pcb制程设计pcba制程改善dfm,ds_en.报告

10/01/2018,1,PCBA Presentation,10/01/2018,2,Content Structure,1, DFM/DFT Introduction,2,PCB Process and Material,3, PCBA Process and SAC305,4, ICT Testing,10/01/2018,3,1, DFM/DFT Introduction,1.1, Why we need to do DFx (DFM/DFT) analysis for PCB checking before we finalize the Gerber files?,First, the PCBs or PCBAs we design should match with PCB or PCBA supplier capability.,This is HAT PCB PanelizationDue to limited G PCB capabilities, 5mm clearance are required. But L PCB supplier can accept 2mm.,10/01/2018,4,Second, find some potential issues, In order to sure to avoid problems for PCB or product assembly.,A,Small issue: no UL logo and PCB supplier information on the PCB. Actually, these words were printed under heatsink.,D,Critical issue: H component cant be located in the center of magnetic Core. It affects PCBA assembly. Were thinking of some methods to fix it.,B,Balanced trace can prevent tombstone issue.,C, Thermal relief for PTH (Plated Through Hole) components insufficient solder issue.,10/01/2018,5,Draw a conclusion: Its necessary to do DFx analysis before Gerber out. The value of DFx in PCBA design and manufacturing can be factored directly into the cost to produce a printed circuit board or assembly. If the PCB/PCBA is manufactured with defects, the manufacturers or LEM will have to bear the high cost for defects and repairs. The only way those defects can be identified is by tests or assembly.,1.2, DFx Benefits,Improved designDecrease the time-to-marketDecrease product costIncrease market share and profitability,10/01/2018,6,1.3,How to implement DFx process,10/01/2018,7,1.4,DFM/DFT check Item,DFM check Item including:Tooling holeMounting holeFiducial marksPTH, NPTH sizeSolder side clearanceComponent clearanceCopper connectionSilkscreenSolder mask colorUL logo/PCB vendorBoard sizePost assembly issue,DFT check Item including:Test coverageTest points on bottom/top sideTest point styleTest points need to added or modified,10/01/2018,8,2, PCB Process and Material,2.1, PCB Material,Laminates,10/01/2018,9,2.2,PCB character explain,Tg: Glass transition temperature,Td: Delamination temperature,T260: Test at 260oC Testing for solderability,T288: Test at 288oC Testing for thermal stress at 3times10seconds,Dicy: Curing agent (Dicy-free for Anti-CAF ; Dicy-cure for process),Halogen: Halogen free good for CTE,Moisture absorption: below 5%,CTE: Temperature expansion coefficient,10/01/2018,10,2.3, RoHS and Reach,SnPb Melting point183oC SAC305 Melting point217oC ( Sn-3.0Ag-0.5Cu),RoHS : Restriction of the use of certain Hazardous Substances in electrical and electronic equipment. Take effect on 1 July 2006 and requires that such equipment must not contain the following chemicals:,Lead (Pb)Chromium VI (Cr 6+)Mercury (Hg)Cadmium (Cd) Polybrominated Biphenyls (PBB)Polybrominated diphenyl ethers (PBDE),10/01/2018,11,2.4, PCB Manufacture Process,10/01/2018,12,10/01/2018,13,10/01/2018,14,2.5,Laminate: 4 layer PCB,10/01/2018,15,The coupon indicates the number of the layer in a window. In case of a pressed multilayer, all layers are legible in the correct order.,10/01/2018,16,2.6, PCB surface finish,HAL SnAgCu Hot Air Solder Leveling, specified at LEM fileChemical Tin Second choice at LEM file Immersion SilverEasier to process ;sufficient barrel fill for PTH;good solderability;no contact issue during ICTtesting probe contact issue,CAF and Wicking issue ; Ionic contamination test; migrationCAF:Conductive Anode filament,10/01/2018,17,3, PCBA Process and SAC305,10/01/2018,18,3.2, SAC305,Why dont use Sn/Pb(63/37)?,Advantage: Excellent plating feasibility Well characterized and understand solderability performance Good deposit properties,assembly compatibility Melting point 183oC,Disadvantage: The only disadvantage is the TOXICITY of Pb,SAC305 Sn-3.0Ag-0.5Cu Melting point 217oCSN100C (Sn-Cu-Ni+Ge) Melting point 227oC,10/01/2018,19,3.3, Reflow profile,10/01/2018,20,Open/ShortAnalog ComponentsDigital ComponentsPower (Voltage testing),Coverage,4, ICT In Circuit Testing,In order to keep the product quality and find PCBA defect (Open-Short, Component value, Missing, Solder Voids,Polarity reverse) in a short time.,10/01/2018,21,4.1,Figure helps to understand ICT testing.,It looks like the same board, Actually it is different. So far ICT is the best way to find the different area .ICT can finish it in 1 second for this PCBA checking.,A,B,10/01/2018,22,Good,NG,ICT can find the different area in a short time.,A,B,10/01/2018,23,1, Short,NG Board,2, Component Missing Component Mismatch,3, Polarity reverse,NG phenomenon,10/01/2018,24,4.2,Guarding theory in complex circuit,Ip current will effect test result. So keep the Ip=0A.,Guarding theory keep the G Voltage equal 0V.,10/01/2018,25,4.3, Some components cant be detected.,RxR1*R2(R1+R2), R2 cant be detected,R=0.999ohm,Resistor parallel with resistor,Capacitor parallel with capacitor,C