Hardware design and development is a difficult area to work in, largely because it can seem so opaque for a new designer. Most engineering companies do not open their doors for anyone to show up and start learning about hardware development. It's very hands-on and sometimes there are not enough resources for new designers. Hobbyist level hardware design is much easier to get into, largely thanks to the number of development products and off-the-shelf modules.
So if you're a hobbyist and you want to make the transition to a professional hardware engineer or PCB designer, it pays to learn the differences between these types of products. Hobbyist electronics designers can ultimately become professional by learning how to design and manufacture PCBs as these are the backbone components that make any electronic product work.
With that out of the way, let's look at the differences between hobbyist circuit boards and professional circuit boards.
I think when most designers get started building boards, they probably look to a dev platform like Arduino or ESP32 for guidance. These are high-quality hardware platforms and their usage is even taught in some universities, so I think they are very easy to start using as learning tools and prototyping platforms. These boards also reveal some of the typical approaches to designing a prototype board or a hobby board.
Here are some of the most common characteristics you will see in hobbyist PCBs:
There are some good reasons for these design choices in hobbyist boards. They tend to reduce cost, allow for easier hand assembly/rework, and the parts tend to be less advanced. In addition, a lot of designers starting as hobbyists are working with the basic parts built into their CAD library, which will usually prioritize the component types listed above (through-hole, large passives, and leaded SMD).
The reason for the pin headers is very simple: it allows connections to external modules via flying leads. If you've kitted out your electronics workspace properly, you probably have a set of flying leads that will tap onto the 100 mil pin headers. This is actually a good way to integrate multiple modules into a single system.
Hobby boards can sometimes start to look like Dr. Frankenstein's monster. [Image source: r/diyelectronics on Reddit]
Circuit boards designed for commercial products look quite different both in terms of their CAD data and the final assembled product. Now let's look at a professional circuit board.
Professional PCBs can be quite different for many possible reasons. There there is often a need to collaborate with engineers from other disciplines, which will create many constraints in the custom board design. This means the designer has less freedom in terms of component selection, it requires a different approach to layer stack design and routing, and more advanced fabrication/assembly are needed.
You might see any of these aspects in a professional PCB:
The other thing to note about professional PCBs is that they look very clean. Components are well-organized, the routes are very direct, the vertical profile is consistent, and the surface layers have been thoroughly cleaned up. These small details really help a professional designer stand out from the crowd.