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Q: Destructive experiment on a dead BS170

 

Hi all

One of the limiting factors in heat dissipation on the BS170 is the plastic package.? The plastic case in its?existing geometry is to provide for easy handling with existing tools.? Since we're not robots, that physical parameter is no longer an issue.

Does anybody have a vertical mill and a few dead BS170s and is willing to mill off some of the plastic case?

This is to see how thick the plastic is before the die and/or leadframe is exposed.? The next step is to take a few good BS170s and mill off part of this thickness to see whether heatsinking becomes more effective.

Experimenters?

73
Jim N6OTQ
 

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Jim (N6OTQ),

I just checked Amazon and there are several vendors for the BS170. Most offer 10 for less than a dollar. I am willing to spend that kind of money for a joint experiment. What say?
73, Billy (N5SE)

From: [email protected] <[email protected]> on behalf of Jim Strohm via groups.io <jim.strohm@...>
Sent: Wednesday, September 13, 2023 11:36
To: [email protected] <[email protected]>
Subject: [QRPLabs] Q: Destructive experiment on a dead BS170
?
Hi all

One of the limiting factors in heat dissipation on the BS170 is the plastic package.? The plastic case in its?existing geometry is to provide for easy handling with existing tools.? Since we're not robots, that physical parameter is no longer an issue.

Does anybody have a vertical mill and a few dead BS170s and is willing to mill off some of the plastic case?

This is to see how thick the plastic is before the die and/or leadframe is exposed.? The next step is to take a few good BS170s and mill off part of this thickness to see whether heatsinking becomes more effective.

Experimenters?

73
Jim N6OTQ


--
N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???

 

Hello Jim
Use to work in a shop about 30 years ago where we crammed 10 pounds of stuff into a 1 ounce bag.
This was before surface mount transistors became readily available. Without knowing it we kind of
made the precursor. We would fixture a TO-92 on the Bridgeport and start removing layers of the
epoxy with an end mill. The amount that could be removed was significant and when done with a?
production device the accepted thickness we used was nominally about 35% of the original
thickness. If memory serves me correct it worked out to 1.1 mm on each side. We then folded
the leads at 90 degrees from the stock plane by using the dull edge of an Xacto # 11? blade, then
bent the leads back 90 degrees to they could be attached to the pc board. We clipped the leads
off to leave about 0.75 - 1.0 mm of the lead that would lay flat on the board, allowing easy
attachment.

We did similar non-standard applications with glass diode packaged devices, cutting the leads as short as possible and milling a slot in the PC board for the diode to lay in.


On Sep 13, 2023, at 1:58 PM, N5SE <bwmoore@...> wrote:


Jim (N6OTQ),

I just checked Amazon and there are several vendors for the BS170. Most offer 10 for less than a dollar. I am willing to spend that kind of money for a joint experiment. What say?
73, Billy (N5SE)



From: [email protected] <[email protected]> on behalf of Jim Strohm via groups.io <jim.strohm@...>
Sent: Wednesday, September 13, 2023 11:36
To: [email protected] <[email protected]>
Subject: [QRPLabs] Q: Destructive experiment on a dead BS170
?
Hi all

One of the limiting factors in heat dissipation on the BS170 is the plastic package.? The plastic case in its?existing geometry is to provide for easy handling with existing tools.? Since we're not robots, that physical parameter is no longer an issue.

Does anybody have a vertical mill and a few dead BS170s and is willing to mill off some of the plastic case?

This is to see how thick the plastic is before the die and/or leadframe is exposed.? The next step is to take a few good BS170s and mill off part of this thickness to see whether heatsinking becomes more effective.

Experimenters?

73
Jim N6OTQ


--
N5SE
Billy Wayne Moore
7066 Shady Knoll Ln
Willis, TX 77318-6324
Phone: 936-537-2975???


 

In lieu of a vertical mill you could use a file, though controlling the depth would be difficult.

Or a drill press with an end mill chucked into it.

Unfortunately I have neither.
Ted
 

If you really need research on this, I have access to a vertical mill and a serviceable micrometer...
 

Ted,

You might get pressed into service.? Do you also have a scale that measures in milligrams?? I don't know whether it's a true need, but it might be interesting to know how much material was removed by weight.

73
Jim N6OTQ



On Thu, Sep 14, 2023 at 5:21?AM Ted via <k3rta=[email protected]> wrote:
If you really need research on this, I have access to a vertical mill and a serviceable micrometer...
Ted
 

Do you also have a scale that measures in milligrams?? I don't know whether it's a true need, but it might be interesting to know how much material was removed by weight.
Funny you should ask.? My lab used to weight filters after sampling for total suspended particulates in the air, years ago before contracting that stuff out.

That's a U.S. penny and the Mint says that should be 2.50 grams....? The scale hasn't been calibrated in years though we still have a weight set around here someplace. It'd do OK for before & after.


 

That'll work.

Jim

On Thu, Sep 14, 2023 at 6:24?AM Ted via <k3rta=[email protected]> wrote:
Do you also have a scale that measures in milligrams?? I don't know whether it's a true need, but it might be interesting to know how much material was removed by weight.
Funny you should ask.? My lab used to weight filters after sampling for total suspended particulates in the air, years ago before contracting that stuff out.

That's a U.S. penny and the Mint says that should be 2.50 grams....? The scale hasn't been calibrated in years though we still have a weight set around here someplace. It'd do OK for before & after.


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