A coin cell with welded tabs is a cheap, hermetic, mechanically rigid energy source — perfect for hearing aids, RTC backups, BLE beacons and small wearables. The choice between nickel tabs, copper tabs and through-hole posts is rarely about cost. It is about what the next assembly step looks like.

Nickel tabs (the default)

0.10–0.15 mm pure nickel strip, spot-welded to the cell can on the negative side and the cap on the positive side. Two welds per side, ~6 mm spacing. Pull strength is typically 25–40 N — well above what any reasonable handling stress puts on a coin cell.

  • Pick when: the device is hand-soldered, hot-bar soldered or threaded into a wire harness.
  • Avoid when: downstream assembly uses ultrasonic welding (nickel-to-nickel ultrasonic is unreliable on tabs this thin).
  • Cost: baseline. ~USD 0.02 / cell over a bare cell.

Copper tabs

0.05–0.10 mm copper strip with a thin nickel plating for weldability. Lower resistance than nickel (about 5× lower for the same cross-section), so worth it when the cell sees pulse currents above 1 C.

  • Pick when: peak discharge currents matter (Bluetooth radio bursts in a beacon, DC-DC inrush in a wearable).
  • Avoid when: the device is reflow-soldered. Copper-tab nickel plating can dewet during reflow and cause weld embrittlement.

Through-hole posts (TH posts)

1.0–1.5 mm diameter brass posts laser-welded to the cell faces, designed to drop into PTH holes on a PCB and wave-solder. Surprisingly under-used.

  • Pick when: the device is a small PCB with through-hole assembly (RTC backup on industrial controllers, BLE beacons in 2025-vintage designs).
  • Avoid when: any vibration spec exceeds 5 G — the posts concentrate stress at the weld interface and fatigue.

Specifying tabs without ambiguity

An RFQ that just says "with tabs" is the most common cause of late-stage redesign. Specify all of:

  • Material and thickness (e.g., "0.10 mm pure nickel, no plating").
  • Length and width (drawing preferred; otherwise "12 mm × 6 mm").
  • Orientation (horizontal lay-flat vs. vertical post-out).
  • Polarity marking (we recommend a permanent ink dot on the positive tab).
  • Pull-strength target if downstream assembly is rough (typical: ≥ 20 N).

For medical programs we add a serial number laser-etched on the negative tab so the cell links back to its formation batch.

Welding parameters Zufek uses

For documentation and audits, the parameters are:

  • Spot welder: 100 J capacitor-discharge, 1.0 ms pulse, 0.5 mm tip diameter.
  • Two welds per tab side, 6 mm centre-to-centre.
  • Pull-test 1 in 100 cells to ≥ 25 N. Failures are diverted out of the medical-program lot.