PCB Cleaning
PCB cleaning technology has evolved a great deal following the ban upon ozone-depleting chemicals- CFCs and HCFCs. This is because of the exponential progress of the electronic technology. Solder pastes and fluxes also underwent a major turnaround; previously RMA and RA fluxes were used, and then came the No-Clean fluxes along with its variants. To cater to the evolving trends in the PCB manufacturing process, several families of cleaning agents are made available in the market.
The cleaning products are broadly classified in the following categories:
- Formulated hydrocarbons – extensive lifetime agents
After the ban of HCFCs and CFCs, eco-friendly formulated hydrocarbons came into being. They are ideal PCB cleaners and can remove all sorts of solid, salt and flux residues as they possess extremely low surface tension (20mN/m). However, these also require rinsing with either semi-aqueous (water based) or solvent based (fluorinated) process. The PCB cleaning through formulated hydrocarbons is the cheapest because of its extensive lifetime.
- Glycols and other modified alcohols
These cleaning agents are used with formulations having surface tension in the range of 25 mN/m – 35 mN/m. Without formulations, these agents are cannot really remove all contaminants. These are high cost cleaning agents.
- Petroleum distillates – best for cold cleaning
Distillates like ketones and petrol are preferred for cold PCB cleaning processes. As it is common knowledge that petroleum products are highly inflammable even at room temperatures, using such cleaning agents in warm conditions is extremely dangerous. The cost of such solvents is moderate.
- Brominated solvents
The formulations of brominated solvents are really simple for utilization in vapor degreasers. Yet, this solvent is not compatible with all sorts of material because of this a compatibility test of all the material that will come into contact with the solvent ought to be conducted beforehand. Despite the fact that these solvents are low cost, they are banned in certain countries (especially European states) because they are not user friendly and are hazardous to the environment.
- Fluorinated solvents
In its pure state, the solvency power of fluorinated solvents is really weak despite having the lowest surface tension as compared to rest of the PCB cleaning agents. But once they are mixed with hydrocarbons, their true power is unleashed. Fluorinated solvents can be used in vapor degreaser methods.
- Detergents – the most commonly used agents
PCB cleaning with detergents is an aqueous process. Different types of detergents are good for different fluxes. Aqueous alkaline detergents are used for cleaning high-end electronic components even. The concentration of the detergents in water matters a lot. Ultrasonic PCB cleaning is also done with the help of detergents. Special considerations should be taken into account because of the agitation effect off the detergent solvent.
PCB cleaning has become mandatory in the present age. The boards must be cleaned scrupulously so that all the production residues, dirt and grime are removed for an efficient performance. As technology evolves further, cleaning agents and equipment available for this purpose will also improve.