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Old 18th January 2010, 03:04 AM   #1
Eric is offline Eric  United States
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Default Enlarge hole in IRF240?

I know I've seen some discussion of this before, but I cannot find it using the forum Search.

Can I drill out the hole in an IRF240 to make it big enough to accommodate an M4 screw without damaging the transistor or should I mount them with a smaller screw?

I was planning on using M4 screws to hold the chassis together and didn't really want to play with tapping different sized holes...

Thanks,
Eric
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Old 18th January 2010, 03:06 AM   #2
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I've drilled them 5/32 to clear #6 screw no problems

Cheers!
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Old 18th January 2010, 03:52 AM   #3
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You can, but just be aware that if you warp the part by clamping it too tightly, you'll crack the silicon- a bad thing. Clamp it too loosely and you'll have it spinning about- a bad thing. Look up the torque specifications for mounting tab devices and you'll see that a large screw isn't necessary. So, proceed with caution, or tap the correct sized holes.

CH
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Old 18th January 2010, 12:10 PM   #4
pjp is offline pjp  India
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What about the effect of vibration ?
Surely it cannot be good for the wires bonded onto the die ?
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Old 18th January 2010, 05:00 PM   #5
flg is offline flg  United States
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What vibration? We try not to ad mechanical noise either(Vibration), do you have your electronics on the top of your sub box?
The wire bonds are "encapsulated" in plastic. They won't vibirate. Your caps are wraped plastic and foil, they potentially are subject to vibration.
BTW, I have also enlarged the TO-247 pkg holes to #6 (USA) screws 100's of times without any problem. I like #6 screws better but, be aware of torque specs and use a big or springy washer or both. Nelson has had good luck with clip hold-downs also.
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Old 19th January 2010, 06:20 PM   #6
Eric is offline Eric  United States
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Thanks for all of the input! I appreciate it very much!

Eric
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Old 19th January 2010, 07:15 PM   #7
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Quote:
Originally Posted by Eric View Post
I know I've seen some discussion of this before, but I cannot find it using the forum Search.

Can I drill out the hole in an IRF240 to make it big enough to accommodate an M4 screw without damaging the transistor or should I mount them with a smaller screw?

I was planning on using M4 screws to hold the chassis together and didn't really want to play with tapping different sized holes...

Thanks,
Eric
I have do this with help of a engineers respective maintenance file set (round styles). A good choice is the brand BAHCO.
Bahco – True professionals’ love for increasing their performance by its ergonomics and design
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Old 19th January 2010, 07:26 PM   #8
Magura is offline Magura  Denmark
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The idea to use a file, is sure good.

To recommend Bacho is however not. They charge the same as Pferd, but the quality of Pferd files is quite a bit better.

PFERD Needle Files

Magura
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Old 20th January 2010, 12:27 PM   #9
Eric is offline Eric  United States
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Another excellent suggestion - Thanks!

Eric
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Old 20th January 2010, 12:43 PM   #10
AndrewT is offline AndrewT  Scotland
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the To247 has a 3.1mm to 3.5mm diam hole. It is tapered
I have drilled many of these to 3.5mm for M3.5 mounting screws.
The plastic on the back face often breaks away leaving a small circular indent around the enlarged hole. I see no problem with this M3.5 mounting.

I have drilled a few To264 to 4mm, but I was a bit wary of this modification.
Experiment on a few damaged ones first.
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