BGA_OPEN_ISSUE

1、FAILURE ANALYSIS REPORT P4B-MX BGA OPEN (一一) 不良現象不良現象3月25日,P4B-MX R1.05 ,F/B測試不良31pcs,顯示不良現象:(1)FF無法開機(2)80卡顯示異常(3)上機有異音(4)D5無法開機(5)D1無法開機(6)WINDOWS當機結論:此上述不良現象與CPU socket478P及北橋相關,故對 CPU socket及北橋作分析. (二)工程分析11.此上述不良現象訊號線與北橋及CPU socket 478P相關,因北橋訊號點位難以測量,故先測量CPU socket與GND之相連點位(主要為HA,HD信號點)的保護二极體是否

2、與正常PCB之相同點位顯示數值有不同.工程針對不良PCBA做驗證,發現有的訊號點位測試值比正常PCBA顯示數值偏大.結論:故判定CPU socket或北橋有本體不良或焊點OPEN狀況. (二)工程分析22.選取不良PCBA 北橋周圍線路位置點,量測線路與CPU socket 478P相連的點位保護二极體是否有異常.量測結果無異常,表明CPU socket 478P本體無不良且焊接點無OPEN狀況,故排除CPU socket 478P不良. 結論:不良的產生是因為北橋本體不良或北橋焊點有OPEN狀況. (二)工程分析 3 3.對不良PCBA做如下分析:(1)首先使用X-RAY觀察焊點,未觀察到異

3、常;(2)再用手下壓BGA本體進行測試,F/B測試PASS;(3)對不良PCBA之BGA進行重熔,測試PASS;(4)將不良PCBA之BGA用BGA rework設備拆除,對拆除的BGA本體進行量測,其量測值正常.結論: 此不良的產生是因BGA 焊點OPEN引起的. BGA區域信號點分布1代表空焊點位 BGA區域信號點分布2 INTEL 82845BGA點陣圖代表空焊點 (三) 切片過程1一.切割: 1 操作流程：準備工作調整各定位機構開啟電源切割關機清理1.1 準備工作 (1) 查看台面是否整潔，切刀附近有無雜物，如有，即時清理。 (2) 查看機內是否切削過多，妨礙機器正常運轉，如有，即時清

4、理。(3) 將擋削蓋壓下，以防止切削飛出。 (三)切片過程21.2 調整各定位機構(1) 根據要求板材切割位置，對照機台刻度標尺，確定橫向定位杆位置。擰松橫向定位杆之定位螺釘，將其移動至要求位置，擰緊螺釘。(2) 如要求斜向切割，需先參照角度定位杆之圓角刻度，將角度定位杆調整至要求角度，擰緊定位螺釘。 (三)切片過程 31.3 開啟電源：接上電源，將啟動開關按至“ON”檔，開啟切割轉刀。1.4 切割：將板子放于操作平台，邊緣緊貼定位杆，雙手壓住板子，並向前送至切刀進行切割。1.5 關機：切割完成後，取回板子，將啟動開關按至“OFF”檔，關閉機器。 (三) 切片過程 41.6 清理 (1) 清理

5、機台上剩餘切削，使其保持清潔 (2) 每星期五下班前擰開機台蓋上螺絲， 打開機台蓋，清理機器內削渣，以保 証機器正常運轉。 2 注意事項：安全操作，避免操作時，身體與切刀接觸。 (三) 切片過程5二:研磨 1 開啟電源開關 2 旋轉轉速開關，使其達到研磨時的速度，并調節水流速度。 3 粗磨：將壓克力模在200目的砂紙上研磨，若是磨線路，則只要磨平就可，若是磨孔則要磨到孔邊。4 中磨：將壓克力模在600目的砂紙上研磨，若是磨線路，則只要磨平就可，若是磨孔則要磨到接近孔半徑位置。 (三)切片過程 6 5 細磨：將壓克力模在1200目的砂紙上研磨，若是磨線則要磨光，若要磨孔，則磨至半圓，同時也使其磨

6、光滑. 6 拋光。 7 在拋光紙在放上一些拋光粉，它的作用是使表面達到光滑，便于后繼顯微鏡。 (三)切片分析1不良焊點正常焊點結論: 不良焊點狀況:PCB之PAD與BGA之錫球分離 正常焊點狀況:PCB之PAD與BGA之錫球與錫膏熔為一體. 不良焊點正常焊點不良焊點與正常焊點放大後比較 (三)切片分析2 (四)BGA不加熱直接拆除分析空焊之PCB PAD空焊之BGA PAD (五) PCB廠商分析1.針對BGA不加熱直接拆除之PCBA,請統盟用EDS元素分析儀進行分析:(1) 拒焊本身由EDS元素分析結果，錫墊表面除錫&鉛成份物質外並無其它非金屬性拒焊雜質成份在，造成因素排除與污染物質有關。(

7、2) 空焊異常PCB生產製作週期橫跨3個週期、再加上空焊問題不良點僅集中發生於北橋固定區域位置，因PCB板本身是採整片浸泡噴錫的作法，空焊不良並不會集中固定發生於相同區域。結論:拒焊發生原因點並非於PCB本身 . (六) BGA廠商分析1Provide Unit without SMT and X-section unit for vendor to analysis: (1)Unit without SMTnNo any other element can be detected except for flux (C,O) and NaCl; nFlux residue due to non

8、-clean process during ball attach and this would impact solder ability;nNaCl may came from sweet hand; (六)BGA 廠商分析2 (2)X-section unitnPoor wetability between one solder sphere and motherboard pad, which resulted in void around pad edge area due to no eutectic solder bulk filled in during SMT process

9、;nStress area was formed due to void and which initiated the crack line along the interface, this is the reason of open;nElements comparison between non-wet interface and good interface shows they are equivalent;nThe Al element may be from fine polishing by chemicals. So it is not clear for the form

10、ation of the non-wet;nNo other element was detected on IMC layer, suspect that there is no other material on top of Cu layer. Based on Intel experience, the IMC formed by Cu/Sn/Pb may not have good joint strength. Dark area due to flux residue.NaCl may de due to touch with hand.Sn, Pb2Sn, C, O, Na,

11、Cl, Pb1 elementSpot12Detected Ball location EDX On Raw Part Solder Ball Surface-1 Detected Ball location Sn, C, O, Na, Cl, Pb, K2Sn, C, O, Na, Cl, Pb, K1 elementSpotDark area due to flux residue.NaCl may de due to touch with hand.EDX On Raw Part Solder Ball Surface-2 FESEM On Non-wet BallCrackvoidvo

12、idcrackcrackPb/SnCumotherboardCrack can be seen between solder ball/motherboard.There is void around pad edge due to no eutectic solder.EDX result refer to page 10.The interface layer (IMC) thickness is around 1.53um averagely. Left edge non-wet solder Ball right Edge ; 1 23 4Sn, C, N, O4Sn, Pb, C,

13、O, N3Cu, Sn, Al, C, O2Cu, Sn, C, O, N1 elementSpotAl may due to chemical when fine polishSuppose the C, O, N, from Flux?EDX On Non-wet Solder Ball Interface FESEM On Good Ball No Crack can be seen between solder ball/motherboard.There is void on solder ball bulk. EDX results refer to page 12.The int

14、erface layer (IMC) thickness is around 2.84um averagely.Cu 1 23 4Sn, C, N, Cu4Sn, Pb, C, O, N3Cu, Sn, Al, C, O, Pb, N2Cu, Sn, C, O, N1 elementSpotAl may due to chemical when fine polishSuppose the C, O, N, from Flux?EDX On Good Solder Ball Interface (七) 改善前迴焊爐曲線 (七)改善後迴焊爐曲線 (七)改善前與改善後的差異 改善前 改善後1.FI

15、RST RAMP-UP :1.3/SEC 1.FIRST RAMP-UP :1.2/SEC 2.SOAK TIME :75.2SEC 2.SOAK TIME :64SEC3.PEAK TEMP : 3.PEAK TEMP : (1)BGA (BIG) TOP TEMP :213 (1)BGA (BIG) TOP TEMP :217.5 (2)BGA (BIG) BOT TEMP :210.5 (2)BGA (BIG) BOT TEMP :216.5 (3)BGA (LITTLE) TOP TEMP :214.5 (3)BGA (LITTLE) TOP TEMP :216 (4)BGA (LITTLE) BOT TEMP :213.5 (4)BGA (LITTLE) BOT TEMP :215.5 (5)QFP 128 PIN TEMP :214 (5)QFP 128 PIN TEMP :221 (6)CPU SOCKET TEMP :208 (6)CPU SOCKET TEMP :211.54.OVER 183 TIME :73.6SEC 4.OVER 183 TIME :73.6SEC注:迴焊爐曲線調節的主要參數為SOAK TIME由原5090sec,更改為 5065sec,以防止錫膏