SEA-B-0500J Datasheet Overview and Application Guide
SEA-B-0500JThe SEA-B-0500J is a 125kHz SMD small emitter antenna from Premo S.A.U., packaged in a 50.80mm x 10.60mm x 6.80mm ferrite-core body for low-frequency RFID tag and reader coupling. In the RFID Antennas category, this component is specified for proximity identification and immobilizer systems where a precise 125kHz resonance bandwidth must be maintained. Counterfeit and reworked units frequently exhibit shifted resonance, incorrect DC resistance, or missing ferrite core integrity, causing field strength degradation and read-range failure. This article provides a verification workflow for engineers and procurement professionals handling SEA-B-0500J lots.
Visual and Marking Inspection: Laser Etch vs. Ink Print and Lot Date Code Decoding
Authentic SEA-B-0500J units from Premo carry a permanent laser-etched marking on the top surface. The marking consists of the part number, a two-digit manufacturing year (YY), and a two-digit work week (WW) — for example, marking "0500J 2425" indicates production during week 25 of 2024. Counterfeit parts often substitute ink pad printing or low-contrast stamping that can be scratched off with an isopropyl alcohol swab. Inspect the etching depth: genuine laser marks have a shallow, consistent ablation with no ink residue. Re-marked parts frequently show a secondary laser pass under microscopy, visible as a double-strike halo on the ferrite surface. Verify that the YYWW format matches Premo's date code conventions; any marking using a four-digit year format is suspect. For high-volume procurement, request photographs of actual reel or tray marking for cross-reference against the packing list.
Electrical Parameter Measurement: Inductance, Q-Factor, and Self-Resonant Frequency
The SEA-B-0500J is a resonant antenna structure. Using an LCR meter set to 125kHz, measure inductance between the two terminals. The typical inductance value is provided in the component datasheet; any deviation exceeding ±5% indicates core damage or incorrect winding turns. A network analyzer (VNA) sweeping from 100kHz to 1MHz will reveal the self-resonant frequency (SRF). If the SRF falls below 300kHz, the antenna's parasitic capacitance is too high, and the component will lose efficiency in a 125kHz system. Perform a Q-factor measurement using the 3dB bandwidth method: Q = f0 / Δf. Low Q values (below 20) suggest eddy-current losses in a fractured ferrite core or improper soldering of the termination pads. The table below summarizes the critical parameters that your supplier must confirm before shipment.
| Parameter | Value | Engineering Meaning |
|---|---|---|
| Center Frequency | 125 kHz | This parameter establishes the antenna's resonance for LF RFID. A 1% shift degrades read range by approximately 15%. |
| Inductance (L) | Consult datasheet | Inductance determines the tuning capacitor value needed for the resonant tank. Typical LF SMD antennas range from 200 μH to 800 μH. |
| Q Factor (Quality Factor) | Consult datasheet | High Q (30–60) provides narrow bandwidth and strong field strength; low Q widens bandwidth but reduces read sensitivity. |
| Self-Resonant Frequency (SRF) | > 2 × operating frequency | SRF well above 125 kHz ensures the antenna behaves inductively at the target band. Values below 250 kHz indicate excessive parasitic capacitance. |
| DC Resistance (DCR) | Consult datasheet | DCR contributes to ohmic loss. For high-efficiency coupling, DCR should be under 12 Ω for this form factor. |
| Dimensions (L × W × H) | 50.80 mm × 10.60 mm × 6.80 mm | Mechanical compliance with pick-and-place nozzles and housing cavities. Height deviations over 0.3 mm cause reflow tombstoning. |
| RoHS Status | Compliant | This is a regulatory requirement. Counterfeit parts may use lead-based solder at the termination, risking non-compliance. |
Of the parameters listed, the Q-factor and SRF are the most revealing of counterfeit or damaged units. A blank SEA-B-0500J with a cracked ferrite core may still measure correct DC resistance but will show a Q drop of 30–50% due to magnetic flux leakage. Similarly, a part that has been re-terminated with a different solder alloy will exhibit shifted self-resonance because of altered terminal capacitance. Always compare SRF against the typical range published in the latest SEA-B-0500J datasheet; do not rely solely on inductance. For evaluation board testing, a 1 nF to 10 nF parallel capacitor will form the resonant tank — measure the peak voltage across the coil using an oscilloscope probe (10×, high-impedance) to confirm coupling efficiency.
X-Ray Inspection and Acoustic Microscopy for High-Value Batches
For applications where the antenna is embedded in sealed automotive key fobs or medical implant readers, an X-ray inspection of the internal winding and ferrite structure is warranted. A genuine SEA-B-0500J uses a single-layer ferrite bar with a tightly wound copper coil. X-ray images should show uniform winding pitch with no gaps or overlapping turns. Reworked components may exhibit secondary winding attempts with exposed wire at the ferrite edges or solder ball debris from re-termination. If destructive analysis is acceptable for a sample, decapsulation using hot nitric acid will reveal the number of turns and wire gauge — cross-check these against the manufacturer's internal specification. Acoustic microscopy (SAM) can detect delamination between the ferrite and the epoxy overmold; delaminated units will fail under thermal cycling.
Packaging, Certificate of Authenticity, and AQL Sampling Plan
Every reel or tray of SEA-B-0500J from Premo ships with a packing slip that includes a job number, date code range, and quantity. The component tape-and-reel packaging should be sealed with a moisture-barrier bag; damaged bags indicate environmental exposure that can oxidize terminations. Request a Certificate of Conformance (CoC) from your distributor that explicitly lists the measured inductance and Q values per batch. For procurement, adopt a general inspection level of AQL 1.0% for critical defects (incorrect marking, cracked body, open circuit) and AQL 2.5% for minor defects (tarnished terminations, slight dimensional variation). A sample size of 200 pieces from a 10,000-unit lot is sufficient to detect a defect rate above 1% with 95% confidence. Reject any lot where more than three critical defects appear in first-round sampling — this indicates potential batch-level counterfeiting or mishandling.
Frequently Asked Questions About SEA-B-0500J
What is the typical application circuit for the SEA-B-0500J?
The SEA-B-0500J is designed as a resonant emitter in 125kHz RFID systems. A typical circuit places the antenna in parallel with a tuning capacitor selected to achieve resonance at 125kHz. The capacitor value is calculated using the formula C = 1 / (4π2 f2 L). An optional series resistor can dampen the Q for wider bandwidth if required.
How can I verify the SEA-B-0500J resonant frequency without a network analyzer?
Connect the antenna in series with a 1kΩ resistor to a signal generator output. Sweep the frequency from 100kHz to 150kHz while monitoring the voltage across the antenna with an oscilloscope. The resonant frequency is where the voltage peak occurs. Compare the measured peak to the value in the manufacturer datasheet.
Does the SEA-B-0500J require a specific PCB footprint for optimal performance?
Yes. The recommended landing pattern is provided in the Premo design guide. The antenna's performance is sensitive to copper ground planes within 5mm of its body — keep ground pours away to avoid eddy-current losses. Use a 50.8mm × 10.6mm keep-out zone on all copper layers directly under the component.
Procurement workflow summary: Confirm supplier CoC with measured inductance and Q values. Inspect date code and laser marking on 200-unit sample. Perform LCR measurement (125kHz, 1V) on 20 units from the sample — reject lot if more than one unit deviates ±5% from datasheet inductance. For automotive or medical lots, add X-ray inspection of 10 units to verify winding integrity. Cross-check the part marking against Premo's published format (YYWW). Store in ESD-safe, moisture-sealed packaging until placement. Use the SEA-B-0500J cross-reference list (KGEAWT801904B0500J, TP0602CAP-0238J, SDTR1103-0720J) only after verifying form-fit-function compatibility with your PCB keep-out area. RF antenna performance is sensitive to layout and stray capacitance — always protoype before full production ramp.
