My iPhone 5 only heating without any response, why?

Hi,

I have changed display as well as battery of my this iPhone 5 on different occasions, it was working properly. All of a sudden once while using the phone, display started getting dim and turned off. After that it never woke up. When i put my phone on charging, it starts getting heated that’s all. No response on display, no backlight nothing. I have checked changing display also but problem remained the same. Please suggest me a repair. Thanks.