TANDEX TEST LABS, INC Business Ctr. Dr. Irwindale CA Phone : Fax :

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1 Page1 TANDEX TEST LABS, INC Business Ctr. Dr. Irwindale CA Phone : Fax : Failure Analysis TANDEX ELECTRONICS TTL# TAN W Date: October 4, 1999 Part Number: CF1267 Cust.Part Number: (REF) Part Type: CAPACITORS Manufacturer: UNKNOWN Quantity: TWO (2) Purchase Order: FL12132 Submitted by: John R. Espenschied Prepared by: Rose Marie Escandon Approved by: Art Nakamoto

2 Page2 TANDEX TEST LABS TTL JOB# TAN W Summary Two (2) Capacitors P/N: DWG.( CF1267) , were received from Mr. David Stanis of WEM ELECTRONICS, Inc. at Tandex Test Labs, for Failure Analysis. The parts were serialized numbers 131 and 150, as received. It was requested to determine the root cause of component failure. Procedure: 1. The parts were visually inspected and photographed in as received condition. See figures 1 thru 6 2. Both parts were then opened to expose the internal structure which revealed electrical overstress. See figures 7 thru 10. Conclusion: The root failure, as observed by the physical evidence and known material characteristics, indicates electrical overstress that exceeded manufacturer s operating parameters. The sequence that resulted in catastrophic failure of the capacitor is detailed below. 1. External voltage/current applied to capacitor exceeds manufactured ratings. 2. Level of power (voltage/current) applied creates logarithmic thermal generation inside the capacitor structure. 3. Heat dissipation and thermal coefficient of expansion of capacitor encasement material was insufficient to contain simultaneous heat of the burning material, and expanded gases. 4. The electrical circuit of the capacitor at this moment became a fuse. Heat expansion will continue until power applied to capacitor superheats the internal conductor resulting in a material breakdown, creating an electrical open circuit or when the velocity of expanding gases,physically destroys circuit through internal combustion. The remnants verify the above sequence of mechanics resulting in the catastrophic failure. The insulation material of the through-hole pin has micro-cracks and corresponding fractured insulation material at glass to metal contacts indicate extreme internal heat and pressure release. The metallic expulsion materials indicating both internal expansion of high temperature gas propelling molten internal solder material and connective circuitry material. Evidence of high internal temperature is observed by the external package surface anomaly on figures 1 and 2. Note that the molten metallics have formed a annular ring which is typical of internal heat dissipation. Externally applied heat would have resulted in a carbonized annular ring with molten metallics in the center. Typical convex surface on internal surface of insulative material surrounding the feedthrough pin finalizes conclusion of intense internal pressures. This structure occurs as expanding gases and molten material begin to a V formation for expulsion at the package s weakest structural location. Propelling the entire glass and feed-through pin assembly was halted by an open electrical circuit preventing necessary time for energy to heat and cause further expansion of gases. Recommendations: 1. Review power supply to the device and associated circuitry to eliminate possibility of external circuitry as cause of electrical overstress. 2. Inspect devices from the same manufactured lot for: a. Leakage delta data after Burn-in. b. Radiographic or acoustical imagery for internal inspections for anomalies. c. Dissipation tests. d. Variable power tests within manufactured ratings using a bread board. Take safety precautions.

3 Page3 TANDEX TEST LABS TTL JOB# TAN W PHOTODOCUMENTATION ALL MAGNIFICATIONS ARE APPROXIMATE

4 TANDEX TEST LABS TTL JOB# TAN W Page4 Fig: 1 Description: Overall view of device in as received condition. Arrow denotes hot spots on surface. Fig: 2 Description: Overall view of device in as received condition. Arrow denotes hot spots on surface. Fig: 3 Description: End view of area B in figure 1.

5 TANDEX TEST LABS TTL JOB# TAN W Page5 Fig: 4 Mag: Description : Close-up of fig. 3 showing carbonized solder. This could have been caused by a reflow of the solder during failure due to excessive heat. Fig. 5 Description: End view of area B in figure 2. Fig. 6 Mag: Description: Close up of area in figure 5. Smaller area than on sample 131 same conclusion.

6 TANDEX TEST LABS TTL JOB# TAN W Page6 Fig: 7 Description : Internal structure after delid of can area excessive temperature caused melt down of capacitor. Note cooling cracks. Fig. 8 Description: Internal view of lid surface. Note areas caused by excessive heat. Fig. 9 Description: Same as figure 7

7 TANDEX TEST LABS TTL JOB# TAN W Page7 Fig: 10 Mag: Description: Same as figure 8