All about solder balls for BGA rework

Solder Balls, also called solder spheres, for BGA rework are miniature balls made from different types of solder alloys and are of various sizes. Most common sizes go from 0.20mm to 0.76mm.

List of common sizes used in most consumer electronics bga packages:

Solder balls 0.20mm
Solder balls 0.25mm
Solder balls 0.30mm
Solder balls 0.35mm
Solder balls 0.40mm
Solder balls 0.45mm
Solder balls 0.50mm
Solder balls 0.55mm
Solder balls 0.60mm
Solder balls 0.65mm
Solder balls 0.76mm

They come in Leaded and Lead Free alloys.

One of the most popular brands is PMTC (Profound Material Technology Corp.) from Taiwan.

For the average repair shop they're available in quantities of 25k and 250k containers.

Solder balls are sensitive to moisture and should be kept in a moisture fee environment. They're usually given a 1 year lifetime before their considered unreliable due to environmental exposure.

For the average repair shop, although not encouraged to do so, if the right ball size is not available we can use the next smaller size to perform a job.

When reballing a chip we need to use the corresponding preform (stencil) for the ball size.

We must make sure we close the solder balls container soon after we've finished using it to diminish moisture exposure.

Solderballs can be cleaned if they have become dirty by flux or any other foreign material. We just dump them in a bowl of alcohol or similar chemical and wash them off then let dry.

We must be aware that it is common to find some smaller (sometimes significantly smaller) solder balls within a given solder ball container. If during reballing a chip we see this we must remove this smaller ball and re-place with the right size. If we dont catch this while reballing and we solder the balls onto the chip, the chip will not have good contact, in comparison to the others, on that pad and will soon cause a cold solder joint.