PCBA + silicone parts
Encapsulating a board is not a sealing problem first. It is keeping solder joints, dome switches and the battery unharmed while the silicone cures around them.
Interface and structure for silicone over PCBA
Every part in this group has live components inside. Temperature, pressure and flow direction all act on them during molding: too much pressure collapses a dome switch or bows the board edge, too much heat affects the cell and some SMD parts. Low-pressure, low-temperature molding, component clearance and stress-relief structure are therefore the starting point, not an optimisation.
Serviceability has to be decided before the tool. Full encapsulation cannot be opened, so a failed unit is replaced rather than repaired. If the product has a service life that includes battery replacement or board-level rework, leave a partial encapsulation or a mechanical lid; changing that decision after tooling means cutting a second tool.
Water is the easier half of the problem. Silicone keeps liquid water out of the cavity, but it is not a vapour barrier: moisture still moves through the wall and condenses on the cold face during temperature cycling. Internal protection (conformal coating, local potting, a dry structure or a breathable membrane) is a separate decision from the seal, and the validation should test immersion and damp-heat cycling separately.
Five points for silicone over PCBA
- Low temperature, low pressure: hold the cavity temperature and injection pressure inside what the cell and components allow.
- Component clearance: leave relief cavities over tall parts, crystals and connectors so stress does not concentrate.
- Key feel: silicone thickness, hardness and dome travel are set together and measured as a force curve.
- Battery protection: room to swell, no direct pressure during fill, and a cure temperature the cell can take.
- Sensor and light windows: electrodes, light guides and breathable membranes are built into the tool, not cut afterwards.
Parts in this group
PCBA + silicone parts
Four parts that all take the full-encapsulation route, with very different component layouts and duty conditions.
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Wearable ECG patch sensor
Silicone encapsulating a PCBA, a coin cell and dome switches: medical grade, sealed against sweat, key feel kept, battery protected.
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Buried grain-silo temperature tag
Silicone over a temperature-sensing board: moisture and insect resistant, stable while buried in bulk material.
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Pool underwater switch module
Silicone over a board with a tactile switch: IP68 sealing, key function unaffected by water pressure.
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E-bike anti-theft alarm module
Silicone over a lithium cell and PCBA: shock and water resistant, tamper and pry resistant.
Dimensions, hardness and tolerances are confirmed from the project drawing. Other parts in this group are published one at a time; if one of them is the structure you are assessing, contact us rather than waiting for the page.
Failure and troubleshooting
Three failures that show up late
Problems in this group tend to appear in ageing tests or in the field, so the early validation has to be more thorough than usual.
- Dead key: silicone too thick or air trapped above the dome eats the travel; read the force curve before changing the structure.
- Cracked solder joint: molding stress or a thermal expansion mismatch, most often at heavy components and board edges.
- Short battery life: long-term pressure, heat or moisture ingress — rule the three out one by one.
Common questions
Questions about fully encapsulated boards
Does encapsulation shorten battery life?
It can, through heat and pressure rather than through the silicone itself. The battery well needs room to swell, the cell must not sit directly in the fill path, and the cure temperature has to stay inside what the cell allows. Measure the cell temperature in the cavity, not the machine setpoint, and confirm the result with ageing data.
How is key feel kept consistent?
Fix the silicone thickness over the dome, the hardness and the dome travel as one set of parameters, then measure the force curve at sampling instead of judging by hand. In volume, hold the same parameters and keep to the mould maintenance interval.
Can an encapsulated part be repaired?
No. Full encapsulation means the part is replaced, not opened. If a product needs service or a replaceable battery, plan a partial encapsulation or a mechanical lid at design stage; adding it after tooling means a new tool.
Other material combinations in composite parts
Change the substrate and the interface changes with it; the other groups are the comparison.
- Metal + silicone parts
- Engineering plastics + silicone parts (group page in Chinese)
- Glass and ceramics + silicone parts (group page in Chinese)
- Composite parts overview
- Overmolding failure modes and the bonding matrix
Send the substrate and the structure
Tell us the board outline, the tallest components, the cell and the target volume; we come back with the encapsulation route and the structure points first, then tooling.