Help with removing chips from iphone

Hello guys, I need a little guidance please. I have been working on apple products for a while and finally have a lower end work station ("ALL IN ONE" X-TRONIC - MODEL #5040-XTS HOT AIR REWORK SOLDERING IRON STATION & PREHEATING STATION), that seems to work alright. I have repaired a few backlights and replaced a few bad components. I have tried to pull a few chips off, but always seem to pull at least one pad off. The boards I have been working with are parts boards (I'm sure a few money boards for some of you guys) so I'm not worried about them, but have been trying to improve my skills. A few questions...



What temperature do you guys use to remove chips? Base band, Wi-Fi, ect? Is there a certain temp for all chips, or different temps for different chips?



I have learned to remove the black epoxy on the sides of the chips with 190 from the hot air, and I have that down, but the epoxy seems to be my problem when removing chips. I'm sure the solder has let go, but the epoxy under the chip seem to have a great holding strength, how do I over come this epoxy?



At what temp are the chip I remove toast? At this point I haven't made it to the point to where I can get one off without removing at least one pad, so I haven't had to worry about the chips I have removed so far, but the time will come....



Thanks for any help guys....

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