An experimental study on thermosyphon boiling in 3-D micro-channels with inclined angle changed from 90 degrees to 0 degrees was carried out, to develop a new passive cooling technology for 3-D chip cooling. The specific micro-channel structure of actual 3-D chip was simulated as evaporating section of thermosyphon, and the critical heat flux and heat transfer coefficient of 3-D micro-channel thermosyphon boiling in different inclined angles were studied in detail. Experiments were carried out using two kinds of working liquids of deionized water and R113. The length and gap (the distance between two heated walls) of test channels with a rectangular section were in the range of 30-100 mm and 30-50 mu m, respectively. Stainless steel wires with different numbers were evenly laid in the channel along the flow direction for forming change in width of micro-channel. The width of rectangular section changed from 0.4 mm to 4 mm. The study results show that the boiling characteristics in 3-D micro-channels thermosyphon can be predicted through the extension of the correlations used for 2-D micro-channels. The present 3-D micro-channel thermosyphon boiling is a promising passive technology for 3-D chip cooling. (C) 2018 Elsevier Ltd. All rights reserved.