Reflow Oven Profile and Solder Paste Log
A reflow profile that drifts slowly is a classic source of latent solder defects. This log keeps peak temperature and time above liquidus next to the paste lot, so margins are visible and a process change can be traced.
| Run date | Assembly | Paste alloy | Paste lot | Peak temp (C) | Peak limit (max) (C) | Peak margin (C) | Time above liquidus (s) | TAL limit (max) (s) | TAL margin (s) | Oven and recipe | |
|---|---|---|---|---|---|---|---|---|---|---|---|
6 | 22 | ||||||||||
3 | 8 | ||||||||||
7 | 20 | ||||||||||
1 | 1 |
Limits must come from the solder paste data sheet, the most heat sensitive component on the board and your process window. A negative margin means the run is outside the limit and needs investigation. Liquidus is about 217 C for SAC305 and about 183 C for Sn63Pb37.
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Optional review of combining profiler data with ERP records.
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How to use the log
After each profile verification or oven recipe change, add a row with the assembly, paste alloy and lot, the measured peak, time above liquidus and the limits you must stay within. The margin columns calculate automatically. Watch the smallest margin in the totals, since a shrinking margin warns you before a failure. Export to Excel for the SPC chart or PDF for the quality binder.
Method and limits
Profile guidance comes from the paste data sheet, J-STD-020 for the component package limits and your own thermocouple measurements on a representative board. Time above liquidus is the time the solder sits above its melting point, around 217 C for SAC305 and 183 C for tin-lead. Too little leads to cold or incomplete joints, too much can build brittle intermetallic layers and stress components.
Common mistakes
Profiling an empty board instead of a loaded one, using one thermocouple location, and skipping verification after a conveyor speed change are frequent errors. Another is forgetting that tin-lead and lead-free assemblies need different limits when a mixed line runs both. Record the paste lot and its time out of refrigeration elsewhere in your paste control log, and compare profiles by recipe, not by date.
Frequently Asked Questions
What is time above liquidus?
It is the number of seconds that the solder joint temperature stays above the alloy's melting point during reflow. Paste data sheets give a recommended range, often 45 to 90 seconds for lead-free alloys.
How often should profiles be verified?
Frequency is set by your process control plan. Many shops verify at recipe setup, after maintenance or oven changes, and at fixed intervals such as daily or weekly.
What peak temperature should I use?
It must be high enough to form proper joints and below the limit of the most sensitive component on the board. Use the paste data sheet and component J-STD-020 limits to set the window.
Does this cover wave soldering?
No, it is built for reflow. Wave and selective soldering need different parameters such as preheat, contact time and pot temperature.
If oven data lives in a profiler or MES, Netray can help pull it into a single quality view alongside ERP work orders.
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