i designed a flight controller board based on STM32F303. i have a weird problem where each time i assembled a complete board, initially there will be no problem and PC will be able to detect and connect with the board via USB VCP. but after a while, the board will be disconnected and USB VCP com port is not detected.
i have to resolder usb pins (PA11 pin32 & PA12 pin33) or reflow the whole board, test it again, no problem but after awhile USB VCP is missing again. if i repeat the whole reflow & retest eventually the USB VCP missing problem goes away.
the board is a two layer PCB with HASL lead surface finish. did i get a faulty STM32F303 batch or should i have used immersion gold surface finish for better solder connection?
Please help me with this weird problem, thank you.