[TechAssist] Re: Heat sink compound
- From: "J Silverman" <greentron@xxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 9 Oct 2004 15:55:17 -0400
The plastic is very thin on the back, only a few thousandths of an inch, but
even this makes the wattage rating of the device several times less than if
it had a metal tab with the die soldered to it. The plastic on the front
might be just as hot as on the back but because it is a poor thermal
conductor, just touching it drops the temperature way down. You would have
to use a none contact method, such as a optical pyrometer to tell what the
front temperature was.
With a plastic device, the heat sink compound is much less critical than
with a metal tab.
Jerry Silverman
Greentron Inc
4 Newland Ave
Greenville SC 29609
Fax/Phone 864 232 3889
mail to: greentron@xxxxxxx
----- Original Message -----
From: "Kevin" <kevintv@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Saturday, October 09, 2004 4:16 AM
Subject: [TechAssist] Re: Heat sink compound
> I believe that both camps are correct. The fact that the heat sink is
> hotter than the front of the semi tells me that the back of the semi
> must be much hotter than the front, but not as hot as the heat sink
> itself--according to Ed's Thermal Energy law. The heat-producing
> junction therefore must be closer to the back of the semi than the front
> to allow maximum heat dissipation to the heat sink. That would make the
> front of the semi cooler than the back.
>
> This theory agrees with Bil's and my observations that the front of a
> semi can be cooler than the heat sink itself. It also allows for the
> back of the semi to be hotter than the heat sink. I hope this makes
> sense.
>
> Kevin Wilks
> Kevin's TV & Video Repair
> Penticton BC Canada
> kevintv@xxxxxxx
>
>
> -----Original Message-----
> From: techassist-bounce@xxxxxxxxxxxxx
> [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Bil Green
> Sent: Friday, October 08, 2004 9:03 PM
> To: gulftech@xxxxxxxx
> Subject: [TechAssist] Re: Heat sink compound
>
> I am simply reporting what I have noticed when touching the plastic
> body of the transistor or chip. And another tech mentioned the same
> thing in his post.
>
> When you try to remove a plastic container from a 350 degree oven
> it doesn't feel anywhere near as hot as a glass container. So maybe
> the plastic portion of the transistor isn't as hot.
>
> I can hold my finger on a hot HOT for a few seconds, but often the
> heat sink is too hot to even touch. Do you guys think this is just
> my imagination?
>
>
>
> Bil Green
> PC 1000
> Mammoth Lakes, CA 93546
> 760-924-1000
>
> Friday, October 8, 2004, 7:39:43 PM, you wrote:
>
> gjc> Come on Bill,
>
> gjc> I respect you and very much enjoy your posts. But, it is
> impossible for
> gjc> a heat sink to be hotter than the transistor attached to it. I
> have a
> gjc> laser thermometer that I use. NEVER have I seen the heat sink to
> be
> gjc> hotter than the transistor. After all, where does the heat come
> from?
>
> gjc> Plastic transistors are hardest to test, but the highest
> temperature
> gjc> measured would be equal to or lower than the actual temp. of the
> gjc> semiconductor.
>
>
> gjc> Ken Smith
> gjc> Gulf Technical Services
> gjc> 3034 Gulf Breeze Parkway
> gjc> Gulf Breeze, FL 32563
> gjc> 850-934-8324 (Voice), 850-932-0819 (fax)
>
> gjc> On Fri, 8 Oct 2004 14:00:41 -0700 Bil Green
> <tv.vcrrepair@xxxxxxxxxxx>
> gjc> writes:
> >> Actually I'm right. When you place your finger against the plastic
> >> section of a transistor or IC which is on a heat sink the
> >> temperature usually feels cooler the heat sink.
> >>
> >> You can't place your finger on the rear (often metal) side which is
> >> against the heat sink (and may be much hotter).
> >>
> >> But the heat sink is often hot enough to burn your finger (and
> >> often the device is definitely NOT). Now maybe the plastic just
> >> doesn't transfer the heat to your finger very well. I'm don't care
> >> about science at this point, only what I see or feel.
> >>
> >>
> >> Bil Green
> >> PC 1000
> >> Mammoth Lakes, CA 93546
> >> 760-924-1000
> >>
> >> Friday, October 8, 2004, 1:22:50 PM, you wrote:
> >>
> >> TTE> Bil...
> >> TTE> Now you know better then that.
> >> TTE> Basic Science.;-)
> >> TTE> That would be Thermal Energy in reverse. The source has to be
> >> more then
> >> TTE> the dissipation.
> >>
> >> TTE> Ask Wayne.;-)
> >>
> >> TTE> -Ed-
> >>
> >> TTE> Tel-Tek Electronics
> >> TTE> Ontario-Canada
> >>
> >> TTE> teltek3@xxxxxxxxxxxx
> >> TTE> teltek@xxxxxxxxx
> >>
> >>
> >> TTE> -----Original Message-----
> >> TTE> From: techassist-bounce@xxxxxxxxxxxxx
> >> TTE> [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Bil Green
> >> TTE> Sent: Friday, October 08, 2004 3:57 PM
> >> TTE> To: J Silverman
> >> TTE> Subject: [TechAssist] Re: Heat sink compound
> >>
> >> TTE> Isn't the heat sink always hotter than the device? Heat rises
> >> and is
> >> TTE> stored by the heat sink.
> >>
> >>
> >> TTE> Bil Green
> >> TTE> PC 1000
> >> TTE> Mammoth Lakes, CA 93546
> >> TTE> 760-924-1000
> >>
> >> TTE> Friday, October 8, 2004, 9:50:46 AM, you wrote:
> >>
> >> JS>> So it sucks so much heat out that the heat sink is hotter than
> >> the
> >> TTE> devices
> >> JS>> doing the heating? Patent it quick!
> >> JS>> Jerry Silverman
> >> JS>> Greentron Inc
> >> JS>> 4 Newland Ave
> >> JS>> Greenville SC 29609
> >> JS>> Fax/Phone 864 232 3889
> >> JS>> mail to: greentron@xxxxxxx
> >> JS>> ----- Original Message -----
> >> JS>> From: "Bil Green" <tv.vcrrepair@xxxxxxxxxxx>
> >> JS>> To: "Paul" <techassist@xxxxxxxxxxxxx>
> >> JS>> Sent: Thursday, October 07, 2004 4:46 PM
> >> JS>> Subject: [TechAssist] Re: Heat sink compound
> >>
> >>
> >> >>> I have been using silicone grease. It's available in a tube,
> >> used for
> >> >>> servicing pools and hot tubs, also boats. Designed for high heat
> >> >>> applications. Has worked well for many years (and it's clear).
> >> >>>
> >> >>> The heat sinks get much hotter than the transistors and chips so
> >> I
> >> >>> know for sure that it's working.
> >> >>>
> >> >>>
> >> >>> Bil Green
> >> >>> PC 1000
> >> >>> Mammoth Lakes, CA 93546
> >> >>> 760-924-1000
> >> >>>
> >> >>> Thursday, October 7, 2004, 10:10:38 AM, you wrote:
> >> >>>
> >> >>> P> Hi Al, been using GC silicone 10-8101 for about 20 years.
> >> Never
> >> TTE> had a
> >> JS>> repeat failure due to its use. I like it because it is less
> >> messy
> >> TTE> than the
> >> JS>> white or pink stuff the mfgs use.
> >> >>> P>
> >> JS>> Paul
> >> >>> P> al m <ampm@xxxxxxx> wrote:
> >> >>> P> I know it's off topic but I haven't thought of what I was
> >> buying
> >> JS>> before.
> >> >>> P> Which is better the non silicone or the silicone compound?
> >> >>> P> Al Marquardt
> >> >>> P> ampm@xxxxxxx
> >> >>> P> Al Marquardt Electronic Repair
> >> >>> P> 206 W Main
> >> >>> P> Girardville Pa. 17935
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> P>>>
> >> TTE>
> >>
> gjc>
> ------------------------------------------------------------------------
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> >> >>> P> Central TV&Video
> >> >>> P> 911W Grand Ave
> >> >>> P> Grover Beach Ca.
> >> >>> P> (805)481-8084
> >> >>>
> >> >>>
> >> >>>
> >> P>>>
> >> TTE>
> >>
> gjc>
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