Finding drop-in replacements for electrolytic capacitors can be an arduous and time consuming task. Comparing footprints, datasheet information, equivalent series resistance (ESR) at operating frequency, and lifetime calculations at rated temperature consume valuable engineering time in exchange for reducing sourcing risk. Manufacturer cross-reference tools and PDFs can help decrease the cost of this analysis, but often these resources do not verify the performance of the two parts at the operating point of the device. In addition, these tools are often out of date and do not find matches for many parts.
The engineers at SourcingBot have developed an automated cross-reference tool to solve these issues. Part replacements are found across the catalogs of all manufacturers and characteristic charts of capacitor behavior at many operating points can be easily compared. This is done with a combination of datasheet information, lab-measured data, and insights generated by the SourcingBot cross-reference tool itself to help verify cross-references at the deepest level possible. In this article, the process of finding a cross-reference for an electrolytic capacitor is examined, and the advantages of using an automated tool to perform much of the process are demonstrated.
Requirements for Electrolytic Capacitor Cross-References
While similar in basic principles to other capacitor categories such as film, ceramic, or tantalum, electrolytic capacitors have their own set of parameters to compare when finding and verifying a cross-reference. In addition to the usual comparisons of footprint size, voltage, and capacitance, the lifetime at operating temperature, ESR, ripple current, and qualifications must be compared in order to be certain of compatibility between two parts. It is also advantageous to perform an analysis of part performance at the operating point of the device, that is, looking at the ESR and impedance at the frequency at which the device will be used. This is one of the most time consuming parts of the cross-reference process, but cannot be ignored due to the risk of purchasing parts which are not compatible with the target product.
Here, two series of surface mount (SMD) capacitors will be compared: Würth’s WCAP-AS5H series of long-life electrolytic capacitors and Panasonic’s EEE-TC series of high-temperature reflow electrolytic capacitors. Let’s look at an example from each series to determine at which operating points the two series can be considered cross-references for one another. The EEETC1E221P from Panasonic and the 865230457007 from Würth are 220uF, 25V electrolytic capacitors with tolerances of 20%. They both have a PCB footprint of 10.3 by 10.3mm. The operating temperature range of the Panasonic part is -40 to 125 Celsius while for the Würth part the range is -40 to 105. The Panasonic part is rated at 125 days at 125 Celsius and the Würth part is rated at 208 days at 105 Celsius. The Panasonic part is AEC-Q200 rated, while the Würth part is not.
Some conclusions about the two parts can already be taken from the comparison of datasheet values. The Würth part cannot be used as a replacement for the Panasonic part at temperatures above 105 Celsius or in automotive applications. However, in general purpose applications it appears that the two parts would be compatible with one another.
Using the SourcingBot Cross-Reference Tool to Reduce Sourcing Risk
The previous section showed that the two series can, in many cases, be used as replacements for each other. It does not, however, check the behavior of the two parts at the operating frequency. To do this, an engineer typically has to visit the websites of the two manufacturers and hope that simulation data is available for the parts, and then try to compare the two parts given different lab conditions and chart scales/units. At SourcingBot, both the datasheet comparison step and the operating point analysis can be done quickly and automatically.
After searching for a part in the SourcingBot database, a match table showing the most similar parts according to datasheet data is generated. The matching process is completely transparent; the values are all shown in an easy-to-compare table and a similarity score out of 100% is calculated. In this table, parts with lab measurements can be compared using the ‘Click to compare’ feature.
Here the impedance behavior of the two capacitors can be compared across frequency. It is clear from this chart that the two parts behave similarly across the useful frequency range. The ESR behavior against frequency is also available to compare. With this data, an engineer can quickly find similar parts according to datasheet information, and verify compatibility by looking at lab data.
In addition to single parts, SourcingBot can handle entire bills of material automatically. At sourcingbot.com/xref-tool, a bill of materials can be uploaded and parameters for the cross-reference search can be defined. Replacements can be found from all manufacturers, all manufacturers excluding the original manufacturer, or a list of desired manufacturers can be given. In seconds, the bill of materials is crossed with the SourcingBot database and the top replacement parts are shown.
Using the SourcingBot cross-reference tool, the process of securing a bill of materials against procurement risk is faster than ever before. Building a list of cross-references can be done in seconds, not hours, and expensive engineering time can be spent elsewhere.