Field Failure FAQs
Field failures can often be a mystery, and it’s confounded when it’s a No Trouble Found (NTF) failure. Often, residues are the root cause of these failures. If none of these FAQs address your specific question, please contact us.
Failure Investigation Protocol
Q. How do you go about investigating the root cause of a field failure?
A. That depends on the field failure and the apparent failure mechanism. The first step is to determine why the unit failed. For example, was it due to a solder joint failure or was it an electrochemical failure? Was it a one-time event or is it systematic? Does it occur in one area consistently? Was it due to the environment or the manufacturing process? We usually try to gather as much information as we can about the assembly process, the field data, and the observable characteristics. We most often use ion chromatography to evaluate the samples. Properly interpreted, the chemical residues can tell a great deal about the failure mechanism, probable cause and possible remedies.
No Trouble Found (NTF)
Q. I have lots of hardware that fails in the field but tests fine in the lab, i.e. no trouble founds (NTFs). Why?
A. In most cases, residue-related field failures will occur in situations of high humidity. When a bench technician tests the returned hardware, it is usually at lab ambient conditions of 25°C/50 % RH. This may not be humid enough to fuel the electrical leakage phenomena. Try increasing the localized humidity using a vaporizer or putting the hardware in a temperature/humidity chamber at 35°C/90 % RH. This should be enough humidity to drive the electrochemical failure mechanism. If you still have an NTF, then try temperature cycling while monitoring the function. The expansion and contraction may exercise marginal solder joints and find the cracked ones.
Environmental / Service Conditions
Q. How clean does my product need to be, or what materials do I need to utilize for my end use environment or service condition?
A. That depends on the end use condition. Obviously, there are vastly different requirements for aerospace applications than for office products. The office environment is the most benign and humidity is often the most difficult factor. Outdoor applications have a wider range of contaminants, such as mixed flowing gasses (SOx and NOx), high heat/humidity, and particulates. Aeropace applications have outgassing concerns. NASA (Goddard Space Flight Center) is a good resource for space application requirements. SAE is a good resource for automotive and outdoor applications. Military specifications (MIL-STD-2000A and MIL-STD-883) are good for outdoor high-reliability applications.