http://www.eng-tips.com/viewthread.cfm?qid=96155
Ảp THUẬN max mà diode chịu được là như thế nào ? Bt chúng ta đều biết diode có áp ngược chịu được là giới hạn, còn áp thuận có giới hạn không ? (Theo phạm vi thông thường chứ ko phải max như KV).
I am having a problem with a 60V Schottky diode. We are having around a 1% failure rate of the diodes in production. This appears to be an early break-in type of failure, since we don't have any failures that show up during life testing. The failure mode is a short. We have not been able to successfully locate the cause of the failure, but have limited it down to 3 causes: overvoltage transient, process damage, or inherent defect.
The function of the diode in the circuit is to act as a barrier diode to block reverse voltage. The load is a DC/DC boost converter. After the diode and parallel to the load we have a filter capacitor. The input range of the circuit is 16VDC up to 42VDC. The circuit also has an MOV on the input.
I have been investigating this problem for the last 2 weeks and haven't gotten very far, so I figured I would turn here for some ideas.
We know that the diode has a avalanche rating of 90V, and confirmed in testing that it can withstand 95V for 1 msec repeating at a 1 Hz rate, but failed at 100V.
We tried a pilot run of 1000 units with a 100V diode and still had a 1% failure rate.
We also know that the MOV does not appear to clamp fast enough, so the diode will try to clamp any negative transients before the MOV can react.
Right now my hunch is that something is happening somewhere in the production process to cause the damage, or else the parts are just bad to start with. We returned some of the failed parts to the vendor for analysis and are holding our breath until we get an answer from them. A one percent failure rate seems to point to a quality problem and not an inherent design defect. If it is indeed a design flaw, then I will probably have to start looking for a new line of work.
Ảp THUẬN max mà diode chịu được là như thế nào ? Bt chúng ta đều biết diode có áp ngược chịu được là giới hạn, còn áp thuận có giới hạn không ? (Theo phạm vi thông thường chứ ko phải max như KV).
I am having a problem with a 60V Schottky diode. We are having around a 1% failure rate of the diodes in production. This appears to be an early break-in type of failure, since we don't have any failures that show up during life testing. The failure mode is a short. We have not been able to successfully locate the cause of the failure, but have limited it down to 3 causes: overvoltage transient, process damage, or inherent defect.
The function of the diode in the circuit is to act as a barrier diode to block reverse voltage. The load is a DC/DC boost converter. After the diode and parallel to the load we have a filter capacitor. The input range of the circuit is 16VDC up to 42VDC. The circuit also has an MOV on the input.
I have been investigating this problem for the last 2 weeks and haven't gotten very far, so I figured I would turn here for some ideas.
We know that the diode has a avalanche rating of 90V, and confirmed in testing that it can withstand 95V for 1 msec repeating at a 1 Hz rate, but failed at 100V.
We tried a pilot run of 1000 units with a 100V diode and still had a 1% failure rate.
We also know that the MOV does not appear to clamp fast enough, so the diode will try to clamp any negative transients before the MOV can react.
Right now my hunch is that something is happening somewhere in the production process to cause the damage, or else the parts are just bad to start with. We returned some of the failed parts to the vendor for analysis and are holding our breath until we get an answer from them. A one percent failure rate seems to point to a quality problem and not an inherent design defect. If it is indeed a design flaw, then I will probably have to start looking for a new line of work.
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