Microelectronics | System Design Reflections

Synopsis

This page contains reflections and thoughts on the work I carried in this field.

The Why

First, because I like electronics. Second, because I like computers.

The whole story is way too long. Keeping it short; around 1996 or so, while examining an 80286-based logic board from a UNiSYS desktop computer, I had this strong feeling that I could make my own hardware. At the time, I had no means to pursue this dream. Most of the parts that I needed were unobtanium. I was familiar with hand drawn PCB layouts, but had absolutely no electronic CAD knowledge. Back then, my main computer was based on an 80386SX processor. It was so weak that I doubt it would've been able to run OrCAD or EAGLE, provided that I knew about them and I had the means to obtain copies. Nonetheless, I continued to draw block diagrams and electrical schematic diagrams for the hardware that I imagined; all on paper.

As time passed, I continued to improve my electronics, computer, hardware, and software skills. Around 1999, I got my first contact with OrCAD. Initially, I was very enthusiastic, but for some reason, that didn't last. Then, a few months later, I discovered EAGLE and that was it. However, it took me another twenty years to have the courage to venture into designing my own x86 hardware. In the meantime, thanks to globalization, I finally had the chance to access the electronic components that I needed.

After I sorted everything out, it was just a matter of time. I started by creating my own libraries. Next, it took me anywhere from a couple of days to a couple of months to produce a schematic and its associated PCB layout.

Finally, I was able to play old games on my own hardware. And the rest is history.

Four Layers

I often receive questions regarding why do I use four layers PCBs for my computer hardware designs.

The first project was the system backplane, and it was a two-layered board. Then, came the 80386DX single board microcomputer card. I initially had some issues with the two-layer design. After re-reading some black magic electronics literature, I improved my designs and completely switched to fou-layer PCBs.

The drawback is that these kinds of PCBs are expensive. However, I usually wait until I have enough PCB designs to exceed 100 square inches. This way, I can access the Medium Run option at OSHPark, considerably lowering the total cost.

Another strong point of four-layer PCBs is that I can make better use of the ground and supply planes while having the entire top and bottom sides for track routing. And since I lay all tracks manually, this also gives me space to paint the canvas as I like.

I don't think that I will ever design a two-layer computer card.

PCB Factory

During the past ten years, I have done some research on accessible printed circuit board manufacturing plants. Most of them are located in China and offer very good services. However, I decided to go with OSHPark in the U.S.A. as the quality of their PCBs is top-notch.

I particularly like the ENIG finish and the quality of the silkscreen. I'd like to see their clear soldermask over black substrate services extended to four-layer PCBs as well. That would be nice.

There's a drawback, though: price. They're not the cheapest, and then there's the shipping fees, depending on where you live in the world. But since I'm just living my (electronics) dream, I assumed the price factor. It's not like I am doing any production, nor do I build hardware for sale.

Finally, my PCB assemblies appear to be industrially built when, in fact, they are fully assembled by my hands.

Components

I always go with top quality mechanical and electronic components, coming from reputable brands. Wherever I can, I go with period correct parts, even though they're harder to acquire. As I am striving for perfection, I eliminate a number of probable electrical issues, just by using quality parts. And I like the looks of the completed assemblies.

Throughout the years, I salvaged a lot of electronic parts from old PCBs. I know how hard it was in the '90s to find quality components. Thankfully, these days I can get everything I need at my favorite online parts store (Mouser).

Every so often, I find myself browsing their site for interesting components, remnants of the '80s and '90s -- think AVX or Kemet tantalum capacitors, Bourns resistor networks, Dale resistors, Texas Instruments semiconductors, and so on. These were used on a large scale on quality computer and industrial hardware back then. And I'm grateful that I can still find them new. Sometimes I backorder parts and I have to wait for the stocks to replenish, but it's worth the wait.

Pushing things to the extreme, sometimes I strive to keep the PCB assemblies chromatics in shades of yellow, brown, and purple, all for a unified appearance. I wasn't good at art, but I have my own definition of art.

As a side note, I like to track the provenience of the components. Thankfully, Mouser lists the originating country. To my surprise, the Harting gold-plated pin header connectors that I heavily use in my designs, are made at a factory located in Romania. Nice find, nonetheless.

Conclusions

Hope you found these writings interesting.

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