TO-220 'lock' washer

G

George Herold

Guest
So we had a few transistors in to-220 pacs de-laminate at the metal tab/
plastic interface. (lost electrical connection to the collector.)
https://www.dropbox.com/s/keg8fwdipubev2z/TO-220.JPG?dl=0
I bent it up...it was just cracked along the edge. The circular mark
around the mounting hole was made by the belleville washer. Which I think
might be the problem. Washer is from Seastrom mfgr. 5809-13-16-P,
https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5809-13-16-P

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.

I'm wondering if there are any spec's for lock washers on TO-220 pacs?
These are being used as temperature sensors over a large range, so I
do want a lot of compliance (or deflection.)

Thanks
George H.
 
On Monday, July 15, 2019 at 4:05:53 PM UTC-4, John Larkin wrote:
On Mon, 15 Jul 2019 12:44:54 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

So we had a few transistors in to-220 pacs de-laminate at the metal tab/
plastic interface. (lost electrical connection to the collector.)
https://www.dropbox.com/s/keg8fwdipubev2z/TO-220.JPG?dl=0
I bent it up...it was just cracked along the edge. The circular mark
around the mounting hole was made by the belleville washer. Which I think
might be the problem. Washer is from Seastrom mfgr. 5809-13-16-P,
https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5809-13-16-P

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.

I'm wondering if there are any spec's for lock washers on TO-220 pacs?
These are being used as temperature sensors over a large range, so I
do want a lot of compliance (or deflection.)

Thanks
George H.

Wavy washers are nice.
Click to expand...
I found a lot of stuff on the web, but mostly about getting heat out.
(which I don't care about.)
I think maybe stack a few bellevilles in opposition to get more defection
and less force.

Do they make wavy washers small enough for to-220? (#4 or #6 screw)

GH
--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Click to expand...
 
On Mon, 15 Jul 2019 12:44:54 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

So we had a few transistors in to-220 pacs de-laminate at the metal tab/
plastic interface. (lost electrical connection to the collector.)
https://www.dropbox.com/s/keg8fwdipubev2z/TO-220.JPG?dl=0
I bent it up...it was just cracked along the edge. The circular mark
around the mounting hole was made by the belleville washer. Which I think
might be the problem. Washer is from Seastrom mfgr. 5809-13-16-P,
https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5809-13-16-P

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.

I'm wondering if there are any spec's for lock washers on TO-220 pacs?
These are being used as temperature sensors over a large range, so I
do want a lot of compliance (or deflection.)

Thanks
George H.
Click to expand...

Wavy washers are nice.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Monday, July 15, 2019 at 3:44:59 PM UTC-4, George Herold wrote:
So we had a few transistors in to-220 pacs de-laminate at the metal tab/
plastic interface. (lost electrical connection to the collector.)
https://www.dropbox.com/s/keg8fwdipubev2z/TO-220.JPG?dl=0
I bent it up...it was just cracked along the edge. The circular mark
around the mounting hole was made by the belleville washer. Which I think
might be the problem. Washer is from Seastrom mfgr. 5809-13-16-P,
https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5809-13-16-P

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.

I'm wondering if there are any spec's for lock washers on TO-220 pacs?
These are being used as temperature sensors over a large range, so I
do want a lot of compliance (or deflection.)

Thanks
George H.
Click to expand...

I found this, but not much info on the washer.
https://www.nxp.com/files-static/rf_if/doc/app_note/AN1040.pdf

GH
 
On 15/07/2019 8:44 pm, George Herold wrote:
So we had a few transistors in to-220 pacs de-laminate at the metal tab/
plastic interface. (lost electrical connection to the collector.)
https://www.dropbox.com/s/keg8fwdipubev2z/TO-220.JPG?dl=0
I bent it up...it was just cracked along the edge. The circular mark
around the mounting hole was made by the belleville washer. Which I think
might be the problem. Washer is from Seastrom mfgr. 5809-13-16-P,
https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5809-13-16-P

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.

I'm wondering if there are any spec's for lock washers on TO-220 pacs?
These are being used as temperature sensors over a large range, so I
do want a lot of compliance (or deflection.)

Thanks
George H.
Click to expand...

I follow the advice in a Motorola/ON Semi SCR/Triac manual which is to
place a flat washer between the TO-220 tab and the belleville. Also be
sure to use a torque driver set to the recommended torque (I forget
right now which figure). Belleville is nice because it is kind of
constant force.

piglet
 
On 15/07/2019 9:16 pm, George Herold wrote:
Do they make wavy washers small enough for to-220? (#4 or #6 screw)

GH
Click to expand...

I have seen metric stainless wavy in all sizes from M2 (2mm dia) upwards.

piglet
 
"George Herold" wrote in message
news:b2f23785-0a1f-4cdb-92ee-3e73cf30e7a3@googlegroups.com...

> Do they make wavy washers small enough for to-220? (#4 or #6 screw)

The first place to look for any kind of hardware what-if question is
www.mcmaster.com, just put wave washer in the search box, they have #0 to
#10 in 18-8 stainless steel. They also have steel and three point wave
washers and belleville washers (and yes, they buy from Seastrom, I've gotten
bags from mcmaster that said Seastrom on the label :)).

--
Regards,
Carl Ijames
 
On 15/07/2019 8:44 pm, George Herold wrote:
I bent it up...it was just cracked along the edge. The circular mark
around the mounting hole was made by the belleville washer. Which I think
might be the problem. Washer is from Seastrom mfgr. 5809-13-16-P,
Click to expand...

The circular mark has cut right thru the plating into the tab base metal
- I think that shows the system was way over-torqued.

piglet
 
On 2019/07/15 2:31 p.m., piglet wrote:
On 15/07/2019 8:44 pm, George Herold wrote:
I bent it up...it was just cracked along the edge.  The circular mark
around the mounting hole was made by the belleville washer.  Which I
think
might be the problem.  Washer is from Seastrom mfgr. 5809-13-16-P,

The circular mark has cut right thru the plating into the tab base metal
- I think that shows the system was way over-torqued.

piglet
Click to expand...

And said torque would twist the tab leading to the case being under
stress, if the leads were soldering in previously to the torquing down,
and eventually separating as it did.

A tiny dab of Green Locktight would probably be enough for the 4-40 nut
and washer if you are mostly looking for securing with a minimum of
torque...

http://henkeladhesivesna.com/blog/the-difference-between-red-blue-green-and-purple-threadlockers/

John
 
On 7/15/19 4:51 PM, piglet wrote:
On 15/07/2019 8:44 pm, George Herold wrote:
So we had a few transistors in to-220 pacs de-laminate at the metal tab/
plastic interface.  (lost electrical connection to the collector.)
https://www.dropbox.com/s/keg8fwdipubev2z/TO-220.JPG?dl=0
I bent it up...it was just cracked along the edge.  The circular mark
around the mounting hole was made by the belleville washer.  Which I
think
might be the problem.  Washer is from Seastrom mfgr. 5809-13-16-P,
https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5809-13-16-P


These take a lot of force and have less defection than other
belleville's.
I also think they were put in with too much force.

I'm wondering if there are any spec's for lock washers on TO-220 pacs?
These are being used as temperature sensors over a large range, so I
do want a lot of compliance (or deflection.)

Thanks
George H.


I follow the advice in a Motorola/ON Semi SCR/Triac manual which is to
place a flat washer between the TO-220 tab and the belleville. Also be
sure to use a torque driver set to the recommended torque (I forget
right now which figure). Belleville is nice because it is kind of
constant force.

piglet
Click to expand...

Which is why you have to tighten a Belleville to the specified
_deflection_ rather than the specified _torque_. Otherwise you're
liable to bottom it out and make this sort of problem.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On Monday, July 15, 2019 at 12:44:59 PM UTC-7, George Herold wrote:
> So we had a few transistors in to-220 pacs de-laminate at the metal tab/

[using Belleville washers]

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.
Click to expand...

The scraping of tin plate indicates they were installed bell-down,
but not necessarily that force was excessive. More important,
would be a torque scewdriver setting so as not to 'max out' the
spring and keep going to higher force (hard edges made a scrape, cannot
tell force from that).

Usually, one puts a spacer over the hole, and attaches through the spacer, so that
the diameter of the washer doesn't impinge on the epoxy. Mechanical lateral
force on a Belleville washer is HUGE, can easily crack things. The spacer, on the
other hand (like a washer) spreads the steel screw pressure over the softer copper of the
TO-220 tab. Loctite makes something that will retain the screw (but nickel plate
screw into galvanized or aluminum doesn't play nice with the iron-catalyzed variants).
 
On Monday, July 15, 2019 at 8:21:30 PM UTC-4, whit3rd wrote:
On Monday, July 15, 2019 at 12:44:59 PM UTC-7, George Herold wrote:
So we had a few transistors in to-220 pacs de-laminate at the metal tab/

[using Belleville washers]

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.

The scraping of tin plate indicates they were installed bell-down,
but not necessarily that force was excessive. More important,
would be a torque scewdriver setting so as not to 'max out' the
spring and keep going to higher force (hard edges made a scrape, cannot
tell force from that).

Usually, one puts a spacer over the hole, and attaches through the spacer, so that
the diameter of the washer doesn't impinge on the epoxy. Mechanical lateral
force on a Belleville washer is HUGE, can easily crack things. The spacer, on the
other hand (like a washer) spreads the steel screw pressure over the softer copper of the
TO-220 tab. Loctite makes something that will retain the screw (but nickel plate
screw into galvanized or aluminum doesn't play nice with the iron-catalyzed variants).
Click to expand...

Yup, thanks everyone for the advice.

George H.
 
On Monday, July 15, 2019 at 5:06:17 PM UTC-4, Carl wrote:
"George Herold" wrote in message
news:b2f23785-0a1f-4cdb-92ee-3e73cf30e7a3@googlegroups.com...

Do they make wavy washers small enough for to-220? (#4 or #6 screw)

The first place to look for any kind of hardware what-if question is
www.mcmaster.com, just put wave washer in the search box, they have #0 to
#10 in 18-8 stainless steel. They also have steel and three point wave
washers and belleville washers (and yes, they buy from Seastrom, I've gotten
bags from mcmaster that said Seastrom on the label :)).
Click to expand...

Right, I think that's how I found Seastrom. (McMaster-Carr has a nice
search engine... their index is a thing of beauty too!)

George H.
--
Regards,
Carl Ijames
Click to expand...
 
On Monday, July 15, 2019 at 4:51:36 PM UTC-4, piglet wrote:
On 15/07/2019 8:44 pm, George Herold wrote:
So we had a few transistors in to-220 pacs de-laminate at the metal tab/
plastic interface. (lost electrical connection to the collector.)
https://www.dropbox.com/s/keg8fwdipubev2z/TO-220.JPG?dl=0
I bent it up...it was just cracked along the edge. The circular mark
around the mounting hole was made by the belleville washer. Which I think
might be the problem. Washer is from Seastrom mfgr. 5809-13-16-P,
https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5809-13-16-P

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.

I'm wondering if there are any spec's for lock washers on TO-220 pacs?
These are being used as temperature sensors over a large range, so I
do want a lot of compliance (or deflection.)

Thanks
George H.


I follow the advice in a Motorola/ON Semi SCR/Triac manual which is to
place a flat washer between the TO-220 tab and the belleville. Also be
sure to use a torque driver set to the recommended torque (I forget
right now which figure). Belleville is nice because it is kind of
constant force.

piglet
Click to expand...

Thanks piglet, I've always used a flat washer on the 'bottom'. We'll
probably add one.

George H.
 
On Mon, 15 Jul 2019 12:44:54 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

So we had a few transistors in to-220 pacs de-laminate at the metal tab/
plastic interface. (lost electrical connection to the collector.)
https://www.dropbox.com/s/keg8fwdipubev2z/TO-220.JPG?dl=0
I bent it up...it was just cracked along the edge. The circular mark
around the mounting hole was made by the belleville washer. Which I think
might be the problem. Washer is from Seastrom mfgr. 5809-13-16-P,
https://www.seastrom-mfg.com/washerdetails.aspx?productNumber=5809-13-16-P

These take a lot of force and have less defection than other belleville's.
I also think they were put in with too much force.

I'm wondering if there are any spec's for lock washers on TO-220 pacs?
These are being used as temperature sensors over a large range, so I
do want a lot of compliance (or deflection.)

Thanks
George H.
Click to expand...

As a temperature sensor only, the issues with mounting of
power-dissipating TO220's go away. Any lockwasher should work, if
applied as designed.

Sensors may not employ the same solid-filled epoxy package structure
as power semiconductors - issues with mechanical damage are different,
and the requirements for environmental protection come from a
completely different book.

RL
 
On Mon, 15 Jul 2019 12:44:54 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>So we had a few transistors in to-220 pacs de-laminate at the metal tab/
....
Lock washers are useless. How many are in your car?
https://www.youtube.com/watch?v=IKwWu2w1gGk


Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place
 
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