I sat with Irene Sterian at the SMTAI technical committee recognition dinner in September. (As an aside, if you’ve never had the pleasure of speaking with Irene, you really should find the time. She could make rubber chicken seem interesting.) Amid conversation on IoT, islands of St. Bernards, Quebec City, Elon Musk and cats, we got to talking about disruptive technology.

It was one of those conversations where you completely abandon the good manners your mother taught you, as you keep interrupting the other party out of excitement about the topic.

To be clear, I believe “disruption” is often an inflated term. Most of what we call disruptive is really just “painful to a certain segment of people or business.” Take ride-sharing, for instance. Type in “Uber” or “Lyft” and “disruptive,” and a Google search returns a combined 850,000 results. But what have those businesses truly changed? We still use what is essentially 100-year-old technology – cars – to get from Point A to Point B. Ride-sharing may have altered the value of the municipal taxi, but it certainly did not change the transportation industry.

Steps for determining the root cause of peeling problems.

Picking the right tool for electrochemical contamination at the rework bench.

A half-dozen versions of the same scenario occurred in the past month, all having to do with materials and processes used in post-op/rework applications. This step of the production process often escapes the attention of engineers because there’s no cool machinery or any real engineering that takes place. Most hand-solder operators are highly proficient and have developed techniques that get the job done, which can lull a supervisor or production manager into a false sense of security. Electrochemical contamination doesn’t normally appear until it has become a dreaded field failure. In fact, if the issue is contamination/corrosion/leakage-related, the first place I look is the rework bench, and eight times out of 10 that’s where the trouble spots lie.

Manual soldering applications have different requirements than upstream processes, and it’s worth detailing these differences to understand the importance of materials selection and proper usage.

Adding just enough material for a set amount of prints can ensure good outcomes.

Although no-clean solder pastes are the most prevalent materials used in electronics assembly today, water-soluble pastes are still in the game. In market sectors like aerospace, military, automotive and industrial, water-soluble materials are frequently the specified-in, legacy product – often because of the reliability requirements to remove flux residues. Printing water-soluble solder pastes, however, is quite a different process than printing no-clean materials. Assembly specialists take note!

Back in the day, no-clean pastes were the more fickle materials, with delicate operating windows and strict storage requirements. Over the years, massive amounts of development and a focus on maximizing process efficiency (i.e., eliminating an unnecessary cleaning step) put no-clean in the processability fast lane, while water-soluble material R&D got lapped. Although new water-soluble pastes have been released in recent years, they are still generally more difficult to print than no-clean pastes, and the finesse required to successfully print them isn’t always well understood. Put simply, the primary challenge with water-soluble pastes is they are hydroscopic (absorb water) in their function, making them a bit sponge-like.