Re: BGA reballing techniques and equipment
My suggestion is to use direct heat stencils. In my expirience the indirect method will work only with bigger bga lik gtx 1070 or so...but with pch you need to be very carefull to work with indirect method.
I also started with indirect method..for me it made much more sense to use indirect heat stencils..and seems to be clearer method...But i didnt get good results and keep reballing same chip several times.... Maybe i am clumsy but i am just writing what i feel and have expirienced.
But when/if you use direct heat reballing it is very important to:
1. use a good quality stencil (one that will not warp easy) from trusted seller,
2. use a good flux,
3. before applying solder balls allways check with microscope assemblies for misaligned holes because it will not be easy to remove stencil from bga if holes were not aligned,
4. apply solder balls,
5. start with heatgun with low air flow...until stencil, solder balls and bga is slowly heating,
6. when you see that solder balls are melted remove heatgun and aplly flux direct on stencil...and again heat it with heatgun,
7. after that waith till everything cools,
8. try to remove stencil from chip but do not make to much preasure,
9. if its not coming off try using a heatgun again but just a little to melt the flux...and you should be able to remove stencil,
10. when stencil removed see if any solder ball is missing on the chip, if yes put it on directly on the chip and try to heat it again with heatgun,
11. clean it with isopropyl alcohol.
good luck!
My suggestion is to use direct heat stencils. In my expirience the indirect method will work only with bigger bga lik gtx 1070 or so...but with pch you need to be very carefull to work with indirect method.
I also started with indirect method..for me it made much more sense to use indirect heat stencils..and seems to be clearer method...But i didnt get good results and keep reballing same chip several times.... Maybe i am clumsy but i am just writing what i feel and have expirienced.
But when/if you use direct heat reballing it is very important to:
1. use a good quality stencil (one that will not warp easy) from trusted seller,
2. use a good flux,
3. before applying solder balls allways check with microscope assemblies for misaligned holes because it will not be easy to remove stencil from bga if holes were not aligned,
4. apply solder balls,
5. start with heatgun with low air flow...until stencil, solder balls and bga is slowly heating,
6. when you see that solder balls are melted remove heatgun and aplly flux direct on stencil...and again heat it with heatgun,
7. after that waith till everything cools,
8. try to remove stencil from chip but do not make to much preasure,
9. if its not coming off try using a heatgun again but just a little to melt the flux...and you should be able to remove stencil,
10. when stencil removed see if any solder ball is missing on the chip, if yes put it on directly on the chip and try to heat it again with heatgun,
11. clean it with isopropyl alcohol.
good luck!
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