iPhone dead after screen replacement. Any ideas on what happened?

I decided to change the screen on an iphone I got from a friend. The lcd was completely destroyed, but it still showed signs of life when connected to a charger. I went ahead, and did the replacement, but when I finished and connected the phone to a charger I got nothing out of it. I took a fully charged battery from another 4 and tried that, still I got nothing from the phone. I should also mention that I broke the home button while replacing the screen, could that cause a problem? I have take the phone apart and put it back together at least a dozen times to make sure all the connections are secure, and each time I get the same result.