Details

Challenge: making PCBs yourself quickly & easily

Take the 3 major phases of making electronics; schematic design, PCB manufacturing and assembly, and try to optimize the process. Assuming you download a .kicad_pcb and has all the parts in a drawer to hand assemble, the longest phase becomes getting the PCB made.

Getting a PCB made can either be affordable or fast, but not both. Quick turn runs cost a lot of money and may not be available in all regions. In the last few years cheaper alternatives have popped up like buying direct from China or batched paneling from oshpark.com (<3 Oshpark!), and while such low-cost options have allowed for a more rapid iteration process, getting them can still take weeks depending on where you live and the customs policy of your country.

Etching is an affordable and low-cost process people have been using for years, but it has it's downsides, which is why many people choose to not etch their own PCBs. The process is finicky, requiring multiple imprecise steps that take many iterations of trial-and-error to perfect. The chemicals used stain everything and are caustic, which means they can't be used in education with kids. Further, those caustic chemicals need to be disposed of at appropriate facilities, which is at best, a hassle. And given all that complexity, most people never bother to add solder masks or silkscreens, the first being critical for working with SMD parts and the latter for sharing with other makers.

Milling machines can also be used to make traces and pads on copper clad. These are great for larger components, but require the highest-end mills to create fine pitch traces or BGAs pads.

There is also a crop of machines trying to use fused deposition modeling (FDM) to lay effectively conductive filament (usually silver-based) on top of a substrate. Like milling, FDM machines have lower resolution and the price of silver continues to go up, raising the recurring cost of consumables.

Solution: automate etching, solder masking and silkscreening

etchr is a desktop-sized machine that takes the best elements of etching PCBs while reducing the pain points described above. The main features of etchr include:

Automated application of chemicals so you never have to touch them
High-fidelity and repeatability using the latest in low-cost Stereolithography (SLA)
Eco-friendly chemicals that are nearly as effective as the alternatives... because science (well, smarter chemical processes.)

etchr has 5 main functional areas:

A UV projector that creates the exposure areas of the board, solder mask and silkscreen layers
A pump and spraying system to apply the chemicals to the workpiece
Reservoirs for the various UV-sensitive chemicals and rinses to be applied
Overflow vat to collect excess chemicals
Electronics to control the projector and pump system

The ultimate goal of etchr is to approach the fidelity of services like Oshpark, with 6 mil trace clearance & trace width, BGA footprints, etc. and even multi-layer boards (someday.) You need crawl before you walk so for the #2017hackadayprize, the first milestone is to print a single-sided board (double-sided is a stretch goal.)

Changing the world: access, S.T.E.A.M. & the environment

Access

Those of us in the US take for granted the fact that we have access to low-cost PCBs with a less-than two week arrival time. Folks in other countries, either due to being far from the East or West or having a slow customs process, do not have that luxury. As an example, a sample lowest price on pcbshopper.com for a 150x75mm PCB (minimum 5 qty) is $36.32 with a 43 day lead-time. A machine like etchr could provide makers around the world quick and low-cost access to the PCBs they need to learn, teach and create businesses.

S.T.E.A.M.

etchr would provide students and educators with a fast tool to learn and iterate while ensuring safety for even the youngest makers.

The Environment

There are many different chemicals and processes that can be used to etch PCBs. The more caustic varieties tend...

tl;dr of PCB manufacturing
Jonathan Beri • 07/05/2017 at 17:36 • 0 comments
PCBs are not a foreign concept to the hackaday crowd; pads, traces, vias, solder mask and silkscreen are part of the lingua franca. But if you're anything like me you really don't know how PCBs are made. Sure, I've etched my own boards and have had them manufactured at our friendly neighborhood purple PCB house but the process was just shy of ✨magic✨. So I went down a rabbit hole, trying to learn everything I can about the process.
Before getting ahead of ourselves, we need to level-set on terms. A PCB serves many roles but the main ones I think about are:
- Electrically connecting components that should be connected
- Electrically isolating things that shouldn't be connected, aka preventing shorts
- Assisting in soldering
- Documenting assembly and debug
- Providing mechanical structure
- Looking pretty*
The process of making PCBs enable these role. Pads and traces of a thin conductor are removed from a non-conductive material through a subtractive process while vias are formed with an additive process. The soldermask and silkscreen are squirted on the board in turn. Of course that's a wildly simplified generalization of the actual process and varies depending on the constraints of the board being made. 2-layer vs 2n, low-cost, fast-turn, large-volumes and flexibility are just some of the attributes that impact the processes implemented.
I could go into each process and their variations but then this wouldn't be a TL;DR post. Instead I'm going to rely on the wealth of knowledge found on YouTube. I've watched just about every video I could find on the subject and have saved the ones that cover the most ground so you don't have to sift through the cruft like I did. Feel free to bookmark the playlist here. I’ve called out the highlights below and broken them into Professional and DIY buckets.
Professional
Dave Jones over at the EEVBlog has a fairly complete overview covering the highlights of making a standard 2-layer board for his µCurrent product. What I like most about Dave’s video is that he calls out the differences between lower-cost, small-volume and legacy processes. When I first watched the video I gained an appreciation of just how important the order of things matter. If you’ve always wondered how through-holes and vias are made - take note; electroplating is the key.
Eurovision produced an educational video of their multi-layer process targeting students and is the complement to Dave’s video (in fact, Dave borrowed a clip or two.) You’ll notice that the process is very similar to the one used for 2-layer - expose copper, etch and repeat. Instead of a thick fiberglass with copper, multi-layer boards use thinner sheets and stacks of thin insulators pre-treated with resin (the “prepreg.”) Then the whole stackup is baked and it is pretty much like a stiff 2-layer board at this point.
The last professional video is from Robert Feranec of FEDEVEL Academy. He’s actually narrating a silent video series and accompanying website from SQP International. I definitely recommend checking out the whole site since it is a wealth of knowledge. I’ve also compiled all the videos found on the site into a playlist, if silent movies are your thing.
DIY
There are many video’s from hobbyists on YouTube, often demonstrating one part of the PCB fabbing process (and sometimes providing wrong information.) upgrdman two-part video is a good representation of the complete process - and it includes reflowing to boot. He’s since done updated videos using a slightly different process.
This video is pretty epic - both how perfectly-aligned the creator gets his double-sided stencils as well as the awesome soundtrack. You’ll notice that most DIYers don’t bother with silkscreen. I wonder if they just don’t know how easy and similar it is to the other steps. 🤔
channelengineer has several videos on PCBs but 2 stand out as unique - he goes through different techniques for making vias and through-holes, including a lab-grade electroplating rig.
I threw in this...
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The plan
Jonathan Beri • 06/25/2017 at 20:58 • 0 comments
This first post is intended to lay out the development plan for etchr. But before that, I need to apologize for the long hiatus since originally posting the project. Life stuff happened and the project is just me (but I'm looking for collaborators!) I'd also like to thank early followers and likers. I hope you enjoy the road ahead and look forward to your feedback.
Generally speaking, etchr is mostly theoretical with a lot of research. While much of the concepts are familiar, not a lot of scientific data readily exists. So expect more posts about experimentation and tests rigs than build updates. With that in mind, I envision 3 major types of posts:
- Theory & fundamentals
- Project update
- R & D
I've sketched out a bunch of posts, especially around Theory & Fundamentals and R & D:
Theories and fundamentals
- tl;dr of PCB manufacturing
- Stereolithography (and friends)
- Pumps
- UV curing
- The chemistry of etching
- Coating
- The physics of spraying
R & D
- Projector teardown
- 3D printed peristaltic pump
- Test pattern in KiCad
- Etchant performance
- Anti-corrosive experiments
- Enhancements (heating, agitation)
- Vias
I think here is a good point to stop for now. Any suggestions on where to start first? Ideas for more topics to explore? Leave in the comment below.
./jberi