• • • ELECTRICAL EQUIPMENT• • •
HOW MANY ZONES DO YOU
REALLY NEED ON A CONVECTION REFLOW OVEN?
BY JOE BOOTH, CEO, ALTUS GROUP S
electing a convection reflow oven is an important decision for any SMT operation.
When properly maintained, a reflow system can remain in production for well over a decade, and in many cases beyond 20 years. With such long service lives, the configuration chosen at installation needs to support both present requirements and the demands that may emerge later in the oven’s operational life. Zone count is often the first comparison point, but it is not always the most reliable. Manufacturers differ in the way their ovens are built, and these variations mean that two systems with the same number of zones may not perform in the same way. For this reason, many engineers find that heated length and cooling length offer a more consistent basis for comparison, as they directly indicate how much thermal path is available within the process. Heated length determines how much time an assembly has to reach the required temperatures without reducing conveyor speed. In general, a longer heated section gives the process more flexibility and can support faster takt times when the profile allows.
Cooling length also forms part of the comparison, as it defines the available controlled cooling path once the assembly leaves the heated zones. These characteristics often provide a clearer view of the usable process window than zone count alone.
The range of available oven configurations is broad. Large systems may offer heated lengths of
around 4.49 m across 13 zones with cooling lengths of approximately 1.66 m in four cooling zones. At the smaller end, compact systems may provide heated lengths of roughly 1.3 m in five zones with 0.4 m of cooling in a single cooling zone. This spectrum of sizes allows manufacturers to select an oven that aligns with their floor space, throughput targets and application requirements.
Throughput expectations and practical benchmarks
Throughput is a key consideration when assessing an oven, and broad rules of thumb can help frame the decision. Typical process planning ranges often referenced in industry include:
• Seven-zone ovens: around 45 - 60 seconds per assembly
• Eight or nine zone ovens: around 30 - 45 seconds • Optimised nine-zone ovens: in some cases under 30 seconds
These ranges are indicative only. The true
performance always depends on the specific assemblies being processed, and the most reliable way to confirm capability is to test with representative boards. Profiling several assemblies using an external profiler provides an objective baseline. Once those assemblies are characterised, they can be run through ovens with varying heated lengths and zone counts to see where the limits of each configuration lie and how each option supports the required profile. Tools that adjust conveyor speed against a target profile can further assist in understanding the available headroom.
Control, flexibility and future capacity
When considering the number of zones, one of the main benefits of having more zones is the
24 ELECTRICAL ENGINEERING • OCTOBER 2026
increased number of heating stages available. More stages allow finer steps within the heating portion of the process, which can be useful when assemblies include components and boards with varying thermal mass.
It is also important to consider future requirements. Even if current batch sizes are modest, future programmes may require shorter takt times or more thermal flexibility. Selecting an oven with a longer heated length can help reduce the risk of early obsolescence and provide additional capacity should production increase. For manufacturers expecting significant throughput growth, dual-lane reflow is another option. With suitable board-handling automation, a dual-lane oven can increase capacity within a similar footprint and without doubling energy usage. In practice, such systems can be integrated into existing single-lane lines using shuttles to manage the transitions between one and two lanes.
Bringing the decision together Ultimately, determining how many zones are required involves more than comparing numbers on a specification sheet. Heated length, cooling length, takt-time requirements, assembly characteristics and space constraints all play a role. Application-specific profiling and comparison testing provide the clearest insight into which configuration best supports the intended production environment.
By basing the choice on measured performance rather than zone count alone, manufacturers can select a configuration that supports stable and reliable reflow over the full operating life of the oven.
www.altusgroup.co.uk electricalengineeringmagazine.co.uk
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