金属电镀培训资料 电镀原理基本知识PPT电镀工作原理.ppt

電鍍工作原理大綱 一 電鍍原理 1 電鍍定義 2 電鍍目的 3 電鍍槽的組成 4 電鍍化學反應二 連接器電鍍的特異性 1 nickelplating 2 goldalloyplating 3 pd niplating 4 tin leadplating三 選擇性電鍍四 電鍍工作站簡介 一 電鍍工作原理 1 定義 definition從牛津字典來定義 plate 1 applyathincoatespofsilvergoldortinto anothermetal 2 cover espaship withplatesofmetalespforprotection而 electroplating 就是 electroplatingistheprocessofdepositingametalliccoatinguponanegativelychargedelectrodebythepassageofanelectriccurrent電鍍是一種將金屬沉積在帶負電的電極上的過程 一般工業界常用的電鍍金屬如表1 表1 typicalelectrodepositedmetalsusedinsurfacefinishingbrasspalladiumcadmiumpalladium nickalchromiumpalladium silvercoppertingoldtin leadgold cobalttin nickelgold nickelrhodiumnickelsilvernickel ironzine typicalelectrodepositedmetalsusedinsurfacefinishingbrasspalladiumcadmiumpalladium nickalchromiumpalladium silvercoppertingoldtin leadgold cobalttin nickelgold nickelrhodiumnickelsilvernickel ironzinc 2 電鍍的目的 1 美觀 耐用2 防鏽3 防磨耗4 提高電氣特性5 提高潤滑性6 提高強度 硬度7 耐熱性 耐候性8 浸炭防止 氮化防止 3 電鍍槽的組成 電鍍槽的組成含tank 電解液 直流電源 電極 參考簡圖fig 1 1 電鍍液 platingsolution 或稱electrolyte電解質 提供導電的功能 補充被鍍的金屬鹽 維持電鍍槽內化學平衡 及ph值的穩定 2 直流電源 dcpowersupply 一直是用整流器 rectifier 來控制dc電流的供出 3 陽極 anode 電解用陽極 可分為可溶性或非可溶性電極 可溶性陽極因電解而溶解 作為補充金屬離子在陰極析出的量為目的 非可溶性電極其材質甚多 如碳極 carbonanode 陶瓷或鈦合金底材塗裝貴金屬氧化物或白金鈮網等 4 電鍍化學反應電鍍槽內的化學反應分陰極反應如fig2及陽極反應fig3 陰極反應 鍍層會沉積 deposit 在底材上 附產品是氫氣等 陽極則是 反電鍍反應 亦是電解反應可溶性陽極在電鍍過程中解離成金屬離子 而不溶性陽極只產生氧氣 本身并無解離發生 anode cathode figure1 schematioftheplatingprocess cathodereactionscathodereductionofionsdrawelectronsfromextermalcircuittypicalreactionsmn ne m02h 2e h24h2o 4e 2h2 4 oh figure2 anodereactionsanodeoxidationofmetaltoionsreleaseofelectronstoextermalcircuittypicalreactionsm0 mn ne 4oh o2 2h2o 4e 2h2o o2 4h 4e figure3 二 connectors電鍍的特異性 一般用在connectorindustry的電鍍工程是鍍鎳 nickel 鍍金鈷合金 gold cobaltalloy 鍍鈀鎳合金 palladium nickelalloy 及鍍錫鉛合金 tin leadalloy 等工藝 1 nickelplating鍍鎳是應用在電鍍底層 因為可提供對環境腐蝕的抵抗力 且防止銅合金底材的銅 鋅擴散 因為電鍍后的端子經儲藏過一段長時間后 會被覆蓋一層來自外界的氧化膜包括氧化鋅 氧化銅或硫化銅 導致可靠性降低而鋅或銅的氧化會因鎳當擴散障礙 diffusionbarrier 而降低 其三的原因是在鍍金區打鎳底可改善金接觸區的耐磨性 其四也因鎳層的存在使porosity問題減少嚴重程度 參考figure4 2 goldalloyplating金是一種貴重金屬 本身不易與它種物質發生反應 也不與空氣反應 所以也不易在表面形成氧化物或污染的膜層 電流很容易穿越過去 因此當connector需要handle低層次 low level 的信號電壓和電流使其具有高可靠度的信賴性必須選用鍍金 純金本身的硬度極低故為增加wearresstance我們會在鍍液內添加微量的鈷 使其在鍍層共同析出鈷約占0 15 至0 25 而鍍層的硬度由低于50knoop增加至200knoop 3 pdniplating鈀鎳合金電鍍因本身密度比硬金小 11 2v s17 5 硬度 延展性 多也性都遠優于金 陰抗電陰亦與金相近 原料价線遠低于金 鈀鎳合金鍍層與金鍍層相比 成本可降低30 70 是一種代金鍍層 如果在pd ni鍍層再加上一層閃亮薄金鍍層 不但其性能獲得改善 并且符合客戶喜愛金色外觀的心理 4 tin leadplating錫鉛電鍍顧名思義是為改善connector的焊接性 solderability 而設計 三 選擇性電鍍 在connectors的貴重金屬電鍍上常選用遮蔽性罩頭來達成省金的目的 罩頭制造的廳特更是know how的所在 以其應用的技朮 可概分2種 一是masking如figure5spotplating 另一種則是brushplating 其工作原理如figure6 其效果如figure7a 7b 四 電鍍工站的簡介 良好的電鍍皮膜須具備a 密著性的確保b 具備色深 緻密 連續性且美觀c 均一電著性且被覆力優良d 無殘留應力且机械強度高e 化學性安定且耐葯品性高 參考figure8電鍍所涉及的工站相當的多 需控制的項目亦極繁雜 如各鍍液的濃度 ph 過濾 溫度 走速 電流等等 一般可依其止的 而概分如下 1 清洗脫脂 去除油污以待電鍍的准備 2 酸活化 將氧化膜由被鍍物去除 提供新鮮的表面 以增進附著性 3 各電鍍槽 提供各机能性電鍍所需的葯水 4 水洗 阻止前制程的葯水沾附在端子上而污染了后制程的槽液 5 qa 提供制程的管制 皮膜厚度 焊錫性的測量一個優良的電鍍制程 除了良好的電鍍机外 仍需有化學實驗室提供正確的分析 嚴格的現場管理 sop的作業 qa的協助 新技朮的開發 才能構筑成功的電鍍工站 unreel electroclean rinse acidactivate rinse nickelplate rinse pdniplate rinse selectivegold goldrecovery rinse snpbplate rinse hotrinse hotairdry reel reel to reelellctroplatingflowchart 上料 脫脂 水洗 酸活化 水洗 鎳 水洗 鈀鎳 水洗 水洗 水洗 熱水洗 選擇鍍金 金回收 錫鉛 烘干 下料 foreignmaterial definitionforeignmaterialisanysubstanceonthegoldsurfaceprobablecausewhentheelectroplatingprocedureisthecauseofforeignmaterialadheringtocontactparts theproblemcanoftenbesolvedbyfiltration seethesectiononnodules itisusuallydesirabletoboilanewclothorplasticfilterelementisa10percentsulfuricacidsolutionbeforeusingitforthefirsttime thisremovesthesizingagentsandplasticizerswhichmightotherwisealterthebrightnessoftheplate othersourcesofforeignmaterialincludepackagingmaterials solder air borneparticlesattractedtothesurfacebyelectrostaticcharges epidermalmatterfromphysicalhandling etc foreignmaterialcanimpairtheproduct sperformanceinseveralways first organictypematerialcouldcausehighresistanceoropen circuitcontacts second anymaterialsharderthanthegoldwouldcauseexcessivewearorgougingofthegoldsurface indentations definitionanindentationisasurfacerecessofdepressionformedbyimperfectionsintheimmediateorunderlyinglayersprobablecausemostindentationsaretheresultofpoorlypreparedbasematerialwithnicks scratches anddentsonthesurface indentationscanoccurduringsometypesofplatingsuchasrackofselectivestripplating inthesecases iftheindentationscannotbeeliminated scratches definitionascratchisapotentialdefect dependinguponitsdepth causedbyascrapingactionoverthesurfaceoftheplatedorbarecontactandcharacterizedbysharpedges probablecausescratchesareobviouslytheresultofphysicalabrasionwithajaggedorsharpobjectscratches thesedetectsmayexposethemetaltotheatmosphere characteristicsharpedgesinherenttoscratches blisters definitionablisteroccurswhenthereisalocalizedfailureofthegoldtoadheretoitsunderlyingmaterial itappearsasasphericalorraisedarea probablecauselarge separateblistersarecausedbypooradhesionbetweenthegoldandtheunderlyingnickelorcopper thistypeofblistercanbeeasilyflattenedorpuncturedwiththetipofarazorbladewhilebeingexaminedwithtipofarazorbladewhile blisters beingexaminedwithalowpowermicroscope andrheblistercanthenbeseentobehollow toeliminatetheproblem followtheprocedureslistedunderadhesionfailure blistersareconsidereddefectsbecauseanyphysicalcontactwiththegoldsurfacesuchasamatingpartmaybreakthebubble exposingthebaselayerstotheatmosphereandpotentialcorrosion blisterscausedbypooradhesionofgoldtonickel drawingd andnickeltobase drawinge blisters base drawinge blistersastheyappearatthegoldsurfaceduetoanickeltobaseadhesionfailure nodules figure26illustratesagrossnodularconditioninwhich atlowmagnification 10 x thenodulesappearasbrightspots figure27 athighermagnification showsanelongatesmodulesurroundedbysmallerones figure28isansemrevealingthenodularmorphologyat700 x porosity deeinitionporosityisadefectofminutesize introducedduringtheplatingoperation whichresultsinanopeningextendingtounderlyinglayers porositytestsshouldbeconductedperx 18453 failuredescriptiontheporositytest whenperformedwithnitricacidvapor resultsincorrosionnormallyrangingincolorfromblue green orblue greentogreen white blue white orwhite insomecases porosity particularlyonnickelunderplatedparts corrosionmayorwhite insomecases particularlyonnickelunderplatedparts corrosionmayappearastransparentamorphousspots figures29and30illustrateporosity decorations ontypicalonnickelunderunderplatedparts notethedeepbluecolor figures31and32arecouuosiondecorationsonproductwithnickelunderplating notethewhitecolor allporositytestresultsshouldbecarefullyviewedtoinsurethatthedecorationsarenot porosity actuallyforeignmaterialorstaining theporositytest whenperformedwithpolysulfide resultsinablackcorrosionproduct note theword decoration isusedtodescribethecoloredcorrosionproductwhichisaresultoftheporositytest theporedecorationsaresimplythesaltswhichformformtheacidvaporreactingwiththebasemetals adhesionfailure polishedcrosssectionsillustratingthepreviouspictorials additionalcopperlayerwasplatedonforedgeprotectionduringpolishing mostofthecrosssectionsusedinthisbookwillalsohavecopperoverplating probablecauseincasesinwhichanickelunderplateisused thefirstthingtodoinseekingthecauseofpooradhesionistolookfornickelontheundersideofthepeeled offgoldfoil ifniispresent thefailureislikelytobecausedbyinadequatecleaningofthebasis adhesionfailure metal scribbingseveralpartsbyhand beforethenickelplating canaidindeterminingwhethercleaningwasactuallytheimportantfactor ifso anexperimentalcleaningprocedureforcopperorcopperalloybasismetalshouldbetried includingthefollowingsteps 1 degreaseinmethyienechloride usinghandscrubbingorultrasonicagitation 2 ringeinisopropanolordenaturedethanol whicharecompatiblewithboththeorganicsolventsandtheaqueouscleaners adhesionfailure 3 rinseinwater 4 useanalkalinecleanerwithhandscrubbingoranodicelectroclean 5 rinseinwater 6 mildacidbrightdiporpickle 1 hclbyvolume 20 hno3 40 h2so4 39 h2ooruninhibitedproprietarymixture 7 rinseinwater 8 rinseindeionizedwater ifthissequencecurestheproblem someofthestepscanbeeliminated oneatatime adhesionfailure untilthemosteffectiveprocedureisfound manytypesofpartcanbeadequatelycleanedbyverysimplemethodssuchaselectrocleaning however acommoncauseofadhesionfailureinsuchcasesisaccumulationofafloatingoillayeronthesurfaceoftheaqueouscleaner becauseofagitation thismaynotbevisiblewhilethebathisbeingused ifitisasuspectedcause thetoplayerofthesolutionshouldbeskimmedoff tincommandments tinortinalloycoatingsarecosteffectiveandrellablealternativestogoldifusedaccordingtothefollowingguidelines 1