Flow boiling in microchannel is a potential technology for the thermal management of high-heat flux microelectronic devices. A microchannel with triangular cavities (TC) is proposed for flow boiling enhancement in this work. Flow boiling experiments with high speed flow visualization are performed in the TC microchannel and the conventional rectangular (R) microchannel using pure acetone liquid as the working fluid. The bubble characteristics, heat transfer, pressure drop and wall temperature performances for the TC microchannel are investigated and compared with that for the R microchannel at inlet temperature of 29 degrees C and mass flux ranging from 83 to 442 kg/m(2) s. Moreover, the effects of mass flux and heat flux on the flow boiling performance are also studied. The experiment results show that the TC microchannel presents significant enhancement of heat transfer, obvious reduction of pressure drop, more stable and uniform wall temperature compared to the R microchannel. The triangular cavity configuration causes the enlargement of heat transfer area, the formation of developing liquid film, the increase of nucleation density and bubble departure. The novel micro heat sink obtains a high heat transfer coefficient with the increment as high as 9.88 and 1.55 times accompanied by a low pressure drop with 50.3% and 12.8% reduction compared to the R microchannel at G = 83 and 442 kg/m(2) s, respectively, which makes it more promising and efficient for microelectronic cooling. (C) 2017 Elsevier Ltd. All rights reserved.