by Jack Goho
Gideon received several Vishay SS26 Schottky rectifiers for failure analysis. It was thought something within the manufacturing process caused the devices to have a premature end of life in what would be considered a non-stressful application.
The Schottky diode is what is called a majority carrier device. It has advantages in terms of speed because it does not rely on holes or electrons recombining when they enter the opposite type of region as in the case of a conventional diode. When making the devices small, the normal RC type time constants can be reduced, making these diodes an order of magnitude faster than the conventional PN diodes. This is the prime reason why they are used in radio frequency applications.
The diode, in addition, has a much higher current density than an ordinary PN junction. This translates into a forward voltage drop which is lower and, thus, making the diode the choice in power rectification applications.
The device is not without drawbacks. The reverse current is relatively high and for many users, this may not be a problem, but it may be a factor in tighter applications.
The overall I-V characteristic follows the typical forward semiconductor diode characteristic, but with a much lower turn-on voltage. At high current levels it levels off and is limited by the series resistance or the maximum level of current injection. In the reverse direction, breakdown occurs above a certain level. The mechanism is similar to the impact ionization breakdown in a PN junction.
All the devices were thoroughly electrically tested before decapsulation. It was found that an overvoltage spike destroyed the guard ring exiting through the underlying p region and silicon dioxide passivation.
Gideon Analytical Laboratories single goal is to diagnose problems with electronics. In this case, we took a look at the manufacturing process as this was the initial thoughts of the client. We deal with all sorts of electronic failures. We can solve problems in the design, manufacturing, application process, or environmental field failures. It doesn’t really matter what the problem is; if it involves electronics, Gideon Analytical Laboratories is the place to contact. We will take care of you and your business. We take the utmost care to give you immediate and accurate feedback to help you remedy the problem. Use any of your currently working electronic devices to call or email us today.