SMT reflow oven thermal profile — every PCB has its own window, not the one of the last board in.

The problem

The oven does not make PCBs — it makes profiles. And every PCB asks for its own.

In an SMT reflow oven, the “golden” recipe the process engineer validated with the profiling card is the recipe of the reference panel. But production puts a different panel in every minute: different SKU, different thermal mass, different copper, different BGAs. And the oven reacts to the real loading — a large panel behind a gap cools the zones down and the next one comes out with a short soak. The IPC window is met for most of them and broken for the panel that happened to be in the odd spot — and the symptom shows up at AOI or, worse, as a field failure.

1. What goes into the oven — the panel: SKU, thermal mass, list of sensitive components (large BGAs, 0201s, connectors). Data from the MES.
2. What happens inside the oven — zone temperatures, conveyor speed, real loading (gaps vs back-to-back panels). Data from the oven PLC, nearly all of it, nearly always.
3. What comes out of the oven — the solder joint, the BGA, the fine-pitch component. And AOI verification catches defects, but it does not catch the thermal cause: only the effect.

The process engineer knows this — but one card profile per shift does not protect panel 47, the one that went in behind five gaps on a Friday at 6pm. What is critical is board-by-board drift, the kind you only see once AOI is already pulling boards with tombstoning.

How it fits the IRIS system

iLEAN does not replace the card profiler — it seals the cracks between the reference and real production.

The reflow problem is not a lack of calibration: it is that the validated reference recipe, the real per-panel oven data, the SKU's list of sensitive components and the AOI result live on islands and nobody cross-checks the four of them board by board. iLEAN acts as the filler that closes those gaps, without asking you to change the oven or the way you calibrate with the profiling card.

Edge sees zone temperature every second. Connect reads panel thermal mass from the MES and the AOI findings. The agent infers the real thermal profile of every PCB and, if it falls outside the IPC window, holds the panel before the oven or routes it to conscious rework. The engineer signs off — never the other way round.

The three iLEAN pieces applied to the SMT reflow thermal profile:

• Edge — terminal integrating the zone thermocouples and a pass camera over the oven. It reads temperature, conveyor speed and real loading every second, and triggers a traffic light or a panel hold when the combination points outside the IPC window. It works with no network. If the MES goes down, Edge keeps reading and holding with the light on the panel.
• Connect — captures the panel's thermal mass and the SKU's list of sensitive components (from the MES, or from the ECAD if that is where it lives), the AOI findings per panel and, from outside, the paste supplier's notice when a new lot arrives. And it captures the process engineer's knowledge — the mental rule about which SKU is the first to drift when the oven cools after a gap.
• Agent — cross-checks zone temperature, thermal mass, oven loading and the IPC window of the most sensitive component. If the combination points outside the window, it holds the panel or routes it to conscious rework before AOI catches it as a defect. The engineer validates and signs off.

See the full IRIS architecture →

Before and after

Profiler per shift vs. board-by-board profile with iLEAN

Aspect	Card recipe + downstream AOI	With iLEAN Edge + Connect + Agent
Profile verification	One card per shift, on a reference panel	Inferred profile for every PCB
Reaction to drift	When AOI pulls a board with tombstoning	Hold or reroute before the oven
SKU changeover	“Golden” recipe adjustment, conveyor at fixed speed	Speed and zones suggested from the SKU's real mass
Oven loading	No compensation	Compensated for real loading (gaps vs back-to-back)
Per-panel traceability	Recipe + AOI result	Per-panel record with inferred thermal profile and IPC window
Operation with no network	n/a	Edge keeps reading and holding with the panel light

Impact estimate

Impact estimate for your plant — to be validated with your numbers.

The block below is an estimate to be validated with the specific data of your line. We put it forward so the committee has an order of magnitude; we refine it during the diagnostic.

• SMT line with a multi-zone reflow oven, multi-SKU EMS with large BGAs and 0201 components, AOI at the exit.
• Edge pilot on the oven (integration with zone thermocouples + loading camera + MES reading + hold actuator). First value expected within a few weeks.
• Reduction of rework from tombstoning and cold joints ≥ 30 % on the recurring recipe-changeover incident (the other failure modes remain a matter of design and paste).
• Indicative payback between 4 and 9 months, depending on the frequency of rework documented in recent lots and the average cost of BGA rework / a field failure found late.
• The hard lever: a single BGA panel recovered on the line pays for a good part of the pilot.

And the CAIO's reasonable doubt

“What if the AI decides to hold a panel that was going to come out fine?” — hallucination is a problem of free generation, not of anchored tasks. In tasks where the AI limits itself to inferring the real thermal profile of a panel from the oven thermocouples and comparing it with the IPC window of the most sensitive component, the best models brought the error below 1.5 % ^[1]. And even so, what is critical is not decided alone: iLEAN holds and the process engineer signs off. The three safety rings are there precisely for this.

^[1] OpenAI paper “Why Language Models Hallucinate”, 2025 — on the reliability of AI in anchored tasks.