It’s been a real journey on my HDD Synth project to understand how to engineer such a device and then make it a reality. The initial genesis of the project was to create a proof of concept, to show that the idea had legs in its most basic form.

After that I moved into expanding the feature set and crafting the device functionality. The final step was to then create a product that could be manufactured and sold at scale. At least, a scale beyond me hand soldering each unit individually.

For the initial versions I used PCBWay to manufacture the PCB and then soldered on through-hole components and breakout boards to provide the required functionality. I knew that PCBWay offered full PCB assembly services, so I decided to look into what that meant.

PCB Assembly

Moving to PCB Assembly (or PCBA as the cool kids say) means that you’ll need to supply a Bill of Materials or BOM along with the rest of your files. This provides details for each of the components that need to be attached to the board.

So for instance component R1 on the PCB would be a resistor. In the BOM it would specify the value of it (e.g. 10K) along with information about that specific size and type of resistor you’d want to use. This enables PCBWay to source these components on your behalf which is known as turnkey assembly. There are options for you to send PCBWay the components that you’d like them to use, however for me it was quicker and easier to let them source what was needed.

Part of this process is a two-way conversation where PCBWay will email back the BOM with any questions they might have. In my case these conversations were about:

• Mistakes on the BOM: I’d specified the incorrect component for the footprint on the PCB, so it wouldn’t fit.

• Components that were difficult to source: for the rotary encoder there were lots of minor variations of the model, so I switched to a more popular version.

• Chinese variants: by default when you submit an order they won’t use Chinese parts, unless you opt in. For me this saved money on parts like pin headers.

As PCBWay was going to fit the components it also meant I could switch to surface mounted components (SMD) which provides multiple advantages, such as smaller sizes and lower costs. These are fitted by automated machines which can very quickly and accurately mount such components. This meant going from quite a large through-hole resistor to something much smaller than a grain of rice. Quite an upgrade!

PCBWay shared with me the final BOM quote so that I could decide if I was happy with the costs before moving ahead with the work. The costs seems competitive to me, based upon sourcing components myself with the previous version. So I gave them the thumbs up to go ahead.

Delivery and first impressions

One of the longest waits of the entire process was whilst PCBWay were sourcing the components. That’s certainly a takeaway for me, in that using more exotic components may cause complications and delays in manufacturing the board.

After a few weeks I was sent a photo by PCBWay showing me the assembled board and inviting me to validate that all the components were mounted as I expected. I excitedly reviewed the photo and referenced it against my schematic and was happy to report back that everything looked as it should.

Following that I eagerly watched the DHL updates as the package made its way across the globe towards my front door. When the package arrived I wasted no time in opening it up and was impressed by the level of care that had been taken. Each bundle of two or three PCBs had been wrapped up in its own set of bubble wrap in addition to each PCB being enclosed in its own anti-static bag.

It was a real pleasure to admire the PCB in person finally. Each component was placed in exactly the right place and it looked fantastic. Compared to the hand soldered PCB from the previous version, this was in an entirely different league. From what I could tell PCBWay had done a fantastic job in bringing my vision to life.

Powering On

However, now it was all on me. Was the design that I had created going to actually work?

Moving from a basic PCB with no components to one that’s been entirely assembled at the factory was a massive leap. I’d not used surface mounted components like this before, it was an entirely different world. Further to that, for this version I’d recreated the breakout boards from the previous version that I’d bought off the shelf and soldered on. Were my PCB design skills up to the task of this new challenge?

Nervously I plugged the USB cable into the Pi Pico on the HDD Synth and into my computer. The first step was to flash it with the CircuitPython image followed by copying over the test files that would allow me to validate each sub-system.

First off, I ran the audio test. This would show if the Pico could communicate with the MAX98357A audio amp on the chip. I nervously clicked the run button and was rewarded with a sharp triangle wave beep, exactly what it should do! Amazing, I felt like a very proud PCB parent.

After this I moved onto the SD card, which again was a breakout board on the previous PCB. Running the test returned a series of successful operations which proved the Pico was able to read from the SD card. Wonderful!

Receiving the fully assembled PCBs has been a night and day difference compared to the previous PCB which required me to hand solder on the components of each board before it would work.

Costs

In terms of costs the 10 PCBs cost $42 to manufacture ($4.20 each) which is the same as the previous prototype PCBs I’d ordered.

Assembly of the 10 PCBs cost $36 with the components weighing in at the largest cost of $186, so $222 to supply and fit the components ($22.20 per board).

So after factoring in shipping costs and a bank handling fee I paid a total of $278 for the 10 assembled PCBs, which equates to $27.80 each which is approximately £21 each at the time of writing.

Final thoughts

My ambition for this project has always been to make something available for those who are interested. One of my concerns has always been how scalable such a product would be, how easily can I create and ship them to meet demand?

From this experience I feel like PCBWay offers a great solution with their turnkey assembly service. Comparing one of my hand soldered MKII prototype PCBs next to the PCBWay assembled MKIII boards is a night and day difference in terms of quality and gives me a solid option to outsource the task of both sourcing components and assembly.

I’ve got boxes full of various components that I’ve ordered in quantity from various suppliers. Being able to hand that task over to a specialist is a real weight off my mind and a space saver in my garage storage.

The process has taught me to pay extra attention to the components I choose to ensure that they’re common and cost effective, to reduce the time and cost of sourcing and assembly. However the clear communication with PCBWay throughout the process has really ensured that I’ve felt confident in stepping into this new process.

I’ve just submitted the HDD Synth MKIV prototype to be manufactured using the same process, so it’s certainly something I’d recommend considering if you are in the same situation as me.