炉温曲线教材.ppt

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1、ProfileCurveForSMTREFIOW形式(HEATER分佈)183oC170oCPreheatingSoakingPeakCoolingPreheating:Solventevaporation溶劑揮發Soaking:FluxreducesandMetaloxides助焊劑還原金屬氧化物Peak:Solderballsmelt,wettingandwickingbegin.&Soldermeltingcompletes,surfacetensiontakesover.錫球熔化,浸潤開始,焊接進行,

2、表面張力起作用Cooling:Cooldownphase.快速冷卻階段140oCReflow的製程條件針對IntelRG82845BGAsoakzonetime:50~65sec;通用規範:PreheatingZone:*SolderPastes’Viscosity錫膏黏度:1.Solventevaporationcauseviscosityhigher.溶劑揮發使黏度變大2.Heatingsolventwillcauseviscositydown.加熱溶劑會使黏度降低HighheatingrateVisco

3、sityLowheatingrateTemperature預熱段各種錫膏在預熱段要求的升溫速律及進入恆溫區的溫度並不盡相同，其主要取決於溶劑(Solvent)的揮發溫度以及松香(Rosin)的軟化點。因松香在進入恆溫區的建議溫度時間時軟化，錫膏裡的溶劑尚是液態，此時錫膏為固液態，因此黏度最低，錫膏流動特性最佳，若預熱段升溫速率過高，錫膏黏度太低，流動特性太好，易造成Slump效應，進而產生短路及R/C旁擠出邊球，此時可適度將預熱段溫度降低，將有助於減少短路及SideBoll產生。*Fluxsoftnesspo

4、int:Fluxsoftnesspointwilldecreasesolderpasteviscosity.助焊劑(松香)軟化會降低錫膏黏性HighheatingrateLowheatingrateVerylowheatingrateViscosityTemperatureSoakingZone:1.Solventevaporatecompletely溶劑完全揮發2.Fluxactivationandoxidation助焊劑被激活並去氧化3.Soakingtimeandtemperature3.1ForN2o

5、ventheSoakingtimecanbelonger.3.2ForAiroventheSoakingtimeshouldshorterthanN2oven4.PCBboardbendingcontrolPCB板彎控制BeforeSoakingAfterSoakingPCBPCB恆溫區恆溫區其目的再於使PCB上所有的零件溫度達到均溫，簡少零件熱衝擊，恆溫區的長度則取決於PCB面積的大小。此時錫膏內劑不斷揮發，活性劑持續作用去氧化，松香軟化並披覆在銲點上，具有熱保護及熱傳媒的作用。恆溫區*PlasticBG

6、AAfterSoakingPlasticBGAPCBbending由於PP的軟化溫度點為140℃,故如可考慮縮短Over140℃的時間來改善空焊,此為一嶄新觀念,其實這種方法在實踐中被証明是有效的.SoakingZone:*Homologousheating(PCB,Componentsandsolderpaste)溫度達到一致(機板,零件,錫膏)*Solderpasteviscositycontrol錫膏黏性控制*Solderwettingandwickingbegin.錫膏浸潤開始*Surfacesold

7、erballsmelting.表面焊料金屬熔融SoakingZonePlasticBGAsubstrate(Tg:1750C)PCBbending1232Lead>1Body>3PadNormalsolderingWickingBridgebywickingMoreheatfromthebottomLessheatfromthetop2Lead>1Body>3Pad3Pad>2Lead>1BodyParametersetting:Tombstoning:T1T3dT2Conditionwhichcausest

8、ombstoningshallbe:T1+T2>T3Inordertoovercometheproblem,themomentumrelationmustbecomeasbelow;T1+T2=T3T1+T2>T3T1T3dT2Partialmelting*PeaktemperatureandReflowtimeshouldbecontrolled焊接與回流焊溫度應被控制*Theflowingabi