Hi there, you should only put your son in time out for 3 minutes (one minute for every year of his life). When he kicks off give him a first warning and tell him that if it happens again he will go to 'time out'. Then if he repeats the incident come right down to his level and tell him firmly (do not shout) and calmly that his behaviour is not acceptable, and take him quietly to his 'time out' area, tell him why he is being taken there, do not talk to him while he is in there, if he comes out quietly take him back and keep repeating until he finally sits for the required 3 minutes. Then return to him and ask him quietly if he understands why you put him there, then ask him to say sorry, once he has done this give him a big hug and let him go off to play again. Always go down to his level and look him in the eyes otherwise it is very hard for him to listen to what you are saying he will just be frightened of you.
This technique really does work if you use it properly. Good luck.