In a featured embodiment, a heat exchanger includes a plate including a plate portion having outer walls. A plurality of internal passages extend between end portions. A ratio between an outer wall cross-sectional thickness at one of the end portions and a cross-sectional wall thickness of the outer wall within the plate portion is greater than 2.5 and no more than 10. An inlet manifold is attached to the inlet end. An outlet manifold is attached to the outlet end.