Various designs of MLCCs that have been suggested by manufacturers to decrease the probability of flex cracking can be summarized as follows: Soldering related cracks in MLCCs and schematics of a standard part (c), floating electrode capacitor (d), and Open Mode design (e) Yellow and blue lines in (c-e) represent electrodes with different polarity. TDK are using similar design approaches to reduce failures caused by cracking (see figure below).
For mid capacitance values, the Open Mode solution that has enlarged end margins that create safe zones on both ends of the capacitor. This design is also known as a Serial Cap design. For low capacitance values, KEMET, similar to other manufacturers, offers the Floating Electrode (FE-CAP) capacitors. To mitigate the risks of cracking-related failures, special designs of MLCCs have been developed. For these reasons, parts with thicker cover plates and larger end margins are more resilient to cracking-related failures. These cracks might affect the reliability of the parts if they are reaching the active area of capacitors and cross opposite electrodes. Most cracks in MLCCs caused by deformation of PWBs during assembly, handling or testing are initiated at the surface close to the terminal areas of capacitors. Examples of different types of cracks are shown in Figure below: Cracks and delamination in MLCCs might originate from manufacturing processes or be introduced during assembly or the following handling and testing of the boards (flex cracks or thermal shock cracks).
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