Estimated reading time: 6 minutes

Maggie Benson's Journey: Learning the Basics

Editor’s note: Indium Corporation’s Dr. Ronald C. Lasky continues this series of columns about Maggie Benson, a fictional character, to demonstrate continuous improvement and education in SMT assembly. Maggie is owner of Ivy Benson Electronics, where Andy and Sue are employees.

Andy Connors had never been so nervous. He was picking up Sue March at her home to get pizza, where they would spend time answering the last five questions of the SMT 101 quiz that was given at Ivy Benson Electronics. The reason for his jitters was that he was going to meet Sue’s parents and he hoped he would pass muster. He had reasons to have doubts, as at their last date it became clear to him that Sue was quite a bit smarter than he was. He walked up to the door and knocked.

A handsome, very fit-looking man answered the door. “You must be the Andy Connors that my daughter can’t stop talking about,” Burt March said.

Andy was stunned. “Can’t stop talking about?” he thought.

Immediately, Sue came to the door, grabbed Andy by the hand, and pulled him into the house.

“Dad, this is Andy, who convinced me to go to college part-time. He is also the best worker at Ivy Benson and the nicest guy,” Sue said, beaming.

At that moment, an attractive woman came into the room. “Welcome, Andy, it is a delight to finally meet you!” exclaimed Peg March. “Sue has told us so much about you.”

Andy almost swooned. He had wondered if Sue had any real interest in him and was not prepared for this heartfelt welcome. He was determined at this point to not let Sue or her parents down.

After a few minutes of pleasant conversation, Sue suggested that they head out for pizza.

“Wow, your parents are amazing,” Andy said once they were in the car. “They are so nice, and your mom looks like she could be your sister.”

“My mom will love that,” Sue replied. “I can tell that they really liked you. Oh, and they want you to come for dinner soon.” Andy never expected this very pleasant turn of events.

After they ordered their pizza, they settled down to answer the remaining five questions. “Let’s look at number 6,” Andy suggested.

 6. In solder paste, what is response-to-pause?

1. When printing is paused, the viscosity decreases while stirring
2. Whether or not the paste viscosity increases when printing is paused
3. Whether or not the paste dries out when printing is paused
4. When printing is paused, the flux separates from the paste and makes a mess

“Hmmm, I know this is important. Even though the new solder paste was more expensive, Chuck mentioned that was one reason they replaced another solder paste, because ‘it had poor response-to-pause,’” Sue commented.

“Yeah, I remember hearing that, too,” Andy replied.

“Well, I don’t think it could be (a), as Chuck mentioned that the printed volume decreases,” Sue suggested.

“I think (d) is out, too,” Andy commented.

“I don’t think the paste dries out and the poor paste was okay after it was printed a few times,” Sue suggested.

“That leaves (b),” Andy said. After searching online, they found the answer.

“Wow, 6 for 6. I’ll bet our luck runs out soon,” Sue said.
“Let’s look at number 7,” Andy suggested.

7. What does ENIG stand for?

1. Energizing nitrogen gas
2. Electroless nickel immersion gold
3. Evolving nitrogen inerting gas
4. None of the above

“I haven’t a clue,” Sue moaned.

“Neither do I,” sighed Andy. “Let’s not guess and call this one a miss.”

Sue did a Google search and found the answer. “ENIG stands for electroless nickel immersion gold. It is a surface finish like OSP. Let’s ask Chuck to tell us more about it tomorrow,” Sue said.

“Okay, here is number 8,” Andy said.

8. What is more typical of a solder paste powder diameter?

1. 5 mils
2. 30 microns
3. 25 mils
4. 5 microns

“I think we can eliminate 5 mils and especially 25 mils. Those sizes are near the aperture diameter of a stencil,” Sue said.

“Twenty-five microns is about one mil and stencil aperture widths are around 10 mils or so, as we saw in question 2. So, I think 30 microns is the best answer,” Andy said confidently.

After searching online again, they found that Andy was correct, and he smiled when he saw that Sue looked impressed.
“Here is number 9,” Sue said.

9. What does CSP stand for?

1. Compound semiconductor package
2. Centering SMT package
3. Chip scale package
4. None of the above

“That one is easy—chip scale package,” Andy exclaimed.

“Wow, I’m impressed. You got two in a row,” Sue teased.
“There were a couple of magazines in the breakroom called Chip Scale Review. I actually browsed through one or two,” Andy said.
“OK, here is the last one,” Sue said.

10. A process has 10 steps; the yield at each step is 99%. What is the end of the process yield?

1. 90.4%
2. 89.1%
3. 90%
4. None of the above

Sue took her smartphone, opened the calculator, and then flipped the phone on its side. “The answer is (a) 90.4%,” Sue said.
Andy seemed deflated. He was shocked that she could determine the answer so quickly. He really did need to up his game, he thought.

“How did you do that?” Andy asked.

“Isn’t it obvious that the answer is 0.99¹⁰ = 0.904 or 90.4%?” Sue said.

“It wasn’t obvious to me,” Andy said dejectedly.
Sue proceeded to show Andy how to make this calculation. She then felt it was time to discuss the results. “Well, nine out of 10 seems pretty good to me,” she said.
“I agree,” Andy said.

“Hey, how do you feel about the pre-calculus class we are taking that starts next week?” Sue asked.

“I’m so nervous, I’m shaking,” said Andy. “I got a Schaum’s Outline of Elementary Algebra and I have to admit that it now seems easy to me. When I was in high school, I saw no purpose for algebra and now I do. Solving some of the problems was kind of fun.”

“Pre-calc seems a little scarier though, I agree,” Sue said. “Hey, isn’t it great that Chuck has developed a class to help us prepare for SMTA Certification?”
“And it’s on overtime pay!” Andy exclaimed.

Sue got up, gave Andy a quick kiss, and grabbed his hand. As Andy stood up, his knees just about buckled.

“It’s still early and the weather’s great. There is a waxing gibbous moon tonight. Let’s go for a walk and check it out,” Sue said coyly. Andy had no idea what a waxing gibbous moon was, but the thought of a moonlight stroll with Sue was enticing.

In the following weeks, the staff at Ivy Benson was almost a little annoyed at Sue and Andy as they kept asking all sorts of questions about electronics assembly.

Note: To my knowledge, there is not a source of material to help a technician or engineer new to electronics assembly to learn the basics. In this series, as we watch Sue and Andy learn the basics, I plan for this to be the source. Cheers, Dr. Ron

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

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