10 PCB Fixtures to Help You Through Product Development
When it comes to test fixtures, most people picture a complicated, large, robust piece of equipment set up on a production line in a factory. While these are critical to the manufacturing process and will be the topic of future posts, we’re here today to shine a spotlight on test fixture solutions that are ideal for your lab bench or desk and will greatly aid in accelerating product development for you and your team.
In our quest over the years to find the best tools for the job, we’ve used each of the solutions presented on the list, as well as others that didn’t make the cut. Certain tools are more appropriate for certain skill sets or phases of development, so we’ve broken the list into four main categories which we hope collectively represent viable fixturings solutions across all project types, team sizes, and budgets.
Tried-and-True Benchtop Staple Solutions
These are the fixture solutions your grandma used when she first started tinning stranded wire and they’re the fixtures your grandkids will use when they need to replace the transistors on their flying robot dog’s logic board for the first time.
1. The Third-Hand, $6 on Adafruit
Most people first encounter a Third-Hand just a few moments after picking up a soldering iron for the first time. Iron in one hand and solder in the other, it becomes immediately apparent that there is no hand left to securely hold the PCB while soldering or reworking. In that very moment, the functionality of this tool becomes completely apparent. The Third-Hand welcomes everyone into the world of PCB fixtures. Just like your kindergarten teacher, Third Hand will teach you a lot and it won't be long until you’re ready to graduate to the next level.
The Third-Hand pictured above features a magnifying glass, which is a great idea in principle, however in practice we always found it challenging to get it into a useful position. Those spoiled by access to a nice microscope or even an inexpensive loupe likely won’t find this feature exceptionally useful. You can also find some versions of this tool with a soldering iron holster, and again this add-on contributes more to the instability and clumsiness of the tool than its functionality from our experience. The Third-Hand neither stands out as an excellent solution for soldering work nor for holding a board still while doing testing, but is a good fall back if you need something to hold a circuit board for a quick fix. If there's no better solution available, it will get the job done; however, this is a perfect example of "You get what you pay for", and we would recommend exploring the other options on the list. It should be noted that the Third Hand works well when partnered with other solutions discussed in the blog - another tool can be used to hold the PCB in place while the Third Hand is used to hold test probes onto the board.
2. Panavise Multi-Purpose Work Center - PV-350, $110 on Adafruit
The Panavise is great for holding mid-sized PCBs for soldering and rework, however it takes up a lot of bench real-estate, both when it's in use and when it's pushed aside. If you have a dedicated, permanent soldering station, then this is a staple. However if space is of the essence, we would recommend going with one of the smaller form-factor options.
Another consideration with the Panavise is board shape. It can be challenging to secure your PCB in the clamps if your board is not rectangular. For more complex board geometries, the magnetic PCB holders are likely more useful.
Overall, the Panavise is very sturdy, securely holds rectangular boards, and is easily adjusted; however, it comes with a relatively large footprint and higher price point. It’s size prohibits it from being used under a microscope for most benchtop setups, so you’ll want to have a loupe handy for visual inspection of your rework.
"Solve it with cables" Solutions
Sometimes the best fixture is no fixture at all. While these solutions won’t be helpful when it comes to holding a board in place while soldering wires to it, perhaps employing one of these fixture solutions will mean that you no longer even need to solder wires to a board.
3. Pogo-Pin Test Fixture Clamp, $7.60 on Aliexpress
These are a relatively recent addition to our development toolkit, but there’s no going back. You can find a variety of these available with varying numbers of pins with either 2.54mm or 1.27mm pitch. We have collected a few variations so far and have found the 2.54mm pitch ones to be incredibly handy as they can easily interface with any PCB designed with generic header pins installed. If you’re designing your own board, just add a row of SMT test pads with 2.54mm pitch near the board edge and you’ll immediately understand how useful it is.
Since there’s no features for alignment, clamping this to your board requires some focus, and it’s possible that it can “drift” out of place over time if you aren’t careful. While you can use this for long-term debugging efforts, we find it most useful for quick events such as flashing code on an MCU, provisioning a device over I2C, loading data into an EEPROM, or loading data onto a SPI Flash chip.
The most inconvenient aspect of this nifty little device is waiting for it to arrive.
4. TagConnect Plug-of-Nails Cable, $35-80 on TagConnect
The TagConnect cable offers an elegant solution to design your board with small, fine-pitch (1.27mm) SMT pogo pads, and then simply use a cable which features built-in pogo pins to hit those pads - no fixture required. These cables are very well designed - compared to the Pogo-Pin Test Fixture Clamp, they offer a smaller form-factor as well as alignment features that ensure the pins hit the test points every time.
These are great for low-volume, non-production hardware. If you’re making some internal test tools or development hardware that will never see mass production, the TagConnect system is a perfect way to make board bring-up as easy as possible. However when it comes to using these in mass production environments, there are some things to keep in mind. Just by its own nature, the cable will never be as robust as a production-grade bed of nails fixture. Additionally, it’s likely that your PCB will have more test points arranged all around the board than a single TagConnect cable can support. As such, you will likely need a bed of nails fixture anyway and there is no real reason to integrate this cable into a bed of nails. We have also had manufacturers hesitate using test points that are 1.27mm pitch preferring instead to have a minimum of 1.5mm pin-to-pin clearance in order to ensure the fixture is robust enough to meet their standards.
Overall, it’s certainly an elegant solution that is well-designed and manufactured with great quality, but at the end of the day, we often use the Pogo-Pin clamp during development because of the lower cost and flexibility using regular SMT test point pads as you would in mass production. For the price of a single cable, you can get a handful of test clamps and distribute them amongst the engineers. From our experience, there is no sense getting caught into the TagConnect ecosystem if the ultimate goal is to scale a design to mass production.
These solutions offer a big bang for your buck to meet your basic rework and testing needs.
5. Adjustable Clamp Board Holder, $20 on Adafruit
While generally not as robust, this adjustable clamp board holder offers a similar level of functionality to the Panavise at a much lower price. Sometimes it can be challenging to work with given board geometry. For example, if you’re reworking an area relatively far from the axis of rotation, it’s possible that you can place enough torque on the board with the soldering iron that causes the entire PCB to rotate. There are locking screws to prevent this rotation, however we’ve found that overtime, these mechanisms wear and lose their efficacy. Additionally, since this is a rather generic product, there can be variability in the quality of the mechanisms based on which brand you choose.
This fixture holds the board up fairly high so also makes it challenging to use this below a microscope, but if you’re using a loupe to inspect boards, this won’t be any issue.
6. Spring-Loaded PCB Holder, $17 on Adafruit
This fixture is a great no frills, low profile solution for when you need to hold something still and flat under a microscope or during rework. Since it's all metal, it also holds up well when reworking SMT components with a hot air gun as well.
This fixture comes with some notable limitations. Due to it's geometry with the metal crossbar running below the PCB, it's not always possible to flip the board upside down. The maximum size of the PCB is limited to relatively small boards, and the board outlines should have at least one set of parallel edges in order to clamp it in securely.
While great for rework, you’ll want to pair this item with a Third Hand to use it while probing signals.
7. Magnetic PCB Holder, $30 on Aliexpress
The magnetic PCB Holder is a great solution for securely holding circuit boards of any geometry under a microscope and/or for rework. The metal construction of this fixture also makes it well-suited for use at a hot-air rework station. It offers the equivalent functionality to the more standard Spring-Loaded PCB holder with greater accomodation for irregularly shaped boards. There is one caveat to point out: the magnets are very strong, such that during rework, sometimes the strength of the magnet will attract loose SMT components. It’s not so challenging to overcome, but can be annoying.
While great for rework, similarly to the Spring-Loaded PCB Holder, you’ll want to pair this item with a Third Hand to use it while probing signals. Couple with 2 x Third Hands, you’ve essentially created a budget-friendly version of the PCBite Kit discussed in the Professional Fixture section.
Professional Fixture Solutions
The fixture solutions presented in this section are for those who are looking for a serious boost in productivity and for whom budget is a secondary concern.
The Sensepeek PCBite Kit is actually the latest addition to our lab bench. Despite our relatively short history with this solution, it has already made a lasting impression. The quality and ease of use of this are unmatched by any other fixture on this list. This kit excels in both fixturing for soldering/rework, as well as for probing signals and debugging.
We love this solution because it's universal; you can securely grab onto a board of any geometry using the magnetic board clips, and then use their flying probes to poke any pin or test point on your circuit board. This tool is particularly useful as it enables folks who aren't skilled at or do not have access to the equipment necessary to solder wires directly to the PCB. The only drawback we can think of with this solution is that it's next to impossible to move it while it's setup. It will need to be reconfigured after each and every move, whether it's across the room to another desk or across the world to another office or factory. It'd be great if the kit came with some sort of travel case as it would be super helpful to throw this in a backpack for trips to the factory.
9. Merifix Fixture Kit, ~$250-$350 on Merifix
This Merifix kit is a fantastic way to get a turn-key custom fixture for your circuit board with minimal effort and at a reasonable price. This is about as good as it gets without doing a fully-custom design and we truly recommend this as an awesome solution if you don't have access to a laser cutter and drill press.
However, there are a few things preventing us from deeming it a perfect solution. Firstly, the footprint, while not prohibitively large, is inefficient in utilizing the space fills. The design of the hinged top means only about half of the base plate can be populated with pogo pins. Another difficulty is the limitations of Merifix’s drilling service. Their recommended spacing between pins is 0.08in/2.0mm with a minimum of 0.075/1.9mm which can be challenging if you’re working on a small, high-density board with limited surface area. Finally, they only offer shipping by Canada Post with no option for overnight or 2-day shipping which can be a factor when you’re on a compressed timeline. These sticking points are admittedly born from our own pickiness, but are worth keeping in consideration when going down this path, and we believe this solution to be an excellent option to consider for your projects.
10. Custom Bed of Nails, <$100 + mental sweat + elbow grease
If you have access to a laser cutter and a basic drill press, then it's actually quite easy to make your own bed of nails test fixture. We will be doing a deeper dive into how we go about designing one of these in a future blog post, but generally there are a few things to consider before going down the custom route. A custom fixture can be as complicated or as simple as you want to make it, but in general any custom fixture is going to take more time on your end to get up and running than the other tools discussed in this blog. While a custom fixture can be tailored to meet your every need, they are by their very nature non-universal. An entirely new fixture will need to be made if revisions to a board move test points referenced in the previous fixture design. That being said, if you take the time to make a well-designed test fixture when it makes sense in your product development process, your firmware developers will thank you as it is a fantastic way for them to interface all of their tools like the Binho Nova Host Adapter with the latest PCB design.
The cost of materials for making a fixture such as the complicated one shown above is well under $100, even including fabrication of custom 2-Layer PCBs. Of course there are some additional costs as it will involve a few hours of labor split between design and assembly, and the overhead costs of owning/operating/maintaining a laser cutter and drill press.
There is no silver bullet when it comes to picking out the best fixturing solution for your project. There are many factors to consider and the solutions discussed above work well in certain uses and are terrible for others. Knowing the options that are available is the critical first step to successfully choosing the best tool for the task. One thing that can be said with certainty about all of the fixture solutions presented above is that they are meant for development purposes and not at the level of production line fixtures. To understand what makes a suitable production line fixture, you can read our future blog post on the topic.