KEMET Electronics introduced the firt to market AEC-Q200 Qualified series for automotive applications in August 2015, the T598. The initial design -in activities were done in Infotainment and ADAS (Advance Drive Assistance Systems ) such as rear cameras and parking sensors . In 2016 KEMET expanded the T598 Portfolio to 35V and 50V capabilities and open a new frontier for automotive applications under Chassis and Safety.Now in 2018 KEMET continues leading the automotive solutions with the 1st to market introduction of a 150ºC product, the T599 Series.
The polymer automotive offering represents an opportunity for miniaturization and cost of overall solution reduction and is important as an alternative in actual MLCC supply chain restrictions . In this white paper, we include technical solution examples.
Last month's news article in the market, highlights issues with potential shortage with MLCC components which creates challenges in the different segments, example is shown in Figure 1.
Due to this fact, R&D teams today call to action to access alternative solutions. But ‘what are the viable technical options?’
The Capacitance and Voltage mapping for different capacitor technologies, as shown in Figure 2a guide us to Tantalum polymer electrolytic capacitors when engineers are limited to 75V and capacitance ranges between 1uF to 1mF. However, the process of converting from an MLCC to a Ta Polymer SMD component is not a one to one process and needs to follow several considerations that are schematically described in Figure 2b
The mechanical and dimensional characteristics are the first parameter to be validated. Table 1 presents a dimensional comparison between MLCC and Ta Polymer: MLCC EIA codes 0805 and 1206 have direct dimensional footprint alternative with metrics P-2012 and A-3216 footprints. The larger MLCC EIA codes 1210 and 2220 have a potential alternative with metrics B3528 and D7343 footprints, althouth the replacement is not direct.
The electrical characteristics need additional comparison efforts in order to determine the adequate solution. MLCC technology is characterized with capacitance drop biased effect, temperature capacitance drop effect and ultimately the aging effect in life. The schematic effects are described in Figure 3; the other side MLCC technology has extremely low leakage current, with an insulation resistance range of 100 to 1000Megohm. The Ta polymer capacitors have a DCL specification define ar 0,1xCxV uA.
Table 2: Different types of Inductors.
In order to support the designers; the replacement examples in the next pages are organized by low voltage power rails and 12V input power rail as described in the schematic below (Figure 4)
In the actual solution a bulk of 10 MLCC capacitors can be replaced with 2 Ta Polymer, 220uF, 2.5V rated voltage capacitors. Figure 5 shows the capacitance in frequency at 85ºC and 1,1V application voltage. The applications require a maximum operational temperature of 105ºC and an ESR (Equivalent Series Resistance) <5mOhm. In Figure 6 we show the ESR frequency behavior at 85ºC and 1,1V application conditions and demonstrate that the solution as an ESR inside the customer requirements. In this case, the board design needs to be adjusted, although a reduction of 21% board space area is achieved.
In this type of application, the usage of 0805 and 1206 MLCC with 10uF and 22uF is common. The maximum operational temperature is limited to 105ºC. An alternative with Ta Polymer SMD can be considered by applying the highest capacitance in P2012-10 (same as 0805) and S3216-10 (same as 1206). In an Automotive Grade solution, KEMET is developing with samples available (contact your sales representative for samples). Figure 7 presents the capacitance in frequency and demonstrates that a large number of components can be replaced with equal footprint, or that 2 components can be replaced by only 1 Ta Polymer with smaller foot print.
In this example a 12V rail application, that operates at 85ºC, used 3 MLCC components of 1210 10uF 50V X7R, the customer was seeking for an alternative to (1) safe board space and (2) piezo noise-free. The total capacitance required can be replaced by 1 Polymer component T598D226M035ATE065, Figure 8
Figure 1. Typical Surface mount Ta-CAP construction .
The design of Ta Polymer in input side requires an explanation of technological differences with the old Ta-MnO2 products. Over the past few years, KEMET has done efforts to clarify that Ta Polymer capacitors offer a benign failures mode, not generating ignition due to the absence of oxygen. In addition, the fact that Ta Polymer T598 Series is fully AEC-Q200 qualified, the usage of these components require some performance evidence of transient capabilities.
KEMET has performed the ISO7637-2 Road vehicles — Electrical disturbances from conduction and coupling — Part 2: Electrical transient conduction along supply lines only pulse tests and concluded that the 35V rated voltage products fully comply with pulse1, 2a,2b,3a,3b, 4 and 5b(suppressed at 13,5+40V) and show limitation at 5a pulse. The 5a pulse limitation requires up-front definition of the pulse shape and parameters for an alternator with centralized load dump suppression or not is use. In most new alternators, the load dump amplitude is suppressed (clamped) by the addition of the limiting diodes.
The usage of Ta polymer as alternative relatively to the high CV MLCC 1210 need special evaluations. In addition KEMET performed the Special Load Dump testing E05 according the VW80000, issue 06-2013 – Electric and Electronics Components in Motor Vehicles up to 3,5t . The summary of the results are shown in Table 2
Table 2. Summary Results – ISO 7637-2 and VW80000 (Load dump E05)
In this example, a 12V rail power train actuator, that operates with a maximum operating temperature of 125ºC and max 13,5V, requires 60uF. The initial evaluations with MLCC 1210 XR7 10uF 50Vparts determine the need for 10 components with the total board are required of 120mm2. Based on the Ta Polymer Automotive technology KEMET has extended the capability to 150ºC by focusing on new conductive layers enablers. The new T599 Series in this example allows the designer to use 2 components of T599 (150ºC) 7343-43 33uF 35V and achieved the required 60uF. This action reduces the space board area to 63mm2, Figure 9.
The new T599 Series offers designers a new type of solution. The new series is fully AEC-Q200 qualified and was subject to rigorous ISO Pulses and Load dump evaluation during the development phase.
With an actual shortage of MLCC components in the market, Ta Polymer product offers new potential solutions to automotive designers where space board saving, piezo noise free solution, and miniaturization are required. The examples described in this document focuses on boundaries where a polymer is a viable alternative and in the main parameters that must be taken into consideration. If in any cases a direct dimensional replacement can be used, the fast majority of solutions requires re-design activity. In the commercial side, the total cost of the solution is the main driver and not the cost per piece. Please contact a KEMET sales representative to support you in your challenges!