8 Verified PCB Testing Methods to Be Assured

According to the IPC PCB, testing a PCB is a must for the security of the product user.

So, one thing is clear you can not launch any sort of electronic product without testing the PCB.

Now, testing a PCB is not that easy. Many manufacturers are still confused about the right testing method to adopt or are doing it wrong. Thus, the best move is to hire PCB design services. Still, just for your information, we are using a blog about PCB testing methods.

Types of PCB Testing Methods

Visual Inspection

Visual inspection is one of the most basic PCB testing methods. All you need to test a PCB via the visual inspection method is a magnifying glass. As it is the simplest method, it is the first test every PCB manufacturer performs.

This method is used to test the components for their orientation, connection, design of the board, soldering, and other defects that can be detected visually.

Though it has limited coverage, it helps detect defects at an early stage, which can help avoid expenses on costly tests.

Advantages:

• The simplest method to test a PCB.
• Costs almost nothing.
• Can be done at any stage of the production process.

Disadvantages:

• Less coverage.
• Relatively less accurate.
• It has the scope of human error.

In-Circuit Testing (ICT)

In-circuit testing is probably the one you heard the most about. It’s one of the most popular tests due to its ability to test products in large batches. As it is an automated test, manufacturers claim its accuracy to be 98%, which makes it one of the most reliable PCB tests.

It is conducted at the end of the production line before the functionality test to check if every component is placed correctly and electrically connected.

The ICT test is also known as the bed-of-nails test. Wondering why so?

The name bed-of-nails explains how the PCB is tested in this robust method. The PCB is tested by connecting probes to the test points, pre-designed in the PCB. The testing apparatus is a system of thousands of sensors and drivers which test the PCB rigorously.

Advantages:

• Quick and efficient testing.
• Zero human error due to fully automated processes.

Disadvantages:

• It is expensive.
• The test jig is product specific. You need to modify or remake the jig to test a different product.
• The test points need to be pre-designed on the PCB.
• Does not test insufficient or excessive soldering and voids.

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Flying Probe Testing/Fixtureless In-Circuit Test (FICT)

Flying probe testing or fixtureless in-circuit test goes one step ahead in the PCB testing methods. Unlike the ICT, FICT can test the PCB on not only the pre-defined test points but also from untended vias. Moreover, it can directly test the PCB components like diodes, capacitors, inductors, transformers, etc.

As the flying probe test does not need the fixtures like the ICT, the cost of testing goes down. The FICT is flexible enough to test different boards quickly with just a quick tweak in programming. This flexibility has made it a common testing method amongst electronics manufacturers all over the world.

Another benefit of this test is that since the probes are free to move, you do not need as many probes as you need in the ICT. You can test the same PCB with fewer probes by moving it from one testing point to another. This fact plays a significant role in bringing the cost of PCB tests down.

Advantages:

• Cheaper than ICT.
• No need to pre-design boards for testing.
• Does not need much modification to test different boards.
• Tests more components

Disadvantages:

• It takes longer to perform the test.
• Only small test batches of products.

Boundary Scan Testing

The boundary scan testing method is to test integrated circuits (ICs). This method helps to test the nodes that are not easily accessible because of the compact design. The boundary test mainly covers the wire linings on the IC.

In this testing method, cells are fixed in the leads from silicon to the external pins. This way, it doesn’t need to reach all the nodes for testing. And that is the primary reason it can test PCBs with multiple layers or high density.

Advantages:

• Can reuse the test vectors.
• Tests JTAG-compatible components simultaneously.

Disadvantages:

• It is a slow testing method.
• It has poor memory testing.

Automated Optical Inspection (AOI)

Automated Optical Inspection is the digitized version of visual inspection. This method is just more accurate and high-tech than the manual inspection PCB testing methods.

In this method, the PCB is scanned by cameras to detect mainly two types of defects which are: catastrophic failures and quality failures. Let’s see a few examples of both.

Catastrophic failures: Missing components, missing connections, broken boards, etc.
Quality failures: Improper component fixing, skewed components, or incorrect connections.

Advantages:

• It is a contactless test method.
• Quite accurate and has fewer chances of human errors.

Disadvantages:

• Can not detect new discrepancies. Only detects the faults that are programmed.
• Have to program every time for every change.

Burn-In Testing

The burn-in testing for PCBs is what road tests are for vehicles. The team stimulates the real-world conditions and programs as per the design. It covers all the functions the PCB has to perform using all the components.

Once the PCB has passed the test, the level is stepped up and the PCB is tested for conditions beyond the mentioned limits. This is to examine the early failures and actual load capacity.

Advantages:

• PCBs are checked in real environments and real functions.
• Ensures product reliability to a great extent.

Disadvantages:

• The product might fail during the test resulting in wastage.
• It is quite a labor-intensive process.

X-Ray Inspection

When dealing with complex PCB designs, testing every soldering joint might not be possible because they are hidden in the layer beneath. And that’s when X-ray comes into the picture. As you might know, X-ray can take images of the layers.

Also, this test is carried out to examine the body of the components. Modern technology helps manufacturers to create 2-D as well as 3D scans of the solder joints to make them 100% defect-proof.

Advantages:

• It has the highest detection efficiency.
• IT can detect even internal defects.

Disadvantages:

• The X-ray testing machine is quite costly.
• Needs trained and skilled professionals to carry out the test.

Well, the list doesn’t end here. There are many PCB tests specific to the testing requirement.

So, let’s quickly talk about a few of those.

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Other Functional PCB Testing Methods

The PCB has to undergo tests for multiple reasons and functions and basically, every function can have its own separate test.

So, covering each of them is next to impossible. However, here are a few common other functional testing methods for PCBs.

Solderability test: It is to make sure surface reliability and chances of forming a strong solder joint.

Micro-sectioning analysis: Investigates defects like short circuits, opens, and other failures.

Time-domain reflectometer (TDR): Practiced to test high-frequency PCBs.

PCB contamination testing: Detects bulk ionics so that your PCB does not get contamination due to corrosion.

Peel test: Covers the strength test of the laminated board.

Conclusion

Testing PCBs is a must task that can not only get you surety about the functioning of the PCB but avoid accidents as well.

So, if you want to test your PCBs, efour is your go-to place. We are experts in high-speed PCB design services ready to provide you with a PCB that you can rely on.