Joint type · BGA
Array packages
Joints you cannot reach with an iron. Everything here is thermal, and the profile is the process.
- In this joint type
- 4/4
- Tip temperature span
- 300–380°C
- Dwell span
- 1.0–3.0s
- Scheduled ahead
- 0
| Technique | Tip | Tip °C | Dwell s | Flux | Alloy |
|---|---|---|---|---|---|
| Depositing paste on a BGA footprint with a mini stencil | chisel 2.4 mm (for stencil cleaning, not for soldering) | 300 | 1.0 | ROL1 mildly activated | SAC305 |
| Wicking and dressing a BGA pad field | knife 2.0 mm | 360 | 1.5 | ROL1 mildly activated | Sn63Pb37 |
| Corner-tack placement before BGA reflow | conical 0.4 mm | 340 | 1.0 | ROL1 mildly activated | SAC305 |
| Hot-air reflow profile for a 0.8 mm BGA | chisel 3.2 mm (for pad dressing, not for the reflow itself) | 380 | 3.0 | ROL1 mildly activated | SAC305 |
Depositing paste on a BGA footprint with a mini stencil
Re-balling with solder balls is the textbook method and the slowest one. A 0.12 mm stainless mini stencil and a squeegee gets the right paste volume onto a 0.35 mm pad field in under a minute, and a properly printed deposit reflows with lower voiding than hand-placed balls.
Wicking and dressing a BGA pad field
After removing a BGA, the pad field must be flat to within about 10 microns or the replacement will not sit evenly. Wicking is easy; dressing without tearing pads is the part that takes practice, because a 0.35 mm pad gives you almost no margin.
Corner-tack placement before BGA reflow
A BGA placed on paste or flux will drift during the ramp unless it is mechanically held. Tacking the four corner balls with a fine iron before the hot-air pass is the cheapest way to hold alignment, and it does not disturb the ball field if you approach at a shallow angle.
Hot-air reflow profile for a 0.8 mm BGA
A BGA cannot be soldered with an iron. Every joint is under the package, so the entire process is thermal: the goal is to get all the balls above liquidus within a few seconds of each other and let the package settle under its own weight. A profile that is too fast leaves the outer perimeter reflowed and the centre still pasty.