2.1.3 plated-through hole strcuture method

OriginatingTaskGroupN/AAfterselectivechemicalremovaloftheglass-epoxyfromaroundthethroughholeanditsassociatedcir-cuitry,anexaminationcanbemadewithamicroscopeoftheplated-throughhole(PTH),pad,andconductoratanyangle.

None

5Procedure

Caution:Hydrofluoricandfluosulfonicacidsandtheirvaporsareextremelytoxicandcorrosive.Theyshouldneverbeopenedorhandledexceptwithfullprotectiveclothingandunderafumehood.

5.1Reagents

2ApplicableDocuments

3TestSpecimenThespecimenisapartofaglass-epoxy

multilayerordouble-sidedPCB,whichcontainsaPTHanditsassociatedinterconnectedcircuitry,whichisselectedforcloserexamination.

4Apparatus4.1

Forthesulfuricchromicsolution,take35ml

ofasaturatedsodiumdichromate(Na2Cr2O7)solutionandadd1literofconcentratedsulfuricacid(H2SO4)inaPyrexvesselimmersedinacoldwaterbath.Inapolyethylenebea-ker,makeafluosulfonicacidmixtureusingonepartbyweightofsulfuricacid(H2SO4)andthreepartsbyweightofhydrof-luoricacid(H.F.48%).

Afumehoodistobeused,duetothecorrosivechemi-calsusedforthisevaluation.

5.2Immersion

Amicroscope,capabletoexaminethespecimenatmagnificationsof50Xto100X

4.24.3

Astirringhotplate,capableofmaintainingatemperatureat50°C.

Equipment

4.4Thefollowingequipmentisneededtoper-

formthistest:•Goggles•Facemask

•Acidresistantapronorcoat•Acidresistantrespirator•Polyethylenebeaker•Polyvinylchloridegloves•Pyrex(glass)beaker

•Sodiumdichromatesulfuricacid(Sp.Gr.1.84)•Supportstand•Hydrofluoricacid(48%)•Thermometer•Utilityclamp•Thermometerclamp

InaPyrexbeakerofpredeterminedsize,

addenoughsulfuricchromicsolutiontocompletelyimmersethespecimen.Heatthesolutionto500°Conahotplateandimmersethespecimen.Afterthereactioniscompleted(thedisappearanceofsmallbubbles),removethespecimenandrinseindistilledwater.Removeexcesswaterwithatissueandimmersethespecimeninafluosulfonicacidmixtureatroomtemperature.Aftertwominutes,removethespecimenfromthefluosulfonicacidmixture,rinseindistilledwater,andremoveexcesswaterwithatissue.Repeatthisprocessuntilthedesiredamountofexposedcircuitryisobtained.Examinethespecimenunderthe

microscopeandobservethestructureandconditionofthePTH,interconnections,andlayer-to-layerregistration.

5.3TestEvaluation

Fluosulfonicacidmustalwaysbecontainedina

polyethylenebeaker.

6Notes

MaterialinthisTestMethodsManualwasvoluntarilyestablishedbyTechnicalCommitteesoftheIPC.Thismaterialisadvisoryonlyanditsuseoradaptationisentirelyvoluntary.IPCdisclaimsallliabilityofanykindastotheuse,application,oradaptationofthismaterial.Usersarealsowhollyresponsibleforprotectingthemselvesagainstallclaimsorliabilitiesforpatentinfringement.EquipmentreferencedisfortheconvenienceoftheuseranddoesnotimplyendorsementbytheIPC.Page1of1