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TTM: Consult Fabricators Early for PCB Designs
July 2, 2015 | Andy Shaughnessy, PCBDesign007Estimated reading time: 6 minutes
Shaughnessy: It looks like something that would make a fabricator say, "Are you serious?"
Ellis: The industry has changed tremendously since I started in it, that's for sure. I used to wire wrap assemblies when I was a kid.
Shaughnessy: In your talk, you mentioned how everyone talks about drilling vias below six mils. But then you point out that six mils is only two times the width of a human hair.
Ellis: Yes. I feel like I’m always splitting hairs when I build fine-pitch stack-ups, because they require trade-off analysis between minimum aspect ratio, hole sizes, pad and antipad sizes, the space left between those pads, and how many traces can be run between the pads, if any. 6 mils is the smallest mechanical drill size we’ll use in North America, and it’s only the diameter of 2 human hairs and smaller than a hypodermic needle. Because 6 mil drill bits break easily, can’t be re-sharpened, and are very expensive, Asia sites rarely use them. So I never design a stack-up for our China sites using a 6 mil drill. But as hole size increases, so do the pad diameters in order to maintain annular ring requirements, and that can kill the routing space between pads.
Come to think of it, another thing I would like to see engineers do more often is consider the production site technical capabilities. Offshore PCBs are significantly lower in cost, because they’re optimized for continuous processes that don’t need to be interrupted or require highly advanced, but slow, equipment or processes. Asia sites have excellent capabilities, but they are not all at extreme tech levels of some of our N. America sites. So designs should be done in accordance with production site guidelines and available materials.
Shaughnessy: Sure. Well, it was a great talk. You covered a lot of really cool cutting-edge stuff. The designers in the crowd really enjoyed it.
Ellis: Thank you.
Shaughnessy: Thank you, Julie. I appreciate your time.
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Maximizing ROI Through Better Wet Process Control
08/20/2024 | I-Connect007 Editorial Team“When things get out of control, the variation in your wet process begins,” says Mike Carano,. “Just because they look like good boards and may even pass electrical test, it does not necessarily mean you have good boards. Once the chemistry is headed toward the right or left side of the process control parameter cliff, the plating is compromised. If the copper is thinner than it should be, when the customer puts it into service, the board may fail after 500 cycles vs. the requisite 1,000 or 2,000 cycles. The root cause issue is that you plated 7/10ths of a mil of copper instead of one-mil of copper because you were not controlling your process. The fact that you passed your own electric test becomes inconsequential.”
The Chemical Connection: Controlling an Alkaline Etch Bath With Low Copper Loading
08/07/2024 | Don Ball -- Column: The Chemical ConnectionThis month, I wanted to continue my discussion on how much process control is actually needed for high-density circuit production. However, in the last month, I have been called on to help with a specific process control problem: how to control an alkaline etch bath when you’re not etching much copper. This problem has been cropping up more frequently as smaller shops (and a few larger ones) concentrate on low-volume, high-value plated through-hole panels such as prototypes, resistor cores, etc.