Failure Analysis on 1N645 Silicon Rectifier Diodes

Gideon Analytical Laboratories received two 1N645 silicon rectifier diodes for failure analysis. One was bad and the other was a quality diode to be used for comparison. A rectifier is an electrical device that converts alternating current(AC), which periodically reverses direction, to direct current(DC), which flows in only one direction. Rectifiers are used inside the power supplies of virtually all electronic equipment. AC/DC power supplies may be broadly divided into linear power supplies ands witched-mode power supplies. The 1N645 silicon rectifier diode has 225V 400mA ratings. It can handle a maximum of 5 Amps surge current and at 25 Degrees Celsius has an average maximum rectified current of 0.4 Amps. The goal was to determine why these diodes were failing.

Without hesitation, we went to work analyzing the 1N645 silicon rectifier diodes. The failed diode showed open at above 55 Degrees Celsius, but below that temperature, the diode recovered. A cure tracer was used to test the diode electrically. A curve tracer is a specific piece of electronic test equipment used to analyze the characteristics of discrete semiconductor devices such as diodes, transistors, and thyristors. Based on an oscilloscope, the device also contains voltage and current sources that can be used to stimulate the device under test. There was a temperature problem. The plastic sleeve was removed, and the die was inspected optically. The die was healthy and had no fractures. There was a solder preform on the top of the anode making contact with the copper clad shank, and there was also a piece of silicon removed from the die corner. The complementary limb where the pre-form was supposed to be soldered had no solder. This was a manufacturing issue.

Gideon Analytical Laboratories has a long and successful history of solving electrical problems. Our team has over 70 years of experience in the industry. We have helped hundreds of companies save billions of dollars by assisting them to produce quality products. To paraphrase Farmers Insurance, we know a thing or two about electrical problems because we’ve seen hundreds and hundreds of electrical issues. We have the experience, the analytical equipment, and the dedication to get the job done. If you are having electrical problems, give Gideon Analytical Laboratories a call today.

Anode shank shows only copper present

Anode shank shows only copper present

Micrograph shows defect associated with dicing and soldering

Micrograph shows defect associated with dicing and soldering

Diode electrically tested again to see if silicon defect affected the die

Diode electrically tested again to see if silicon defect affected the die

Curve trace was normal below 55 Degrees Celsius

Curve trace was normal below 55 Degrees Celsius

Die can be seen throughout the glass, piece of silicon removed, in red circle

Die can be seen throughout the glass, piece of silicon removed, in red circle

Glass etched off, preform has not melted or changed in any way

Glass etched off, preform has not melted or changed in any way

Complementary shank, no solder on it

Complementary shank, no solder on it