What Types Of Standardized Testing Are In PCB/PCBA?

Printed Circuit Boards, shortened as PCBs, are one of the primary things in electronics. PCBs allow you to place multiple electronic components neatly, as it does not involve long soldering lines. With that said, the conductive layers of copper are responsible for connecting the electronic components. Moreover, you can develop a permanent circuit with PCBs, which otherwise is not possible on a breadboard.

Numerous PCB designing software allows you to create customized PCB boards. However, you must know that there are some specific PCB tests that you should conduct after designing it.

But not getting your PCB made by a professional PCB manufacturing company can make conducting those tests strenuous. Now, the question arises what those specific tests are? Well, this is what we will be covering today.

Types of standard testing in PCB/PCBA

Below specified are some of the standard testing methods. Or procedures that help a PCB manufacturing company know their manufactured PCBs are in optimal working condition.

In-Circuit Testing or ICT

In-Circuit Testing or ICT is one of the most popular and effective testing methods in PCB/PCBA. This method lets manufacturers know if their developed PCBs have any design flaws. Moreover, the ICT test also helps PCB manufacturers analyze the board's proper working. And the electronic components embedded in it. ICT system involves a test system that is built using different instruments, such as:

• Multimeter
• Waveform Generator
• LCR Meter
• Power Supply
• Frequency Counter
• Logic Analyzer, and more.

PCB manufacturers can find between 85%-90% of faults with the ICT testing method. Due to this, the ICT testing method is considered one of the efficient PCB/PCBA testing methods. You must know that the In-Circuit testing method is done at the end when a PCB has been fully developed. And all the electronic components, according to their place in a PCB, are soldered.

Some of the common faults that testers in a PCB manufacturing company can find using the ICT testing method are:

• Tombstoning. The fault refers to when an electric component is not soldered properly. Or when an electric component comes off from one of the printed circuit board pads.
• Solder shorts. It is one of the most common faults. And occur when electronic components that are not meant to be connected are connected via soldering. Such as the two terminals of the same IC.
• Missing components or pads. ICT testing method also allows PCB testers to identify missing pads that house the electronic components.
• Raised IC or other electronic component's pins. This is another common fault, and it can interfere with the working of other electrical components.
• Loose or poor soldering connections. Poor soldering can cause an electronic component to not work properly. Or can even cause it to come out from its pad in a printed circuit board.

How is the test done?

ICT test system involves an instrument made using different instruments, as mentioned earlier. This instrument is fixed. You need to put the PCB inside it. Moreover, the instrument body also consists of multiple probes.

PCB testers place a PCB board concerning the probes inside the fixture. It is because each probe has a different testing function. And are needed to be connected to specific test points in a PCB board. Not connecting the board accordingly with the probes won't allow you to run tests on your PCB successfully.

In addition, probes are connected to fixture interface pins, and fixture interface pins are connected to module interface pins. Module interface pins are connected to the tester pin card, which is what detects faults.

When the fixture cover is lifted, and the board is placed, signals flow from the card to the board. And then from the board back to the tester pin card. A default software with the ICT testing instrument displays the status "Pass" when the board has no error. And "Fail" when there are errors in a PCB/PCBA.

Pros

• As the ICT instrument is made using multiple instruments, you can conduct several tests at once. And that too without needing any other testing instruments.
• Most efficient PCB/PCBA test.

Cons

• It is very costly.
• You cannot conduct the test at home.

Flying probe test

Another PCB/PCBA test is the Flying Probe Test. This testing method is different from ICT testing. This test does not involve any fixture that housed the instrument. Instead, numerous probes are fixed on a framework (flying probe tester). The framework can move along the X, Y and Z axis.

With Flying Probe Test, PCB testers can run tests such as:

• Short Circuit Test
• Open Circuit Test
• Thermal Test
• Power Test
• Nodal Impedance Test.
• Color Optical Test, and more on a PCB/PCBA.

Moreover, with Flying Probe Test, PCB testers can also find:

• The resistance value of resistors embedded on a PCB.
• Value of different capacitors.
• Inductance.

By using this method, we can perform this test.

First, PCB testers or manufacturers create a code uploaded to the flying probe tester. The code is an integral part of the test process, and without it, you cannot conduct the test. It is because how would the tester know what it should be testing. After uploading the code to the flying probe tester, a PCB/PCBA is tested. Flying Probe Tester will test whatever is written in your code.

Pros

• Fast testing method.
• Suitable for low production PCBs.
• Inexpensive as compared to the ICT testing method.
• Customizable. You can change the code according to your preference and test different boards.

Cons

• Not suitable for manufacturers that produce PCBs on a large scale.

Functional Circuit Test

This is another one of the standard testing methods in PCB/PCBA. With this test, PCB manufacturers can analyze whether the developed PCB is according to the standards. And is it working properly or not. A functional Circuit Test is usually done at the end of the manufacturing process, and after all, the final assembly is done.

The functional Circuit Testing method is somewhat similar to the ICT testing method. The testing method consists of an instrument (fixture) that gives you the pass or fail status.

The fixture can either contain probes just like those of ICT or can contain edge connectors. The status is based on the behavior of a PCB board. The instrument monitors how a PCB behaves, including any abnormality, and then gives the output. Functional Circuit Test also needs a set of different programs to test the behavior of a PCB.

How does the test work?

Functional Testers connect with a PCB/PCBA through the connectors or probes and then monitor its behavior based on the program. If all the design specifications and working of electronic components pass the program, PCB is deemed healthy PCB.

Pros

• Monitors the behavior of a PCB which no other test method does.

Cons

• It is a bit time-consuming.

Automated Optical Testing

As the name suggests, Automated Optical Testing involves testing your PCB means of image comparison through software. The software is the default software in this testing method and is one of the precise testing methods.

PCB testers take images of a manufacturer PCB utilizing a camera with high precision levels. Using a camera with high precision levels is an integral part of the process. Images are present in the software because the images are then compared with the reference.

If the quality of the images is not good, it can affect the test results. A proper comparison cannot be made, for example.

By this method, we can determine these faults

Some of the faults that can be determined by this method are:

• Improper soldering
• Loose pads
• Missing electronic components.
• Alignment, and more.

Pros

• Automated process.
• Does not require too much manual effort.
• Efficient and fast.

Cons

• Requires high-quality images of a PCB.

Boundary Scan Method

JTAG is also known as the boundary scan method. It is a process that is used for debugging of ICs. In such devices, a cell for boundary scan is present. Data is then moved past within these cells when it is present in shift register mode.

By this method, we can determine these faults

• Enables to know TAP controller state.
• Checks the timing of the cell.
• Rechecks the incoming data.

Pros

• Very trustworthy.
• Honest test results.
• Easy to use.

Cons

• Quite a difficult setup for beginners.

X-RAY INSPECTION

It is also known as AXI and is often used for checkup reasons. It comes with two types of AXI that are 2D and 3D. Professionals often use it as it needs experienced workers.

By this method, we can determine these faults

• Fuse connections.
• Inner hints.

Pros

• Detect problems to the core.
• Very reliable.

Cons

• Very time-consuming.

Burn-in method

This intense method for a large capacity is mainly used. It uses a high power for moving power through your electrical gadgets. It works for almost 2 days or more. If it somehow is not successful, results can be fatal as well.

By this method, we can determine these faults

• Checks the reliability of those parts that might be responsible for early failure.

Pros

• Can avoid the promotion of useless products.
• Avoids using dangerous products.

Cons

• High intensity can cause damage.

Conclusion

Looking out for what types of standardized testing are in PCB/PCBA? Do not forget to refer to the mentioned details about it.