Mikroe MCU CARD for STM32 STM32F446ZE allows for installation and replacement of a microcontroller unit (MCU) on a development board. The new MCU Card standard enables compatibility between the development board and supported MCUs, regardless of pin number and compatibility. MCU Cards are equipped with two 168-pin mezzanine connectors. This allows them to support MCUs with high pin count. The design allows for usage with the plug & play concept of the Click board™ line.