A tutorial on spray-under-immersion post soldering cleaning
As electronic assemblies become increasingly complex and component spacing continues to shrink, the importance of effective post-solder cleaning has never been greater. Flux residues left behind after soldering can lead to leakage currents, electrochemical migration, corrosion, poor conformal coating adhesion, and ultimately premature product failure. These risks are particularly critical in high-reliability industries such as aerospace, automotive, medical, defense, and industrial electronics.
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While no-clean fluxes were originally developed to reduce or eliminate the need for post-solder cleaning, they often leave residues that are more difficult to remove than traditional rosin-based fluxes. During the reflow process, these residues can polymerize and form highly resistant deposits underneath low-standoff components, bottom-terminated devices, power modules, and densely populated assemblies.
In many applications, products that were previously left uncleaned now require cleaning due to increasing reliability requirements, stricter cleanliness standards, the widespread use of conformal coatings, and the growing adoption of electronics in mission-critical systems. As a result, manu-
facturers need cleaning systems capable of removing stubborn residues completely and consistently, even from the most difficult-to-access areas beneath today’s compact components.
The effectiveness of a cleaning process is therefore no longer determined solely by the cleaning chemistry. Equally important is the ability of the cleaning system to apply sufficient mechanical
force and deliver fresh filtered cleaning agent chemistry to every contaminated surface of the substrate. It should continuously remove dissolved residues from the process, and prevent
recontamination during both cleaning and rinsing.
This is where MBtech’s patented Spray-under-Immersion technology makes a difference. Since 1993, MBtech, a French specialist in electronics cleaning equipment, has developed a unique cleaning approach that has set a new benchmark for cleaning performance, efficiency, and sustainability.
The secret: spray-under-immersion technology
Unlike traditional spray-in-air cleaning systems, MBtech fully immerses assemblies in a cleaning bath before applying mechanical cleaning action. Boards, wafers, lead frames, and power modules
are positioned vertically in adjustable or dedicated carriers and submerged in the cleaning fluid.
A moving spray bar then cleans the products from both sides while the carrier simultaneously moves up and down, ensuring complete and uniform exposure to fresh cleaning chemistry.
This combination of immersion and targeted spray action offers several key advantages:
• Complete contact between the cleaning fluid and all product surfaces.
• Elimination of shadowing effects that can occur when products are stacked or positioned at angles.
• A 90-degrees impact, forces the cleaning agent under low stand-off component to remove flux residues underneath.
• Consistent cleaning performance across the entire assembly.
• Effective removal of even the most challenging flux residues.
Separate subsequent cleaning, rinsing, and vacuum drying tanks allow parallel processing and improve throughput. As a result, flux residues can typically be removed in a total cycle time of just 10 to 15 minutes, including rinsing and complete drying.
Continuous filtration for maximum cleanliness
MBtech systems continuously remove contamination from the cleaning chemistry throughout the cleaning process. Heavy particles are filtered from the lower section of the cleaning tank, while lighter floating contaminants are removed from the liquid surface by an overflow into a smaller tank, from where they are filtered and returned to the main bath. The cleaning fluid is continuously purified through micron filters and returned to the process via the spray bars. This continuous filtration approach maintains cleaning efficiency, extends bath life, and minimizes the risk of redepositing contaminants onto cleaned assemblies.
Enhanced rinsing and vacuum drying
After cleaning, products are automatically transferred to dedicated DI-water rinse stages. The closed-loop rinsing system continuously monitors deionized water quality and uses resin and activated carbon filtration to maintain optimum performance.
The final step is vacuum drying in a separate chamber. By lowering the pressure, moisture is removed at reduced temperatures, shortening drying times, lowering energy consumption, and minimizing thermal stress on sensitive electronic components.
More efficient than conventional spray-in-air systems
Many conventional cleaning systems operate much like industrial dishwashers, spraying cleaning chemistry onto products placed in baskets. This arrangement can create shadow areas where the cleaning fluid cannot effectively reach contaminated surfaces. In addition, rinsing is often performed in the same chamber used for cleaning, meaning that not only the products but also the entire process chamber must be rinsed. This increases rinse-water contamination and decreases overall process efficiency.
MBtech’s vertical product positioning and immersion-based process, combined with dedicated cleaning and rinsing tanks, eliminate these limitations. Only the carrier and the assemblies themselves require cleaning and rinsing.
The result is:
• Faster and more effective cleaning.
• Improved rinsing performance.
• Up to five times lower cleaning-agent consumption.
• Reduced evaporation and heat losses.
• Lower pump energy consumption.
• Less cleaning agent cross-contamination into the rinsing water
• Increased throughput and shorter overall cycle times.
Designed for sustainable manufacturing
Sustainability is built into the MBtech concept. All systems operate in a fully closed-loop configuration, continuously filtering and reusing both cleaning chemistry and rinse water. No process liquids are discharged to the sewer, helping manufacturers reduce their environmental footprint while lowering operating costs.
Vacuum drying consumes significantly less energy than conventional hot-air or blower-based drying systems, further improving the overall sustainability of the process.
Proven worldwide
Today, close to 600 MBtech flux-cleaning systems are installed worldwide. Leading manufacturers, including several well-known companies in the Benelux, rely on MBtech technology for their high-reliability cleaning requirements.
Known for their robust construction, long service life, and low maintenance requirements, MBtech systems continue to be a trusted solution for demanding electronics manufacturing environments.MBtech’s Spray-under-Immersion technology combines superior cleaning performance, lower operating costs, and sustainable operation, making it one of the most advanced flux-removal solutions available to today’s electronics manufacturing industry.
