How Failure Analysis Prevents Small Problems from Becoming Major Issues

Modern manufacturing, regardless of industry, involves complicated configurations of powered equipment. The signal flow of electric power must pass through multiple interfaces in order to be delivered to the various components at the prescribed voltage levels. Oftentimes, somewhere along the sequence of cables, couplings and power converters, a small malfunction can occur which affects signal flow within the configuration. Loss of power can have exponentially negative effects on efficiency, production, bottom line, and facility safety.

Failure analysis services provide the unique ability to use a set of objective protocols to diagnose malfunctioning equipment and pinpoint the precise location of the problem. This process provides clients with valuable information about certain types of equipment to help them decide whether to seek out more reliable components.

A Summer, 2020 Failure Analysis Case

Recently, a client presented Constellation PowerLabs with a failed DC power supply module. The component was the same model that was being used in the client’s generating configuration to supply rack power to the company’s VME (virtual machine environment) facility turbine controllers.

The objective was to determine why the module’s output power source (PS) connectors PS ”A” and PS ”B” were not delivering the proper voltages.

Step-by-Step Process

Once the unit manufacturer and model were identified and recorded, the failure analysis services team inspected the component for external signs or odors of stress and/or damage. None were detected, and it was noted that the unit was in good cosmetic condition.

Next, a PQI (Parts Quality Initiative) test was performed. The fault reported on the unit’s LEDs could not be cleared by the toggle reset switch. The test confirmed the failure mode, as each of the 14 output terminals in the PSA and PSB connectors were registering no output voltage. This initial characterization test was recorded as a failure — prompting the team to investigate further.

Failure Analysis Investigation

The cover of the power supply unit was then removed, revealing two printed circuit boards (PCBs) which were mounted to the heat sink. Examination of the module revealed the use of DC to DC converters to derive the output voltages. Without the schematic for the module, the team was still able to determine the way the module functioned by using the component datasheets.

Manufacturer Data Sheets Consulted

All 14 modules on the output PCB were identified according to the manufacturer’s data sheets. It was initially noted that the disable pins were engaged on all 14 modules — explaining why they had no power output. The manufacturer datasheets also conveyed to the failure analysis systems engineers that the 5V module had special features.

Unlike the other modules, the 5V had no input voltage (125V DC), and if the under-voltage detector for this module is tripped, all the other modules will be disabled until the 5V output returns to a voltage above the under-voltage threshold. This provided a clear explanation why the other modules were disabled.

Extract and Examine

It was determined that the PCB would need to be totally disassembled. If the PCB remained intact, it would be impossible for Constellation PowerLabs’ engineers to view and diagnose the condition of each module on the underside of the PCB. The output PCB was then extracted by unscrewing sixty fasteners and disengaging the thermal paste holding it to the heat sink.

Once loosened, the PCB was removed from the heat sink and turned over. This exposed the input module fuses on the underside of the PCB. In this position, the seven voltage DC/DC modules could be easily observed. In this failure analysis, it revealed that the fuse to the 5V module input was blown preventing the 5V module from powering. Prompted by a careful study of the manufacturer’s datasheet, it was found this particular 5V module had control signal features to the other DC/DC modules. When this module failed, the other modules shut down as designed.

Failure Analysis Prevents Reoccurring Issues

In addition to consulting manufacturer data sheets, key personnel from the manufacturer’s technical design team were personally contacted by the Constellation PowerLabs failure analysis service team of engineers.

Establishing clear lines of communication is a crucial step in the failure analysis process. In this case, the manufacturers were willing to work with the engineers to suggest various courses of action, document the process and ultimately — to resolve the issue. Oftentimes, analyzing defective products and failure-prone components can lead to a redesigned piece of equipment that delivers superior performance to its users due to the failure analysis process.

A Definitive Conclusion

The failed module was extracted from the PCB using desoldering techniques. The 5V module was then tested removed from the PCB, confirming a short was caused by a problem within the DC/DC module and not due to some other problem on the PCB. Once this determination was made, Constellation PowerLabs engineers relayed the information to the manufacturer’s technical support personnel.

This discussion revealed that “common mode noise” can cause this type of damage to this particular model. This info was relayed to the customer so they could prevent this type of failure in the future.