Re-certify a reflow oven after moving

After moving an existing reflow oven to a new site, what steps do we need to perform on the machine and the heat exhaust system in order for the machine to be re-certified?

Q. N.

Expert Panel Responses

To re-qualify or re-certify the oven and venting system, my suggestions would be to re-profile all the boards and see how these new profiles correspond to the old profiles. The venting system should have had air flow monitoring established and I would reinstitute those air flows. I would also try to determine the air flow around the equipment especially with air conditioning ducts and vents. Any changes subtle as they may be, can create strange currents of air around the equipment which will impact the temperature of the ovens.

Leo Lambert
Vice President, Technical Director
EPTAC Corporation

At EPTAC Corporation, Mr. Lambert oversees content of course offerings, IPC Certification programs and provides customers with expert consultation in electronics manufacturing, including RoHS/WEEE and lead free issues. Leo is also the IPC General Chairman for the Assembly/Joining Process Committee.

I am not sure I understand what is meant by re-certifying the heat exhaust but when moving an oven to a different site or moving an oven within a site it is always a good idea to make sure everything is working correctly. A simple method is to follow the start-up check list that should have been provided by the oven manufacturer during the original installation. If it not available, see you oven manufacturer. Re-calibration should be done if the oven has been moved to a separate facility or if it has been more than one years since it was done. The goal of a reflow oven is to produce a thermal profile that produces good product, so the next step would be to profile the oven with actual product to confirm that you have the correct recipe.

Fred Dimock
Manager, Process Technology
BTU International

Mr. Dimock is the manager of Process Technology at BTU International. His extensive experience in thermal processing includes positions at Corning, GE, and Sylvania. He has authored numerous articles on lead free processing and process control, taught classes at SMTAI, and participated in the IPC Reflow Oven Process Control Standard committee.

Critical requirements for your specific reflow oven will be outlined by the oven manufacturer. Normal requirements generally consist of:

A clean / dry air supply of sufficient CFM
A correct and clean voltage supply with a phase to phase differential within the manufacturer's specification, measurable with a Volt meter.
Proper exhaust CFM, which can be verified with an anemometers, and balanced utilizing dampers in the individual exhaust ducts.
If the oven is fitted with edge carrying rails, verify these have not been damaged in the move. A simple way to accomplish this is to string a line from one end to the other, looking for dips or bows in the rail system.

While all of these will affect oven performance, supply voltage and exhaust ventilation are the two which most commonly cause equipment issues. Simple characterization can be accomplished by re-running a common product profile, or a range of profiles, comparing them to the originals. A more thorough characterization can be performed utilizing elaborate equipment and fixtures which can readily identify any anomalies found inside the oven. Check reflow profiler equipment suppliers for specifics.

Mike Scimeca
President
FCT Assembly

Mike Scimeca created FCT Assembly after the purchase of Fine Line Stencil, Inc., and consists of two major operations: stencil manufacturing and the manufacturing of electronic assembly products such as solder paste, flux and solder bar.

Despite what some folks may think, not all Reflow ovens are created equal. Consulting with the original equipment manufacturer will save both your time and money. Generally, the Reflow system must be positioned and leveled in accordance to the OEM's specifications. All utilities must be properly facilitated and comply to their requirements. This is especially important with a N2 oven's exhaust system. Depending on the sophistication of the Reflow oven, certain sub-systems may require following particular re-start procedures such as some gas monitoring equipment, cooling systems or flux collectors. If the original "Start-Up and Installation" documentation is no longer with the system, it's likely available from the OEM. Independent whether the system was purchased new or used, obtaining a complete copy of the Reflow system documentation package is worth the nominal charge. For that matter, I recommend purchasing a one day OEM on-site visit to ensure your Reflow system operates trouble free.

Al Cabral
Regional Sales Manager
Finetech

Al Cabral is Regional Sales Manager for Finetech and Martin rework products. His expertise includes through-hole, surface mount and semiconductor packaging with an emphasis on soldering and heat transfer. Al has been a significant contributor to the development and optimization of reflow and rework processes and systems, particularly lead-free transitions and microelectronic applications.

Most ovens can be transported without difficulty. If you would like a process verification of the oven itself there are devices that can be used for this. Profiling companies such as KIC, ECD and Data-Pac offer calibrated thermal devises that would allow you to baseline the system thermally before shipment. Upon proper installation at the new site you would run one of these devises to confirm the thermal print of the oven has not changed. Same can be done with a referee assembly instrumented with a number of thermocouples. But the calibrated devices are better suited. When it comes to facilities you should not allow make sure the new installation has the proper facilities, exhaust flow, N2 and air if needed. Then need to be set at the same proper settings after the transfer. You may want to document these prior to shipment from your facility. Exhaust can be checked with a manometer of a water column that measures static pressure. These meter can be found in MSL or Grainger catalogs. make sure you purchase the right range for the W/C. N2 (if used) should be documented with N2 flow amounts and the PPM of O2 in various sections of the oven. I hope this information helps

John Norton
Eastern Manager
Vitronics Soltec

John Norton started his soldering career in 1983 for Hollis Engineering. He has also worked with Electrovert as a technical training manager and Vitronics Soltec for the last ten years. He has held various technical development and sales positions.

Good question. The fact that you're asking about the exhaust is encouraging, as oven fans and exhaust fans are common contributors to "changes" in convection rate, whether the oven has been moved or not. If you have not yet moved the oven, it would be prudent to run a base-line profile to "fingerprint" convection through the oven, at one of your typical thermal profiles. Then, do whatever the oven manufacturer recommends, post-move, to return it to normal operating conditions. Next, run your benchmark profile again, to compare convection...toward the "certification" you mentioned. The oven heaters may be delivering what you've set them for, while one or more oven or exhaust fans is operating sub-par, and hence the "convection" is not sufficient for proper reflow. Our most diligent SMT practitioners utilize the OvenRIDER (machine maintenance profiling system) to ensure the machine has returned to its' former ability to provide and replicate the desired thermal profile. It has the ability to detect changes in convection that the oven likely would not.

Grant Peterson
Vice President; Marketing & Sales
ECD

Grant Peterson has 30+ years of professional experience including construction-management in the military, sales and operations management in display technologies, software and thermal process management technologies.
NOTE: Mr. Peterson is no longer working at ECD

Reader Comment

Leo Lambert brings up an excellent point regarding air conditioning ducts and vents. As the airflow from the exhaust duct pulls in ambient air at the entry and exit points of the conveyer, temperatures in the oven near those points can be greatly affected by the HVAC. In the summer cooler air is being pulled in, while in the winter warmer air is coming out of the HVAC ducts. These changes in ambient air temperatures and their effects on the temperatures at the ingress and egress points prompted us to relocate the HVAC ducts to minimize the thermal influence.

Rafael Munoz, Alcon Laboratories, USA

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