Since 2015, KEMET Electronics has expanded the 1st to market Polymer SMD product portfolio in case sizes, voltage range, and maximum operational temperature. The polymer automotive offering represents an opportunity for miniaturization and cost of overall solution reduction and is an important alternative in continuos concerns regarding MLCC supply chain limitations. This article describes the new product offering extension, T597 Small Automotive Grade, and the board saving opportunity.
Starting in 2018 the MLCC supply chain has shown some instability, due to this fact R&D teams are 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 1a guide us to Tantalum polymer electrolitc capacitors when engineers are limited to 75V and capacitance ranges between 1uF to 1mF. However the process of converting from a MLCC to a Ta Polymer SMD component is not a one to one process and need to follow several considerations that are schematically described in Figure 1b.
Figure 1a. Mapping of Capacitors Technologies
Figure 1b. Parameters to be consider during a process to convert from MLCC to a Ta Polymer SMD
The mechanical and dimensional characteristics are the first parameter to be validated. In the Table 1 is presented a dimensional comparison between MLCC and Ta Polymer: While 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 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 chataracterize with with capacitance drop biased effect, temperature capacitance drop effect and ultimately the aging effect in life. The schematic effects are describe in Figure 2. In 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 as 0,1xCxV uA (C rated capacitance in uF and V rated voltage in V).
Table 1. Dimensions Comparison between MLCC and Ta Polymer
Figure 2. Schematic Representation of Capacitance Effects at MLCC and Ta Polymer Technologies
During the last years KEMET offered a limited polymer automotive portfolio with 3528-21 minimal dimension. Now we are adding the ultra small case size 3216-12 (aka 1206) and developing further the 2012-10 (aka 0805), figure 3. The T597 (125ºC) Series is fully AEC-Q200 qualified.
Figure 3. T597 – Part Number Offering, March 2020
In addition to the AEC-Q200 requirements the T597 Series were also tested in board flex (5mm, 60sec), showing all the electrical characteristics with specification and no cracks, figure 4.
Figure 4. T597 EIA 3216-12 – Board flex (5 mm/60 seconds)
The Automotive segment megatrends in ADAS requires miniaturization and this new case size can be a solution when space is crtical concern. An example is describe below:
Low Voltage Power Rails – output – 5V power rails – Board saving in ultra miniturization ADAS application as front and rear camera.
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 consider by applying the highest capacitance in P2012-10 (same as 0805) and S3216-10 (same as 1206) in a Automotive Grade solution.
Figure 5. Capacitance in frequency comparison – Small case size solutions – http://ksim.kemet.com/
With the remain instability with MLCC components in the market Ta Polymer product offers new potential solutions to automotive designers where space board saving, piezo noise free solution and miniturization are required. The example described in this document focus in boundaries where polymer is viable alternative and in the main parameters that must be taken in consideration. If in few 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 actual challenge!
