Vishay Optotriac 4208

Gideon Analytical Laboratories received two Vishay phototriac 4208s for failure analysis. A TRIAC is a generic trademark for a three-terminal electronic component that conducts current in either direction when triggered. Its formal name is bidirectional triode thyristor or bilateral triode thyristor. A thyristor is analogous to a relay in that a small voltage and current can control a much larger voltage and current.TRIACs are a subset of thyristors and are related to silicon controlled rectifiers(SCRs). TRIACs differ from SCRs in that they allow current flow in both directions, whereas an SCR can only conduct current in a single direction. Most TRIACs can be triggered by applying either a positive or negative voltage to the gate. We were given no information regarding these Vishay phototriac 4208s. The goal was to determine why they were failing.

Failure analysis was performed on the Vishay phototriacs. We began with the first sample. It was electrically tested, and a resistive short was found between pins 1-2. Dye penetration revealed the package to be susceptible to ingress along the lead frame. SEM-EDS was performed. Micrographs of the diodes were taken, and a spectrum produced. The EDS spectrum showed silver. The second sample went through the same process. We tested it electrically and resistance measured 224 ohms. Pad 5 on sample 2 had minimal carbon deposits. SEM-EDS analysis was performed. In conclusion, there were several problems with the Vishay phototriac 4208s. Silver had migrated from the lead frame up the sides and on to the top diode surface.

Gideon Analytical Laboratories solved this problem with precision. As usual, we delivered expert analysis in a timely fashion. Over the years, Gideon Analytical Laboratories has solved hundreds of problems for the electronics industry. Although there is cost up front to have failure analysis, it pays for itself in savings. Failure analysis upholds the old adage “an ounce of prevention is worth a pound of cure”. Save yourself time, money,recalls, headaches, lawsuits, negative publicity and all the other things requisite with failing products. You can count on us for results. If you are having problems with electronics, call Gideon Analytical Laboratories today.

SEM Micrograph of the GaAs diode

SEM Micrograph of the GaAs diode

EDS Spectra shows silver on diode

EDS Spectra shows silver on diode

Vishay phototriac 4208

Vishay phototriac 4208

Radiograph of Sample 2

Radiograph of Sample 2

Sample 1 is susceptible to ingress

Sample 1 is susceptible to ingress

Micrograph of the base of the gold ball bond, sample 1

Micrograph of the base of the gold ball bond, sample 1

Pad 5 on sample 2, had minimal carbon deposits

Pad 5 on sample 2, had minimal carbon deposits