Crack Degradation Model Derived From Experimental Strain-Stress Data

Abstract

Abstlract chanlge inl failure mode, with failures occurrm-lg inrl the Ã. new cocp.flftm rdcto fsleonsi componlenlt body or inl the substrate rather thanl inrl the prsntd bae on -.faiu.ylneprmn ne solder.iother:mal conrlditions.L A co:mmonrl approach of lifeti:me A co:mprehenlsive unlderstanldinlg of the :mechanlical predictionrl of solder j oinlts is based onrl damage model behaviour of SnrlPb solder has beenrl built up over :more based onrl the Coffin-MansLonl equation,L which uses the thanl 50 years. However, with the imple:menrltationl of the plastic strainl rangLe fro:m a singLle hysteresis loop to ,Europeanrl legislationrl, lead-conrltainlinlg solders have nrlow calculate a nrlumber of cycles to failure. This was later beenrl banned inl certai:n applicationls fro:m I July 2006, anld modified b Eglae.' there is a dearth of inrlfor:mationrl onrl the :mechanlical r IClhrn A [stfs17r 35tzlrsnrf qr ea rr rz hOff snbehaviour of their lead-free replace:menrlts. :H:enrce there is The Moro deLveloe aV damag modeYt v l b7[v L Llased 11tt[ GonUt1....,,. . . .~~~~~~~a critical requiremenrlt to acquire :materials data for thLese strainr enrlergy denrlsity, which takes the area of a sinrgle ne la-fe sodes boht-ancnfdneihi hytrei lop Ths stessri yteei op r perfor:manlce andLc to supply the perfor:manlce inflor:mationr calculated~~~ĩ n FE moelig bu wihteasmtoh tfor reliability :modellinrlg. At the sa:me timLe there iS a there is no cr_ack. HenceV onlly eninLeLvering v7alues of strainS **** >*-andstrs ar esiatd and the loadn-berm are oL1nSLf anrk realisationrl thlat acquirmLrg data inrtenlsionrl fro:m typical sode jon isasmdt ecntn n orce. ' materials laboratory inrlstrumenlts iS nrlot appropriate anld This iS clearly anl over si:mplificationrl as solder will crack thtaynwmerlsdasoudbotiedfm .. . . ..........~solder sa:mples havinrg volumes si:milar to those of solder under fatigue conditi~~~~~~~onsduighrmlcylin.Afrhr jits. Moreover the joinrlts should be loaded inshear (nrot ..i.p.ification.is.that the sress scaulaefrm n tnson), mirrorinrg the practical situation inrl the field. inverse~~s outo of seodr cre.aeqain Conrlsequenrltly, there is a requiremenlt to genrlerate nrlew data The correct approach should reflect the true stress anld ontenwmtras'n t cur hmi ha strainr (measuremenrlt of force anrld actual load bearing area) moe hspprdsrbsanwapoc eeoe.a developed inid aslejonasafctnofim. A NPL to overcome these conlstrainlts, resu.ltinlg inla nlew clear correlationl of solder joinrlt area with electrical intuetRfIpp48wthasmlgoeryht resistance~~' ca be shw.oeit ecetela ern permits small solder volumes to be studied. in shear. area an beobtaned b moniorin of slder oint Creep, relaxationl and. fatigue are the key parameters elcria reitne and thrfr the tresrsscnb that nleed to be measured. These mechanlical calclatd.easremntsfollwin ths aproch how measuremenlts must be made at various temperatures.that~~t h stansrs hytrei loparadesnt olps ice small samples are to be studied the displacemenlt (uin a costn dipacmn cotole prfl of ...

Thermo-mechanical damage accumulation during power cycling of lead-free surface mount solder joints

“…The ability of solder to withstand considerable fatigue damage is critical for the reliable functioning of electronic products. Stronger solder materials that could resist these thermal stresses without fatigue damage could result in an unacceptable change in the failure mode, with failures occurring in the component or substrate rather than in the solder [1]. The most commonly used solders in electronic applications are Sn based.…”