Vintage Fairchild IC Proves Tough To Decap

You’d think that something called “white fuming nitric acid” would be more than corrosive enough to dissolve just about anything. Heck, it’s rocket fuel – OK, rocket fuel oxidizer – and even so it still it wasn’t enough to pop the top on this vintage Fairchild μL914 integrated circuit, at least not without special measures.

As [John McMaster], part of the team that analyzed the classic dual 2-input NOR gate RTL chip from the 1960s, explains it, decapping modern chips is a straightforward if noxious process. Generally a divot is milled into the epoxy, providing both a reservoir for the WFNA and a roughened surface for it to attack. But the Fairchild chip, chosen for dissection for the Maker Faire Bay Area last week specifically because the features on the die are enormous by modern standards, was housed in an eight-lead TO-99 case with epoxy that proved nigh invulnerable to WFNA. [John] tried every chemical and mechanical trick in the book, going so far as to ablate epoxy with a Nd:YAG laser. He eventually got the die exposed, only to discover that it was covered with silicone rather than the silicon dioxide passivation layer of modern chips. Silicone can be tough stuff to remove, and [John] resorted to using lighter fluid as a solvent and a brush with a single bristle to clean up the die.

We applaud the effort that this took, which only proves that decapping is more art than science sometimes. And the results were fabulous; as Hackaday editor-in-chief [Mike Szczys] notes, the decapping led to his first real “a-ha moment” about how chips really work.

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CNC Your Own PCBs With A 3D Printed Mill

Yes, you can whip up a design for a printed circuit board, send it out to one of the many fab houses, and receive a finished, completed board in a week or two. There are quick-turn assembly houses that will manufacture a circuit board and populate it for you. But sometimes you need a board now, and that’s when we get into home PCB fabrication. You can do this with either etching or milling, but [Renzo] has a great solution. He built a 3D printed milling machine that will make a printed circuit board.

The design of this tiny micro mill is based on a handheld rotary tool, also called a Dremel, but that’s like Kleenex, so just buy a Proxxon. This mill is designed with 3D printed T-track and constructed with linear bearings on smooth rods with standard NEMA 17 stepper motors and herringbone gears for little to no backlash. There is quite a bit going on here, but lucky for us [Renzo] has a video tutorial of the entire build process available for viewing below.

We’ve previously seen some of [Renzo]’s previous efforts in homemade PCB fabrication, up to and including applying green soldermask with the help of Fritzing. This is good, very good, and the only thing that really separates this from manufactured PCBs is the lack of plated through holes. That’s just a bit of graphite and electroplating away, and we’re looking forward to [Renzo]’s further adventures in making PCBs at home.

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CNC Your Own PCB With This Tutorial

It is getting so easy to order a finished printed circuit board that it is tough to justify building your own. But sometimes you really need a board right now. Or maybe you need a lot of fast iterations so you can’t wait for the postal service. [Thomas Sanladerer] shows how he makes PCBs with a CNC machine and has a lot of good advice in the video below.

He starts with Eagle, although, you could use any creation package. He shows what parameters he changes to make sure the traces don’t get eaten away and how to do the CAM job to get the files required to make the boards. If you don’t use Eagle, you’ll need to infer how to do similar changes and get the same kind of output.

We’ve only heard a few people pronounce Gerber (as in Gerber file) with a soft G sound, but we still knew what he meant. We have the same problem with GIF files. However, once you have Gebers, you can join the video’s workflow about 5 minutes in.

At that point, he uses FlatCAM to convert the Gerbers to a single G-code file that integrates the paths and drill files. There were a few tricks he used to make sure all the tracks are picked up. Other tricks include leveling a spoil board by just milling it down and mounting different size bits. He also has ideas on aligning the Z axis.

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DIY Vacuum Table Enhances PCB Milling

CNC milling a copper-clad board is an effective way to create a PCB by cutting away copper to form traces instead of etching it away chemically, and [loska] has improved that process further with his DIY PCB vacuum table. The small unit will accommodate a 100 x 80 mm board size, which was not chosen by accident. That’s the maximum board size that the free version of Eagle CAD will process.

When it comes to milling PCBs, double-sided tape or toe clamps are easy solutions to holding down a board, but [loska]’s unit has purpose behind its added features. The rigid aluminum base and vacuum help ensure the board is pulled completely flat and held secure without any need for external fasteners or adhesives. It’s even liquid-proof, should cutting fluid be used during the process. Also, the four raised pegs provide a way to reliably make double-sided PCBs. By using a blank with holes to match the pegs, the board’s position can be precisely controlled, ensuring that the back side of the board is cut to match the front. Holes if required are drilled in a separate process by using a thin wasteboard.

Milling copper-clad boards is becoming more accessible every year; if you’re intrigued by the idea our own [Adil Malik] provided an excellent walkthrough of the workflow and requirements for milling instead of etching.

Homebuilt CNC Software, Brewed To Taste

Mainstream productivity software from the big companies is usually pretty tight, these days. Large open source projects are also to a similar standard when it comes to look and feel, as well as functionality. It’s when you dive into more niche applications that you start finding ugly, buggy software, and CNC machining can be one of those niches. MillDroid is a CNC software platform designed by someone who had simply had enough, and decided to strike out on their own.

The build began with the developer sourcing some KFLOP motion control boards from Dynomotion. These boards aren’t cheap, but pack 16MB of RAM, a 100-gate FPGA, and a microcontroller with DSP hardware that allows the boards to control a variety of types of motor in real time. These boards have the capability to read GCODE and take the load off of the computer delivering the instructions. With the developer wanting to build something robust that moved beyond the ’90s style of parallel port control, these boards were the key to the whole show, also bringing the benefit of being USB compatible and readily usable with modern programming languages.

To keep things manageable and to speed development, the program was split into modules and coded using the author’s existing “Skeleton Framework” for windowed applications. These modules include a digital readout, a jogging control panel, as well as a tool for editing G-code inside the application.

For the beginner, it’s likely quite dense, and for the professional machinist, industry standard tools may well surpass what’s being done here. But for the home CNC builder who is sick of mucking around with buggy, unmaintained software from here and there, it’s a project that shows it doesn’t have to be that bad. We look forward to seeing what comes next!

Want to see what else is out there? We’ve done a run down of DIY-appropriate CNC software, too.

Bandpass Filters From The CNC Mill

A bandpass allows a certain electrical signal to pass while filtering out undesirable frequencies. In a speaker bandpass, the mid-range speaker doesn’t receive tones meant for the tweeter or woofer. Most of the time, this filtering is done with capacitors to remove low frequencies and inductors to remove high frequencies. In radio, the same concept applies except the frequencies are usually much higher. [The Thought Emporium] is concerned with signals above 300MHz and in this range, a unique type of filter becomes an option. The microstrip filter ignores the typical installation of passive components and uses the copper planes of an unetched circuit board as the elements.

A nice analogy is drawn in the video, which can also be seen after the break, where the copper shapes are compared to the music tuning forks they resemble. The elegance of these filters is their simplicity, repeatability, and reproducability. In the video, they are formed on a CNC mill but any reliable PCB manufacturing process should yield beautiful results. At the size these are made, it would be possible to fit these filters on a business card or a conference badge.

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Soundproofing A CNC Mill Conversion

The Proxxon MF70 is a nice desktop sized milling machine with a lot of useful add-on accessories available for it, making it very desirable for a hacker to have one in his or her home workshop. But its 20000 rpm spindle can cause quite the racket and invite red-faced neighbors. Also, how do you use a milling machine in your home-workshop without covering the whole area in metal chips and sawdust? To solve these issues, [Tim Lebacq] is working on Soundproofing his CNC mill conversion.

To meet his soundproof goal, he obviously had to first convert the manual MF70 to a CNC version. This is fairly straightforward and has been done on this, and similar machines, in many different ways over the years. [Tim] stuck with using the tried-and-tested controller solution consisting of a Raspberry Pi, an Arduino Uno and a grbl shield sandwich, with stepper motor drivers for the three NEMA17 motors. The electronics are housed inside the reclaimed metal box of an old power supply. Since the Proxxon MF70 is already designed to accept a CNC conversion package, mounting the motors and limit switches is pretty straightforward making it easy for [Tim] to make the upgrade.

Soundproofing the box is where he faced unknown territory. The box itself is made from wooden frames lined with particle board. A pair of drawer slides with bolt-action locks is used for the front door which opens vertically up. He’s also thrown in some RGB strips controlled via the Raspberry-Pi for ambient lighting and status indications. But making it soundproof had him experimenting with various materials and techniques. Eventually, he settled on a lining of foam sheets topped up with a layer of — “bubble wrap” ! It seems the uneven surface of the bubble wrap is quite effective in reducing sound – at least to his ears. Time, and neighbours, will tell.

Maybe high density “acoustic foam” sheets would be more effective (the ones similar to “egg crate” style foam sheets, only more dense)? Cleaning the inside of the box could be a big challenge when using such acoustic foam, though. What would be your choice of material for building such a sound proof box? Let us know in the comments below. Going back many years, we’ve posted about this “Portable CNC Mill” and a “Mill to CNC Conversion” for the Proxxon MF70. Seems like a popular machine among hackers.