Rework BGA Processor with Solder Paste or Solder Balls?

[2X]

Hello, I want to ask if it is better to solder a big BGA chip/processor (big compared with the BGA chips with pins ~20pins that I use to rework with paste) with solder paste or with solder balls? I read on the below thread that balls make a better alignment of the chip. What is your opinions? Also do you have to suggest me any thermal profile for a chip like this (unfortunately I can't find any datasheet of this chip to look for a thermal profile from his manufacturer). For a hot Air I have the below.

https://www.eevblog.com/forum/beginners/bga-reballing-maybe-a-dumb-question-but/

https://www.jbctools.com/jtse-power-hot-air-station-product-1261.html

[Harry_22]

Hi!

Rolling balls is a very simple procedure that improves fine motor skills. It will take half an hour to make such a chip without skills.
The most important thing is to apply a thin and very even layer of flux otherwise the balls will stick together during melting.
But you will need a microscope.

[daisizhou]

You need a steel mesh as shown below to easily complete the work.
About working curve --Usually the BGA workstation has a default curve, you can select the default one. If you choose lead-free solder balls, then select the corresponding curve, which is done automatically.

[2X]

Thanks for your reply. For your opinion us I understand the balls are better from paste?
Also, because I have never use balls; the appropriate size/diameter of the balls for each stencil is for example at your image the 0,6mm that writes on it?

[daisizhou]

Thanks for your reply. For your opinion us I understand the balls are better from paste?
Also, because I have never use balls; the appropriate size/diameter of the balls for each stencil is for example at your image the 0,6mm that writes on it?

NO Usually the paste is suitable for small BGA chips。For example, the type of mobile phone MCU。
If paste is used for large BGA, it is easy for the paste to leak out during actual operation, resulting in failure.And it is difficult to ensure consistency
0.6mm is the specification (diameter) of the solder ball