Shrinking IoT with Integrated Antennas

The Internet of Things (IoT) vision — billions of connected sensors, actuators, and devices deployed everywhere from factory floors to agricultural fields — demands wireless modules that are small enough, cheap enough, and power-efficient enough for ubiquitous deployment. Traditional wireless module architectures with discrete antennas connected to separate RF transceiver ICs are too large for many IoT applications. Antenna-in-Package (AiP) technology solves this by integrating the antenna directly into the semiconductor package, creating complete wireless modules smaller than a fingertip.

At INDNIX Technology, our packaging division has developed AiP solutions for multiple IoT frequency bands, including Bluetooth Low Energy (BLE) at 2.4 GHz, Sub-GHz LPWAN (LoRa/Sigfox) at 868/915 MHz, and mmWave radar at 60 GHz.

AiP Architecture Options

Antenna on Package Substrate

The most straightforward AiP approach uses the multi-layer organic substrate of a standard BGA or QFN package to implement the antenna. Copper traces on the top layer or within internal layers form the antenna elements, while the lower layers carry the RF transceiver die interconnects and power distribution.

For 2.4 GHz BLE applications, a meandered inverted-F antenna (IFA) implemented on a 10mm by 10mm package substrate achieves antenna efficiency of 60 to 75 percent — sufficient for communication ranges of 50 to 100 meters in typical indoor environments.

Antenna on Mold Compound

An alternative approach patterns antenna elements on the surface of the epoxy mold compound that encapsulates the package. This method utilizes laser direct structuring (LDS) technology, where a laser activates a metallic catalyst within the mold compound surface, followed by electroless plating to build up the antenna conductor.

LDS antennas offer design flexibility because three-dimensional antenna shapes (helical, conformal) can be created on the curved or angled surfaces of the mold compound. This is particularly valuable for IoT devices with irregular form factors.

Antenna on Redistributed Fan-Out Wafer

Fan-out wafer-level packaging (FOWLP) provides the thinnest possible AiP implementation. Antenna elements are formed in the redistribution layers (RDL) using standard copper plating processes. The die and antenna coexist side-by-side in the fan-out area, achieving total package heights below 0.5 millimeters.

This approach is ideal for medical implant and wearable applications where every millimeter of height reduction matters.

Design Considerations

Antenna-Die Interaction

When an antenna is placed within millimeters of an active semiconductor die, electromagnetic coupling between the antenna and the die's bond wires, ground plane, and active circuits can significantly alter antenna impedance, radiation pattern, and efficiency. Our AiP design methodology uses full-wave 3D electromagnetic simulation (HFSS or CST) of the complete package including die, bond wires, substrate, and mold compound to predict and optimize antenna performance.

Ground Plane Effects

The ground plane area available for the antenna is a primary determinant of antenna efficiency and bandwidth. For electrically small antennas (dimensions much less than the wavelength), the ground plane contributes significantly to radiation. A 2.4 GHz AiP on a 7mm by 7mm package — only 0.056 wavelengths on a side — has fundamentally limited bandwidth and efficiency compared to a larger PCB-mounted antenna.

We design our AiP ground planes to maximize the effective radiating aperture by using partial ground plane cutouts, parasitic ground extensions that utilize the host PCB, and ground clearance recommendations that we communicate to customers as part of our application guidelines.

Frequency Band Coverage

Many IoT applications require multi-band operation — for example, simultaneous BLE (2.4 GHz) and Sub-GHz LoRa (868 MHz) connectivity. Dual-band AiP designs use either two separate antenna elements or a single wideband/multiband antenna with appropriate matching networks. Our dual-band AiP solutions achieve better than minus 6 dB return loss in both bands simultaneously.

Regulatory Compliance

Integrated antennas must meet the same regulatory requirements (FCC, CE, TELEC) as external antennas. Because the antenna is inside the package and its performance is affected by the package materials, every AiP design must undergo regulatory pre-compliance testing to verify compliance with emission limits, SAR limits (for body-worn devices), and spurious emission requirements.

We maintain an in-house anechoic chamber for radiation pattern measurement and pre-compliance testing, enabling rapid design iterations without the delays of external test house scheduling.

Performance Benchmarks

Our AiP solutions achieve the following performance metrics:

Parameter	2.4 GHz BLE AiP	868 MHz LoRa AiP	60 GHz Radar AiP
Package Size	7x7x1.2 mm	12x12x1.5 mm	6x6x0.8 mm
Antenna Efficiency	65%	45%	80%
Peak Gain	1.5 dBi	-2.0 dBi	8.0 dBi (4x4 array)
Bandwidth	100 MHz	30 MHz	7 GHz
Range (typical indoor)	80 m	2 km	15 m

Material Considerations

The dielectric properties of the package materials critically affect AiP performance. Standard epoxy mold compounds have dielectric constants of 3.5 to 4.5 and loss tangents of 0.01 to 0.02 at microwave frequencies. For mmWave AiP at 60 GHz, these losses become significant. We have qualified low-loss mold compounds with loss tangents below 0.005, specifically optimized for mmWave AiP applications.

Similarly, the package substrate dielectric must be selected for low loss and stable dielectric constant over temperature. Our preferred substrate materials for AiP applications include Rogers RO4350B (loss tangent 0.004) for high-performance designs and standard BT-resin laminates (loss tangent 0.015) for cost-sensitive consumer IoT.

Manufacturing and Test

Antenna Measurement

Every AiP unit undergoes wireless performance verification. For volume production, we use over-the-air (OTA) testing in a miniature anechoic test fixture that measures radiated power and receiver sensitivity in a controlled RF environment. Test time is approximately 5 seconds per unit, enabling 100 percent production testing at high throughput.

Reliability Qualification

AiP packages undergo the same reliability qualification as standard IC packages, with additional antenna-specific testing:

• Moisture sensitivity level (MSL) testing per J-STD-020 to verify that reflow soldering does not degrade antenna performance
• Temperature cycling to verify that CTE mismatch between antenna conductors and substrate does not cause antenna impedance drift
• Corrosion testing for exposed antenna elements using mixed flowing gas (MFG) and salt spray environments

Conclusion

Antenna-in-Package technology is an essential enabler for the compact, low-cost wireless modules that the IoT market demands. By integrating antennas directly into IC packages, AiP eliminates external antenna components, reduces module size by 30 to 60 percent, and simplifies customer integration. At INDNIX Technology, our AiP design expertise and packaging capabilities span multiple IoT frequency bands, delivering complete wireless solutions that accelerate our customers' time to market.