Eight factors must be considered to successfully clean circuit boards – electronic assemblies.

  1. Circuit Board to Be Cleaned: The part being cleaned drives the cleaning process.
    • Where is the source of circuit board contamination?
    • Are there areas where cleaning fluid can enter or be entrapped?
    • Are there components that can be affected by the PCB cleaning process?
    • Are there secondary post cleaning steps such as wire bonding or coating?
    • What level of energy is needed to penetrate, wet and flush away soil(s)?
    • What are the through put rates?
  2. Soil(s)
    • What is the chemical nature of the soil(s) being cleaned?
    • Will the PCB cleaning agent remove the soil(s)?
    • Soil classification
      a. Highly Soluble in Cleaning Agent ~ Easily Cleaned
      b. Soluble in Cleaning Agent ~ Time and Temperature are key factors
      c. Marginally soluble in Cleaning Agent ~ Requires strong cleaning agents
  3. Processing Conditions
    • Soak and Hot Reflow profiles may oxidize and harden soils
    • Multiple reflow conditions before circuit board cleaning may harden soils
    • Baking soils before cleaning harden soils
  4. Bottom Terminated Components
    • Gap heights less than 75µm (3 mils) increase the cleaning difficulty
    • Gap heights greater than 75µm reduce soil levels ~ easier to clean
    • Low gap heights require stronger mechanical forces
    • Low gap heights require longer cleaning time
  5. Material Compatibility
    • Engineering PCB cleaning agent with material compatibility in mind is critical
    • Metallizations may interact (react / corrode) with aggressive cleaning agents
    • Part markings can degrade from both cleaning agent and applied energy
    • Non-hermetically sealed components can entrap cleaning agents
    • Bonding, staking components and coatings may degrade
    • Cleaning time, cleaning concentration, temperature and impingement are key factors
  6. PCB Cleaning Agent
    • Cleaning agent must be matched to the soil(s)
      a. Harder to clean soils require stronger cleaning agents
      b. Poorly matched cleaning agent will not remove the soil
      c. Concentration and temperature are key factors
    • Soil can change cleaning agent properties as they load
    • Controlled losses (drag-out) is critical to long tank life
  1. Cleaning Machine
    • Applied impingement energy is needed to penetrate low gaps
    • Wash time is a function of applied impingement energy
    • Low applied energy may not clean low gaps
    • High flow intermixed with strong impingement improves cleaning rate
  2. Process Control
    • Controlled additions of cleaning agent and water optimize performance
    • Critical soil load is the point at which cleaning drops off
    • Steady state is the balance between lose and replenishment real time
Cleaning at the benchtop is a very common practice in electronics manufacturing operations. While often the final crucial step in cleaning PCBs (e.g. rework, repair and prototype), manual cleaning is accomplished in a variety of ways. KYZEN has a complete line of topical cleaners to address each situation.
These processes completely immerse the product being washed, so that the cleaning agent fully contacts every surface of the device. Most immersion applications utilize either Ultrasonic energy or Spray -Under -Immersion (SUI) forces to circulate the fluid and apply mechanical energy to the substrate surface.
The vapor degreasing cleaning process is integrated around an engineered solvent composition that dissolves (matches up) with the soil(s) being removed. The engineered cleaning fluid is often a blend of solvents which behave like an azeotrope, forming a constant boiling system at a specific temperature range.
KYZEN offers an array of PCB cleaning agents that are formulated to take advantage of an Inline washer’s powerful combination of high flow, impact energy, and deflective forces. These conveyorized machines provide the highest production throughput and faster fluid penetration under low gap components like challenging QFN’s.
Batch cleaning machines are designed to efficiently wash, rinse, and dry assemblies in a small footprint. Groups of electronic assemblies are sealed inside the machine where they are typically washed, rinsed, and dried in a single main process chamber, hence the name “Batch”.

Process Care Center

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