Joe Fjelstad Breaks Down His Occam Process

Estimated reading time: 21 minutes

Fjelstad: Exactly. The “Finstrate” structure that HP came up with was a real landmark. HP was one of the greatest gold users of all time, though.

Holden: That’s because we never had any tin-lead or reflow.

Fjelstad: I wasn’t aware of that.

Holden: We had tin-nickel and put gold on tin-nickel. I started reducing the thickness of gold, and we introduced bright acid tin on top of tin-nickel. Then, we went to SMOBC, an emergent silver, but never any tin-lead.

Johnson: Earlier, you made a point around not seeing solder go away, but it would change how much we use it so that tin-lead comes back into play. Where do you see the trade-off now that you’ve been working with your Occam process? If we go down this path, what are the circuits going to look like?

Fjelstad: I’ve been working with a very talented designer and Athena Tech founder, Darren Smith, off and on for a number of years. Darren picked up on the Occam idea when I first trotted it out a dozen years ago. He’s a very competent designer, and he jumped on it. He said it absolutely made sense, and he did a design comparison. It was pretty dramatic. We complemented each other, and I tended to challenge him. A few years back, I said that I needed to show something to somebody, and he did a redesign of something he had designed for traditional assembly. It was impressive. That reminds me that a good designer can understand pretty quickly. Early on, I was invited to give a talk at one of the PCB design shows early on about it. I gave a little keynote address in a room full of designers; for the most part, the designers listening nodded their heads, grasping the potential. On the other hand, they look at it and think, “Who’s going to make it?”

Again, my thinking goes back to the idea that if we’d picked up on the general Occam concept with one of the major vertically integrated OEMs that built it all, from ICs to packages and PCBs, including all of the raw materials. It would have already been done. IBM was a showcase of vertical integration because they made silicon, ICs, lead frames, glass, copper, and epoxy. They made everything that was required for their circuits, and I always thought they were a bit crazy until I visited their manufacturing facility in Endicott, and discovered that they weren’t crazy; they were genius with how they set and controlled everything. It’s important to note that in the early days of this industry, every circuit was designed using a standard grid. That was because component terminations were all provided on 100-mil centers.

As a quick side note on that, however, when I went to work in the Soviet Union, their dual-inline packages were 2.5 millimeters—not 2.54 mm (100 mils). With a 16-pin DIP components could be interchanged, but if it got big, then the run-out didn’t work. In other words, you could pretty quickly get a run-out on the things they would work for a few pins, but when you got to larger pin counts, it didn’t work anymore. That was serious but also an amusing by-product of using English versus metric units.

I need to go back to Darren to complete a thought. A while back, I gave a paper at IPC on the Occam concept and wanted to show the potential savings, so enlisted Darren’s help. I said to him, “If you don’t mind, take something you’ve designed—non-proprietary, please—and then do a redesign using the Occam concept for reverse manufacturing. Have every component with terminations on a common grid. 0.5 millimeter is preferred because below 0.5-mm assembly yields for solder typically drop off.” That paper included an example of what he did. It went from 12 layers to six layers, and, as I recall, it went from an original 110 mm by 140 mm down to 70 mm by 30 mm. Then, he got creative and made it into a rigid-flex and separated digital from analog so that it all folded up. It weighed a fraction of what the original design was, and he consumed a small amount of the space. Something I forgot to say earlier is that I told him at the time not to go to DigiKey of other component catalog and look for actual components but pretend as if those components existed with terminations on 0.5-mm pitch, including a 442 I/O FPGA that was the centerpiece of that design.

Holden: If you want the figures for the Occam, you have them in our circuit designer’s guide to solderless assemblies. All the Occam figures you need are in high resolution in your free eBook.

Fjelstad: I’ve been trying to keep that comparison image out there in front of people to allow it to sink into their minds. At the same time, most of them are going to look at it and say, “Wow! That’s a neat idea.” Invariably, people are agreeable to the fundamental idea, but on the other hand, they have to do what they have to do to get through the day. I understand that. When I’m asking a semiconductor packaging manufacturer to make a device, make all your packages with 0.5-mm pitch terminations, including depopulations of the fundamental pitch. Again, I chose 0.5-mm pitch because that’s about the point where the wheels fall off for most people in terms of solder assembly. In other words, it’s a potential for being able to use design for both solder and solderless assembly. When you’re getting ready, you can finally embrace Occam.

The only not insignificant problem is that with solder, the designer needs to provide room for rework and repair. One of the things I stress with Occam assembly is that rework and repair are crutches to support a technology that has lots of problems. That’s what you have to do when you don’t do the job right or when you have a technology that’s incapable of being able to deliver the kinds of quality that you need for your product. Solder is a great technology, but it doesn’t need to be used for everything.

Holden: Joe, have you been following our articles about vertical conductive structures (VeCS)?

Fjelstad: I have been looking at that, and I’ve also been an admirer of Joan [Tourné]’s work for a long time.

Holden: I’m also talking with Joe Dixon, who is the VP of R&D for WUS and happened to work for me in Palo Alto at a PCB shop in the latter part of the ‘70s. WUS had been building all these things and supplying them to customers, but I introduced him to your pictures of multiple nets per via. What company was that with?

Fjelstad: I was still at Silicon Pipe then. I had some good responses to that idea of being able to build a split via and get rid of a lot of the inductions and other limitations relative to traditional vias. We had fun in the early days and were completely unfettered by convention.

Holden: That’s part of my lecture for the electrical engineering students at Michigan Tech on future technologies they may see in their careers. Why should a via only have one net connection? Why can’t a via have two, three, or four nets using the same via?

Fjelstad: I’m also keen on the idea of using vias as resistors and putting a dab of resistive material in some of the holes between process steps and then plating it over; they’re not necessarily great for high power, but printing resistors and capacitors, etc. You can establish a fairly precise resistor. It won’t necessarily be great for high power, but most resistors aren’t high power.

Holden: It would be interesting to know that. I licensed an Occam-like process from the University of Helsinki since they never recognized you or gave you any money, but embedded ICs is the Occam process because we do it exactly the way you outlined. You laser drill down onto the pads of the silicon and then plate directly for embedded.

Fjelstad: The one thing that I’ve held in a very stringent way was the idea of putting everything in packages and testing them. If ICs change with each die shrink, and the pad out changes, then you have to rip up and throw away everything it did. If you put it in packages, then what you did is still good, and you don’t have to go back and rethink and redesign because somebody went through a die shrink. The packages provide the standards, which are the glue that will hold them together.

Johnson: What I’m picking up from this conversation is that it’s a combination of how you’re securing the components and then working with standard die sizes or standard pad sizes and placements. Those are two separate but not necessarily connected ideas; when you put the two of them together, that’s where the real benefit to the Occam process comes into play.

Fjelstad: Yes, and there’s an overarching view that needs to be taken into this thing. Viewed in isolation without perspective, it doesn’t make a whole lot of sense. I see this holistic overview of what it all looks like. Again, the Lego module that I put together is the linchpin for the Occam approach. It’s something that anybody can get their heads wrapped around quickly. Legos definitely work. If every one of the chips used has its own unique pad out or it’s on a different pitch, it all falls apart. It doesn’t make any sense, but if you adhere to fundamental precepts and standards, it works. This is part of the lesson we tried to teach at Tessera where we talked about using TLS. Tessera laminated substrate a 0.5-mm substrate that looked like an early breadboard much like IBMs standard boards from the 1970s.

The idea of building a standard substrate like what we proposed at Tessera early on is where I fully grasped the idea of needing to have something that created order and made sense, but it involves doing things differently. Circling back to that idea of the IC package foundries, remember that they have all of these different lead pitches. They are all depopulations of all these different pitches, and then you have all the different sizes of these structures and various finishes for them. I don’t want your nickel and gold or your solder on the termination. Give me bare copper; now, how much more are you going to charge me for making your process simpler and with fewer steps to control and validate? It all costs money.

There’s a great quote I read when I was at Boeing almost 40 years ago, when I first picked up a copy of Wind, Sand and Stars by Antoine de Saint-Exupéry. There was a passage in the book of him talking about the wing of an aircraft that really struck me: “A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away.” That has been a cornerstone of my thinking in the four decades since.

Holden: What’s the status of the Occam prize?

Fjelstad: Thanks for mentioning that, Hap. It’s on hold at the moment, but I will resurrect that at some point in time. I was frankly disappointed that I didn’t get enough people to participate earlier. The biggest impediment is the designer will have to start learning something new and a bit different. I was trying to incentivize designers with a monetary prize to expand the horizons of their thinking and consider something both new and ultimately simpler. I am confident that a tipping point will eventually be crossed.

Johnson: Joe, we really appreciate it. Best of luck with Occam. It would revolutionize the industry.

Fjelstad: Thank you, Nolan. I’ll keep at it.

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