资源描述：
《smt印制电路板热设计探讨（discussion on thermal design of smt printed circuit board）》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。
1、smt印制电路板热设计探讨（DiscussiononthermaldesignofSMTprintedcircuitboard）Thisarticleiscontributedbyqiuzhihua1987PdfdocumentsmayexperiencepoorbrowsingontheWAPside.ItisrecommendedthatyoufirstselectTXT,ordownloadthesourcefiletothelocalview.DiscussiononthermaldesignofSMTprintedcircuitboardFirst,withthedevelopme
2、ntofmicroelectronictechnology,surfacemountdeviceapplicationshavebecomeverycommon,andthetechnologyofSMTisquitemature.Thehighdensitysurfacemountdevicepinspacingisgenerallylessthan0.5mm,thewiringdensityofprintedcircuitboardisalsomoreandmoredense,generallythediameterof0.1-0.3mm,spacing0.2-0.3mm,will0.0
3、5-0.1mmwirediameterand0.1mmspacingdevelopment;multilayerboardwillalsobedevelopedtomorethan20layers.Theincreaseoftheassemblydensityofprintedcircuitboardwillinevitablyincreasethedissipationpowerperunitareaandformahighconcentrationofheatontheprintedcircuitboard.Individualdevicesandcomponentsoftheincre
4、aseoftemperaturewillaffectthestabilityandreliabilityofthecircuit,themainhazardsareasfollows:1)electroniccomponentsinacertaintemperaturerangeofthealternatingthermalstressreachesacertainnumberofcycles,componentswillfailduetothermalfatigue.2)changesintemperaturecausechangesintheperformanceofelectronic
5、devices.Asthetransistor'scurrentamplificationvarieswiththetemperature,itwillcausethedriftoftheoperatingpoint,causetheinstabilityofthesystem,andreducethelifeandreliabilityofthedevice.3)thetemperatureofthecomponentistoohigh,whichwillleadtothedeteriorationoftheelectricalandmechanicalpropertiesofthepri
6、ntedboard,andleadtotheblackeningandevenburningoftheprintedboardinseriouscases.Forexample,theglasstransitiontemperatureoftheepoxyglassfiberis1250C,thecoefficientofthermalexpansion(CTE)is13-18ppm/0C;thehighesttemperatureFR-6continuousglassfiberepoxyprintedcircuitboardis1050C.4)temperatureincreasesPCB
7、orcomponentmoisture,dustabsorptionabilitystrengthened,electrochemicalreactionspeed,corrosionresistance,reducetheresistanceofprintedcircuitboardelectrostaticcapacity.Therefore,thethermaldesignofelectronicequ
