LED lighting apparatus including (a) a circuit board which has a plurality of light sources spaced thereon, (b) a heat sink to which the circuit board is thermally coupled, and (c) a securement structure which includes a rigid peripheral structure applying force along a peripheral area of the circuit board toward the heat sink to increase the thermal coupling therebetween to facilitate heat transfer from the light sources during operation. The lighting apparatus may also include an optical member with a plurality of lens portions over corresponding light sources and a peripheral region, the securement structure engaging the peripheral region which sandwiches a gasket against the heat sink. The apparatus may use manipulation involving surface convexity, such as bowing, thereby allowing the securement structure to further facilitate surface-to-surface thermal coupling between the circuit board and the heat sink.