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I'm going to use two PB-case bridge rectifiers of a certain product in my circuit. I need to know the electrical connection of its heat-sink plate (i.e.; to what pin it is connected to, or if it is connected to any), so that I can decide whether I connect them to a single heat-sink or separate ones.

Datasheet of the product doesn't give any clear information about this. Is there any standard for this package type on this matter?

hkBattousai
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3 Answers3

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The "Enhanced Iso-Cink(TM)" legend on the datasheet, though not fully explained, may be explained in other Vishay documentation. It seems to mean "Isolated Case/Heatsink" and the datasheet says "Dielectric tested ... to withstand 1500V".

One way to use it then would be to mount the heatsink to chassis ground, if the equipment has a safety ground connection. Then any breakdown will isolate the equipment by tripping breakers or fuses, and the heatsink will not carry dangerous voltage in case of failure.

The alternative would be an isolated heatsink; in that case, it must be inaccessible, because in case of breakdown it could reach dangerous voltages.

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The heatsink does not appear to be electrically connected to any of the pins. Therefore you should not electrically connect the heatsink to any particular net. I would recommend a separate, unconnected pour or heatsink for these.

JYelton
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  • Did you extract this information out of the datasheet? May I ask source of this information? – hkBattousai Nov 04 '13 at 21:21
  • No, as you indicated the datasheet gave no information about the electrical connection for the pad. I was just offering advice based on other parts that have had an isolated pad for heatsink; I don't recall where I have seen documentation about it specifically. – JYelton Nov 05 '13 at 00:28
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Manufacturer does not state clearly about the electrical isolation between metal pad and live parts of the device, as some other manufacturers doing. However,

-UL1557 tests runs applying potential between live parts and accessible dead metal parts of the equipment, as clearly stated in paragraph 14. -The Rθja value of 20 oC/W (PB package thermal properties) usually indicates an epoxy layer between junction and case metal pad (in this case an 0,8 to 1,0mm thickness, of about 0,08W/mC insulator material), as it is common in old KBPC package …but -They are state that “if device is mounted in Floating Ground (F.G) application insulation is recommended to use to meet safety requirement”. This confuse me, that’s why I send them an email for a clear answer. I will post here the answer (if there is one!)

GR Tech
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