Reflow Soldering: Profiles for China PCB Assembly
2 resources tagged with "Reflow"
Reflow soldering is the stage where surface-mount parts get permanently bonded to the board, and the thermal profile decides whether joints are reliable or cracked. Most China PCBA lines run lead-free SAC305 with a peak around 245–250°C, versus leaded Sn63Pb37 peaking near 215–220°C; the ramp rates, soak, and time-above-liquidus all follow profiles validated against J-STD-020 moisture sensitivity limits.
When you audit an assembly factory, ask to see the actual reflow profile graph and oven recipe for your board, plus how they handle MSD (moisture-sensitive device) bake-out — a wrong profile causes tombstoning, voids, or popcorning under BGAs. The common pitfall is assuming any line that does SMT runs a controlled profile; cheap shops often reuse one generic recipe for every board.
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FAQ
What is the difference between lead-free and leaded reflow profiles?
Lead-free SAC305 peaks around 245–250°C; leaded Sn63Pb37 peaks near 215–220°C. The higher lead-free temperature stresses components and demands tighter MSD control and profile validation.
What goes wrong with a bad reflow profile?
Too fast a ramp causes tombstoning and solder balling; insufficient peak gives cold, weak joints; excess heat or trapped moisture causes BGA voids and popcorning. Ask the factory for the measured profile, not just the setpoint.
How do I verify reflow quality before mass production?
Request AOI results, X-ray of any BGA/QFN joints, and a sample profile graph during the DVT or first-article build. A quick on-site inspection at first production confirms the line is running the agreed recipe.
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