A heat exchanger assembly , comprising: a first end plate , a second end plate , a folded fin core comprising a plurality of fin walls ; wherein the folded fin core comprises a ridge end positioned about the first end plate , and a trough end positioned about the second end plate , and wherein the folded fin core comprises a first one half folded fin at the ridge end and a second one half folded fin at the trough end ; wherein the first end plate is positioned about the ridge end of the folded fin core ; wherein the second end plate is positioned about the trough end of the folded fin core ; and wherein the first end plate and the second end plate comprise a plurality of protrusions thereon wherein the first end plate and the second end plate comprise a first side second to last protrusion sized to accommodate the first one half folded fins and a second side second to last protrusion sized to accommodate the second one half folded fins, the heat exchanger assembly further comprising a first side plate and a second side plate extending from the first end plate to the second end plate , wherein the first end plate and the second end plate comprise a first side last protrusion sized to accommodate the first side plate and a second side last protrusion sized to accommodate the second side plate , characterized in that the first and second side plates are not directly joined to the folded fin core and the fin core is joined to the side plates without a fixturing device, such that the first side second to last protrusion and the second side second to last protrusion provide a distance between the first and second side plate and the folded fin core , respectively. a first end plate , a second end plate , a folded fin core comprising a plurality of fin walls ; wherein the folded fin core comprises a ridge end positioned about the first end plate , and a trough end positioned about the second end plate , and wherein the folded fin core comprises a first one half folded fin at the ridge end and a second one half folded fin at the trough end ; wherein the first end plate is positioned about the ridge end of the folded fin core ; wherein the second end plate is positioned about the trough end of the folded fin core ; and wherein the first end plate and the second end plate comprise a plurality of protrusions thereon wherein the first end plate and the second end plate comprise a first side second to last protrusion sized to accommodate the first one half folded fins and a second side second to last protrusion sized to accommodate the second one half folded fins, the heat exchanger assembly further comprising a first side plate and a second side plate extending from the first end plate to the second end plate , wherein the first end plate and the second end plate comprise a first side last protrusion sized to accommodate the first side plate and a second side last protrusion sized to accommodate the second side plate , characterized in that the first and second side plates are not directly joined to the folded fin core and the fin core is joined to the side plates without a fixturing device, such that the first side second to last protrusion and the second side second to last protrusion provide a distance between the first and second side plate and the folded fin core , respectively. <EOS>