A reflow-mountable lithium cell is rare, useful, and very easy to abuse. ML2032 and ML2430 survive standard lead-free reflow if — and only if — your profile is built around their physics, not the JEDEC J-STD-020 default. Here is the profile we recommend after qualifying ML cells across roughly 80 customer SMD programs.

What the cell can take

Both ML2032 and ML2430 are rated for 260 °C peak reflow with the constraints below. The hermetic stainless-steel can is what makes this physically possible — a pouch cell would never survive. Three thermal limits matter:

  • Peak temperature ≤ 260 °C, with no more than 30 seconds above 250 °C.
  • Time above 217 °C ≤ 90 seconds, ideally 60–80 s.
  • Total time above 200 °C ≤ 150 seconds.

The standard J-STD-020 envelope allows up to 150 s above 217 °C. ML can take a "soft" J-STD-020 profile but will lose noticeable capacity if you run the upper-bound profile twice (e.g. on a double-sided board). Always assume one reflow pass per ML cell unless your profile sits well inside the envelope.

The profile we recommend

From cold board to fully-soldered, four phases:

  1. Preheat 25 → 150 °C at ≤ 3 °C/s, total 80–100 s. The cell internals equalise; nothing dramatic.
  2. Soak 150 → 200 °C over 60–80 s. Flux activates. Cell temperature lags board by 4–8 °C; that's fine.
  3. Reflow 200 → 250 °C over 30–40 s. Stay above 217 °C for 70–80 s. Peak the cell can just reach 250 °C; do not push higher.
  4. Cooldown 250 → 100 °C at 3–5 °C/s. Forced air OK; do not water-quench.

Total time above 200 °C: ~120 s. Peak: 250–255 °C. This sits in the 75th percentile of customer profiles that pass our 12-month aging test (≤ 8% capacity loss after one reflow pass).

The mistakes we see most often

Profile from a JEDEC reference board. JEDEC reference profiles assume a thin SMD package; an ML cell has 2–3 mm of can mass that lags. Always thermocouple the cell can, not the PCB.

Two-pass reflow on the same cell. If the board has components on both sides, the ML cell must go on the side that reflows first, then be protected with foam tape during the second pass. Two passes through a full profile typically halves cycle life.

Hand-touch-up after reflow. Soldering iron temps (350–400 °C) damage the crimp seal. If a tab needs rework, use a hot-air rework station with the cell shielded.

Pre-conditioning before SMT

Store ML cells at 20 °C ± 5 °C and < 60% RH. If shipped through humid logistics, bake the cells at 60 °C for 24 h before placement. Moisture in the can during reflow is the most common failure mode (visible as bulging or split crimp).

Test plan to qualify your specific profile

  1. Thermocouple 5 sample cells inside the oven at the placement location.
  2. Run 30 cells through one pass; measure OCV and IR before vs. after.
  3. Cycle 10 of those 30 to 200 cycles at 0.2C; compare to a non-reflowed control.
  4. Acceptance: < 5% delta IR, < 3% delta capacity at C200.

For medical and automotive programs we do this qualification with a serial-numbered batch and keep the data for 10 years per ISO 13485 retention.