I’m working on a BGA application and need to source solder spheres, but I’m unsure which diameter would be suitable for the component I’m working with. I’ve checked the available specifications but still can’t figure out which size would be the right choice.
What’s the best way to determine the correct solder sphere size for a BGA application?
Thanks
Sphere diameter is typically 50–60% of pitch. If you have the part numb er of what you’re working with you can start with looking up the spec in its datasheet. The manufacturer’s datasheet (or package outline drawing) should specify pitch — common values are 1.0mm, 0.8mm, 0.65mm, 0.5mm, 0.4mm, down to 0.3mm for fine-pitch parts. If you have the original part number, this is the fastest route: look up the JEDEC or vendor package drawing, which often lists the nominal ball diameter as-shipped directly.
If you’re reballing/reworking and don’t have that spec, measure
Use the general sizing rule of thumb
Common industry-standard pairings:
| Pitch | Typical ball diameter |
|---|---|
| 1.0mm | 0.5–0.6mm |
| 0.8mm | 0.4–0.45mm |
| 0.65mm | 0.3–0.35mm |
| 0.5mm | 0.25–0.3mm |
| 0.4mm | 0.2–0.25mm |
Account for reflow collapse
Spheres shrink in height (and spread slightly in diameter) during reflow — expect roughly 20-25% height reduction as the ball wets and collapses onto the pad. If you need a specific standoff height for a particular mechanical or thermal reason, size up slightly to compensate.
Pad type
NSMD (non-solder-mask-defined) pads generally give a bit more consistent, taller standoff than SMD pads for the same ball size — worth factoring in if standoff height matters for your application (e.g., underfill clearance, thermal cycling reliability).
You might need to do a bit of a testing run…the good news is you can usually re-try be de-soldering and attempting again