Metal re-ball stencil or nonmetal

I personally like metal stencils. It offers the advantage of using solder paste which can then be spread on the stencil like butter on bread. Then the solder paste can be transferred to the ball grid array with heat while the stencil is still on top of whatever you are soldering too. It has an advantage over non metal because you don't need to find the proper size of solder balls to manually load each ball 1 by 1 onto your stencil to then transfer to your grid array. You also don't need sticky flux to keep the solder balls in place after lifting up the stencil. In the end metal stencils are less tedious and less prone to error.

Metal stencil use example: https://www.youtube.com/watch?v=3_DsWcg0...

• skip to 5:48

As for non metal, it’s hard to find an example because it’s an old and inefficient way of completing a re-ball task. The flow goes as follows:

1. Make sure chip is cleaned and ready to receive solder.
2. Apply sticky flux to the ball grid array on the chip.
3. Put non metal stencil over sticky chip.
4. Manually load each pre-made proper sized solder ball onto your stencil.
5. Verify that each hole in the stencil has a solder ball in it, and that there are no extras to be found in a single hole.
6. Lift up the stencil with a hope that the sticky flux did its job in keeping the solder balls attached to the ball grid array. This is usually never the case and you need to readjust a few tiny solder balls and remove some that may have stuck to your stencil.
7. Apply heat with the hope that the solder balls don’t move and that you don’t end up with a shorted ball grid array.