SENSORS Measuring more than temperature


in modern refl ow soldering Chris Williams, head of European sales, Solderstar


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efl ow soldering is a critical process in electronics manufacturing, where precise control of process conditions is essential to producing reliable solder joints. For many years, temperature profi ling has been the primary method used to verify refl ow performance. However, as assemblies become more complex and refl ow systems evolve, temperature alone no longer provides a complete picture of what is happening inside the oven.


The use of vacuum refl ow technology and inert processing environments has introduced additional process variables that can infl uence soldering outcomes. At the same time, manufacturers are under pressure to improve effi ciency, minimise waste and maximise equipment utilisation. The long-established principle of “if you don’t measure it, you can’t manage it” remains highly relevant, making comprehensive process measurement increasingly important.


Beyond temperature profi ling Temperature profi ling continues to form the foundation of refl ow process control, but oxygen monitoring has become an important consideration in ovens operating with inert atmospheres. Maintaining the correct oxygen concentration is essential. If oxygen levels are too high, manufacturers may not achieve the full benefi ts of inert soldering. Conversely, if oxygen levels are lower than necessary, nitrogen consumption may increase without delivering additional process benefi ts, leading to higher operating costs. Very low oxygen levels may also contribute to defects such as tombstoning.


Traditional oxygen monitoring typically relies on measurements taken at a single point within the oven. While this provides a useful indication of process conditions, it offers limited visibility of oxygen levels throughout the process chamber. Measuring oxygen concentration across the full oven length enables engineers to identify localised variations, detect leaking seals and optimise nitrogen usage. This can help support stable process conditions while reducing unnecessary gas consumption. Vacuum refl ow introduces another set of parameters that require careful monitoring. By removing gas trapped within molten


solder, vacuum technology can reduce voiding within solder joints. However, the effectiveness of the process depends on several factors, including pull-down rate, target vacuum level, hold time and release rate. Applying vacuum too quickly can contribute to component movement, while incorrect settings may reduce the effectiveness of the void reduction process. Measuring and verifying the complete vacuum cycle enables engineers to optimise both process performance and production throughput.


Vibration is another variable that can affect


refl ow performance but can be diffi cult to identify without the right data. Mechanical issues such as worn bearings, damaged pallets, tight conveyor links, drive problems or airfl ow-related disturbances can introduce vibration into the process. In vacuum refl ow systems, the vacuum conveyor and vacuum process itself may also contribute. Measuring vibration across multiple axes allows maintenance teams to identify developing problems before they result in production issues.


The benefi ts of comprehensive measurement


Modern profi ling systems can capture a wide range of process parameters during a single pass through the oven. In addition to process top and bottom heating and process air temperatures, advanced systems can measure oxygen concentration, vacuum performance, conveyor vibration across X, Y and Z axes and conveyor speed. This wider data set allows manufacturers to apply a consistent approach to process control across different oven types and


22 JUNE 2026 | ELECTRONICS FOR ENGINEERS


production lines. It also enables cross-oven benchmarking, helping engineers compare thermal performance, identify variations and establish best-practice settings. Comprehensive measurement is also valuable for maintenance. Before-and-after comparisons can help confi rm whether maintenance work has corrected a fault or introduced a process deviation. Heating effi ciency can be tracked over time, allowing engineers to identify developing heater or convection failures before they compromise production. Oxygen profi ling provides further operational benefi ts. Abnormal changes in the oxygen profi le may indicate leaking seals or other gas management issues, while full O2 PPM profi ling can help optimise nitrogen usage and reduce unnecessary consumption. This supports both process control and cost management. Vacuum profi ling gives engineers visibility of pull-down rate, ultimate vacuum level, hold time and release rate, helping confi rm that void reduction processes are operating as intended. This is important because vacuum settings infl uence both solder joint formation and line throughput.


Vibration monitoring supports preventative maintenance by helping identify mechanical wear or conveyor-related issues early. Faults can then be investigated, spare parts ordered and repairs planned before downtime occurs. Conveyor speed measurement provides a further check that the oven is running in line with the programmed recipe, supporting process compliance and repeatability.


Increased visibility Temperature profi ling remains an essential part of refl ow process control, but modern soldering processes increasingly demand a broader view of process performance. As ovens incorporate more advanced technologies and process requirements become more demanding, manufacturers are turning to innovative profi ling solutions capable of capturing multiple process variables in a single pass. This wider visibility helps engineers make more informed decisions, improve process control and support more effi cient manufacturing operations.


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