With supply chain interruptions and component shortages continuing to affect the electronics industry, PCB (printed circuit board) fabricators are looking for ways to boost their productivity and eliminate PCB waste. Companies that implement 5S manufacturing methods at the benchtop consistently realise major benefits to waste reduction. 5S is a lean manufacturing concept of maintaining an orderly and clean workplace. When applied to a PCB cleaning bench, this method can help you improve PCB cleaning quality and minimize scrapped boards.
Manual cleaning, also known as benchtop cleaning, is an important step in quality PCB production. Any contaminants such as flux residue, dust or fingerprints, left on the PCB surface may negatively affect the board’s performance. “Dirty” PCBs are susceptible to corrosion, shorting, interrupted signals and noise on the board.
If the benchtop cleaning is ineffective, PCBs typically will not make it to the later stages of production or pass final inspection. Contaminated boards simply will not function reliably and are susceptible to costly rework or possible rejection. So, to maintain quality and reliability, PCB cleaning is a must.
The History of 5S
5S Plus Safety Graphic: Optimising cleaning tools and workflow will lead to better quality components and higher productivity
Optimising cleaning tools and workflow will lead to better quality components and higher productivity
The Toyota Motor Company developed the 5S methodology in the 1950s. It is part of the larger Kaizen principle of Lean Manufacturing. 5S focuses on keeping workspaces clean and organised to improve quality and output. The strategy consists of five Japanese words: Seiri, Seiton, Seiso, Seiketsu and Shitsuke. This translates into Sort, Set, Shine, Standardise and Sustain. Some PCB fabricators also add in the extra step of Safety. Here is how 5S can be applied to benchtop cleaning.
A dispensing system improves PCB cleaning results by targeting dirty areas on the board and getting under low mounted components and inside tight spaces
Determine if the equipment on your workbench needs to be there. Remove it from the benchtop if it does not. Sort out and keep only the essential cleaning fluids and tools you need and use regularly. Everything on the benchtop should serve a purpose. For example, only keep essential cleaning tools like flux remover cans, lint-free wipes, brushes and swabs. Removing excess clutter helps technicians work faster with quicker cleaning times.
One essential tool to have on every PCB cleaning benchtop is a controlled cleaning fluid dispensing system. When used properly, the dispensing system improves PCB cleaning by more easily delivering cleaning fluid under low surface-mounted components and inside tight spaces. Additional benefits include the ability to control the cleaning fluid flow to reduce fluid waste and improve worker safety by limiting the amount of cleaning fluid fumes released into the air.
The Set step means there is ‘a place for everything and everything in its place’. Organise and position equipment in a logical way. This helps establish a systematic way of storing and retrieving items, to maximize accessibility, limit excess motion and stop wasting time searching for misplaced items. For example, move cleaning fluid aerosol cans off the bench and into a handy bench-mounted bracket. This keeps the benchtop clear, yet still keeps the cleaning fluid close to hand.
Having a set location for benchtop tools and cleaning fluids provides visual cues and helps auditors with inspections. For example, an empty bracket means the PCB cleaning fluid has gone missing and needs to be replaced.
Shine means keeping the benchtop clean. Proper benchtop housekeeping is often overlooked, but it can impact the effectiveness of PCB cleaning. If the workbench is dirty, it is more difficult to keep the PCB pristine. A regular benchtop wipe-down with a good quality ESD (electrostatic discharge) prestaurated cleaning wipe goes a long way in keeping mats, bins and tools clean. The wipes remove dirt, dust and other contaminants that can make their way onto the PCB, all without leaving lint, residue or static charges behind.
Implementing standardised PCB cleaning processes will help ensure the previous steps of sort, set and shine are not forgotten or overlooked. Use these steps as a standard operating procedure (SOP). When performed regularly, these steps can help improve efficiency and ensure that consistent high-quality PCB cleaning is standard.
Pride in an orderly workplace can improve morale. Involve the entire workforce in the 5S process from the PCB cleaning technicians to those in charge of inspection and quality control. Taking steps to ensure that everyone understands the 5S methodology and why it is important will help facilitate the indoctrination of the concept into the company’s culture, thus help ensure long-term success.
Safety is an extra, yet vital step of the 5S process. This means focusing on what you can do to eliminate workplace risks to technicians and improve the quality of the workplace.
Review the cleaning fluids and tools and check the SDS (safety data sheets) carefully to ensure they are safe to use. Advanced PCB cleaning fluids are engineered to be nonflammable and have excellent toxicity profiles with high Threshold Limit Values (TLVs), making them safer for exposed workers to use.
Consider using a controlled cleaning fluid dispensing system. Because a cleaning fluid dispensing tool is a closed aerosol system, technicians do not pour liquid cleaning fluids from open buckets or drums into pump bottles or smaller containers. This reduces the risk of spills and fire hazards and limits worker exposure including any potential fumes.
Make the Most of Every PCB
Contaminated PCBs typically will not pass final inspection
Experts predict that component part shortages will likely continue into 2024, so it is important to make sure every PCB you produce is functioning and reliable. Whether during initial manufacture, touch-up in post-reflow assembly, or during rework and repair, cleaning is vital to PCB quality.
When reviewing your manual benchtop PCB cleaning processes, consider using the 5S (plus Safety) method. The six, easy-to implement steps can help you optimise your PCB cleaning workflow, improve safety and, over time, will allow you to produce more high-quality PCBs with less waste.
Elizabeth Norwood is a Senior Chemist at MicroCare, LLC, which offers precision cleaning solutions. She has been in the industry more than 25 years and holds a BS in Chemistry from the University of St. Joseph. Norwood researches, develops and tests cleaning-related products. She currently has one patent issued and two pending for her work. For more information, visit www.microcare.com.