Bricked iPhone 6S fixed by HDD (4K)

In this video we are showing how to fix doesn’t power on iPhone 6s by re soldering HDD IC. The question is how does i diagnosed this phone? The user informed me that the phone was bricked by dropping first i Connect it to iTunes and it connected automatically in DFU mode with no serial number. Indeed the serial number is programmed in HDD(flash chip).so it indicates that the issue was with HDD(flash chip) because the phone was dropped by user. It means the HDD(flash chip) might be disconnected with