Though it’s quite popular today to predict the demise of Moore’ Law, (“the number of transistors on a chip doubles approximately every two years”) nonetheless high reliability electronic devices continue to build faster processing speed and memory capacity using increasing smaller platforms.
These highly dense assemblies reduce the spacing between conductors while yielding a larger electronic field. As the relentless move to higher functionality, miniaturization, and lead-free soldering continues, studies show that cleanliness of the assembly becomes more important. For example, residues under low standoff components, with gaps less than 2 mils, are just one of the increasingly difficult cleaning challenges. Collaboration from cleaning equipment and cleaning material companies has led to innovations for improving throughput and complete residue removal under low standoff components.
The first, best way to clean the board is through an automated cleaning process, either a vapor degreaser or some type of aqueous cleaner. Like the dishwasher or the car wash, this delivers an automated form of wet, scrub, rinse and dry. The human factor is eliminated. Without doubt, this process produces the most consistently clean boards over the longest possible term.
However, automated cleaning is often not practical. Many parts are sensitive to water – which is one of the primary reasons for hand soldering a final few components onto a board in the first place. Often, the cleaning machines are in distant parts of the facility, or are operating at capacity, or too slow for high-throughput requirements. So the benchtop technician needs a faster, cheaper answer.
There are brushes and jars of alcohol often seen used, but if you can’t rinse, you can’t clean. A better option is an aerosol flush. This is a very good solution and delivers fast and reliable cleaning, especially with today’s fast-drying, ozone-safe solvents. The problem is that techs will run through a lot of cans…quickly. It’s a sloppy, wasteful and often expensive process, but it will deliver clean boards, if you can afford it.
The best option is to use some form of dispensing system on an aerosol solvent to control the flow of the cleaning fluid. In this process, the brush’s mechanical scrubbing action is complemented by a controlled spray from an aerosol container. It forces the technician to implement “wet, scrub, rinse and dry” every time. It also allows the technician to clean better, more consistently and thoroughly, with far less solvent. Because the solvent is fresh and pure (“virgin” is the term in the cleaning industry), it will deliver far better cleaning than some tired, contaminated alcohol sitting in a dirty pump bottle.