PC Board Debugging & Troubleshoot Guidelines

Engineers have to test the PCB thoroughly to see if it’s functional and fulfills its purpose of design. But, some manufacturers don’t do it which leads to intermittent issues or PCB failure, and such issues are hard to deal with while debugging. Whereas it becomes a disaster if a PCB fails in the field. You can avoid PCB issues by testing it thoroughly, besides it should be built by a good manufacturer. First, you should know the basic troubleshooting methods, so let’s begin.

Basic PCB Troubleshooting and Debugging

PCB of a printed circuit board has copper traces and insulators to connect heavy components to develop an advanced circuit. It is a great challenge to troubleshoot a circuit board in terms of thickness, size, signals, layers, and the types of different components as they are all very important.
Some circuit boards are simple and don’t need a deep inspection, but there are also complex PCB designs that need special tools for troubleshooting. Generally, the basic test is easy to do through ordinary equipment to assess the currents, traces, and signals on the PC Board.

Choosing the Right Tools

Simple troubleshooting of a Printed Circuit Board involves a few tools, such as a multimeter which is quite common. But, deep troubleshooting of complex boards depends on high-end tools, especially if the problem is big. Like, you will have to use the oscilloscope, an LCR meter, a logic analyzer, and the power supply to assess a circuit board’s response in terms of function.

A Visual Inspection

Initially, you have to test your circuit board visually to see some obvious issues, such as overheating, overlapping of traces, burnt or damaged components, as well as the missing parts of a PCB. You can detect the burnt components through smell as they are not easy to detect otherwise. PCB components often get burnt due to overheating or excessive current. Sometimes the components bulge due to high temperature or heat which helps you identify the damage, like in the case of electrolytic capacitors.

Physical Testing

After visual inspection of your PCB comes the physical testing by applying the power to the board. You can easily find hot spots on the circuit board by touching its surface. So, you don’t need a costly thermographic camera to find heated areas. After finding the hot parts, you should cool them with compressed air to see how PCB components function at low temperatures.

How To Troubleshoot Or Debug A PCB Deeply

Experts use four techniques for PCB tests which come up with both pros and cons. Some common methods are ICT, cable scan, flying probe, and a functional test, so let’s study them one by one.

1: The Flying Probe Technique

This method of PCB troubleshooting involves multiple probes that check the PCB by flying around. Like, there are two to six probes in this case. This technique is ideal for large circuit boards, like backplanes. It is also cheaper than the ICT, and it debugs the pcb assembly issues that occur due to poor solder connections. The flying probe also checks components’ presence and their polarities and different values. It is a simple test and can handle the revisions of a PCB.

Cons of The Flying Probe

The flying probe techniques have some flaws in terms of PCB functionality testing, unlike ICT. The flying probe also works slowly compared to ICT because several probes contact the entire PCB testing points. However, it is ideal for low volume PCBs and its total cost is also lower than other techniques.

2: ICT Or In-Circuit For PCB Troubleshoot

The ICT is a PCB testing technique that involves multiple probes which are also called the bed of nails. In this process, the ICT probes connect with the testing points of the entire PCB to check its circuits to see if the assembly is correct or wrong. Like, it tests the bad solder joints or short circuits.

This method can perform even a deeper test by adding other modules or adapters to it. ICT also tests the overall function of PCB and values of the critical components.

Cons Of ICT

Though ICT is a great tool for PCB testing, it has some disadvantages too. Like, it has costly fixtures ranging from $8000, and they go up to $ 15000. Besides, the cost increases with any changes in the technique.

You can have maximum benefits from ICT if the technician knows the testing software and other tools. ICT is the best method for large volume testing.

3: The CableScan

Another troubleshooting technique is the cablescan, which is ideal for PCBs with several connectors having a complicated interface, like the backplanes. The tester attaches the cablescan with the circuit board and it tests all the pins against each other to evaluate the assembly issues, like a solder opening or shorts.

Cablescan also helps check jumpers’ configuration and quality of the diode, besides, it also accesses the capacitance and resistance.

Cons Of Cablescan

There are some flaws with cablescan due to its limits. Like, you have to see the size of the connectors it can test in one go. Moreover, it involves an additional cost to create the hardware interface.

You have to get wetting connectors, but their wiring with the system gets delayed due to the cost or other issues. The cablescan technique and its setup take lots of time, depending on the number of connectors and their complexity.

4: Functional Testing Technique

Another essential thing is to see if a PCB is ready to function or not. The functional test consists of test probes, software, and connected cables, and it determines PCB behavior according to design specifications.

The CM can also create the hardware and software or test fixtures to test the PCB function. This process is ideal for simple and small PCB layout designs. The engineers also develop fixtures for a bench test and make a plan to target the assembly issues involving less time and cost to assess the components. The functional test also helps see if the entire circuitry is working as you want. However, you need detailed debugging to find different faults and remove them.

Role of Engineers and Technicians In PCB Troubleshooting

You need experienced people to troubleshoot a PCB, such as engineers and technicians. Besides, these experts should know how to use the testing tools. Like, in the case of ICT, the engineer should know how to test the semiconductor. He should also know the DFT, end-user applications, as well as ICT optimization. The knowledge of hardware and software development is equally important.

When it comes to the cablescan, the troubleshoot company should have a huge inventory of already built connector interfaces. You can reduce the development cost and time by having all resources in hand.

Likewise, the technicians should debug with a flying probe according to the circuit board. In other words, the testing method should be compatible with the PCB design.

Most engineers use the LabView for a functional test, as it works according to the frequencies, variable supply levels, and several other PCB requirements. Such a deep examination of the PCB involves less amount of hardware, unlike surface-level testing.
Both basic and deep troubleshooting methods help you to find the right PCB issues, leading to an effective product by removing those issues.

Frequently Asked Questions

What Is ICT In PCB Troubleshooting?
ICT is a PCB testing technique that involves multiple probes which are also called the bed of nails. The ICT probes connect with the testing points of the entire PCB to check its circuits to see if the assembly is correct or wrong.
What Is The Flying Probe In PCB Debugging?
This method of PCB troubleshooting involves multiple probes that check the PCB by flying around. There are two to six probes in this case. This technique is ideal for large circuit boards, like backplanes. It debugs the assembly issues that occur due to poor solder connections.

What Is The Role Of A Functional Test In PCB?
The functional test consists of test probes, software, and connected cables, and it determines PCB behavior according to design specifications. The functional test also helps see if the entire circuitry is working as you want.
Is Basic Troubleshooting Enough For Circuit Boards?
No, the basic testing involves only visual and physical tests at basic levels. You need deep testing with specific tools, especially for complicated circuits.

Final Thoughts

PCB of a printed circuit board has copper traces and insulators to connect heavy components to develop an advanced circuit. It is a great challenge to troubleshoot a circuit board in terms of thickness, size, signals, layers, and the types of different components as they are all very important.
Some circuit boards are simple and don’t need a deep inspection, but there are also complex PCB designs that need special tools for troubleshooting. Generally, the basic test is easy to do through ordinary equipment to assess the currents, traces, and signals on the PCB. Whereas deep troubleshooting involves different techniques.
Would like to know more about PCB debugging, troubleshooting printed circuit board assembly? Email us at sales@pnconline.com

Written by Sam Sangani

Sam Sangani is the President & CEO of PNC Inc., a Nutley, NJ based Printed Circuit Board manufacturer. Sam graduated from L. D. Engineering College with a BS Degree in Mechanical Engineering. He also continued his education and graduated from Steven’s Institute of Technology where he acquired a Master’s degree in Computer Science.

After completion of his BS, Sam worked as a QC Manager, for Xerox, Romania and London. He was responsible for the Quality Control of Cable and Wire Harness imports from Romania. After completing his Master’s Degree, he worked as a Senior Programmer with IBM, Tucson, Arizona. Sam was responsible for leading the Mainframe System Programming Team.

In 1997, Sam acquired PNC INC., a Nutley, NJ based PC Board fabrication Shop. From 1997-2013, Sam has made tremendous improvements and changes within PNC INC., as he added many new Products and Technologies in PNC’s portfolio. With his proven track record and leadership, PNC has never had an unprofitable year and has continued its growth yearly since 1997.

His current responsibilities are Strategic Planning, Corporate Management, New Business Ventures, Sales & Marketing, Trade Shows, Professional Services and leading productive teams to achieve peak potential. He has also utilized Lean Management techniques which have built a foundation for PNC’s high-paced growth. Sam also enjoys real-estate investing, web design & SEO, trading stocks, options, futures and Forex markets.