MPM制程

Finepitch鋼板印刷&製程應用2•OverviewofFPTPrinting鋼板印刷的變數–錫膏(Solderpaste)(3~9)–鋼板設計(StencilDesign)(10~23)–刮刀(Squeegee)(24~27)–印刷參數(Printingparameters)(28~42)–印刷機(Printer)(43~56)3錫粉尺寸–角距(Leadpitch)–網目(Mesh)–粒子尺寸(Particlesize)註:所得到的錫粒子,若其粒度大小分佈均勻適合時,要經由篩選過程。例:角距為16mil時,使用之網目為TYPE4,3,錫粒子之範圍在–400/+500之間。4常用錫膏的融解溫度Eutectic:Sn63/Pb37Tmelt=183oCw/Silver:Sn62/Pb36/Ag2Tmelt=179oCNoLead:Sn96.5/Ag3.5Tmelt=221oCHighTemp:Sn10/Pb88/Ag2Tmelt=268oC-302oC5FinePitch與錫膏使用關係–LeadPitchMeshParticleSize–25milType3-325/+400–25milType3-325/+400to500–20milType3-325/+500–16milType4,3-400/+500–12milType4-400/+625PastePowderSizes6Mesh尺寸Designation(um)(in)Type1(200)740.0027Type2(250)580.0023Type3(325)440.0017Type4(400)370.0015Type5(500)300.0012Type6(625)200.00078325400500(-325+400)Mesh(網目):每一方寸內有多少錫球例:使用TYPE3角距為20mil,其錫粒子為1.7mil(0.0017in)錫膏顆粒尺寸7黏度表示通常有兩種a.K.C.P.Sb.M數值越高黏度越高製程方式黏度要求–點膠-SyringeDispensing200-400kcps–網版-MeshScreenPrinting400-600kcps–鋼版-StencilPrinting400-1200kcps錫膏黏度8錫膏的管理錫膏要冷藏(最好使用錫膏冷藏設備)。錫膏不用時一定要蓋好蓋子。錫膏最好不要停留在鋼板上超過1小時以上,錫膏不要使用2次。錫膏回溫必須要2小時以上。錫膏不能用任何方式回溫。9錫膏的管理(續)錫膏使用前一定要攪拌,(攪拌時一定要同方向,3-5分鐘,工具要用圓角,不傷錫粒子)。錫膏接拌機之缺點:高速離心會破坯化學成分。錫膏使用溫度問題:–a.21℃印刷不好印(較不黏),但好脫模。–b.25℃印刷好印(較黏),但脫模不易。10何謂準確性●化學蝕刻法為±1μ(mil)雷射切割法為±0.3μ(mil)Mark點到零件中心點之座標偏移量不只鋼板有偏移量,PC板偏移量:±0.5mil機器本身(指Vision)也有偏移量:±0.5mil所以通常要看鋼板準確性(誤差範圍)。11節省錫膏減少擦拭次數(節省時間,降低擦拭紙用量)得到良好的銲點減少錫球的產生鋼版製作12化學蝕刻-ChemicalEtch雷射切割-LaserCut電鑄-Electroformed鋼版製作方式13鋼版製作-ChemicalEtch照相製版酸液蝕刻價格便宜印刷後脫模不易14使用pcbfile資料,與PCB有一致性精度比化學蝕刻高表面粗糙價格比化學蝕貴印刷後容易脫模鋼版製作-LaserCut15適用於高密度印刷製程鋼板開孔的孔壁平滑95%錫膏停留在錫墊上降低鋼板須擦拭清潔次數(線接觸)鋼板單價最高鋼版製作-Electroformed16ChemicalEtchLaserCutE-FABStencilBoardPadApertureProfiles鋼版製作-ApertureProfiles17ChemicalEtchStencilAperture(250X)鋼版製作18LaserCutStencilAperture(250X)鋼版製作19E-FABStencilAperture(250X)鋼版製作20PCB具有良好硬度且板緣沒有毛邊PCB低變型量(warpage)Fiducials位於PCB的對角鋼板孔模應該少於銲墊20%,否則將容易造成短路,橋接與錫球Board/Pad設計21正確的運用綠漆(防焊漆),在高密度零件上會得到較高的良率。綠漆高度應該低於銲墊(pad)高度。綠漆不可印到Pad。Board/SolderMask(綠漆)22Misaligned/shiftedsoldermask綠漆印刷偏移20milpitch零件.(12milpad)Misalignedsoldermask.Soldermaskisontopofpad.綠漆蓋到Pad12milpitchdevice.(8milpad)26Board/MaskProblems23Board/MaskProblemsPaste溢出SolderMaskoverPadsSilkscreen,andlabelscanpropupthestencilandpreventsgoodgasketingwhichcausesbleedout.綠漆太厚標籤貼紙24ReduceseffectofScoopingorScavenging.LastslongerthanPolyBlades.CanbeFragile.Mostpopular.MetalSqueegee25Canvarypastedepositbyinitiatingscooping.–LessexpensivethanMetal.–MaybenecessaryifusingaStep-DownStencil.–90orHigherDurometerrecommended.PolyurethaneSqueegee26METALBladePolyurethaneBladesStencilStencilSqueegeeBlade–Scooping橡皮刮刀鋼刮刀鋼板鋼板27RecommendedSqueegeeParameters(Note:ThesenumbersarePastedependent)TrailingEdgeTrailingEdgeMetalBladesPolyBladesForce1-1.5lb.1-2lb.perlinearinchperlinearinchofsqueegeeofsqueegeeDownstop0.070”-0.085”0.055”-0.065”Speed0.5in/secto1in/secto6.0in/sec6.0in/sec•SqueegeeParameters28VisionModelsSnapoffVs.On-ContactPrintingProperBoardSupportSqueegeePressure,DownstopandSpeed.StencilWiping,(VacuumWipe)PostPrintVerificationEnvironmentalControlPrintingParameters29VisionModelsUselocalfiducialsonBoththeStencilandtheBoard.Globalfiducialscanbedisturbedfromboardroutinganddecreaseaccuracy.Choosefiducialacrossthediagonaloftheboard.Thisenablestheprintertomakethebestangularcorrection.AperturesandPadsmaybeusedbutaccuracywilldecreaseastheaperturefillswithpaste.UniquenessVisionModels30VisionModelsFiducialTeachingPad/ApertureTeachingLeaveabout0.25”ormorespacearoundthefiducialforthe1stbox.Thisistheactualmodelthatthemachinelooksforduringalignment.ThismustbeuniqueintheFieldofView.Makethesecondbox(crosshairbox)fittightlyaroundthefiducialchosen.Iftherearenofiducialsonthestencilorboard,thenpadsandaperturescanbetaughtasVisionModels.Thesemustbetaughtuniquely.PLCCendpadsorSOICendpadsarethebesttochoose.Tomaketheseuniquetheusercanbox2padsinthenmovetheboxsothatisonlyhastheendpadcontainedinitthentheusercanchoosethecentroidofthepad(donotboxinanytracesthatexist)inthesecondstep.31ApplyingVisionOffsets0.002”0.001”+X-Y-X+YXOffset=+0.001”YOffset=-0.002”0.002”0.001”+X+Y-X-YXOffset=+0.001”YOffset=+0.002”PrintOffsetCorrections(Ultraprint3000)Theprintoffsetscanbeviewed2differentways:bylookingdirectlyattheboardandbylookingatthescreenonthemachine(typicallyduringViewErrors).WhenlookingatthemonitoronthemachineitisimportanttorememberthattheYaxisisupsidedown.Seethe2illustrationsbelow.RememberyouaremovingTHEBOARD,nottheprint.LookingDirectlyatthePrintedBoardLookingattheMonitorDuringViewErrors32SnapoffVs.On-ContactPrintingOnContactprintingcombinedwithaSlowSnapofforslowboardreleasewillyieldthebestresults,butaddstooverallcycletime.ContactPrintingreducestheeffectofstencilstretch.Snapoffprintingmaybenecessarywhenprintingathighspeeds,whenslowsnapoffcannotbeused,andwhencycletimeiscritical.Snapoffprintingmayyieldvaryingpasteheightswhengettingclosertoedges.Snapoffvs.OnContact33BoardSupport–VacuumHoldDown.–SideSnuggingofBoard.–Propersupportandholddownofboardisamustforaccurateprinting.Thispreventstheboardfrommovingw