Large Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2.5
Communication Breakdown; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict
Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification
Procedure; Human Factors
Completely saturated sector.  Aircraft X checked on climbing out of MHT on PPORT SID; and I climbed him to FL230.  I was also working on a three-way BGR tie further north in the sector; vectoring to BOS; and issuing an instrument approach.  A contributing factor was the high sector; 01/02; was completely saturated as well and unable to provide sequencing to me on handoffs descending into my sector.  Training on my D-side with a relatively green trainee that wasn't contributing much to the operation.Shortly after the Aircraft X was issued a climb clearance the pilot said something to the effect of 'request vectors to avoid traffic'.  My eyes immediately went back to him even though I had much higher priorities; and I saw a mode C intruder target that had already merged with him at his altitude (085).  At that same moment the Boston Approach controller (East sector) called on the land line; but we were just way too busy to even begin to answer.  I can only assume he was calling about the Aircraft X and the VFR traffic. As I was unable to determine a safe course of action for the Aircraft X; and didn't want to make the situation any more dangerous.  I just told the pilot he was cleared to maneuver at his discretion (the targets had already merged).  Almost seconds after; I observed the Aircraft X leaving FL091 and stated 'traffic no factor'.  The pilot then casually commented about how 'that could have been bad'; and I agreed with him.I can't say I feel good about the situation.I honestly don't know that much could have been done differently here; other than Boston Approach not shipping Aircraft X until he was clear of the VFR traffic; or calling me well ahead of the targets merging.  The sectors could have been split which would have provided more range.More importantly; I think the high side should have been split long before.  It was being staffed by a non-Certified Professional Controller (CPC) radar controller and non-CPC D-side controller.  They handed me lots of traffic conflicts that required increased amounts of attention.
A Boston Center (ZBW) Controller reports of an airborne conflict between an IFR and a VFR aircraft. The Controller did not issue traffic as they didn't observe it until the pilot called about it.