Precision silicone overmolding · drawing review → sampling → volume
Two electronic product families show the same logic at work: an RFID chip has to be protected without losing read range, and an LED module has to be sealed against weather without losing light.
Encapsulating an electronic assembly in silicone is not only about water and dust. A chip, an antenna or an LED module sits inside a layer that absorbs impact, keeps moisture out and takes up thermal movement, while the part stays soft enough to wear on a wrist or to touch.
Both cases below come from product directions supplied by customers. What we take on is the overmolding and composite molding step: coverage area, wall thickness, gate position and surface finish are fixed from the chip package, the operating environment and the appearance requirement.
Case direction one
The same chip becomes a wristband, a ring or a tag depending on how the part is loaded and worn, and each shape leaves a different margin for coverage thickness.
Straight and flat-head band types, with the chip and antenna encapsulated inside the band for access control, membership, events and gyms.
A small part with a tight bend radius: the chip and coil have to be moulded inside a very thin layer, which makes shot weight the hardest thing to control.
Band width, length and colour follow the project, and different colours can be combined on one band.
Used on linen, workwear and rental textiles, the tag meets water, detergent and heat on every wash, so the coverage layer has to resist hydrolysis as well as temperature.
A card chip is sealed into a flexible silicone band so the part can be worn on the wrist while contactless payment still works.
Pet tags stay exposed, taking abrasion and temperature swings; cold-chain labels have to stay readable at low temperature and through frost.
What decides chip overmolding
The chip is rigid; the silicone flows around it under pressure. Whether the part can be made comes down to controlling three things at the same time.
During clamping and filling the chip is pushed in six directions. Our positioning method holds displacement to within 0.5 mm per side, so the chip ends up where the design puts it inside the coverage layer.
Molding temperature is limited by what the chip can take. The target is a fully cured silicone without damage to the internal structure, so the part still works after encapsulation and keeps working through repeated use.
Compound entering the cavity drags the chip with it. Runner and gate position are laid out around the chip and antenna so the fill stays steady and the chip is not pushed off centre or its solder joints damaged.
How these three interact, and what sampling has to prove, is described in silicone overmolding failure: 8 modes and a bonding matrix.
Case direction two
The encapsulation layer on an outdoor LED module sits in UV, rain and thermal cycling for years, which makes it one of the parts that decide how long the screen lasts.
The usual route is potting the LEDs or the module with a resin. The overmolding route covers the module surface directly with precision liquid silicone, forming an elastic light-transmitting layer in place of the resin encapsulation.
For outdoor use, what has to be checked is how the layer behaves under UV and thermal shock, how brightness and viewing angle change after coverage, whether the water and dust path across the module is continuous, and how the module can be reworked later.
| What to confirm | Why it has to be settled before tooling |
|---|---|
| Coverage method and thickness | Liquid silicone flow and cavity structure decide whether the layer is even; thickness drives both light transmission and protection. |
| LED and solder joint protection | A gate placed straight onto a component will push it off or damage the joint while the cavity fills. |
| Outdoor weathering | UV, rain and thermal cycling age the layer; compound and hardness follow the actual climate the product ships into. |
| Water and sealing path | Module frame, connectors and cable exits are where water gets in, so the coverage layer has to continue the seal across them. |
| Rework and repair | How the module comes apart has to be considered at design stage, or a single failed LED scraps the whole board. |
Related directions
Glass protection follows the same idea: wrapping tempered glass in a silicone edge has to absorb a glass thickness tolerance of about 0.03 mm, keep the glass centred on all four sides, and still resist impact and disassembly. Metal inserts and PCBA assemblies are the two parallel main lines, judged by the same logic.
Material and hardness options are set out in material selection, surface effects in surface finishing, tooling and molding routes in molding and tooling, and interface bonding and verification in bonding to other materials.
The metal carries strength and the connection; the silicone covers and seals. Both are joined in one molding cycle, and the assessment centres on insert location and coverage area.
See the capability
Composite molding built around a circuit board for water, dust or impact protection, with gate positions laid out around the components.
See the capabilityCommon questions
Coverage thickness, the dielectric properties of the compound, and how the chip and antenna sit relative to each other all affect reading. At proposal stage we confirm the chip and antenna package first, then fix coverage thickness and position, and verify by actually reading the part during sampling.
This is the main risk in chip overmolding. We confirm what the chip and antenna can take, then set molding temperature and injection and packing parameters so the silicone cures without damaging the internal structure. With runner design controlling the fill force, the encapsulated chip still works and can be used repeatedly.
During clamping and filling the chip sees forces from six directions. Our positioning method holds displacement to within 0.5 mm per side, and runner and gate positions are arranged so the fill does not squeeze the chip, which keeps it where the design puts it inside the coverage layer.
On the sample products shown here, the wristband is marked -20 to 180 degrees C and the laundry tag -50 to 250 degrees C. For a project the operating temperature is confirmed from the actual use case before a compound is chosen.
Four things are checked: how the encapsulation layer holds up under UV and thermal cycling outdoors, how brightness and viewing angle change after coverage, whether the water and dust path across the board is continuous, and how the module can be reworked or repaired later.
Yes. Printing, spray coating, laser marking and colour filling are the usual options for this product type. Colour and artwork are confirmed from the drawing supplied by the customer, and physical samples are checked at sampling.
The page explains the directions we take on and how the decisions are made. A real project needs the chip type or a drawing, the operating environment and the assembly requirement; structure and coverage are assessed first, then tooling and sampling are arranged.
Send the chip type, the operating environment and the appearance requirement. Structure and coverage are confirmed first; tooling and sampling come after that.