In-circuit tests (ICT) have long been a practical method to verify the quality of a printed circuit board (PCB). As an ODM with PCB Assembly capabilities, we typically employ bed of nails test fixtures to test the boards we produce (in addition to AOI scans). Only by testing every single board, can we guarantee consistent and high-quality PCBA. This is by no means a rare or uncommon practice, it’s just the responsible thing to do. After years of building relationships with clients and suppliers alike, we came to rely on a small, but mighty shop to produce custom ICT fixtures for all our projects.
However, even with our reliable supplier, we still found some qualities less than ideal. As Pete lamented in his post on modern in-circuit testing, traditional bed of nails testers suffer from some drawbacks due to their single-design usage. Here are the four pain points that ultimately convinced us that we could do better:
First, the cost of materials and labor. We had found an excellent supplier, but the very nature of ICT fixtures entails producing a custom machine from client specifications. Even in fair transactions, there are some costs that cannot be avoided. Typically, we’re able to plan for these costs, but the material waste felt egregious to us (which will be discussed in later points).
Second, the time to produce an ICT fixture. Similar to the first point, ICT fixtures are not simple machines. Even experts need time to build these things. While we did not mind having to wait for an excellent test fixture that would fit our needs, this becomes an issue if clients realize they actually need a different board design than what they originally ordered.
Third (and probably the most annoying thing), the shipping costs for a heavy and oddly shaped tool full of delicate wires and pins. An online shopaholic might find something delightful in anticipating a product’s arrival and of course, there’s always a feeling of excitement when you open a box and find exactly what you wanted. However, if you are in the electronics manufacturing business, shipping can be your worst enemy. Even if our expert supplier can guarantee speedy production and fair pricing, shipping costs (which are always a tradeoff between time and money) are much harder to control. As a company with offices on two different continents and clients in even more continents, this was very painful.
Fourth, storing and setting up a typical bed of nails tester is a huge hassle if you like to keep things neat and tidy. Pete, our company president, refers to the mess of wires inside a typical ICT fixture as a “bowl of spaghetti” and frequently laments the lack of streamlined design. Even if you’ve never been on an assembly line, you can assume that loose wires and mess do not make production any easier.
All of these pain points were a major factor in how and why we invented our own proprietary method for ICT fixture design and production. We were so creative in naming it, we called it the ICT with Pogo Pin Cassette.
A Modern Solution
After we introduced the PLT, a cloud native hardware test automation device, we realized that an ICT fixture would be the perfect accessory. However, traditional test systems usually require wires to connect your ICT fixture to a complex test system, leading to what Pete would call a messy “bowl of spaghetti” with tangled wires adding more chaos to a production line floor. Instead, we solved this by designing a wireless bed of nails tester that uses a custom PCB that connects to the PLT using a 78 pin connector. By combining the PLT and ICT, you get the quick testing capabilities of a traditional ICT fixture and the streamlined interface we built for the PLT.
But enough on the PLT, this post is to discuss the ICT and why/how we built it. Keeping in mind all of our pain points with traditional ICT fixtures, we designed our ICT to be something that is more efficient in terms of cost, waste, and customization. This led to a relatively simple solution: standardizing. When you look up google images of ICT fixtures, specifically bed of nails test solutions, there’s a wide variety of machinery that comes up. On one hand, this makes sense because PCB design and layouts vary greatly depending on a product’s needs. However, the overall variation in the structure of ICT fixtures is something we thought to be unnecessary. So we started by designing a standardized silhouette.
To do this we broke ICT fixtures down into two general parts: 1) a standard component that facilitates pressing pogo pins (which provide a connection to the DUT) onto the PCBA, which we call the ICT fixture base, and 2) a component customized to a board’s test points, which we call the Pogo Pin Cassette, this is where the pogo pins live.
Of course, since we pride ourselves on our background as an ODM, we took this opportunity to redesign the traditional ICT fixture to be more sleek, while also being durable enough to withstand repeated use for production line testing. By separating an ICT fixture into two main components, we made it so that the bulky part (the ICT fixture base) can be reused for new projects. Meanwhile, having a smaller isolated custom component (the Pogo Pin Cassette) makes it so that we still get the benefit of bed of nails testing, but without the hassle of having to make a new sturdy enclosure every single time.
Wireless bed of nails testers have existed before we made ours, but what makes ours special is how well it fits BCD’s core competencies. Since we can do PCB design and fabrication in-house, it is possible for us to design and assemble a custom PCBA and bed of nails (or pogo pin) arrangement for all custom orders. Of course, in order to standardize something like an ICT solution, we had to make some decisions about what kinds of boards we would focus on and which we would leave for when the need arises. While PCBA can vary greatly in size, for now our proprietary ICT solution is designed to test boards no larger than A5 (148*210mm). This limiting factor might prevent us from letting clients with unusual board sizes use our ICT solution as it is, but it means we can set up a system that lets us save time and material costs on custom ICT solutions. However, now that we have a proprietary system in place, we can easily replicate the process for larger board sizes if a client actually needs it.
At Blue Clover Devices, we “Dare to Innovate” wherever possible, which is why we redesigned traditional bed-of-nails testing to give this useful tool a place in the modern world. Ultimately, creating a streamlined design that matches our company's core competencies means we can deliver custom ICT solutions in less than two weeks, including the time it takes to confirm test point placements.