What is a Bare PCB Board?

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Nov 9, 2020|Product Innovations and Design

Photo by Shawn Stutzman

Simply put, a bare PCB board refers to a printed circuit board without any through-holes or electronic components added. They’re commonly referred to as a bare PCB, a blank PCB, and sometimes just PCB. An empty PCB board has only the essential pathways, patterns, metal coating, and PCB substrate.

What Are Bare PCB Boards Used For?

What is a bare PCB board, and what is it used for? A bare PCB board is the skeleton of a traditional circuit board. How does a PCB board work? It guides the currents and electricity through the appropriate paths and is used in most computational electronics. 

The simplicity of the blank PCB gives plenty of freedom for engineers and designers to add components as needed. This blank slate provides flexibility and makes the bare PCB boards viable for mass production instead of making them unique for each order. 

These PCB boards require more design work than other wiring methods, but the assembly and manufacturing tend to be automated afterward. The automation makes PCB boards the cheapest and most efficient option. 

It truly becomes useful when the necessary components are added to it. Becoming a circuit board is the bare PCB board’s end goal and can be extremely versatile if matched with the right components. 

However, this isn’t the only thing they are used for. A blank PCB is the best stage in the circuit board making process to perform some bare board testing. This is crucial to prevent a number of issues from popping up later on. 

Why Use Bare Board Testing?

There are a number of reasons why it’s essential to test the bare boards before adding any additional components. Being the circuit board framework, the PCB board failing after installation can lead to many problems. 

While not common, the bare PCB board can already be defective before any components are added. The main issues that pop up are over-etchings, under-etchings, and holes. Even a minor flaw can result in a complete failure. 

The increasing demand for multi-layered PCB boards due to their increased component density is another reason to use bare board testing. Once a PCB has been put together into multiple layers, it becomes almost impossible to make repairs in case of failure. 

If the PCB board is the circuit board’s skeleton, then the components are the organs and muscles. Components can get expensive and are oftentimes delicate, so having a solid framework can prevent wasting high-end components in the long run.

Types of Bard Board Testing

How do I know if my PCB is bad? You’ll need to test it in two different ways: electrical and resistance.

Bare board testing considers both the isolation and continuity of the electrical connections. Isolation testing measures connections between two separate connections, while continuity testing checks to make sure there are no open points that could mess with the electrical current. 

The most commonly used is the electrical test, while the resistance test isn’t as common. Some companies use a combination of both instead of sticking with one over the other. 

The resistance test sends an electric current through the conductor to measure the resistance to the flow. Longer or thinner connections results in much more resistance than shorter or thicker ones.

Large Manufacturer Testing

A printed circuit board manufacturer will likely use the pinned fixture test, otherwise known as the “bed of nails.” This test uses spring-loaded pins to test every connective surface on the PCB board at once. 

The pinned fixture test is extremely efficient and only takes a handful of seconds to finish. The main downsides are the high expenses and the lack of flexibility. If a different PCB design is required, a whole new fixture and an array of pins are required. 

Small Manufacturer Testing

What is bare PCB board testing like for smaller companies? They typically use the flying probe test. Two robotic arms with poles use a software program to test the board’s connections. 

It takes much longer to complete but is more affordable and flexible than the pinned fixture test. Switching to a different design is as simple as uploading new software. 

Benefits of Bare Board Testing

There are numerous benefits to bare board testing and no real disadvantages to doing so. This small extra step in the manufacturing process can save much heartache further down the line. The slight investment early on can save thousands of dollars in repair and replacement costs.

Bare board testing helps to identify issues early on in the manufacturing process. Finding the issue early on means that it’s far easier to find the problem’s source and fix the problem at its roots. 

Catching an issue late in the process makes it much harder to find the source. Once the PCB board is covered in components, there’s no telling what would be responsible for an issue. Early testing helps remove a big piece from the equation for troubleshooting. 

The testing also ends up streamlining the entire process. If issues are caught and fixed in the prototyping stage, then the later production phases can move on unhindered.

How Testing Saves Time

Now that you know the answer to “What is a bare PCB board?” it’s easy to understand why testing is so important.  

Even if the initial process is considerably slower due to the testing, the time saved towards the end more than makes up for it. Knowing for sure that the skeleton of the circuit board is error-free also makes troubleshooting much easier. 

The early stages are also the most cost-effective time to test the bare PCBs. If a fully assembled PCB ends up being faulty, it can cost 100 times more to fix in the field as opposed to improving during the testing phase. 

If the base is weak, then the odds of it breaking shoot up drastically. It’s also the worst time to find out the bare PCB is faulty once expensive components have already been soldered onto it. Problems caught in this late stage usually result in the entire thing being scrapped. 

Even if the difference between fixing early in manufacturing and fixing in the field wasn’t so drastic, the extra efficiency and accuracy that the testing provides make it well worth the effort. Thousands of components could go to waste if the PCB board ends up malfunctioning.