Underfill 維修指南

1、1Rework ProcessDispense & Cure UnderfillRemove Defective ComponentClean Pad Site2The Typical Profile for SAC AlloyTC-1TC-2TC-31000C3000C2000C100 s400 s300 s200 s500 sTop Nozzle HeaterBottom HeaterRecommended DT of (TC-1,2 3) within 10oC3Remove solder and underfill residue4Proper Substrate Cleani

2、ngExcessive Pressure / Time5Rework Guidelines 準備工作/Equipments needed：加熱裝置(維修工作臺/熱風(fēng)槍)Heating Equipment(Rework Station/Hotair gun)頭部楔形的小木棍/牙簽Small wood stick with cuspidal end or toothpick助焊劑/Flux棉簽/Cotton stick尖頭鑷子/Nipper with cuspidal end吸錫帶/焊錫絲/Solder wick and solder wire若有可能的話加上顯微鏡/Microscope if p

3、ossible6 Rework Guidelines Remove the adhesive around the BGA (fillet)加熱/Heating： 設(shè)置熱風(fēng)槍溫度到150C熱風(fēng)槍加熱PCB板的BGA區(qū)域Set the temp to 150C, then heating the BGA area of the PCB with hot air gun 若用維修工作臺可設(shè)置溫度值在150C150C temperature setup is suggestion if use rework station 溫度不要超過焊球熔點Never exceed the solder ball

4、 melting point原因/Why： underfill在加熱到100C左右時會變得較軟，容易去除Its easy to remove softened underfill above 100C 超過焊球熔點后，去膠時易把周邊小元件碰掉Too high temperature may cause small component around BGA be removed;7Rework Guidelines Remove the adhesive around the BGA (fillet)去周邊膠/remove the underfill around the BGA：在基板底部使用

5、熱風(fēng)，加熱至100C左右,在此狀態(tài)下可使用尖銳木制工具（如牙簽等）去除元器件周圍的膠粘劑。Heating PCB to 100C-150C, remove underfill around the BGA with wood stick (eg. Toothpick)在此狀態(tài)下，焊錫尚未熔化，不會影響周邊靠得較近的元件Small component around BGA will never be removed because the temperature is lower than the melting point或者使用帶溫度的尖頭烙鐵直接去除芯片周邊的膠（這需要較熟練的維修人員）O

6、r you can remove the underfill around BGA with cuspidal iron tip directly (this operation only for the professional rework operator )原因：分離芯片與周邊器件的膠連接Divide the BGA from the components around it保證芯片能被輕松卸下而不損及周邊器件及PCB板To be insured that the BGA will be removed without damage to the component around it

7、.8Rework Guidelines - Remove the BGA加熱/Heating：調(diào)整熱風(fēng)槍加熱溫度至BGA焊球熔點以上（如350C）Adjust the hot air guns heating temperature to above the melting point of solder joint（eg.350C)保持一定時間以保證焊球熔化，不要加熱太長時間（正常小于1分鐘）Keep some time to melt the solder ball, but too long time is not suggested維修工作臺可以設(shè)置溫度曲線（具體要根據(jù)實際相應(yīng)調(diào)整）Y

8、ou can setup a profile if use rework station according to the test result在保證焊球熔化的前提下溫度盡可能低點Set low enough temperature if the solder ball can be melted in one minute原因/why：使焊球熔化以取下芯片Melt the solder ball to remove the BGA過快溫度上升/過高溫度/過長時間加熱會對PCB板造成損傷Too fast temperature ramp up/too high temperature/too

9、 long heating time may do damage to PCB and components;9Rework Guidelines - Remove the BGA10芯片卸下/Remove BGA：到芯片卸下時間點，使用金屬鑷子在芯片一角輕撬芯片，并將芯片從基板分離Right time to remove, we can prize the BGA from one corner with cuspidal nipper只要加熱至BGA下焊球熔化，此時即可撬下芯片而不會損壞PCB板，膠在100C時已變軟，很容易取下Only solder ball was melted, BG

10、A can be remove without damage to PCB, because the adhesive is softened when the temperature is higher than 100C.Rework Guidelines - Remove the BGA11Rework Guidelines -Remove the BGA檢查卸下芯片的焊球/inspect the solder ball of BGA removed：加熱溫度不夠，或卸芯片不及時Heating temperature is not enough, or its too late to r

11、emove the BGA, solder balls were solidified again加熱不均勻，局部地區(qū)溫度不夠或卸芯片不及時Heating is not good, some areas temperature is not enough, or its too late to remove the BGA加熱溫度足夠Heating is enough12Rework Guidelines - 去殘錫/remove the solder residue清除殘留焊錫/remove the solder residue：加助焊劑Put the flux on PCB with th

12、e residue of adhesive and solder用烙鐵加吸錫帶盡量清除PCB板上殘留的的焊錫To remove the solder residue with solder wick and iron原因/why： 使焊盤表面光滑無毛刺，在去殘膠時不易帶起焊盤To smoothen the surface of the Pads, then the Pads will be not easy to be removed when we clean the adhesive residue on PCB 注意/Attention：千萬小心，不要損及PCB板上的焊盤Be caref

13、ully, dont do damage to the Pads on PCB13Rework Guidelines - 去殘膠 /Remove the adhesive residue在顯微鏡下用加熱器加尖頭鑷子清除殘膠/use heating equipment + cuspidal nipper to clean the adhesive residue under the microscope用棉簽涂助焊劑于PCB上殘膠處Put the flux on the adhesive residue with cotton stick設(shè)置熱風(fēng)槍至150C，加熱PCB上的殘膠Heating t

14、he adhesive residue with the 150C hot air用尖頭鑷子小心去除殘膠Remove the adhesive residue with cuspidal nipper carefully原因/why：助焊劑可以在一定程度上幫助殘膠軟化Flux may soften the adhesive under high temperature溫度越底，PCB板所受的熱沖擊越小，焊盤強度越大Lower temperature under melting point can keep the pull strength of PadAfter cleaningBefore

15、 cleaning14Rework Guidelines - 去殘膠 /Remove the adhesive residue當(dāng)PCB板上有較多的被刮下來的殘膠時，可能會影響視線，可用棉簽清理一下When too much removed adhesive stay on the PCB may affect the view, you can clean these with cotton stick然后再在顯微鏡下檢查一下焊盤上的錫是否有毛刺等，可能會影響去膠時把焊盤拉脫，如有的話，涂點助焊劑，用烙鐵清理一下，使焊盤表面光滑。Check the Pad, coating flux and

16、smoothen the solder surface on the Pad if there are burr on the Pad, or the Pad may be pull down during the adhesive cleaning.然后再返回上一步，繼續(xù)在顯微鏡下用尖頭鑷子去殘膠Back to the previous step, continue to clean the adhesive residue with cuspidal nipper under the microscope 15Rework Guidelines - 焊盤上錫/tin the Pads焊盤上

17、錫/tin the Pads：用烙鐵和錫絲給焊盤再上錫(滾錫),保證焊盤上無殘膠或其它雜質(zhì)污染,均勻上錫Tin the Pads to confirm there is no residue on the Pads原因/why：保證BGA再次安裝后，芯片底部無雜質(zhì)影響再次underfillTo be insured that the BGA can be underfilled again after re-assembly滾錫以驗證焊盤上無污染Tin the Pads to check there is no residue polluted16Rework Guidelines - BGA安裝/BGA re-assembly重新焊上新的BGA/ BGA Re-assembly加助焊劑于PCB上Put the flux to the PCB按正常換BGA程序安裝新的BGARe-assemb