PCB cleaning | clean boards - electronic assemblies

Edwin

Zestron

8 factors to get the best results and succesfully clean boards - electronic assemblies

Determine which part on the boards needs cleaning. The part which needs being cleaned drives the cleaning process. To determine this easily take this in consideration;
- What is the source of circuit board contamination
- Are there areas where cleaning flied can enter of is trapped?
- Are there any components which can be affected by the PCB cleaning process?
- Are there secondary post cleaning steps like wire bonding or coating?
- Which level of energy is needed to penetrate, wet and flush away soil(s)?
- What are the through put rates?
Determine the chemical nature of the soil(s) which needs being cleaned?
- Will the PCB cleaning agent remove the soil(s)
- Check the Soil Classifcation; is
  - Highly Soluble in Cleaning Agent – easily cleaned
  - Soluble in Cleaning Agent – Time and Temperature are key factors
  - Marginally soluble in Cleaning Agent – Requires strong cleaning agents
Processing Condition;
- Soak and Hot Reflow profiles may oxidize and harden soils.
- Multiple reflow conditions can be harden the soils before circuit board cleaning.
- Baking soils before cleaning harden soils
Bottom Terminated Components
- When the Gap Heights less than 75µm will reduce soil levels and it is easier to clean
- A low gap heights require stronger mechanical forces and longer cleaning time
You need to keep in mind the Material Compatibility with the Engineering PCB cleaning agent.
- Metallization's may interact (react or corrode) with aggressive cleaning agents
- Part markings can degrade from both cleaning agent and applied energy
- Cleaning agent can entrap Non-hermetically sealed components
- Key factors are cleaning time, cleaning concentration, temperature and impingement
- Staking components, bonding and coatings may
The PCB Cleaning Agent must be matched to the soil(s) you want to clean. When a soil is hard to clean you require a stronger cleaning agents. So when the cleaning agent is not matched perfectly you will not remove the soil. Key facts to make a match is concentration and temperature.
Also keep in mind that soil can change the properties of the cleaning agent as they load. And Controlled losses (drag-out- is crucial for long tank life.
Cleaning the Machine
- To penetrate the low gaps you need to apply impingement energy
- A function of applied impingement energy is Wash Time
- Low gaps may not clean at low applied energy
- You're improving the cleaning rate when using High flow intermixed with strong impingement
You need to Control the Process
- Controlled additions of the cleaning agent and water will optimize the performance
- Critical soil load is the point at which cleaning drops of
- The steady state is the balance between lose and replenishment real time

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