Why Do Logic Boards Fail?

One of the most common questions I receive as a technician is “why did [x,y,z] part fail, I mean, I take great care of my computer and have only had it a year…” and so on. This question is easier to answer when we’re talking about components with moving parts, like HDDs and optical drives, or if the customer was having a party and their spouse had too much to drink near the unit. Barring liquid damage, catastrophic impacts, and uncontrolled power surges, the reason for logic board failure has proven to be quite elusive.

The complexity of a contemporary computing main circuit board — referred to in Apple circles as a “Main Logic Board (MLB)” or in PC circles as “mother board” — is both fascinating and humbling to me. So many years of trial and error have driven progress in efficiency and manipulation of data-moving electrons in main boards and this certainly will continue for many decades to come. The problem with subatomic particles in this instance is that they are subatomic; their pathways are so very small and often not visible to us without proper aid. We are required, for instance, to wear grounded ESD (Electro-Static Discharge) control wrist straps, work on ESD-free mats, and transport or store sensitive modules in ESD-free bags because all it takes is some static electricity to blow a hole into a board: a hole nobody would know about without a microscope.

So one of the reasons boards fail is structural damage on a scale we are unable to see. What causes this? Shorted circuits, weak and/or deteriorated cold solder joints, flexion (extremely rare but possible, especially if you’re good and rough with plugging things into the I/O side of the board), dirty power or inconsistent voltage, and of course heat. In some instances, a connected board such as RAM may be failing and affect the MLB by presenting improper voltage at the point of connection. Because it is responsible for so many aspects of the unit, and thus so broad in its scope of influence, I have to admit that I never tell a customer why a logic board has failed unless there is obvious liquid damage or charred residue from a short circuit. Otherwise it is safe to assume manufacturer defect, age, or unconscientious use.

How can you do your part to avoid an extremely expensive logic board failure out of warranty? As a general rule, always make sure there is proper air ventilation around your computer. We all love to get cozy in bed with our laptops at some time or another but if you are setting the unit on a puffy set of sheets, you are effectively blocking important airflow underneath. While internal fans serve the purpose of dissipating heat away from the CPU, GPU, and other heat-making components they don’t negate the need for external airflow. Make sure you are plugging into a reliable power source with consistent voltage levels. Power supplies do regulate the DC level, though a voltage spike that is too high will overpower this and potentially damage the logic board. I advocate blowing dust off of your boards and fans (if you feel comfortable enough to remove the bottom case to your laptop in the case of MacBooks and MacBook Pros or Airs) with compressed air.

If you find your computer is running so hot that you can barely touch it, fans race excessively, you experience kernel panics regularly, and you generally have boot and performance issues, it behooves you to run Apple Hardware Test or bring your unit into an Apple Authorized repair center like Small Dog.