深圳市福英達工業技術有限公司/一站式錫膏解決方案供應商OptimizingSolderPasteShapetoImproveResistorFatigueLife

Itiswellknownthatthedevelopmentofelectronictechnologyhasputforwardhigherrequirementsforsolderdensityandminiaturizationofsolderjoints.Asthevolumeofsolderjointsdecreases,theopeningsofstencilsusedforsolderpasteprintingmustbecomesmaller.Asthesizeofthesteelmeshopeningisadjusted,thevolumeofsolderpasteonthesolderpadwillchange,resultinginthesolderjointsevolvingintodifferentshapesduringthereflowprocess.CrackswillformbetweenthecomponentsandPCBduetothedifferentcoefficientsofthermalexpansionduringthermalcycling.However,thefatiguelifeofsolderjointscanbeimprovedbyoptimizingtheshapeofthesolderpasteafterreflow.ExperimentDesignInordertounderstandwhatsolderjointshapescanachievehigherfatiguelifeofsolderjoints,Haetal.usedaspecificthicknessofstenciltoprintsolderpasteonresistorsR1005andR0402.Bycalculatingthesoldershapecorrespondingtothestencilopeningarea,theypreparedfoursolderjointshapes,includingconcave,straight,tinyconvex,andconvex(sortedfromlowtohighsolderpastequantity),tofurtherdeterminetheimpactofsoldershapeonreliability.

Figure1.Solderjointswithdifferentshapes.Athermalcyclingtestisanimportantmeanstoverifythefatiguelifeofsolderjoints.TheconditionsforthethermalcyclingexperimentusedtotestthereliabilityofR1005andR402were-55℃

to150℃.ResultInthisexperiment,infinitelylargeresistancewasconsideredassolderjointfailureratherthana20%resistancechangerate.FromFigure1,itcanbeseenthataconcaveshapehastheshortestfailuretime.Thecorresponding

failuretimeofR1005andR0402wasonly10873cyclesand12728cycles,respectively.Onthecontrary,whenthesoldershapeisconvex,thefailuretimeoftheresistoristhelongest.Fromthedata,thefailuretimeofconvexshapesis30%longerthanthatofconcaveshapes.

Table1.TheeffectofsolderpasteshapeonthefailuretimeofR1005andR0402.

Duetothedifferentcoefficientsofthermalexpansion,solderjoints,andresistorsaremorepronetofatigue.Thethermalshockcracksinmostresistancesamplespropagatealongtheboundaryoftheresistorterminals.Whentheamountofsolderpasteincreases,theheightofthesolderjointincreases,leadingtoalongertimeforthesolderjointtocrack.Figure2.SAC305solderjointfatiguefailureimages;(a)Concave,(b)straight,(c)tinyconvex,(d)convex.Fitech'ssolderpasteShenzhenFitechiscommittedtotheresearchandproductionof

ultra-fine(T6andabove)printingsolderpastes.Fitech’sprintingsolderpastehasstableviscosity,longstencillife,excellentprintability,andcanadapttostencilswithdifferentthicknessesandopeningsizes.Welcomethecustomerswithneedstocontactus.ReferenceHa,J.,Lai,U