Cleaning Misprints

Best Practices

Spray-In-Air Misprint Cleaning Perspective 

Can a spray-in-air cleaning system be utilized to clean misprinted assemblies? 

The process is very risky. 

At issue is the fact that while the flux component of solder paste solubilizes in to the wash solution, the solder spheres never solubilize or dissolve. Any and all spray-in-air based cleaning systems will cause the individual solder spheres to distribute "wildly" through the air once the flux portion of the solder paste has been "solubilized". While most of the solder spheres will be directed down into the sump tank and into filters or other capture devices, there is no guarantee that all of the solder spheres will follow that route. Considering that there are tens of thousands or even hundreds of thousands of individual solder spheres on any misprinted assembly, it only takes a few spheres pushed into vias or lodged under "A-Side" components to cause real issues. Additionally, it is unlikely that 100% of all of the individual solder spheres will be captured and segregated. Some of the solder spheres will remain in the spray system and be dislodged in subsequent wash cycles. 

Aqueous Technologies would not recommend cleaning raw solder paste in any spray-in-air product. Ultrasonic technology which utilizes a cavitation process which pulls the solder spheres off of the assembly rather than pushing them off is far superior and less likely to result in unintended solder sphere redistribution.


Aqueous Technologies' StencilWasher ZDO utilizes precisely controlled sound waves to remove un-reflowed solder paste from stencils, screens and misprints. At 40 kHz, the ultrasonic energy is gentle enough not to damage delicate parts yet is highly effective in the removal of dried pastes on fine-pitch stencils. The built-in ultrasonic "sweep" generator oscillates the cleaning frequency between 37 kHz and 43 kHz, preventing damage to wire bonds and other delicate devices.

StencilWasher ZDO is capable of removing all solder pastes and uncured SMT adhesives without sending any fluids to the drain. StencilWasher ZDO is capable of cleaning stencils or misprints up to 29" x 29" in size (full immersion).

StencilWasher ZDO is equipped with many standard features including:

  • Complete zero discharge operation
  • Programmable digital wash cycle timer 
  • Safe 31 watts per liter power ratio 
  • Wash solution heating system with programmable digital temperature controller 
  • Closed-loop wash solution filtration system with stainless steel housing
  • Closed-loop rinse water filtration system with stainless steel housing
  • Hand-held rinse wand
  • Hand-held airknife
  • Fully enclosed (cabinetized) 
  • Ten year limited transducer warranty

StencilWasher ZDO is designed to remove all solder-paste types and incurred adhesives in cycle times averaging less then five minutes. 


Features / Capabilities:

Pastes Removed: All
Removes Adhesives: Yes
Discharge: None
Wash Solution Recycler: Standard
Wash Solution Filter: Standard
Rinse Water Filter: Standard
Drain Pump (if needed for service): Standard
Rinse Wand: Standard
Hand-Held Airknife: Standard
Wash Solution Heater: Standard


Dimensions: 48" L x 34" W x 40" H
Weight: 600 lbs
Construction: Welded Tube Steel Frame
16 Gauge Steel Panels
Finish: Powder-Coating Epoxy
Electrical Requirements (North America):
208/240 VAC 1 Phase 40 amps
Electrical Requirements (Export)
230 VAC 1 Phase 20 amps
Wash Tank Capacity: 34 Gallons (128 Liters)
Maximum Stencil Size (full immersion): 29" x 29" (736.6mm x 736.6mm)
Drain Requirements: 3/4" NPT
Wash Cycle Digital Timer: 1-99 Minutes
Ultrasonics: 1000 Watt Side Mounted 
Hand-Held Rinse Wand: Standard
Hand-Held Airknife: Standard