STMicroelectronics EFL1K0AF39

Overview

EFL1K0AF39 from STMicroelectronics is a solid-state rechargeable lithium thin-film microbattery with 1 mAh nominal capacity, 3.9 V nominal voltage, 3.0–4.2 V operating range, 80 Ω internal resistance, and ultra-thin 160 µm profile in a 25.8 mm × 28.8 mm footprint. It serves as embedded backup power for low-power IoT sensors and wearable health monitors requiring stable micro-energy storage.

For engineers reviewing the EFL1K0AF39 datasheet, EFL1K0AF39 pinout, EFL1K0AF39 application, or EFL1K0AF39 equivalent, key selection criteria include its 4000-cycle life at 25 °C, 20% non-recoverable capacity loss over 10 years, pulsed discharge capability up to 15 mA (100 ms on), and strict 0% SOC requirement prior to embedded assembly.

Technical Context

The EFL1K0AF39 uses a LiCoO₂ cathode, LiPON ceramic electrolyte, and metallic lithium anode - enabling all-solid-state construction with no liquid or gel components. Its 80 Ω internal resistance and 15 mA pulsed discharge current support intermittent wake-up loads in energy-harvesting nodes.

Operating temperature spans −20 °C to +60 °C, but cycle life degrades above 60 °C; self-discharge is 3% per year (recoverable) and 20% over 10 years (non-recoverable). Charging requires a regulated 4.2 V ±0.05 V source, with >90% capacity restored when charge current falls below 0.1 mA.

Key Specifications

Pinout & Package

The EFL1K0AF39 is a two-terminal solid-state microbattery with nickel-strip termination (F suffix) and no active control pins. Its EnFilm™ package is a flexible, metallized laminate with exposed anode/cathode pads on opposite edges of the 25.8 mm × 28.8 mm substrate.

Key Features

Applications

Availability

EFL1K0AF39 is available at Aetrix Electronics and suitable for wireless sensor nodes, smart cards, wearable health monitors, and RFID tags with sensing requiring stable component supply across high-mix, low-volume production runs.

Supply support for EFL1K0AF39 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power management ICs, MEMS, and advanced discrete devices for industrial, automotive, and consumer markets.

The EnFilm™ microbattery product line targets ultra-low-power, space-constrained applications including energy harvesting, implant-adjacent wearables, and secure identification systems where traditional coin cells are mechanically or chemically unsuitable.

FAQ

What is the maximum continuous discharge current for EFL1K0AF39?

The maximum continuous discharge current is 5 mA at 25 °C, as specified in Table 2 of the datasheet. Exceeding this value risks accelerated capacity degradation and thermal stress due to its 80 Ω internal resistance. For higher peak loads, the device supports 15 mA pulsed discharge (100 ms on, 900 ms off) down to 2 V cutoff.

Can EFL1K0AF39 be soldered directly onto a PCB?

No - direct reflow soldering is prohibited. ST's TN1249 technical note mandates adhesive mounting only, with strict limits on pressure (<2.6 MPa) and temperature (<125 °C for ≤3 minutes) during embedded assembly. The battery must be at 0% state of charge before lamination to prevent irreversible internal resistance increase.

What charging voltage and current profile is required?

A constant voltage of 4.2 V ±0.05 V is required; current limiting is optional. Charging completes when current drops below 0.1 mA, restoring >90% of capacity. ST recommends using a dedicated Li-ion charger IC with voltage regulation tolerance tighter than ±1% to avoid overvoltage-induced cathode degradation.

Is EFL1K0AF39 suitable for implantable medical devices?

No - ST explicitly prohibits use in implantable medical devices (defined as devices placed under the skin) per Section 2 of the datasheet. It is approved for external wearable health devices (e.g., hearing aids, ECG patches) but not for surgical or intracorporeal applications due to safety certification limitations.