Should I ume the mortgage for a joint property?

I and my partner are going to buy some property (in joint tenancy) but he has a bad credit. I have a superb credit to get a very good interest rate. Would his bad credit affect the interest rate if we take the mortgage together? I am also thinking that it might be better just let me to take the mortgage (he will pay his share through me). In case we split in the future, I can just pay him off for his share without refinancing.