Failure Analysis on Pulse Transformers

Gideon Analytical Laboratories received six pulse transformers, three of which were failures, three of which were reliable. The objective was to determine the cause of the failures and inspect the unused transformers for anything that could contribute to the cause of failures. Transformers are devices that transfer electric energy from one circuit to another, usually with a change in voltage. Pulse transformers are transformers optimized for transmitting rectangular electrical pulses. Ideally, pulse transformer designers try to minimize voltage droop, rise time, and pulse distortion. Gideon Analytical Laboratories conducted a thorough failure analysis on these pulse transformers.

Each of the six pulse transformers was electrically tested for hermetic, cavities, neck down, chlorides, penetrated with dye, and potted. The failures clearly stemmed from neckdowns and scintillation. The neck down was occurring because the package had allowed moisture to penetrate preexisting cavities, which expose the magnet wire to an electrolyte and voltage that dissolve the copper and deposit it on a post of opposite polarity. Ubiquitous cavities in the presence of non-hermetic seals suggested poor encapsulation process and reliability concerns about exposing the wire to moisture.

SEM-EDS analysis was performed on five of the six samples, yielding elemental analysis in relation to the intensity of the element at a specific wavelength or energy level. The presence of chlorides was detected in four samples. Lack of hermeticity, copious cavities, and the presence of chlorides all contributed to the failures occurring because copper has been dissolved by the presence of an electrolyte and voltage within the cavity.

Gideon Analytical Laboratories has a proven track record of successful failure analysis. For over two decades and on hundreds of occasions, the experts at GideonAnalyticalLaboratories have been helping electronics companies solve their problems. By using information provided by GideonAnalyticalLaboratories, electronics companies have been able to save time, money, and resources. Knowing how and why a device fails is of paramount importance and can help companies better prepare for the future.

Pulse transformer

Choke winding

Pulse Transformer

Pulse transformer

Dye showing cavities

Dye showing cavities

Large cavity under bobbin

Large cavity under bobbin

Liquid ingress at corners

Liquid ingress at corners

neck down

neck down