No paternity established

I live in Pennsylvania. The father of my son, now 4, has never been apart of his life. He never signed paternity papers and has never made an attempt to see him. I did put his name on the birth certificate though. I never went after child support or anything from him because I believe that he would have been an intermittent, if at all, part of his life and that is not in the best interest of my son. My husband has been the father in his life since he was 8 months old and my son considers my husband to be his real father. My son has my last name. We would like for my husband to adopt my son and give him his last name. I need to know what to do to get started and I'm hoping to not have to have any contact with the biological father. I don't believe that he should have to give his permission so that my son can legally be my husbands child. Any suggestions would be appreciated.

First you have to remember that the biological father has the right to know what is going to happen to his son, regardless your personal feelings for the person it is part his son too. You would have to post a notice stating that said adoption is going to happen and give the man so many days to respond if he fails to do so after the days given, then his consent isn't needed.
You need to find a adoption lawyer and make sure you have your son's rights protected.
I know you want the best for your child and might not think that the man who helped make him, is any good for the child, but please keep in mind you aren't your son.
Do you have medical background for the biological father's side, again you might never need this ( and I pray you don't) but your son has a right to know this information.
I agree with the statement "Any man can make a baby, but it takes one heck of a MAN to be a Father".
Good luck and I wish you nothing but the best.....