Electronics　cooling　has　become　a　key　factor　for　improving　the　performance　of　electronic　devices.　An　effective　thermal　spreader　can　remove　hot　spots,　level　surface　temperature　distribution　and　thus　enhance　heat　dissipation　of　heat　sinks.　Flat　plate　heat　pipes　are　one　of　the　highly　effective　thermal　spreaders.　In　order　to　observe　boiling　and　condensation　phenomena,　a　transparent　visible　flat　plate　heat　pipe　is　manufactured　and　the　phase　change　heat　transfer　characteristics　of　the　heat　pipe　were　studied　experimentally.　The　performance　of　the　flat　plate　heat　pipe　with　different　working　fluids　was　measured　under　different　heat　fluxes.　The　experimental　results　show　that　the　flat　plate　heat　pipe　has　a　good　ability　of　temperature-leveling　and　produces　a　very　uniform　temperature　distribution　of　the　condensation　surface.　Poor　cooling　on　the　external　side　of　the　condensation　plate　deteriorates　the　performance　of　the　flat　plate　heat　pipe.　Within　the　tested　heat　flux　range　in　our　experiment,　the　flat　plate　heat　pipe　with　water　as　working　fluid　has　a　better　performance　than　the　flat　plate　heat　pipe　with　ethanol　as　working　fluid.　We　also　studied　the　effects　of　the　grooved　evaporation　surface　on　enhancing　boiling　heat　transfer.　Our　experiments　prove　that　the　flat　plate　heat　pipe　with　a　grooved　evaporation　surface　has　much　better　performance　due　to　the　enhanced　heat　transfer　on　the　evaporation　surface.