It happens to many of us when we remove the UEM. It takes a lot of effort you might have some tracks with no green lacqour ( specially on the light green boards )
What i made, is coating the board with a blue marker, and dry it with cold air (fan). When its dry, we have a small problem ! How do I fit the new or old reballed UEM without using flux ?
I have solved it using the following method :
1 : For new uem
A : Put some flux at the UEM IC balls and heat it with mid heat and the nozzel around 2 inches from the IC
B : Clean the IC and the balls untill all balls are bright and shining
C : Fit the UEM in place and use mid heat and mid air, but here you'll have to use longer time than usual, around 3 to 4 min
Now your done !
2 : For reballing the same UEM it's alot easier since theres still some solder left on the pads. Clean it up and fit the same way as above.
N.B The success of this proccess depends on ******* the UEM exactly in it's place credit to Raheeeeb
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