Printed Circuit Board Failure Analysis - The basics
Complex electronic devices have relied on integrated circuits (ICs) on Printed Circuit Boards (PCBs) for quite a while now. Though several advances in technology have been made, the fundamentals remain the same. Pressure to pack more circuitry into a smaller area has increased the density of these boards and along with such designs, come many different errors. Greater complexity ensures that new types of flaws will emerge and the small size of the chips makes them difficult to detect.
Printed Circuit Board Failure Analysis deals with the detection of these errors. Over the years, many techniques have either emerged or been modified to detect flaws with divurgent degrees of details and perspectives. In this article, we take a brief look at some of the flaws in PCBs as well as the techniques for detecting them.
Flaws in PCBs
Broadly speaking, we can name three major types of flaws that plague PCBs. Flaws relating to material defects, flaws involving faulty electrical connections and flaws involving a physical breakdown.
PCB materials are built to precise specifications. Semiconductors need to have the exact specifications in order for them to have the precise design properties. When trace materials are present above the threshold, the PCB won't work as specified. Finding out whether or not it contains trace materials is the job of failure analysts.
Due to the complexity of the circuits, electrical problems can be very common. But it's often difficult to isolate these flaws. One electronic failure analysis technique we use to test is to create a heat map of the entire chip. Overheating in any area is a strong indication of an electrical fault though the actual problem might lie elsewhere. Nevertheless, it's a useful starting point.
Finally, physical breakdowns such as rust and fractures are also common. There are many types of cracks such as fatigue cracks, brittle cracks and environmental stress cracks. Finding out which type of crack it is enables us to also address the underlying problem which led to the flaw in the first place, which is the of course, the final goal of this exercise.
A large number of failure detection techniques have been developed by electronic failure engineers to deal with each type of flaw. Spectroscopoy is used to uncover trace elements, microthermography is used to detect minute heat traces. Various types of penetrant testing are used to discover physical flaws in the substance.
Each type of detection has many techniques, each of which has its own pros and cons. For example, microscopy can include emission spectroscopy, acoustic microscopy, and electron microscopy. Microthermography includes Liquid crystal imaging and fluroscent microthermal imaging. Physical breakdowns can be detected using acoustic microscopy and x-ray imaging. Sometimes many different tests are necessary to get a complete picture of what's gone wrong.
The failure analysis company, the type of test required, and the budget will all combine to determine which one is used. WIthout Printed Circuit Board Failure Analysis, we would be completely lost when a PCB malfunctions.