Edge-Launch SMA Installation Do’s & Don’ts

Posted byOBAdmin

Edge launch SMAs can short into the internal copper layers with some installation methods. Watch for these gotchas.

The DON’Ts

  • Don’t use high-powered (or any) soldering iron or air only locally at the one installation point without any other board heating applied
    • WHY:
      • (a) The local heat stresses the board and can damage the board
      • (b) AND delaminate the board layers, allowing solder to wick into the inner layers
  • Don’t use a huge amount of solder
    • WHY:
      • (a) The extra solder can wick around the edge of the connector, off the pads and into inner layers or wherever else there is copper, especially if local high-powered heat is used
  • Don’t finish or round over the PCB edge – it may remove enough fiberglass to expose copper to the edge – not a good thing

The DOs

  • DO use a whole-board pre-heater with temperature control. Look up solder heat profile soak temperatures for examples and use an IR thermometer to check actual board temperature.
    • WHY:
      • (a) Less, stress on the board because it will uniformly bring the board up to a working baseline temperature, including thermally-heavy inner copper layers
      • (b) Once pre-heated, less local heat intensity is required to install a component, especially an SMA which ties into the grounds and thus the most difficult copper to heat (because there is much of it, among other reasons)
      • (c) It will make your life easier.
  • DO use just enough solder to get good flow (wetting) and profile onto the pads that are intended to receive the SMA, but not more. The strength will still be adequate. Heavier strain relief should be taken up by bulkhead panel mounts and other strain relief equipment.
    • WHY:
      • (a) Sometimes less is more
      • (b) So you don’t create opportunity for solder to wick along the edge and into inner copper layers, especially if the edge has been finished or filed, or if high local heat is being used to force the ground copper layers to heat up enough to flow solder
  • DO consider using an edge sealant or coating prior to installing the SMAs, and or consider using some spacer (depends on board and clearances) – as long as this is all compatible with your application