23 Pa. C.S. § 3332
A motion to open a decree of divorce or annulment may be made only within the period limited by 42 Pa.C.S. § 5505 (relating to modification of orders) and not thereafter. The motion may lie where it is alleged that the decree was procured by intrinsic fraud or that there is new evidence relating to the cause of action which will sustain the attack upon its validity. A motion to vacate a decree or strike a judgment alleged to be void because of extrinsic fraud, lack of jurisdiction over the subject matter or a fatal defect apparent upon the face of the record must be made within five years after entry of the final decree. Intrinsic fraud relates to a matter adjudicated by the judgment, including perjury and false testimony, whereas extrinsic fraud relates to matters collateral to the judgment which have the consequence of precluding a fair hearing or presentation of one side of the case.
23 Pa.C.S. § 3332