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 (160,170) are not directly joined to the folded fin core and the fin core is joined to the side plates (160, 170) 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 (160, 170) 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 (160,170) are not directly joined to the folded fin core and the fin core is joined to the side plates (160, 170) 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 (160, 170) and the folded fin core, respectively.