Cheap PCB story | Hacker News Reader

Cheap PCB story

github.com

100 pointshardenedlinux30 comments

Great to see people learning and designing PCBs themselves - it's a fun and rewarding hobby!

There are a whole bunch of improvements I'd suggest with this particular design and article though: (also, doing six respins for a board this simple is a bit painful, and I'd encourage people to submit their layout to someone for a design review before going through this many iterations - I've reviewed things for friends in exchange for a pint of beer!)

- this board has no ground plane, and no return paths near the data traces - this will be an absolute EMI nightmare and also signal integrity will suffer. At very least, dedicate the bottom layer to ground (and flood-fill it) - the return path for digital signals (and anything above a few KHz) is directly below the signal path - see https://incompliancemag.com/wp-content/uploads/2017/04/1705_....

- (the clock design, in particular, is completely against ST's recommendations - there's no ground plane and traces running directly underneath!)

- panelisation: as others have mentioned, even for large-scale production runs, the PCB manufacturers will do a better job of panellising themselves, and can stack your boards in amongst other boards on the same panel if you're not taking up a whole panel.

- unless you've got a good reason to do it, having a serial programming interface with a serial/USB chip isn't the easiest way of doing it - exposing SWDIO/SWDCK/SWO to a suitable connector and using an ST-Link in-circuit programmer is generally an easier and more space-efficient way! They seem to have gone that way in the last couple of revisions.

There are a bunch of other things I'd probably do differently, but this is all to say - if you do decide to take up this hobby, please do get your designs looked at by someone knowledgeable, you'll learn a lot that way!

I’ve got a few designs planned over the next couple months that I’d love some help with. I am a software guy and my circuits “work” but are probably not the ideal designs. We’re talking single layer PCBs that I etched myself using a laser printer, an iron, and some acid... would love to see them be actual PCBs, but the complexity of my circuits is quite low. Any way I could get your contact info? My email is in my profile, would love to pick your brain on how I could improve, and send you some virtual coffee or something!

https://old.reddit.com/r/PrintedCircuitBoard/ is a good resource. Their FAQ has an excellent list of gotchas.

This page is great! One thing to note is how little analysis work is required these days. One just needs to know basic things like Ohm's law, where to start, and how to read datasheets. But, it's missing 2 things:

1. Microcontroller selection. This can be a daunting task. Best to just pick one with good dev kits and community support. You can tailor the part number if you need more IO for a specific project. The only real choice to make is if you want/need to work in the low-power embedded realm (eg Arduino or STM32), or in higher-power/userspace realm (eg raspberry Pi or Beaglebone/Linux).

2. Rules of thumb for the design. You mentioned some great ones. I would add - use 4 layers unless you need more (and you will know if you do) - Put signals on the outer layers so you can access them for troubleshooting, unless you have a reason to have ground planes on the outer layers (you'll know if you do) - Use the internal 2 layers for ground and power. The keyword "polyfill" will let you know how to do this. - Don't try and make PCBs at home. It's so fast and cheap to order them. And a home-made one, even if you make it with a router instead of the printer/acid method, will not have a solder mask. You can easily spend 3 days troubleshooting. Watch movies for 3 days while you wait for your delivery, instead. - If you have any doubts, use a breadboard for prototyping. If you have confidence on your 3rd board design, skip the breadboard. - Put a hole in each corner, with a healthy clearance from any circuit to a fastener. At some point you will want to mount the PCB somewhere. - Put some spare IO on a connector if you have space - Use a barrel connector or USB for input power if you can. If you need more than 5V, USB-C at another voltage is trivial to add these days (as this page shows). It's a matter of when, not if, you mess up your settings on your bench power supply. - Use 2.54mm pin headers where you can instead of weird connectors - Ask yourself: Can I buy something that will work instead? - Invest in 3 kits: surface mount resistors, surface mount capacitors, through-hole resistors. eg: https://www.sparkfun.com/products/10969 - Spend at least $100 on a soldering iron with temperature control

I've done a similar journey during this lock down year. I started off with a small design of a custom latency measurement thingie that was a "rats nest" with wires and components soldered to an arduino. Converting it to a PCB, I used easyeda.com. I recommend that over KiCad, which I later tried but it's clunky compared to Easy EDA. KiCad feels like blender before the re-work they did. Or InkScape. Opensource has such incredibly crappy ui:s sometimes... Yay Blender!

First batch was bare PCB from jlcpcb.com and components from digikey. Handsoldered it. And it worked!! OMG, the JOY!! I highly recommend to do some simple own pcb design.

Then I did v2: STM32, ws2812b, tiny smt components. I used jlcpcb assembly service, complemented with some components they didn't have in their (limited!) smt library. Bringup of the first stm32 was a bit of a nightmare. I had missed pulling a boot0-pin low (~2 days wasted). A co-worker is madly in love with rust and made me write the whole code in Rust (2 weeks maybe, not "wasted" per se - but oh man can embedded rust be... a lot of fun... sometimes). Missed pullups on i2c lines. So much learning on version two.

Version three I tried to keep is simple. But also smaller. I had an idea to use 3.5mm audio cables for power and data. I thought SMD audio cable contacts would be rugged. I was wrong - they came off. I had bought a syringe with solder paste and one with flux. Totally recommend getting a flux syringe! So good! But that solder paste... I maybe didn't grok how to use it, but it did not reflow well enough to make the audio cable contacts stay put when used.

Got version four a couple of weeks ago. Doing pcbway.com with them doing the full smt and through hole soldering. This is how to do it! I do not at all understand why all are raving about jlcpcb.com - they have such a limited library. Why not make a proper pcb shop solder it all? It doesn't cost that much more. If time is a factor it is a lot cheaper. V4 feels like a winner - shipping them out to customers now.

I've also done some other boards during the lock down, such as control boards for RC cars in three versions, and three versions of an Ethernet connected microphone. I'm still on EasyEDA, but as mentioned I now let pcbway do soldering of everything.

+1 for EasyEDA, way simpler to learn for me as well.

Through hole connectors are nice to use for rugged designs. And incidentally, you can find 3.5mm connectors that are rated for power (eg: 1A).

Yup, I should have used a through hole part.

Power over audio cable felt iffy too - feels like it will short on insertion? Maybe it needs some thermal fuse in line with it or something.

I hadn't thought of that good point. It's also an invitation to one day accidentally plug 12V into your stereo or laptop.

Have you looked at the price difference between jlcpcb's assembly service and PCBway?

>It's feasible make multiple smaller boards on the bigger ones by panelizing the PCB. The joints between the boards are specially processed, which is easier to divide later. Rails can be added around the boards for fixing during processing.

I've seen at least one PCB shop that asks customers not to panelize for small lots, so they can mix layouts from several customers and get better packing efficiency.

I have too, but when I have an option between 1x the price and 1x the boards and 2x the price and 9x the boards, I usually pick the latter.

Even for runs off a few hundred PCBs all the PCB assemblers I've worked with prefer to do it themselves. They know their machines much better than I do.

I recently went through the process of designing a board based on an STM32F411RE. I highly, highly recommend the YouTube channel, Phil's Lab. With his tutorial I was able to produce a working board on the first try.

https://youtube.com/c/PhilS94

"0201 package is too small. 0603 is more convenient for manual welding."

I much prefer soldering 0402 and 0201 components than larger SMD parts, including 0603. What's needed is soldering paste, liquid flux and heatgun and macro lens attached to a phone for inspection.

What's nice with hot air soldering tiny SMD components is that you don't need a lot of heat when soldering, desoldering and get zero tombstoning.

I really like using a USB microscope for taking a close look at PCBs. They're pretty cheap, free up a hand, and you can put the picture on a large monitor.

pro-tip: your phone's magnifier app can be used as a perfectly good digital scope, you just need something to hold it up with.

ios: Settings > Control Center > Customize Controls > Magnifier

you can definitely hand solder 0201s without solder paste, if you have thin solder, a thin tip (on your soldering iron) and decent magnification. I have successfully done 01005s with this method.

Hand soldering 0201s and anything above is trivial. The problem is that managing components gets harder and harder the smaller they are. I did two practice kits and the problem is that I lost two 0201s out of 10 and couldn't find them.

The nice thing about larger SMD components is that you can route interconnect between the terminals. This way you get a "free" layer in the form of components.

I didn't know KiCad can place components at a 45 degree angle.

You can actually place components at arbitrary angles, and even do so programmatically through the scripting interface.

It can. I've modified my rotation interval to be 45°, it's handy for placing SoCs and things near the board edge.

The AMS117 should really have tantalum caps on the output for stability - though I must admit, I have got away with ceramics on my own boards. Reduces the BOM cost significantly.

I'm going to create my first commercial PCB, thank for post your complete journey, lot of useful information.

Please just use jlcpcb, they do PCB and SMT at very cheap prices.

Are there any alternatives?

I use pcbway. Note that they have a bunch of fronts for the same factory (pcbgogo, for example, is the same as pcbway).

I have confirmed this by ordering a custom pcb with weird specs (color, thickness, etc.) and they were all going thru the same manufacturing steps at the same time, down to the second.

This bridged my knowledge needs perfectly, I have made a few PCB's but it was a struggle. Thanks!

I can't recommend JLCPCB enough - tiny PCBs, good prices, quick turnaround.

Reply on news.ycombinator.com