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Maggie Benson’s Journey: Melancholy Endings and Exciting Beginnings

Editor’s note: Indium Corporation’s Ron Lasky continues this series of columns about Maggie Benson, a fictional character, to demonstrate continuous improvement and education in SMT assembly.

It was the last night class for pre-calculus. Andy and Sue were eating dinner at their usual pizza shack before heading to class.

“I think I get how integration works. The integral of x is x²/2, so why isn’t the integral of sin (x) = (sin(x))²/2?” Andy said, groaning.

“Because when you integrate x, you integrate it over dx,” Sue commented, then wrote down the equation as she said, “The only way you could get (sin(x))²/2 would be if you integrated it over d(sin(x) (Figure 1)”.

“Ah, makes sense,” Andy replied.

After class they had stopped for ice cream at their favorite parlor before preparing for the last SMT class they were teaching.

“I feel kind of melancholy,” Andy commented, “that this is the last of both our pre-calc and SMT classes.”

“I know, I feel the same way,” Sue replied. “It seemed like such a burden at first, but soon both classes became fun.”

Neither would admit out loud that the presence of the other made it such a pleasant experience.

“Well, let’s start working on reflow profiling,” Sue suggested.

“Let’s use this solder paste spec (Figure 2) and this reflow profile (Figure 3),” he responded.

“Look at the first part of the solder paste spec,” Sue said. “It says the recommended ramp rate should be between 0.5°C and 1°C per second.” (Note the red triangle in Figure 2.)

“Yeah, then if we look at the reflow profile, by dividing the change in temperature at the melting point (217 - 20°C = 197) by the change in time (230 seconds), we see that the slope is 0.857°C per second, so it is nicely in the spec limits,” Andy said.

“The time of liquidus is easy, too—just subtract the time at D (290 seconds) minus the time at B (230 seconds) and get 60 seconds, also within the spec,” Sue added.

“The peak temperature is certainly easy to find at point C, or 240°C,” Andy said.

“And the cooling slope is -2.8°C, also within the spec,” Sue chimed in. (Can you calculate this number?)

They then developed the PowerPoint slides to teach this material in their class.

“That Excel software tool you developed to make all these calculations was really impressive,” Sue complimented Andy. “I heard Maggie discussing it with Chuck Tower. They thought it was amazing.”

“’Twern’t nothing, me lass,” Andy responded in a gallant way (Figure 4).

Both agreed that the students could use this Excel software tool after the class, but they had to know how to perform the calculations by hand.

Eighteen months later…

Sue and Andy continued their night school classes at the local community college. With the recommendation of Ivy University Professor Patty Coleman, they received some equivalent credit for work they had performed teaching SMT classes, as well as some other projects they worked on at Ivy-Benson Electronics. Both students were granted their two-year AAS degrees. The more interesting development was that Professor Coleman pulled some strings and enabled them to transfer to Ivy University as juniors to work on their bachelor’s degrees. They would take a reduced course workload and work at Ivy-Benson part-time.

All these events transpired in June and the two future Ivy U students would have to wait until September to start class.

Right after graduation, Andy and Sue were asked to meet with Maggie Benson. Both felt a little nervous. As they entered Maggie’s office, they were even more so when they saw that Professor Coleman had joined the meeting.

As they entered, Maggie said, “Hola, Sue y Andy. ¿Le gustaría ir a México y evaluar una empresa para que la compremos?” For those whose Spanish is a little weak: “Hello, Sue and Andy. Would you like to go to Mexico and evaluate a company for us to buy?”

Although they all spoke Spanish (Sue had really worked on hers with her mom lately), Maggie reverted to English, “Business is so booming that we are considering buying a small assembly plant in Mexico. We want to send Chuck Tower to perform an evaluation but felt you two could help him as you speak Spanish.”

“Yikes! I’m not sure my Spanish is that good,” Sue warned them.

“You’re too modest,” Andy chimed in. “You’ve come a long way in the last 18 months.”

Maggie, Andy, and Sue started discussing the details.

Patty chimed in, “Ivy University has a self-study course. Sue and Andy, if you write a detailed report of what you learned during this project, I’m quite sure it can count as your first course.”

The meeting ended. Sue and Andy were left feeling like their heads were spinning with all these exciting and challenging opportunities.

Stay tuned to see how the adventure in Mexico plays out.

References

1. If you would like a copy of the Excel reference, email Dr. Ron at rlasky@indium.com.

Ronald C.?Lasky is an instructional professor?of engineering?for the Thayer School of Engineering at Dartmouth College, and senior technologist at Indium Corporation.?Download The Printed Circuit Assembler’s Guide to… Solder Defects by Christopher Nash and Dr. Ronald C. Lasky. You can also view other titles in our full I-007eBooks library.

This column originally appeared in the October 2022 issue of SMT007 Magazine.