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A reflow profile is a measured product history

A lead-free reflow profile describes temperature over time at a defined location on an assembly. It is not the list of temperatures entered into the oven zones. The board, components, copper distribution, supports and loading influence how the product responds to the oven. Releasing a recipe therefore requires measured assembly temperatures and applicable material and component limits, not merely a familiar conveyor speed and a visually plausible curve.

The goal is a usable process window across the relevant locations. A demanding joint must receive sufficient exposure for the selected paste, while a sensitive package must remain within its allowed conditions. The hottest and coldest useful measurement locations may be different. One thermocouple cannot establish that every location on a complex assembly satisfies all requirements, and a higher peak is not automatically a better soldering process.

This guide separates four things: supplier guidance, component limits, recorded thermal traces and production settings. The worksheet helps calculate features of one recorded trace against limits entered by the user. It does not generate an approved oven recipe, prescribe a universal soak or certify a board. Keep the complete measurement report and process-owner review with the manufacturing release.

Know which temperature and which limit you are comparing

The distinguish reflow and wave guidance and provide product-oriented profiling resources. Their role is to support development of a process, not to eliminate measurement on the actual assembly. Choose guidance for the exact material and record the revision. If different documents appear inconsistent, resolve the conflict before treating their values as a valid combined window.

Select measurement locations that answer the risk

Prepare a board map before attaching sensors. Identify large thermal masses, plane-connected regions, small exposed components, shielded locations and the components with restrictive temperature limits. Include the parts of the assembly that make this product different from an easier board. The map should state what each channel represents and why that location was selected, so another engineer can interpret the trace without guessing.

Sensor attachment is part of the measurement method. A sensor that moves, loses contact or measures an unintended surface can produce a credible-looking trace that answers the wrong question. Follow an appropriate profiling procedure and document the attachment method, instrument configuration and relevant calibration status. Inspect the instrumented assembly before and after the run, especially when the measurement location is difficult to access.

Record the actual process configuration: board revision, populated sides, fixture, direction, conveyor setting, loading and atmosphere where relevant. If a profile board differs from the production assembly, identify those differences and their significance. A report without configuration information cannot support a reliable comparison after the tooling, component population or oven loading changes.

Build the permitted window before judging the trace

Collect the exact paste documentation and the applicable component assembly limits. Also review the board construction, sensitive materials and any prior thermal exposures. Do not infer component capability from package appearance or from the fact that a different part survived a similar process. Where a limit applies to a particular measurement location or duration, preserve that definition alongside the number.

Separate peak temperature, heating rate, time above liquidus, time in a specified band and cooling behavior. A trace can satisfy one and fail another. The term lead-free does not assign values to all of these fields. A recipe based on a different alloy or flux system needs an explicit review, even when its overall curve shape looks familiar. Missing requirements should remain missing rather than being replaced with a generic online value.

The describe package-handling and soldering considerations within TI's component context. Use the documentation for the actual part and its package. Qualification limits and assembly process development are related but different tasks; a package classification profile should not be copied blindly as the board's preferred production recipe.

What the online trace reviewer calculates

Enter two to two hundred pairs of elapsed seconds and degrees Celsius, one pair per line. Timestamps must increase strictly. The tool reports the largest recorded temperature, the interpolated time strictly above the entered liquidus, the largest sample-to-sample heating and cooling rates, and the largest interval between samples. These calculations are useful for checking the arithmetic in a small trace excerpt.

Time above liquidus is found by adding the portions of each straight line segment that lie above the entered threshold. For an illustrative triangle with readings of 200 degrees at zero seconds, 240 at ten seconds and 200 at twenty seconds, a 220-degree threshold is crossed at five and fifteen seconds. The calculated duration is ten seconds. These values illustrate interpolation; they are not a recommended soldering profile.

The tool does not recover a temperature spike between samples. Coarse data can miss a peak or underestimate a rapid change. A segment exactly on the threshold contributes zero time strictly above it. A trace that begins or ends at or above liquidus is flagged because it may omit part of the interval. Preserve the original high-resolution recording and use the worksheet only within its stated linear-interpolation scope.

Compare a measured channel with supplied limits

Enter the liquidus and the approved peak, duration and sampled heating-rate limits from the applicable documents. Also enter the component ceiling relevant to the measurement location. The displayed example has illustrative values so the behavior can be explored, but project mode starts blank. A comparison without flagged items means only that the entered arithmetic did not exceed these selected criteria; it is not an assembly approval.

The plot joins the supplied points and shows the entered liquidus. It updates when you calculate, with no automatic playback or background simulation. The downloaded brief includes all supplied pairs and limits. Changes invalidate the old export. The tool neither uploads a profile file nor transfers the trace to Contact automatically; attach the report manually if you want the process team to review it.

Investigate the conflict rather than chasing one target

If the cold joint needs more exposure but a nearby component is already near its ceiling, increasing the entire oven temperature may not solve the problem. Review heat distribution, fixture influence, loading, material selection and the product constraints with the process owner. The appropriate response may require changes beyond one zone setting. Keep each trial connected to the particular conflict it is intended to address.

A paste window that extends beyond a component ceiling is not necessarily unusable throughout, but its overlap must be evaluated. The tool flags that situation rather than silently treating the paste maximum as permission to heat every device to that value. Other time and rate limits may further restrict the usable window. The worksheet does not evaluate their complete intersection or account for every channel automatically.

After a process change, inspect the relevant final joints and product evidence. A curve alone cannot prove acceptable wetting, absence of hidden defects or functional reliability. Likewise, a visually acceptable joint does not establish that all components remained within their handling limits. Thermal measurements and inspection address complementary questions and should remain linked in the trial report.

Control the conditions that make the recipe repeatable

Treat the approved recipe as a revision-controlled manufacturing input. Preserve the board, material, sensor map and machine configuration used to establish it. Changes to population, copper distribution, board thickness, fixture or conveyor loading may alter the thermal response. Define which changes require review or re-profiling rather than relying on an operator to infer equivalence from the product name.

For double-sided assemblies, maintain the order and history of thermal exposures. A measurement on the first pass does not describe the second pass automatically. Parts already soldered may experience another heating cycle, and the support configuration may change. Review component permissions and the whole assembly route. Do not reset the exposure history simply because the board has reached a new operation or work order.

The PCB assembly process overview places reflow between material preparation, printing, placement and inspection. For molten-solder contact processes, use the separate wave soldering temperature guide. Reflow and wave measurements involve different locations and mechanisms, so an oven profile should not be relabeled as a wave soldering setup.

Send evidence that makes an engineering review useful

For a thermal review, identify the assembly revision, paste product, critical components and build quantity. Include the sensor map, original traces and the document references used to select the limits. Mark any unknown attachment, loading or handling history. This allows the reviewer to distinguish a materials question from a measurement problem or a genuine conflict in the product's thermal requirements.

For a new assembly without a measured profile, provide the available files and state that process development is required. You do not need to invent an oven recipe to request a quote. Ask which development runs, measurement records and inspection activities are included in the proposed scope. Clear expectations around evidence are more useful than a promise that one standard curve works for every board.

Reflow profile questions

Standards and controlled documentation

Consult the for the applicable profiling and assembly documents, then use the authorized revision required by the project. Keep paste guidance, component limits and measured production evidence distinct. This page does not reproduce a universal IPC temperature recipe.