TC-L-08 — SX1276 QFN28 solder joint and thermal pad inspection

Inspect the SX1276 QFN28 solder joints under magnification (or X-ray if available).

Key risk: the exposed thermal pad on the bottom of the QFN (GND). If not properly soldered, the chip may be floating on GND — this degrades supply decoupling and RF circuitry even if digital/SPI function appears normal.

Check:

• All peripheral QFN pads: adequate fillet, no bridges, no cold joints
• Thermal pad: ideally confirmed by X-ray; visually check for any sign of package lifting or poor wetting at the perimeter

Pass: no visible solder defects on peripheral pads; thermal pad solder quality confirmed acceptable (X-ray preferred, visual inspection acceptable if X-ray unavailable).