1N4148 Glass Diode Failures

Gideon Analytical Laboratories received several intermittent diodes failures and two good ones for comparison. The failed devices were checked for intermittent operation. The three diodes open-circuited between 65 and 80C. The lead frame makes contact with a solderable copper-clad steel plug under the glass.

This picture shows the lead frame to plug interconnect. If the solder fails to wet sufficiently the lead frame to plug interconnect, then intermittent opens can occur. This is also true of cold solder joints at this juncture.

The electrical continuity of these joints was tested after hermeticity. These joints were not affected by temperature or the hermeticity test. Two out of the three diodes opened circuited and remained open after the hermeticity test. The third diode tested as an intermittent failure at about 75C. The diodes packages were etched to remove the glass and inspected to reveal any anomalies.

The above picture shows the cathode backside metallization delaminating from the silicon die. In some cases, the metal peeled off in layers. In all three failures, the diode tested normally once the chip was revealed. All die were electrically tested with the anode still soldered to the lead frame.

The anode side of the die shows normal construction with no sign of electrical overstress and no anomalies.

Gideon Analytical Laboratories can solve problems related to component manufacturing anomalies. This was a lot problem associated with a certain date code. Solve your component problems by using our experience and expertise.