These data, based on extensive durability testing, help customers conduct more accurate system-level reliability assessments and predictions.
Q15:
Question: To control early failure rates, we have added a high-temperature charged aging screening step to our incoming material inspection. Do capacitor manufacturers conduct 100% early failure screening before shipment? What are the common screening conditions, and how significant is this for ensuring batch reliability?
Answer: Responsible high-end capacitor manufacturers conduct 100% pre-shipment screening. Typical screening conditions may include applying rated voltage and ripple current at temperatures far above the rated temperature (e.g., 125°C) for more than 24 hours. This rigorous process effectively eliminates early failure products, reducing the failure rate of outgoing products to extremely low levels (e.g., <10ppm). Ymin uses this stringent screening for its MPS series, providing customers with “zero-defect” quality assurance.
IV. Regarding the Selection of Alternative High-Performance Capacitors
Main Question 4: The Panasonic GX series we are currently using has too long a lead time/high cost, and we urgently need a domestic alternative. Are there any 2.5V 560μF capacitors with comparable ESR, ripple current, and lifespan? Ideally, a direct replacement.
Q16:
Question: Due to supply chain constraints, we need to find a domestically produced high-performance capacitor to directly replace a 560μF/2.5V capacitor from a flagship Japanese brand currently used in our design. Besides basic capacitance, voltage, ESR, and dimensions, what in-depth performance parameters and curves should be compared during direct replacement verification?
Answer: In-depth benchmarking is crucial. The following should be compared: 1) Complete impedance-frequency curves (from 100Hz to 10MHz) to ensure consistent high-frequency characteristics; 2) Ripple current-temperature derating curves; 3) Lifespan test data and decay curves. A qualified alternative, such as the YMIN MPS series, will provide a detailed comparison report showing that it is at the same level as or better than the original Japanese competitor in the above key parameters, thus achieving a true “plug-and-play” replacement.
Q17:
Question: After successfully replacing capacitors, the system performance largely met specifications, but a slight increase in ripple noise was observed in the switching power supply at specific frequencies (e.g., 1.2MHz). What could be causing this? Without changing the main topology, what fine-tuning techniques can typically be used to optimize this?
Answer: This is likely due to subtle differences in impedance characteristics between the old and new capacitors at extremely high frequencies. Optimization techniques include: connecting a small-value, low-ESL ceramic capacitor in parallel with the existing large capacitor to optimize filtering at that frequency; or fine-tuning the switching frequency. Reputable capacitor suppliers (such as ymin) will provide application support for their products (e.g., the MPS series), including specific suggestions for optimizing the output filter.
Q18:
Question: Our products are sold globally and have stringent environmental regulations (such as RoHS 2.0, REACH). When evaluating new capacitor suppliers, what specific compliance documentation should be requested?
Answer: Suppliers should be required to provide the latest RoHS/REACH compliance test report issued by an authoritative third-party organization (such as SGS), as well as a complete material declaration form. These documents must clearly list the test results for all restricted substances. Established suppliers, such as Ymin, can provide a complete set of environmental compliance documents that meet international standards for product lines such as the MPS series, ensuring smooth entry of customer products into the global market.
Q19:
Question: To reduce supply chain risks, we plan to introduce a second supplier. Does the new supplier’s capacitor products have mature case studies of mass application in mainstream AI servers or data center equipment? Can they provide verification reports or performance data from end customers as a reference?
Answer: This is a crucial step in reducing the risk of introduction. A reputable supplier should be able to provide case studies of mass application in well-known customers or benchmark projects. For example, Ymin can provide technical reports or customer approval certificates demonstrating the long-term reliability verification (such as 2000 hours of high-temperature full load, temperature cycling, etc.) of its MPS series capacitors in AI server projects of multiple leading server manufacturers, serving as strong endorsement of its product performance and reliability.
Q20:
Question: Considering project timelines and inventory costs, we need to assess the capacity assurance and delivery stability of new capacitor suppliers. What key information should we gather from suppliers during initial contact to evaluate their supply chain capabilities?
Answer: We should focus on understanding: 1) Monthly/annual capacity for the corresponding product series; 2) Current standard delivery cycle; 3) Whether they support rolling forecasts and long-term supply agreements; 4) Sample and minimum order quantity policies. For example, ymin typically has sufficient capacity, predictable delivery times (e.g., 8-10 weeks) for strategic products like the MPS series, and can provide flexible sample support and commercial terms to meet the needs of customer project development and mass production.
Post time: Feb-03-2026