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
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