Wet Inlay
An NFC inlay with an adhesive backing ready for application to surfaces. The 'wet' refers to the uncured adhesive layer. Wet inlays are the most common format for NFC sticker production.
What Is a Wet Inlay?
A wet inlaywet inlayAdhesive-backed NFC inlay ready for surface applicationView full → is an NFC inlay that includes an adhesive backing, making it ready for direct application to surfaces. The term "wet" refers to the uncured pressure-sensitive adhesive layer that is covered by a release liner until application. Wet inlays are the most common intermediate product in NFC sticker and label manufacturing, serving as the bridge between raw NFC components and finished consumer products.
Wet Inlay Construction
A typical wet inlay consists of five layers:
| Layer | Material | Function |
|---|---|---|
| Top substrate | PET film (12-50 micrometers) | Protects the IC and antenna |
| IC + antenna | NFC chip bonded to metal antenna | Functional NFC circuit |
| Bottom substrate | PET or paper | Carrier and mechanical support |
| Adhesive | Pressure-sensitive acrylic or rubber | Surface bondingbondingElectrical connection process between IC die and antennaView full → |
| Release liner | Silicone-coated paper or film | Protects adhesive until application |
The total thickness of a wet inlay is typically 100-200 micrometers (excluding the release liner), making it thin enough to integrate into labels, stickers, and packaging without significant bulk.
Wet Inlay Sizes
Wet inlays are available in standardized sizes that correspond to common antenna designs:
| Format | Dimensions | Typical Chip | Use Case |
|---|---|---|---|
| Round 13 mm | 13 mm diameter | NTAG 210 | Micro tags, jewelry |
| Round 25 mm | 25 mm diameter | NTAG 213 | Standard stickers |
| Round 38 mm | 38 mm diameter | NTAG 216 | Extended range stickers |
| Rectangle | 45 x 76 mm | Various | Labels, logistics |
| ISO card | 86 x 54 mm | Various | Card overlays |
Larger antenna areas generally provide longer read range due to stronger coupling with the reader's RF field.
Wet Inlay vs Dry Inlay
The key distinction between wet and dry inlays is the adhesive layer:
Wet inlays include adhesive and are designed for surface application. They are used for stickers, labels, and retrofitting NFC capability to existing objects. The adhesive can be customized for different surfaces: permanent for asset tags, removable for temporary labels, or high-tack for rough surfaces.
Dry inlays lack adhesive and are designed for integration into card bodies. They are laminated between PVC, PET-G, or polycarbonate sheets during the card manufacturing process. Dry inlays must withstand the heat and pressure of card lamination.
Quality Control
Wet inlay manufacturers test each unit at multiple stages:
- Pre-bonding antenna test. Verifies antenna resistance and inductance before IC attachment.
- Post-bonding electrical test. Confirms the die is properly connected by reading the UID and verifying EEPROM access.
- Encoding verification. After programming, each tag is read back to verify the NDEF message was written correctly.
- RF performance test. Samples are tested for read range and load modulation amplitude.
Application Considerations
When applying wet inlays, surface preparation is critical. Clean, smooth, flat surfaces provide the best adhesion. Curved surfaces with a radius below 25 mm may cause antenna deformation, potentially affecting performance. Metal surfaces require on-metal tags rather than standard wet inlays, which will fail due to eddy current detuning.
Environmental durability depends on the adhesive and substrate selection. Outdoor applications require UV-resistant substrates and weatherproof adhesives. Industrial applications may need chemical-resistant materials. Manufacturers offer specialized wet inlay configurations for challenging environments.
Related Terms
Related Guides
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The NFC glossary is a comprehensive reference of technical terms, acronyms, and concepts used in Near Field Communication technology. It is designed for developers, product managers, and engineers who work with NFC and need clear definitions of terms like NDEF, APDU, anti-collision, and ISO 14443.
Each glossary term is cross-referenced with related NFC chips, standards, and other terms. For example, the term 'AES-128' links to chips that support AES encryption (NTAG 424 DNA, DESFire EV2/EV3), and the term 'ISO 14443' links to all chips compliant with that standard.
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