Underfill 维修指南

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 准备工作/Equipments needed：加热装置(维修工作台/热风枪)Heating Equipment(Rework Station/Hotair gun)头部楔形的小木棍/牙签Small wood stick with cuspidal end or toothpick助焊剂/Flux棉签/Cotton stick尖头镊子/Nipper with cuspidal end吸锡带/焊锡丝/Solder wick and solder wire若有可能的话加上显微镜/Microscope if p

3、ossible6 Rework Guidelines Remove the adhesive around the BGA (fillet)加热/Heating： 设置热风枪温度到150C热风枪加热PCB板的BGA区域Set the temp to 150C, then heating the BGA area of the PCB with hot air gun 若用维修工作台可设置温度值在150C150C temperature setup is suggestion if use rework station 温度不要超过焊球熔点Never exceed the solder ball

4、 melting point原因/Why： underfill在加热到100C左右时会变得较软，容易去除Its easy to remove softened underfill above 100C 超过焊球熔点后，去胶时易把周边小元件碰掉Too high temperature may cause small component around BGA be removed;7Rework Guidelines Remove the adhesive around the BGA (fillet)去周边胶/remove the underfill around the BGA：在基板底部使用

5、热风，加热至100C左右,在此状态下可使用尖锐木制工具（如牙签等）去除元器件周围的胶粘剂。Heating PCB to 100C-150C, remove underfill around the BGA with wood stick (eg. Toothpick)在此状态下，焊锡尚未熔化，不会影响周边靠得较近的元件Small component around BGA will never be removed because the temperature is lower than the melting point或者使用带温度的尖头烙铁直接去除芯片周边的胶（这需要较熟练的维修人员）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：分离芯片与周边器件的胶连接Divide the BGA from the components around it保证芯片能被轻松卸下而不损及周边器件及PCB板To be insured that the BGA will be removed without damage to the component around it

7、.8Rework Guidelines - Remove the BGA加热/Heating：调整热风枪加热温度至BGA焊球熔点以上（如350C）Adjust the hot air guns heating temperature to above the melting point of solder joint（eg.350C)保持一定时间以保证焊球熔化，不要加热太长时间（正常小于1分钟）Keep some time to melt the solder ball, but too long time is not suggested维修工作台可以设置温度曲线（具体要根据实际相应调整）Y

8、ou can setup a profile if use rework station according to the test result在保证焊球熔化的前提下温度尽可能低点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过快温度上升/过高温度/过长时间加热会对PCB板造成损伤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：到芯片卸下时间点，使用金属镊子在芯片一角轻撬芯片，并将芯片从基板分离Right time to remove, we can prize the BGA from one corner with cuspidal nipper只要加热至BGA下焊球熔化，此时即可撬下芯片而不会损坏PCB板，胶在100C时已变软，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检查卸下芯片的焊球/inspect the solder ball of BGA removed：加热温度不够，或卸芯片不及时Heating temperature is not enough, or its too late to r

11、emove the BGA, solder balls were solidified again加热不均匀，局部地区温度不够或卸芯片不及时Heating is not good, some areas temperature is not enough, or its too late to remove the BGA加热温度足够Heating is enough12Rework Guidelines - 去残锡/remove the solder residue清除残留焊锡/remove the solder residue：加助焊剂Put the flux on PCB with th

12、e residue of adhesive and solder用烙铁加吸锡带尽量清除PCB板上残留的的焊锡To remove the solder residue with solder wick and iron原因/why： 使焊盘表面光滑无毛刺，在去残胶时不易带起焊盘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：千万小心，不要损及PCB板上的焊盘Be caref

13、ully, dont do damage to the Pads on PCB13Rework Guidelines - 去残胶 /Remove the adhesive residue在显微镜下用加热器加尖头镊子清除残胶/use heating equipment + cuspidal nipper to clean the adhesive residue under the microscope用棉签涂助焊剂于PCB上残胶处Put the flux on the adhesive residue with cotton stick设置热风枪至150C，加热PCB上的残胶Heating t

14、he adhesive residue with the 150C hot air用尖头镊子小心去除残胶Remove the adhesive residue with cuspidal nipper carefully原因/why：助焊剂可以在一定程度上帮助残胶软化Flux may soften the adhesive under high temperature温度越底，PCB板所受的热冲击越小，焊盘强度越大Lower temperature under melting point can keep the pull strength of PadAfter cleaningBefore

15、 cleaning14Rework Guidelines - 去残胶 /Remove the adhesive residue当PCB板上有较多的被刮下来的残胶时，可能会影响视线，可用棉签清理一下When too much removed adhesive stay on the PCB may affect the view, you can clean these with cotton stick然后再在显微镜下检查一下焊盘上的锡是否有毛刺等，可能会影响去胶时把焊盘拉脱，如有的话，涂点助焊剂，用烙铁清理一下，使焊盘表面光滑。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，继续在显微镜下用尖头镊子去残胶Back to the previous step, continue to clean the adhesive residue with cuspidal nipper under the microscope 15Rework Guidelines - 焊盘上锡/tin the Pads焊盘上

17、锡/tin the Pads：用烙铁和锡丝给焊盘再上锡(滚锡),保证焊盘上无残胶或其它杂质污染,均匀上锡Tin the Pads to confirm there is no residue on the Pads原因/why：保证BGA再次安装后，芯片底部无杂质影响再次underfillTo be insured that the BGA can be underfilled again after re-assembly滚锡以验证焊盘上无污染Tin the Pads to check there is no residue polluted16Rework Guidelines - BGA安装/BGA re-assembly重新焊上新的BGA/ BGA Re-assembly加助焊剂于PCB上Put the flux to the PCB按正常换BGA程序安装新的BGARe-assemb