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Soldering Guide

The nRF9151 Micro Breakout uses 1mm pitch castellated pads which require care to solder reliably. Its compact size is an advantage for space-constrained IoT applications but demands extra attention when hand soldering to a carrier assembly (see Carrier Board Design for carrier-specific notes).

Hand Soldering

Practice first

It is strongly recommended to practise on a disposable Practice Board before soldering the real Micro Breakout to a carrier assembly.

Required Tools

Essential

  • Soldering iron — Use a high-quality iron with a clean, fine tip (ideally knife tip). A high, variable-temperature iron will provide the additional heat needed for GND pads.
  • Solder — The castellated pads are 0.8mm wide, so ultra-thin solder (<1mm) gives better control over the quantity applied per pin. Flux-core solder eases application.

Useful

  • Flux — Additional flux improves solder flow. A flux pen is ideal for applying a controlled amount to each pad.
  • Tweezers — Useful for positioning the Micro Breakout on the carrier.
  • Solder braid — Effective for cleaning up bridges across adjacent pins. Avoid solder suckers as they may disturb the board position.
  • Board heater — A pre-heater may help bring large ground planes up to temperature, making GND joints easier to achieve.
  • Microscope — Not essential, but assists in inspecting solder joint quality.
  • Good lighting — A well-lit work area improves visual inspection.
  • Latex gloves — Prevents finger grease contaminating the pads prior to soldering.

Technique

Suggested technique

One recommended approach — other tools and techniques may work equally well.

  • Solder each corner first; apply gentle pressure so the Micro Breakout sits flat against the carrier with no gap between the castellated pins and carrier pads.
  • Apply flux liberally to one edge of castellated pins at a time.
  • Using a knife tip, flood solder across multiple pins simultaneously and drag the iron along the edge to flow and level it.
  • If pins are bridged by excess solder, use the knife tip to scrape it away from the Micro Breakout.
  • Areas with large GND planes will sink significant heat; a higher iron temperature may be required for these pins.

Common Mistakes

  • Dry joints on GND pins due to the heatsinking effect of the Micro Breakout's internal GND layers and the carrier board ground plane.
  • Bridged adjacent pins — inspect carefully with magnification or probe electrically after soldering.

Check for shorts

Before applying power to a freshly soldered Micro Breakout, verify that power and GND are not shorted. Then verify all other pins are connected as expected.