Relay Failure Analysis

Gideon Analytical Laboratories received several RY4S-UAC110-120V power relays for failure analysis. A relay is an electrically operated switch. Many relays use an electromagnet to operate the switch, but other operating principles are also used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuits must be controlled by one signal. Relays are used to control a high power or high voltage circuit with a low power circuit. The low power is isolated from the high power circuit. The RY4S-UAC110-120V power relays have 4PDT contact configuration, 5A contact current, quick connect relay terminals, and silver contact material. Their coil resistance is 4.29kohm. When given the RY4S-UAC110-120V power relays, we were to tasked with determining the stuck core/contact cause.

Gideon Analytical Laboratories received one failed relay with one good one for comparison. The failed relay was intermittent @ 2 KHz.

A reed relay is a switch that uses an electromagnet to control the turning off or on within a circuit. The contacts are of magnetic material and the electromagnet acts directly on them without requiring an armature to move them. Sealed in a long, narrow glass tube, the contacts are protected from corrosion and are usually plated with silver, which has very low resistivity but is prone to corrosion when exposed, rather than corrosion-resistant but more resistive gold as used in the exposed contacts of high-quality relays. Multiple reed switches can be inserted into a single bobbin and actuate simultaneously. The glass tube is wrapped in copper windings and closes the switch with an inductive action when the copper is energized.

Gideon Analytical Laboratories received three sample NEC 104PW161 power inverter boards for failure analysis. A power inverter is designed to convert direct current (DC) to alternating current (AC). Inverters are used to operate all types of electrical equipment that uses batteries. DC current is what batteries store, but most electrical devices need AC current. These NEC104PW161 inverters had an output voltage of 520V and an output current of 5.5mA. The goal was to determine why they were failing.

Relays are very susceptible to contamination because the leads are made of copper and vulnerable to corrosion and leakage current if not protected from the environment.

The liquid shown here was thought to have come from the flux residue and, therefore, an organic analysis FTIR was required as opposed to inorganic XRF. However, the liquid was acidic in nature and XRF was employed. The material was a filled, glass fiber reinforced material containing a phosphorus species along with an antimony/bromine fire retardant package. The original formulation likely contained antimony oxide and a poly-brominated organic, such as diphenyl ether or a tetra-bromo BPA polyester or polycarbonate. The bromic acid has leached out of the fire retardant material. This material is not compatible with most electronic circuits or components.

Gideon Analytical Laboratories performed failure analysis on several Sky CKC-1C-12VDC 12A/120V relays. These relays have a contact resistance of 100 Mohms and have a surge resistance of 1000V. The devices had a liquid on the inside surface and corrosion on several of the leads. The liquid and corrosion is pictured at the top left.

The drop was analyzed using FTIR. The liquid was thought to have come from the flux residue and, therefore, an organic analysis FTIR is required as opposed to inorganic (XRF). The pH is 0.0. The liquid is very acidic. Since the liquid appears to be inorganic, an XRF was performed. A 2-microliter aliquot of DI water was added to a region showing a large number of droplets. The drop was moved about the surface and then recovered using a 2µ1 capillary and transferred to a Prolene film mounted on an XRF sample cup. The XRF sample cup consisted of Chemplex XRF sample cup cat. No. 1430 and a Prolene thin film cover (4µm Prolene, Chemplex cat. No. 426). The backside of the sample cup was removed to permit application of the sample solution to the back of the Prolene film.