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Docs Build & Assembly Glue and Adhesives

Glue and Adhesives

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The adhesives used in the beacon build: hot glue, epoxy, RTV silicone, and the rule about what each one is allowed to touch.

Glue and Adhesives

Every case has joints that fasteners do not reach. The beacon uses three adhesives, each with a strict territory.

The three adhesives

AdhesiveUseNot for
Hot glueStrain relief, cable entries, temporary holdsAny load-bearing joint
Epoxy (2-part)Load-bearing joints, permanent mountsAnything that will be opened
RTV siliconeSeals, water barriersElectrical insulation of hot parts

The territory rules

JointRight adhesive
Cable entry into the caseHot glue or silicone
Antenna mount reinforcementEpoxy
Case seam (permanent build)RTV silicone (see Waterproofing)
Board to case (temporary)Hot glue
Board to case (permanent)Epoxy, with standoffs

The rules

  1. Nothing conductive: no adhesive near the radio’s RF path unless verified; some epoxies contain metal fillers.
  2. Outgassing: hot glue and some silicones outgas solvents that can fog the OLED in a sealed case. Cure fully before sealing.
  3. Repairability: if you may need to open it, use the adhesive that lets you: hot glue over epoxy.

The cold behavior

Adhesives stiffen in the cold. RTV silicone stays flexible (good), hot glue gets brittle (bad for strain relief), epoxy is unaffected. Winter builds favor silicone for anything that flexes (see Winter Pack).