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Clive AshmoreOne approach: Aperture designs that reduce paste volume from the inside wall.

While the primary theme of this column over the past few years has been miniaturization’s impact on stencil printing, standard SMT process challenges are alive and well. In many applications, where average device dimensions are large compared to the latest package footprints, reducing traditional defects is still a battle. One such frustration: mid-chip solder balls. To understand how to correct this well-known defect, one must appreciate the origin.

Mid-chip solder balls are most often observed with passive devices, specifically, resistors and capacitors. Since these chips have terminations on each end, solder paste material is deposited on two corresponding pads on the board; an open space of solder mask-defined PCB lies between them.

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Susan MuchaIs the bigger issue a lack of trust of those who don’t “look” like us?

A month ago I had a conversation with a guy who worked for me in my corporate days. We were discussing the #MeToo movement, and he said, “I’m no longer sure where the line is drawn.” This surprised me because over the two decades I’ve known my friend he has never been anything but great to work with. When someone like him is concerned about crossing an invisible line, it scares me. To me, the #MeToo movement has started a conversation that could end up improving opportunities and working conditions for women, or hardening the glass ceiling.

Before the “you don’t know what women have gone through” mail starts, let me say I deeply understand the pain and anger that drives #MeToo. I’ve been inappropriately propositioned in a board room and at industry events more times than I can count. But what was much harder to deal with as I moved up in my career was getting a boss who really didn’t think women should run sales organizations and dealt with that by doing everything possible to destroy my credibility with his boss and my team. I won’t go into details, but I left for a job that paid twice as much and the best boss I’ve ever had.

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Robert BoguskiExplaining solder joint defects, one interruption at a time.

“Thank you all for promptly joining this morning’s webmail conference call. Today we are going to review the x-ray images our outside lab FTP’d us yesterday. Please set your phones on mute by pressing *6 if you are not speaking, and set your computers to the link provided by the meeting invite. You can unmute your phones in the same way, by pressing *6, if you wish to contribute to the conversation. You may listen via phone link, or by plugging earbuds into your laptops and activating sound. If you feel compelled to speak, unmute your phone and speak one at a time. We’d like to give equal time to as many members of our several participating engineering groups as possible. We have a big agenda, and many participants, so let’s get started.”

Here we go. Amateur hour.

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David Bernard

A practical approach for BGA void analysis.

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Hom Ming ChangThe challenge created by system variation is sometimes best solved by moving test operations offline.

A paced assembly line with inline functional test balanced through careful application of Lean manufacturing principles is a model of efficiency. Achieving that level of efficiency requires careful coordination among engineering and production personnel.

Paced lines that integrate functional testers deal with several challenges, including:

  • Length of test time vs. standard time per assembly station.
  • Accommodation of system variation.
  • Determining the best mix of automation and human interaction.
  • Fixture reliability in a high-volume environment.
  • Fail-safing the process from operator error.
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Tim O'NeillSoldering is the only process where the outcome can be impacted in real time.

One of AIM’s field engineers came back from a cross-country trip this week with stories of a profiling issue that was giving the client difficulties. Ultimately, the issue was design-related with a large ΔT that could not be overcome with the equipment used in production. It took a full day of attempts to make that final assessment.

Many engineers and technicians I work with rank reflow profiling alongside getting their teeth cleaned or an early morning workout. You know you need to do it, and the benefits are significant, but they aren’t immediate, and it is an unpleasant chore. Let’s take a minute to go over best practices for reflow profiling. Ideally, a “golden board” will have been supplied as part of the work kit by your customer or your design team. This board (FIGURE 1) will be a sacrificial, fully populated assembly with thermocouples attached (ideally five to seven) with high-temperature solder in strategic locations across the assembly. This board can be processed through the reflow oven to collect detailed information to ensure proper solder reflow temperatures are achieved within the temperature constraints of other components on the assembly.

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