Circuits Assembly - April 2008 - (Page 30)

Benchtop Cleaning hardest residues and starts to begin to dissolve the waterresidues formed during soldering,” as Munson notes, if based contaminates. Grabbing a sponge, we scrub the surthose residues are not removed from the board, they will faces (both sides, please!) and dislodge the residues. Do we have been released from their encapsulation to damage then put the plate in a rack to dry? Never (or I’m not comthe PCB. ing to your house for Thanksgiving)! Instead, we rinse the No-cleans do not need to be cleaned after automated plate thoroughly with scalding hot water, removing the last soldering because the temperature control is generally traces of Mom’s cooking, as well as any soapy residues. Now perfect. But hand soldering is far less precise. Some porthey’re ready to either air dry or wipe with a dishtowel. tions of the flux quite close to the soldering iron tip will With everything you clean, the process is the same. The get sufficiently hot for the encapsulation to occur, but dishwasher uses the other areas, millisame four steps. The meters farther from drive-through car the tip, will not. wash? Wet, scrub, These unencapsurinse and dry. In lated residues can the shower? Who and will cause leakcan forget the stern age, corrosion, den“wet, lather, rinse, drite growth and repeat” every sham“infant mortality.” poo carries on its So hand cleanlabel? It’s a simple ing hand-soldered truth: If you can’t boards is essential, rinse, you can’t even with no-clean clean. fluxes. In addition Back to the to the unencapworld of electronsulated activators ics. It is amazing in the no-cleans, engineers around erratic cleaning the world think a on a PCB will disjar of alcohol and solve the encapa dirty toothbrush sulation around are suitable tools properly cured actifor benchtop cleanvators. It was this ing. Sure, it may double-whammy have worked in the that Munson found 1960s, but today’s in his SIR testing: tiny, dense, hot cirthe unencapsulated cuitry absolutely activators were not will fail if the four removed because Figure 1. The typical dip-and-brush bottle with IPA is unsatisfactory in most instances. steps of cleaning are of the inadequate not properly used. cleaning , which Benchtop cleaning options. The first, best way to clean released the encapsulated activators from their cages, the board is through an automated cleaning process, permitting corrosives to run amok on his boards. either a vapor degreaser or some type of aqueous cleaner. Four steps. At the heart of the issue is the realization Like the dishwasher or the car wash, this delivers an that every cleaning process requires four steps: wet, scrub, automated form of wet, scrub, rinse and dry. The human rinse and dry. Whether washing your car in the driveway, factor is eliminated. Without doubt, this process produces your hair in the shower or the baby in the tub, every the most consistently clean boards over the longest poscleaning process requires the same four steps: wet, scrub, sible term. rinse and dry. However, automated cleaning is often not practical. Consider the humble chore of the dinner dishes. Many parts are sensitive to water – which is one of the Slathered in gravy and bits of your favorite meatloaf, primary reasons for hand soldering a final few components they dried rock-hard while you watched Dancing with the onto a board in the first place. Often, the cleaning machines Stars. But now it’s your time to face the music; the dishes are in distant parts of the facility, or are operating at capacaren’t going to clean themselves. So what to do? ity, or too slow for high-throughput requirements. So the First, we rinse the largest chunks of debris from the benchtop technician needs a faster, cheaper answer. plates using the hottest water we can get. This softens the 30 Circuits Assembly APRIL 2008 circuitsassembly.com http://circuitsassembly.com

Table of Contents Feed for the Digital Edition of Circuits Assembly - April 2008

Circuits Assembly - April 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Screen Printing Better Manufacturing Design and Modeling of High-Speed, High-Density 3-D CSPs and Memory Modules The ‘Big Brush Off’ Revisited Impact of Soldering Atmosphere on Solder Joint Formation Beyond Moore’s Law ESD Control For Class 0 ESDS Devices Growing Your Brand This Year’s Model Tech Tips Reflow Soldering Process Doctor Pb-Free Lessons Learned Getting Lean Equipment Advances Apex Product Preview Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - April 2008

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