Issue link: https://iconnect007.uberflip.com/i/1469343
64 SMT007 MAGAZINE I JUNE 2022 Aer 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. "ey are so nice, and your mom looks like she could be your sis- ter." "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. Aer 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? a) When printing is paused, the viscosity decreases while stirring b) Whether or not the paste viscosity increases when printing is paused c) Whether or not the paste dries out when printing is paused d) 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 expen- sive, Chuck mentioned that was one reason they replaced another solder paste, because 'it had poor response-to-pause,'" Sue com- mented. "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 aer it was printed a few times," Sue suggested. "at leaves (b)," Andy said. Aer 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? a) Energizing nitrogen gas b) Electroless nickel immersion gold c) Evolving nitrogen inerting gas d) 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 tomor- row," Sue said. "Okay, here is number 8," Andy said. 8. What is more typical of a solder paste powder diameter? a) 5 mils b) 30 microns c) 25 mils d) 5 microns "I think we can eliminate 5 mils and espe- cially 25 mils. ose 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 confi- dently. Aer 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? a) Compound semiconductor package b) Centering SMT package c) Chip scale package d) None of the above "at one is easy—chip scale package," Andy exclaimed. "Wow, I'm impressed. You got two in a row," Sue teased.