SMT Troubleshooting Guide - Solder World

1 Le of ContentsBridgin g3In suf ficien t Fill7In suf ficien t Solder8Ra ndo m Sol de r Ball s9So lder Spat ter ing11 Mid-C hi p Solder Balls12 Tom bst oning14 Voi di ng15 BGA Head -o n-P illo w17Gr ainy Jo ints19Co oks on Ele ctr on ic sTr ou ble shooting Gui deWith this eas y-t o-useTroubl eshoot in g Guide ,you canlearn to trou bl es hoot commonSMT issues. Aft er usingit a fewtimes,it wi ll bec ome an essentialco mpanionfor you and any onein your company responsibleforoperating an SM T lin Guid e offe rs troubleshoot ingad vice for commonSMT assemblyiss ues by proc es s defect.

2 If youriss ue is not re solv ed after follow-ing the ste ps to help identifyth epo ss ibl e root caus e and solut io n,pl ea se co nta ct your CooksonElec tron ics rep re sentative whowil l be abl e to provideyou wit hfu rther ass is ta nce . ks on Con fi de ntial For Authori zed Use OnlyBr idg ingPossibleCaus es : PCBD escriptionSM D pads wi ll co ntributeto cop lan ari ty issue re sult -ing in poor ga sket ingdurin g pri nte r se tu ghly rec omm end edto remov e so lder maskbetw een adja cent pad sesp ecia lly for fin e-pi tchcom pon en tsPossibleCaus es.

3 Ste ncilDescriptionDir ty ste ncil with pasteunde rn eat h wi ll con tam -inate th e bar e bo ard onth e ne xt pr int, at tribu tinga pote ntia l bri en cil tensi onApe rtu re De sig nRecommendations Veri fyzer opr intgapsetup . Ensur e min imum pri ntpres sure . Incr eas e wip e fr equency. Use diff erent cle aningchemi cal re stenc il tensi on isti ght . Poo r sten ci l tensi onwil l ma ke it impo ss ibl eto ha ve a goo d setup forcons istent pri nt defini tio fine pitc h co mpo nent,it is hi ghl y re com mende dto ha ve the op eningsli ght ly sma ller tha nlan ding padsizetoimpro veste ncil to PCB gas ke ting.

4 De fini tio n:So lder connecting,in most cases, miscon -ne cti ng two or more adj acent pa ds that come intoco nt act to form a conductive pa idg ingPossibleCaus es : ScreenPrinterDescriptionPoor gas ket ing pasteooze s out ben ea th sten cildurin g pri nti ng , increasingcha nc e of we t so lderpa st e brid gesMis alig ned pr int willcha llen ge the paste topull bac k to pads du ringmolt en sta ge, increasin gth e pote nt ial fo r ear ing and bri dgingphen ome no n on the nextpr int ed bo ar d af ter stencilcle anin g op er at ionPoor print de fi nit ion withdog ears esp ecia lly onfi ne-p itc h co mponen tsDe nte d squeegee bladescould re sult in une ve npr int pr essur Zer o print gap bet weensten ci l and PCB Chec k pa st e sme arund ern ea th sten ci l.

5 Chec k suf ficient ste nci lten sur e pri nt accu racy andco nsi ste nc y for bo th pr intst rokes . Veri fy ste nc il is dr y aft erclea ni ng and bef ore nextprint. Sta nd ard clean ing modeis wet /va cuu m/ dr y. Chec k bo ar d supp or t. Adjus t sepa ra ti on spe edto achi ev e mi ni mum dogear : Dif fer ent pasteche mis tr y requ ire sdif fere nt sep ar ationspe ed to min imizedo g ea ec k sq uee ge e bla desco idg ingPossibleCaus es : ComponentPlac em entDescriptionPlac emen t ina ccu racy willna rrow the gap betwe enpa ds , inc rea sin g thecha nc e of bri ce ssi ve com pone ntpl ac eme nt pressure willsqu ee ze pa ste out ofpa ds.

6 Recommendations Veri fy com po ne ntplac eme nt pr es sur e. Use X- ray to ve rify BGAplac eme nt . Usemicro sc ope for QFP s. Veri fy ac tua l com pone nthei ght agai ns t da taent er ed in the mach ine Compo nen t pla ce menthei ght sho uld be 1 /3of paste hei gh es : ReflowProfi leDescriptionEx ten de d soa k will inpu tmor e heat to the pasteand res ul t in pa ste ho tslu mp pheno men opt a stra igh t ra mp tosp ike pro file, without soa kzon e if possibl es : SolderPas teDescriptionDr y pas te pheno me non irr eg ular pr int sh ape andincon sistent print vo lumePas te oo zes ou t of pads,ma y for m con nect ion withadjac en t pad Past e expi ry Oper at ing tem per atu rewithin suppl ier s re com -men dat ion s.

7 Chec ktem per atu re ins ideprinter. Norm al requ ire-men t aro un d 25 C,50% RH Do not mix usi ng ne wand ol d pa ste . Oper at ing tem per atu rewithin suppl ier s re com -men dat ion s Veri fy wi th ano the r bat chof paste to conf irm pr ob -lem is batc h-r elate d. Perf orm co ld and hotslum p tes t res ul t usi ngIPC-TM -65 0 Met .3 idg Fi llPossibleCaus es : Ste ncilDescriptionPas te scoop ing eff ectesp ec ially on larg e padsRecommendationsSegm ent the largeopeni ng into sma lleraper tur te do es no t roll intoapert ureRecommendations Reduc e pri nt spee d.

8 Incr ea se pr int pr essur e. Adopt lower sque ege econt act pr int . Ensu re pa ste is notexp ired or dr y. Ensu re suff ici en t boar dsupp ort. Reduc e sq ueegeepres sure .300 mDe fini tio n:Amo unt of Solder past e deposi ted onPWB at pr int er stat ion is much less than ste ncilope ning des es : Sol derDe fini tio n:Am ount of Solder pa st e deposite d on PWBat printe r st atio n is much less tha n st encil open ingde sig n or, af ter reflow, insufficient sol de r to form a filletat the lder paste ad heres onth e sten ci l aper tur e wallsRecommendations Area ratio > 6 Aspec t rat io > No bur r on ste ncilaper tur e edgePossibleCaus es.

9 Ste ncilDescriptionPrin t defin itionsRecommendations Veri fy pri nt setup Reduc e pri nt spee d toprovi de suf ficient timefor pas te to ro ll intoaper tur es : ScreenPrinterDescriptionMis mat ch in CT E betwe encomponent and PCB cancau se sol der wi cki ng ef fectwh ich may look likeinsuffic ient sol der on Atta ch th er moc oupl e oncompo nen t an d PCB. Apply so ak pr ofi le tomini mi ze del ta T be for eref low zon e. Set botto m zo ne s to behigher tem per atu re ifpossible, to kee p PCBhott er than compone ntlea es : ReflowProfi leDescriptionSo lder paste viscosityRecommendationsCh ec k pa ste condi ti onssu ch as dry pa st ephen ome no n by ver ifyi ngif paste rolls or skids alon gpri nt dire cti es : SolderPas ndo m Solder Bal lsDe fini tio n.

10 Aft er reflow, smal l sphe ri cal particles withva ri ou s diametersar e for med away from the mainsol der poo te stu ck und er theste nc il wil l be transf erre don to th e sol der mask ofth e ne xt Veri fy zer o pr int gap se tup. Chec k minimum pri ntpres sur e us ed. Chec k clea ni ng effi cie ncysuch as wet /dr y/va cuu m. Chec k wipe frequ ency .PossibleCaus es : Ste ncilDescriptionFa st ra mp-up rat e orpr eh eat rat e will notall ow suff icie nt ti me forth e sol ve nt to va po ri zeof f gradua ow preh ea t rat e isre com men de d, ty pi ca lly< 1.