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From: John Fields on 21 Jun 2010 16:40
On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
<presence(a)MUNGEpanix.com> wrote:

>Phil Allison <phil_a(a)tpg.com.au> wrote:
>>
>> "Cydrome Leader"
>>> Phil Allison
>>>> "Cydrome Leader"
>>>
>>>>> I had a hard time recently locating a specific power transistor in a
>>>>> TO-218 case, with the metal tab and not the lump of plastic with a metal
>>>>> back like everything seems to be now.
>>>>
>>>>
>>>> ** Why bother ??
>>>>
>>>> TO-218 is virtually the same pak and construction as TO-3P except you no
>>>> longer need to use an insulating bush with the latter.
>>>
>>> to not have to modify existing heatsink clamps. The setup in the product
>>> was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
>>> not sure why the transistor wasn't just screwed down. There was a screw
>>> and nut for the clamp anyways.
>>
>> ** A well designed clamp does a far better job with TO-3P and similar single
>> hole packs than using a bolt does. Normally the clamp supplies high pressure
>> along the CENTRE line of the plastic body of the device. The body spreads
>> the pressure evenly over the tab and there is then no tendency for it to
>> lift up at the lead end as there is with a bolt.
>>
>>
>>>> TO-3 is a whole nuther animal with many advantages over plastic paks.
>>>
>>> the TO-218 is actually somewhat compatible with the TO-3.
>>
>> ** The main advantage of the TO3 pak is that there is no plastic in contact
>> with the chip which sits in a hermetically sealed environment - means
>> chips have a much longer service life even when running near max temps.
>
>I'm not arguing that a TO-3 is better all around- it's just that fewer and
>fewer semiconductors are packaged as nicely these days so that's what you
>have to work with most of the time. The hermetically sealed and welded
>metal can obviously costs more than some plastic resin molded around a
>sliver of metal.
>
>Sanken uses to have the most exciting TO-3 cases. The base was
>surprisingly thick and they felt like they were made of gold.


>
>> Internal feed wires can be sized to fuse immediately if a device fails - a
>> valuable feature not seen in plastic paks.
>
>But the plastic ones explode and burn.
>
>> Two bolt mounting is easy to get right - long as you avoid those soft
>> plastic ( Nylon ? ) insulating bushes that crush under heat and pressure.
>
>I think they were a glass filled plastic. I may still have some mounting
>kits with the mica washer, nuts, washer and lug.

---
They're in the present tense, actually, and available in Nylon and
glass-filled polyphenylene sulfide.
---

>I've seen lots of power supplies now have the power semiconductors glued
>to the heatsinks, or the thermal pad is sort of like a really hard two
>sided tape. I can't figure out if there is any repair method for that type
>of stuff.

---
http://www.braceface.com/medical/Surgery_set_images/CW_instruments_images/Bone%20hammer%20and%20chisel.JPG


From: krw on 21 Jun 2010 18:42
On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
<presence(a)MUNGEpanix.com> wrote:

>Phil Allison <phil_a(a)tpg.com.au> wrote:
>>
>> "Cydrome Leader"
>>> Phil Allison
>>>> "Cydrome Leader"
>>>
>>>>> I had a hard time recently locating a specific power transistor in a
>>>>> TO-218 case, with the metal tab and not the lump of plastic with a metal
>>>>> back like everything seems to be now.
>>>>
>>>>
>>>> ** Why bother ??
>>>>
>>>> TO-218 is virtually the same pak and construction as TO-3P except you no
>>>> longer need to use an insulating bush with the latter.
>>>
>>> to not have to modify existing heatsink clamps. The setup in the product
>>> was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
>>> not sure why the transistor wasn't just screwed down. There was a screw
>>> and nut for the clamp anyways.
>>
>> ** A well designed clamp does a far better job with TO-3P and similar single
>> hole packs than using a bolt does. Normally the clamp supplies high pressure
>> along the CENTRE line of the plastic body of the device. The body spreads
>> the pressure evenly over the tab and there is then no tendency for it to
>> lift up at the lead end as there is with a bolt.
>>
>>
>>>> TO-3 is a whole nuther animal with many advantages over plastic paks.
>>>
>>> the TO-218 is actually somewhat compatible with the TO-3.
>>
>> ** The main advantage of the TO3 pak is that there is no plastic in contact
>> with the chip which sits in a hermetically sealed environment - means
>> chips have a much longer service life even when running near max temps.
>
>I'm not arguing that a TO-3 is better all around- it's just that fewer and
>fewer semiconductors are packaged as nicely these days so that's what you
>have to work with most of the time. The hermetically sealed and welded
>metal can obviously costs more than some plastic resin molded around a
>sliver of metal.
>
>Sanken uses to have the most exciting TO-3 cases. The base was
>surprisingly thick and they felt like they were made of gold.
>
>> Internal feed wires can be sized to fuse immediately if a device fails - a
>> valuable feature not seen in plastic paks.
>
>But the plastic ones explode and burn.

Metal ones can explode and throw shrapnel around the room.

>> Two bolt mounting is easy to get right - long as you avoid those soft
>> plastic ( Nylon ? ) insulating bushes that crush under heat and pressure.
>
>I think they were a glass filled plastic. I may still have some mounting
>kits with the mica washer, nuts, washer and lug.
>
>I've seen lots of power supplies now have the power semiconductors glued
>to the heatsinks, or the thermal pad is sort of like a really hard two
>sided tape. I can't figure out if there is any repair method for that type
>of stuff.

Thermal pads are really crappy.
From: JW on 22 Jun 2010 05:56
On Mon, 21 Jun 2010 17:42:21 -0500 "krw(a)att.bizzzzzzzzzzzz"
<krw(a)att.bizzzzzzzzzzzz> wrote in Message id:
<iiqv1650144gv9gu9kju00tl8ec8abqlau(a)4ax.com>:

>On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
><presence(a)MUNGEpanix.com> wrote:
>
>>Phil Allison <phil_a(a)tpg.com.au> wrote:
>>>
>>> "Cydrome Leader"
>>>> Phil Allison
>>>>> "Cydrome Leader"
>>>>
>>>>>> I had a hard time recently locating a specific power transistor in a
>>>>>> TO-218 case, with the metal tab and not the lump of plastic with a metal
>>>>>> back like everything seems to be now.
>>>>>
>>>>>
>>>>> ** Why bother ??
>>>>>
>>>>> TO-218 is virtually the same pak and construction as TO-3P except you no
>>>>> longer need to use an insulating bush with the latter.
>>>>
>>>> to not have to modify existing heatsink clamps. The setup in the product
>>>> was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
>>>> not sure why the transistor wasn't just screwed down. There was a screw
>>>> and nut for the clamp anyways. JW: Cue AlwaysWrong!
>>>
>>> ** A well designed clamp does a far better job with TO-3P and similar single
>>> hole packs than using a bolt does. Normally the clamp supplies high pressure
>>> along the CENTRE line of the plastic body of the device. The body spreads
>>> the pressure evenly over the tab and there is then no tendency for it to
>>> lift up at the lead end as there is with a bolt.
>>>
>>>
>>>>> TO-3 is a whole nuther animal with many advantages over plastic paks.
>>>>
>>>> the TO-218 is actually somewhat compatible with the TO-3.
>>>
>>> ** The main advantage of the TO3 pak is that there is no plastic in contact
>>> with the chip which sits in a hermetically sealed environment - means
>>> chips have a much longer service life even when running near max temps.
>>
>>I'm not arguing that a TO-3 is better all around- it's just that fewer and
>>fewer semiconductors are packaged as nicely these days so that's what you
>>have to work with most of the time. The hermetically sealed and welded
>>metal can obviously costs more than some plastic resin molded around a
>>sliver of metal.
>>
>>Sanken uses to have the most exciting TO-3 cases. The base was
>>surprisingly thick and they felt like they were made of gold.
>>
>>> Internal feed wires can be sized to fuse immediately if a device fails - a
>>> valuable feature not seen in plastic paks.
>>
>>But the plastic ones explode and burn.
>
>Metal ones can explode and throw shrapnel around the room.

A TO-3 explode? I've *never* seen that happen, and hope I never do!

From: Cydrome Leader on 22 Jun 2010 14:44
JW <none(a)dev.null> wrote:
> On Mon, 21 Jun 2010 17:42:21 -0500 "krw(a)att.bizzzzzzzzzzzz"
> <krw(a)att.bizzzzzzzzzzzz> wrote in Message id:
> <iiqv1650144gv9gu9kju00tl8ec8abqlau(a)4ax.com>:
>
>>On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
>><presence(a)MUNGEpanix.com> wrote:
>>
>>>Phil Allison <phil_a(a)tpg.com.au> wrote:
>>>>
>>>> "Cydrome Leader"
>>>>> Phil Allison
>>>>>> "Cydrome Leader"
>>>>>
>>>>>>> I had a hard time recently locating a specific power transistor in a
>>>>>>> TO-218 case, with the metal tab and not the lump of plastic with a metal
>>>>>>> back like everything seems to be now.
>>>>>>
>>>>>>
>>>>>> ** Why bother ??
>>>>>>
>>>>>> TO-218 is virtually the same pak and construction as TO-3P except you no
>>>>>> longer need to use an insulating bush with the latter.
>>>>>
>>>>> to not have to modify existing heatsink clamps. The setup in the product
>>>>> was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
>>>>> not sure why the transistor wasn't just screwed down. There was a screw
>>>>> and nut for the clamp anyways. JW: Cue AlwaysWrong!
>>>>
>>>> ** A well designed clamp does a far better job with TO-3P and similar single
>>>> hole packs than using a bolt does. Normally the clamp supplies high pressure
>>>> along the CENTRE line of the plastic body of the device. The body spreads
>>>> the pressure evenly over the tab and there is then no tendency for it to
>>>> lift up at the lead end as there is with a bolt.
>>>>
>>>>
>>>>>> TO-3 is a whole nuther animal with many advantages over plastic paks.
>>>>>
>>>>> the TO-218 is actually somewhat compatible with the TO-3.
>>>>
>>>> ** The main advantage of the TO3 pak is that there is no plastic in contact
>>>> with the chip which sits in a hermetically sealed environment - means
>>>> chips have a much longer service life even when running near max temps.
>>>
>>>I'm not arguing that a TO-3 is better all around- it's just that fewer and
>>>fewer semiconductors are packaged as nicely these days so that's what you
>>>have to work with most of the time. The hermetically sealed and welded
>>>metal can obviously costs more than some plastic resin molded around a
>>>sliver of metal.
>>>
>>>Sanken uses to have the most exciting TO-3 cases. The base was
>>>surprisingly thick and they felt like they were made of gold.
>>>
>>>> Internal feed wires can be sized to fuse immediately if a device fails - a
>>>> valuable feature not seen in plastic paks.
>>>
>>>But the plastic ones explode and burn.
>>
>>Metal ones can explode and throw shrapnel around the room.
>
> A TO-3 explode? I've *never* seen that happen, and hope I never do!

I've not seen or heard of it, but never worked with high power stuff and
to-3 cans.

The fist sized plastic shrouded mosfets or IGBTs they use in large online
UPS explode though, and splash what seems to be silicone gel all over the
place. That's not counting the sooty fire that usually happens at the same
time.
From: krw on 22 Jun 2010 20:22
On Tue, 22 Jun 2010 05:56:43 -0400, JW <none(a)dev.null> wrote:

>On Mon, 21 Jun 2010 17:42:21 -0500 "krw(a)att.bizzzzzzzzzzzz"
><krw(a)att.bizzzzzzzzzzzz> wrote in Message id:
><iiqv1650144gv9gu9kju00tl8ec8abqlau(a)4ax.com>:
>
>>On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
>><presence(a)MUNGEpanix.com> wrote:
>>
>>>Phil Allison <phil_a(a)tpg.com.au> wrote:
>>>>
>>>> "Cydrome Leader"
>>>>> Phil Allison
>>>>>> "Cydrome Leader"
>>>>>
>>>>>>> I had a hard time recently locating a specific power transistor in a
>>>>>>> TO-218 case, with the metal tab and not the lump of plastic with a metal
>>>>>>> back like everything seems to be now.
>>>>>>
>>>>>>
>>>>>> ** Why bother ??
>>>>>>
>>>>>> TO-218 is virtually the same pak and construction as TO-3P except you no
>>>>>> longer need to use an insulating bush with the latter.
>>>>>
>>>>> to not have to modify existing heatsink clamps. The setup in the product
>>>>> was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
>>>>> not sure why the transistor wasn't just screwed down. There was a screw
>>>>> and nut for the clamp anyways. JW: Cue AlwaysWrong!
>>>>
>>>> ** A well designed clamp does a far better job with TO-3P and similar single
>>>> hole packs than using a bolt does. Normally the clamp supplies high pressure
>>>> along the CENTRE line of the plastic body of the device. The body spreads
>>>> the pressure evenly over the tab and there is then no tendency for it to
>>>> lift up at the lead end as there is with a bolt.
>>>>
>>>>
>>>>>> TO-3 is a whole nuther animal with many advantages over plastic paks.
>>>>>
>>>>> the TO-218 is actually somewhat compatible with the TO-3.
>>>>
>>>> ** The main advantage of the TO3 pak is that there is no plastic in contact
>>>> with the chip which sits in a hermetically sealed environment - means
>>>> chips have a much longer service life even when running near max temps.
>>>
>>>I'm not arguing that a TO-3 is better all around- it's just that fewer and
>>>fewer semiconductors are packaged as nicely these days so that's what you
>>>have to work with most of the time. The hermetically sealed and welded
>>>metal can obviously costs more than some plastic resin molded around a
>>>sliver of metal.
>>>
>>>Sanken uses to have the most exciting TO-3 cases. The base was
>>>surprisingly thick and they felt like they were made of gold.
>>>
>>>> Internal feed wires can be sized to fuse immediately if a device fails - a
>>>> valuable feature not seen in plastic paks.
>>>
>>>But the plastic ones explode and burn.
>>
>>Metal ones can explode and throw shrapnel around the room.
>
>A TO-3 explode? I've *never* seen that happen, and hope I never do!

Yep. One failure mode the base lead came *though* the case like a bullet. In
another the whole top of the case came off and ricocheted around the room.
They ended up putting the power supplies in a bullet-proof test chamber for
their christening. Secondary breakdown can be an impressive event.
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