SMT Oven Cleaner - An Essential Quality Tool

Introduction
Since the introduction of no-clean processes into the surface mount industry, the possibility of contamination by condensation has increased. For some, a "no-clean" process is also a "no residue" or "low residue" process. In reality, a no-clean process is one that meets a device's operational performance requirements without cleaning, flux residues notwithstanding.

Soldering
The function of a soldering flux is to remove the oxide from the joint surface and prevent it from re-oxidizing while the solder becomes liquid and flows between the surfaces and makes a joint.

As this happens, some of the flux evaporates. With hand soldering, in an open environment, this is not a real problem. It is dispersed in the atmosphere, perhaps condensing into micro milligrams of residue in the surrounding area. Current health & safety practice mandates that these soldering vapours are safely vented away from operators. These extraction systems may be subject to "clogging up" from the flux residues.

A mass reflow device (an oven or a wave-soldering machine) operates in a closed environment. The flux residue condenses on or in the machine. Manufacturers of modern ovens take steps to manage this, by using a combination of airflow and condensation plates. Some claim to eliminate the problem altogether, but it is doubtful that this is completely true. In any event, many units are still in service in factories with no or inefficient flux residue management systems.

The reflow oven
During the heating part of a reflow profile, volatiles come off the solder paste and condense in the oven, on the conveyor, the heating elements or IR emitters, the exhaust outlet, etc. Sometimes, these condensed volatiles collect and fall onto the printed circuit assemblies, causing cosmetic, quality or even performance problems.

Residues build up over time in the oven, depending on its design efficiency. The results are often a loss of efficiency in the oven, contamination of the pcb by residues and unsightly marks around the entrance and exit of the oven.

Wave soldering machine
During wave soldering, vapours are formed which condense on the conveyor, heaters and fluxer of the machine. The residue can be hard or sticky depending on the flux type.

Conclusion
Both processes heat soldering materials to the temperature where flux resins, solvents, tackifiers, etc, evaporate. As these cool, they are precipitated on to the conveyors, chassis and heaters in the machines. In time, this will cause loss of efficiency and contamination in the process.

TEC 1647 SMT Oven Cleaner
The residues formed during the process are difficult to remove. At high temperature for long periods, some resins turn into a lacquer. Others remain fluid and can be very sticky.

It is considered necessary to remove these residues periodically to maintain process integrity, machine efficiency and appearance. As these machines run at high temperatures, they can take a long time to cool, sometimes many hours. To minimize down time, it is required to have a cleaning solvent powerful enough to remove the residues at the highest feasible temperature.

TEC 1647 SMT Oven Cleaner has been formulated to work at temperatures up to 40°C, thus saving many hours of down time.

• Apply TEC 1647 SMT Oven Cleaner to the oven when it reaches 40°C
• Leave for 4-6 minutes to allow the residues to soften
• Wipe residues away with a TEC 2350 Techclean Wiper
• Use regularly to maintain cleanliness

Notes
Text by Peter Swanson from source material written by Paul Salmon, European Sales & Marketing Director, Tech Spray.