Time Conjunctions (while, as, when, as soon as, until, before, after, by the time, once) go with the TIME CLAUSE.
They can be put either at the beginning of the sentence, or in between the two clauses (except for UNTIL, which always goes between).
The verb in the MAIN CLAUSE is in the FUTURE, whereas the verb in the TIME CLAUSE is in the present.
There is a comma after the TIME CLAUSE if it is put first. EG:
As soon as you come to my office, I will tell you the truth.
I will tell you the truth as soon as you come to my office.