Breadbee: Build your own (tiny) single board computer (2020) | Hacker News Reader

Breadbee: Build your own (tiny) single board computer (2020)

wtarreau.blogspot.com

115 pointsgoodburb23 comments

Oh man, the soldering job on this _hurts_ me, and I've done a lot of hand-soldered 0201/QFN stuff.

If you're reading this, _never_ thin out your solder paste with flux. You're better off dabbing tiny bits of it onto the individual pads with a toothpick than letting it ooze everywhere and get under your components causing shorts.

If I were soldering this board by hand without a stencil, I'd use solder paste and hot air reflow only on the ground pads of the CPU, the PMIC, and maybe the inductors next to the PMIC. Everything else I would be able to do faster by flooding the board with paste flux and drag-soldering all the pads with a solder-wetted hoof tip (There are some great videos on Youtube for professional drag-soldering).

And when you're done, scrub with a toothbrush and distilled water, rinse in more distilled water, soak in a small puddle of denatured alcohol for a few minutes, then dry with gentle hot air.

> Everything else I would be able to do faster by flooding the board with paste flux and drag-soldering all the pads with a solder-wetted hoof tip

About this, could you recommend some brands for the tools, both for the iron, and also for the paste flux? Thanks!

> then dry with gentle hot air.

Do this in another room than the bin of alcohol is in.

You're right, what the hell is this? https://imgur.com/m9Hgm30

if you're going to make a board like this, get a stencil, they're not expensive and you don't have to worry about carefully blobbing the correct amount of paste on every pad

personally I use a hot plate for small boards

I just use soldering iron, splurge some flux and hope for best.

I should probably get a hot plate...

iron and drag technique is fine for parts with legs, even tiny ones, but this one also has a heat sink center pad, so it needs hot air or oven or plate for that.

Personally I'd have done that part first not last, so that you can heat the whole area up without worrying about loosening all the neighboring parts.

Everything else can be hand soldered with less fuss than air or oven. I hold parts down with a sharp bamboo skewer or fine tweeser tips, just pushing down on the center while tacking.

I've done the heat sink center pad thing by putting a big plated hole in the middle of it, and filling it with solder. This lets me get down to the bottom with my tip, to ensure actually getting the solder to melt in there.

Winning at life. I like it.

Yes, this looked like an absolute mess. Repurposing a toaster oven as a reflow oven would have given much better results or just using a hot plate.

I think there are even some toaster-oven priced hot plates on aliexpress

If you get one, open it up and redo all the connections.

I got one and it was just as bad as some youtube videos showed. 2 of the mains wires female spade connectors were loose and barely making contact, not actually grabbing the male spade. But they WERE making contact, which means the machine would appear to work fine if you never looked inside, at least for some unknown time.

And this was actually through Amazon not Aliexpress, so not even the cheapest example, but the same thing of course.

A useful write-up - because - it rather thoroughly documents an SMD assembly with minimal tools. Trying this, trying that. A naive approach. Lots of things that didn't work, lots of extra comments, lots of photos. Beautiful. We know what it's supposed to look like done neat and tidy, with stencil and at least a minimal reflow oven - that would be less useful. Perhaps not the first to do that, but an interesting project (the write up) with current packages pushed to its publication.

It's often tempting to mess with such tiny boards without the "proper" tools. This serves as proper warning.

Or how about you just use a damn soldering iron for such an easy job?

Called 'BreadBee', but designed with a form factor that is allergic to breadboards‽ I know a lot of younger engineers prefer to solder jumpers to in-line pins, but come on

https://github.com/breadbee/breadbee/raw/master/blinky.gif

That's how it is supposed to be plugged in, giving maximum amount of space for other things on breadboard

As a side question, is there a helper/tool where I can place a list of components (wifi chip, digital microphone, battery management components) and it outputs a PCB which could incorporate them?

As an amateur I always thought a “marketplace” of reference designs with criteria you could filter on (through-hole, easy to hand solder, pitch, programming, etc.) would be a great resource. You could even make an attempt at compatibility (I2C, SPI, # of GPIO pins) with certain MCUs. If something works in theory, let me pay the designer and get the schematic and footprints in KiCAD or other EDA.

Some printed circuit design tools have "auto routing." But in my experience for small, simple projects, once you've got everything else in place: The schematic, component footprints, etc., the actual routing is pretty easy. And nothing that I know of automates the whole process.

Looks like the chip has SD card support. I wonder if there's any plans for debian like the pi? I know it's overkill but that lets us linux noobs break the barrier of entry.

It's not that it's overkill, but with 64 MB of RAM it was never really meant to run a generic purpose desktop distribution. Even without desktop they need much more RAM. This was meant for barebone, goal-specific Linux distros, running only what's really indispensable.

Why, I ran Slackware on 32MB back in 1996. /s

The chip capabilities (64MB RAM, 16MB flash) are barely enough to run some stripped down Linux version like the one supplied with the GitHub link at the bottom of the article, and possibly OpenWRT.

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