锡须检测与判定标准课件

,LF_,Tin,Whisker,LF_ Tin Whisker,目 錄,錫須的定義及危害,錫須的形成機理,錫須的預防措施,錫須測試的方法,錫須測試的標准,案例分析,錫須測試的儀器,_SEM,簡單介紹,目 錄 錫須的定義及危害,錫須定義及危害,定義：,锡须是从元器件和接头的锡镀层表面生长出来的一種,細長形狀的錫單晶，直徑,0.3-10um(,典型,1-3um),，長度,在,1-1000um,不等，錫須有不同的形狀，如針狀，小丘狀,，柱狀，花狀，發散狀等，見圖,1,危害：,如果这些导电的锡须长得太长的话，可能连到其他线,路上，并导致电气短路，斷裂後落在某些移動及光學,器件中引起這些器件的機械損害，如處於相鄰導體之,間可能產生弧光放電，燒壞電氣元件等,由於錫須通常在電鍍之後幾年甚至幾十年才開始生長，,因而會對產品的可靠性造成潛自在的危害比較大,錫須定義及危害 定義：锡须是从元器件和接头的锡镀层表面生长,圖,1,錫須的各種形狀,圖1 錫須的各種形狀,圖,2 Non-whisker,凝固狀,小丘,錫表面電鍍之後,錫表面電鍍高溫高濕之後,圖2 Non-whisker 凝固狀 小丘 錫表面電鍍之後,錫須形成機理,錫須產生的原因,錫與銅之間相互擴散，形成金屬間化合物,(IMC),致使 錫層內應力迅速增長，導致錫原子沿著晶體邊界進行擴散，產生錫須,電鍍之後鍍層的殘余應力，導致錫須的生長,機械應力：沖壓，冷卻，加工造成基底初使應力，外在的機械負,載,(,固定件的扭轉,),和震動沖擊產生應力,化學應力：電鍍化學物質,(,如有機添加劑，光亮劑,),可能增加鍍層,殘余應力,熱應力：鍍層與基體之間熱膨脹系數不匹配,錫須形成機理錫須產生的原因,生长机理,Cu6Sn5,擠壓純錫晶格疆界，純錫的晶界出現錫須,FIB cross-sections of whiskers,生长机理Cu6Sn5擠壓純錫晶格疆界，純錫的晶界出現錫須,預防措施,不要使用亮錫，最好使用霧錫,霧錫與亮錫的比較：,a.,有機物或碳含量較亮錫少的多,(,亮錫約為霧錫的,X20-100),b.,微晶顆粒較大,1-5um(,亮錫,0.5-0.8um),大晶粒,(2um),鍍層有利,於降低晶須的生長,.,因為大晶粒較小晶粒間隙少，為,Cu,擴散提,供較少的邊界，大晶粒具有零值壓應力或較低壓應力,使用較厚的霧錫鍍層,(8-10um),以抑制應力的釋放,電鍍後,24,小時內退火,(150/2hrs,或,170/1hrs),，以減少錫層的應力,電鍍後,24,小時內回流焊接，作用同退火,用,Ni,或,Ag,做阻擋層,(1.3-2um),防止,Cu,擴散形成,Cu,6,Sn,5,的,IMC,錫須預防措施,預防措施 不要使用亮錫，最好使用霧錫錫須預防措施,錫須,檢測,種類,產生機理,測試方法,恆溫錫須,基材金屬（,Cu,）擴散至,Sn,而引起的內應力,常溫儲存,（,AS,）,20-25,，,55,25%RH,1000,小時,濕熱錫須,Sn,氧化而產生的內應力,濕熱試驗（,THT,）,60,，,90,5%RH,1000,小時,熱衝擊錫須,基材金屬（,Cu,）,/,過渡層金屬和,Sn,鍍層之間熱膨脹系數不同引起的內應力,溫度衝擊試驗（,TCT,）,-40/-55,85,，,1000,循環,錫須,分類,錫須檢測種類 產生機理 測試方法 恆溫錫須基材金,三種老化測試,分類,測試標準,D,S,TCT,-55C to+85C,1000 cycles Ramp rate 20C/min,10 min,-35C to+125C,1000 cycles Ramp rate 20C/min,10 min,THT,60C/95%,1000 hours(IC Type:4000 hours,-FFC/FPC:2000 hours),85C/85%,1000 hours(IC Type:4000 hours,-FFC/FPC:2000 hours),AS,20C,to 25C,30%to 50,%,1000 hours(IC Type:4000 hours,-FFC/FPC:2000 hours,20C to 25C,30 to 50,%,1000 hours(IC Type:4000 hours,-FFC/FPC:2000 hours,三種老化測試分類測試標準DSTCT-55C to+8,锡须检测与判定标准课件,锡须检测与判定标准课件,锡须检测与判定标准课件,锡须检测与判定标准课件,锡须检测与判定标准课件,Tin whisker Record,Measurement Type,General Method,Comments,Full Scan,Measure from top and 2 sides of all leads.,1.Measurement full length of whisker to be measured.,2.Side measurement at 45 degrees.,3.Measure the complete top side of the lead-not just to top of it(including bend points),Record all whiskers that are 30um or greater,Magnification minimum 150 x-250 x,SEM Measurement.Must be able to resolve whisker 30um,Tin whisker RecordMeasurement,Tin whisker Record,Measurement Type,General Method,Comments,Detailed Scan,Minimum Sample Size 10 pins,1.If pin during full scan has whisker 30um,use that pin for Detailed scan.,2.If no pin 30um is found during full scan,randomly select pins from each side of component.,3.If less than 10 pins are found during full scan with 30um,randomly select other pins(max 10)for detailed scan,Measure from top and 2 sides,See Diagram below Must be 400 x,Record count and length of all whiskers that are 30um or greater,Record count of all whiskers between 20-30um,1.Length recording not necessary if whisker 30um exist,2.If no whiskers 30um are found,must record the maximum whisker length per sample,Whiskers less than 20um do not have to be recorded,If no whiskers of 30um are found,must record the maximum whisker length per sample,Tin whisker RecordMeasurement,Tin whisker Record,Whisker Length criteria,Minimum Conductor Spacing 140um,50um maximum,Minimum Conductor Spacing 50um,30%of whiskers 30um.,If no whiskers are greater than 30um,must show image of maximum whisker found,Must show image of top measurement and side measurement example at full scan magnification.Select one pin from the first two samples of each test condition,Must show image of top measurement,side measurement,and bottom measurement example at detailed scan(400 x).Select one pin from the first two samples,Provide all images in the SEM Image sheet.Images must be clear and be of high enough resolution to allow for expansion of images.,Tin whisker RecordWhisker Leng,Some Pass and Fail Examples,130.7um,79.3um,Fail,Fail,Some Pass and Fail Examples130,Some Pass and Fail Examples,Tin whisker length:88.63um,Physical view(top),SEM image,Partial SEM image enlargement,Fail,Some Pass and Fail ExamplesTin,Some Pass and Fail Examples,Tin whisker length:131.42um,Physical view(top),SEM image,Partial SEM image enlargement,Fail,Some Pass and Fail ExamplesTin,Some Pass and Fail Examples,Tin whisker length:93.62um,Physical view(top),SEM image,Partial SEM image enlargement,Fail,Some Pass and Fail ExamplesTin,T,in,W,hisker,Tin Whisker,SEM,(Scanning Electron Microscope),在真空中加熱鎢燈絲時,發生熱電子,.,在燈絲外圍的陰極和位于相反的陽極之間施加高電壓,.,拉出熱電子,熱電子束透過電子透鏡,掃描線圈等作用成為極細的電子束,(,電子探針,).,把這束電子照射于物體（被檢試樣）的表面,並掃描表面所定的區域,.,根據電子束和試樣之間的相互作用，從試樣表層產生各種信號,SEM(Scanning Electron Micros,二次電子圖像,在,SEM,中查出的主要是二次電子，透過二次電子查出器查出，圖像稱為二次電子圖像準確的反映著試樣表面的形態（凹凸狀況），圖像具有立體感,二次電子是高加速入射電子照射于試樣表面，從試樣表面產生的，不是入射的電子，因此稱為二次電子,二次電子圖像 在SEM中查出的主要是二次電子，透過,SEM,樣品的選擇,樣品必須是固體,(,塊狀，粉末狀均可,),樣品的尺寸以能放入樣品台上為宜,(3cm*3cm),太大要切割取樣,樣品要有良好的導電性，對於導電性差的樣品,要在表面鍍一層約厚,0.01um,的金屬膜,SEM 樣品的選擇 樣品必須是固體(塊狀，粉末狀均可,小 結,錫須的定義及危害，形成機理，預防措施,錫須,測試的方法，測試的標准，可以參考,JEDEC JESD22A121,典型的錫須案例分析,