iPhone 5S dead after U2 ic replacement.

I have an iPhone 5s that battery was draining very fast, this happened after using cheap iPhone chargers. I decided to replace the U2 ic, after job done, phone started, booted to IOS and worked fine. I tried to charge this and when I put cable on the phone the screen got black and phone went completely dead. I replace the U2 chip again and no sigh of life. Can someone help me, why is this happened? Why is this worked only for some minutes? I burn any resistor? What parts need to test to find the problem? Thank you!