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July 2018

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Subject:
From:
Carl Van Wormer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Carl Van Wormer <[log in to unmask]>
Date:
Tue, 17 Jul 2018 17:00:27 +0000
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I purchased kit for a Tesla coil driver and noticed something that seems like a possible thermal problem.  There is significant activity on the company’s user forum discussing the failure of the IGBT driver transistors, so I am guessing that the high failure rate might be due to a thermal problem.  The two TO-220 package driver transistors are mounted with slightly overlapping Sil-Pads using Nylon screws.  The overlapping Sil-Pads give an asymmetrical thickness for the compressed Sil-Pads, which may reduce the effectiveness of the thermal transfer.  Reading the data sheet, I see that the Sil-Pad thermal specifications are listed for 50-PSI compression.  I have no way to determine the compression of this Nylon screw mounting method, but I don’t think that small Nylon screws are that strong.



  1.  Can a nylon mounting screw provide sufficient compression (50-PSI) for effective Sil-Pad thermal performance?

  2.  Do any of the Tech-Netters have experience using Nylon screws to mount transistors to heat sinks?



Thanks,

Carl





​​​​​

Carl B. Van Wormer, P.E., AE7GD

    Senior Hardware Engineer

Cipher Engineering LLC

    [log in to unmask]<mailto:[log in to unmask]>     http://cipherengineering.com<http://cipherengineering.com/>

    503-617-7447x303

Location: 45.5475299,-122.89403270000003

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                        Hillsboro, OR  97124

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                  Hillsboro, OR  97124



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