The same technique should work well with other (bigger) ball sizes too, however there are rarely issues when handling bigger packages and less care is usually needed there.
The technique uses premade solder balls, not solder paste.
Equipment:
- Solder balls of correct size (0.3mm for eMMC)
- Stencil to hold the balls with correct configuration for the package eg eMMC 153/169 standard stencil
- Kapton tape (narrow)
- Package holder (optional)
- Solder wick
- Flux(es) -- one tacky eg. rosin-based liquid or pen, one of your choice (I used Amtech NC-559-ASM-UV)
- Preheater
- Hot air station and soldering iron
- Small tweezers to pick balls with
- Holder plate/platform optinally
Not required, but makes it so much easier to work with. Apply Kapton tape to fix the package in place so it doesn't move around too much.
Every little bit of it should go. This ensures balls do not roll off the pads.
Ensure the stencil does not touch the package, but also does not let the balls roll as they please. It is supposed to only hold the balls on their pads but not too much. A good criterion is that you can't feel placed balls with your finger tip but a second ball should roll easily off the one already in the stencil hole.
Rosin flux pen is probably the best, liquid rosin-based flux also works fine. The flux should hold the balls in place when dropped through the stencil. Paste flux may be used in very small quantities; it is prone to liquefy and pull balls together if too much is applied.
Make sure there is only one ball in any hole. Swipe excessive balls off the stencil. Tweezers can be used for that purpose.
The balls should stay on the pads due to the flux. If balls roll off, more flux should be applied next time. It may happen that a few balls get stuck in the stencil; replace those manually by using tweezers.
Use small tweezers, a needle, a thin wire -- whatever you are comfortable with. The end result does not need to be pretty but make sure no balls are touching or too close to each other. The applied flux should make sure balls dont get picked up or roll off the package.
Place the package (in the holder plate if you use that) over the preheater, or in the reflow oven if you have one, and let the balls reflow. Hot air can be applied on the minimal flow only as it blows the balls off otherwise; remember flux is already liquid at that point. When done right, you should see the balls aligning themselves and popping into the place.
It might happen that the balls oxidize due to minimal flux amount. This manifests in the balls not liquefying properly, not wetting the pads, etc. In this case carefully apply a bit of flux outside the pads and let it flow over the pads and eventually balls, removing the oxides and enabling the solder to flow.
Congratulations! Well done. :-)
bro you can try this tool ;)
https://github.com/TheSnowfield/Pit-BGAFixer