In order to debug a printed circuit board (PCB) correctly, you must first find out the reason for the malfunction.
The most common faults in a PCB are caused by physical damage, which is typically easy to identify. This type of problem is called “obvious damage.” Checking for obvious damage is the first step to debug a PCB, but if the flaws go beyond the physical appearance, you’ll have to take additional steps. Here you will find a list of PCB debugging techniques that will be useful for your projects.
Investigating PCB Connection
In order to use this PCB debugging technique, we first have to talk about the two types of associated problems — wrong connection and no connection.
Wrong Connections
Wrong connections or “misconnections” can be the consequence of a design communication failure or an error that occurs early in the design and persists until the PCB is manufactured. It can also be caused by an incorrect connection in the wiring. A wrong connection can cause intermittent shorts in the PCB or, more commonly, keep it from working it all.
Another common cause is an excess of conductive material used while soldering the board. This type of mistake can lead to two things: first, it can create a connecting bridge that conducts electricity to parts of the card where there should not be any electricity at all. Second, it can cause welded pieces to detach and conduct energy to the wrong places in the PCB. In either case, PCB debugging is required to locate these errors.
No Connection
A “no connection” problem is usually related to the procedures that are performed before and during the manufacturing process. The errors associated with the design range from an incorrect interpretation of the blueprint to external agents that alter the photolithography. On the other hand, a lack of communication between the designers and the factory can also cause problems. In some cases, a blueprint is sent to the manufacturer and the designers continue working on adjustments and improvements, but the manufacturer continues to work based on the original drawings.
Connection problems mean a lack of power. The best PCB debugging technique, in this case, would be the signal injection method, which seeks to confirm the existence of signals in each component.
To implement it, a signal source is applied to the input. With the help of an oscilloscope, the waves are measured at each of the points in order to identify where and when the signal ceases to exist. This allows you to isolate the element where the error exists.
There are two main reasons for a no connection failure:
- Excessive noise caused by EMI/SI: Electromagnetic interference (EMI) and signal interference (SI) can cause the integrated circuit to switch on and operate erroneously, ultimately causing the component to fail completely.
- Electrical networks: High or low voltage variations can overheat or restart the device, causing it to fail momentarily — despite this being a temporary failure, it might become recurrent, eventually causing permanent damage to the element.
Bad Components
One of the reasons a circuit fails is due to faulty components that work as broken jumpers on the PCB. Any process that is involved or connected to any defective components will not occur, and if these elements work in series with others, the energy will not reach other sectors of the PCB.
There are various reasons why a component might fail. It may have been purchased in poor condition, it may have been damaged during storage, or it may have been damaged during assembly or after installation. Regardless of the reason, it’s necessary to debug the PCB.
Start by measuring the voltage with a multimeter. Find any missing connections or raised spots in the solder and measure the resistance value between the component and its raised or exposed spot. You can use a similar process to find shorts and open systems. If the voltage value is equal to zero, a short circuit is present.
Checking Heat
PCBs overheat due to voltage variations in the system — if the voltage gets too high, the components heat up. It is important to recognize if the voltage impact is continuous or sudden, as this determines the time it will take for the system to respond.
The PCB debugging techniques used to discover this type of fault are based on two basic procedures:
- Touching: If it ain’t broke, right? The simplest method can sometimes be the best: simply touch each component to find hot spots on the PCB. For more precise measurements or to gauge the temperature of smaller spaces, you can use a thermometer instead.
- Freezing spray: Using a freezing spray can help you determine which component is conducting the most heat. Spray the board, then watch for the speed at which the cold gas evaporates on various parts to identify the hottest elements.
Partner With a PCB Manufacturer
In general terms, most of the failures that a PCB can suffer are associated with problems in the initial plan or in the final manufacturing. This speaks volumes about the importance of having a reliable PCB manufacturing and EMS supplier partner with the experience and professionalism you need to save time, money, and resources.
A distinguished partner can keep PCB debugging processes to a minimum — reliable PCBs come out of good communication and excellent quality assurance processes. These common PCB failures can be avoided by teaming up with a manufacturer like SVTronics.
To learn more about PCB failures, read 4 Reasons Behind PCB Failure.