copper area size

metebalci · 28th July 2004, 08:51 AM

Hi,

How do you calculate the required copper area to be used as a heatsink for components e.g. rectifier diodes ? (I think this area is called Thermal Territory)

Regards,

MB

Sch3mat1c · 28th July 2004, 09:14 AM

3 things. Tube diodes (except possible high power specialty types) do not use, nor need heatsinks; SS diodes (except zeners) do not dissipate enough power to bother; and heatsinks are rarely copper.

Tim

metebalci · 28th July 2004, 11:17 AM

OK. First of all, I am talking about SS diodes. For example, SB560 (package: DO-201AD) has theta-ja 25C/W. Assuming 3W dissipation (it is rated at 5W), its temperature rises to ambient + 75C. That seems too much and must be taken into consideration. Only thing can be done is to mount diode in vertical direction and leave a copper area. This is mentioned in ON Semiconductors - Rectifier Applications Handbook - Chapter 2.

SY · 28th July 2004, 12:31 PM

metebalci, to eliminate confusion (and maybe help you get an answer more quickly), I've moved this over to Solid State.

tubetvr · 28th July 2004, 12:37 PM

The SB560 has a voltage drop of 0.67V so if you have 3W dissipation you have a current of ~4.5A which is very close to max rating.

I would never use a diode in this package for 3W dissipation, If I needed 4.5A I would select a TO 220 package and screw it to the chassis, it is very bad engineering practice to be so close to device limit as you indicate in this case. I would never exceed more than half the max rating for a rectifier diode, it is easy to find diodes for higher ratings so there is no need to be so close.

Regards Hans

metebalci · 28th July 2004, 05:18 PM

SY, Thanks...

tubetvr, OK. I got it...

cpemma · 28th July 2004, 07:26 PM

Quote:

Originally posted by metebalci
...Only thing can be done is to mount diode in vertical direction and leave a copper area. This is mentioned in ON Semiconductors - Rectifier Applications Handbook - Chapter 2.

A few specs will quote thermal resistance mounted on a pcb, example is Zowie spec for DB102 1A bridge. Junction-to-ambient 40C/W, falls to 15C/W mounted on 0.5" square copper pads, quite significant.

ON's AN1040/D (Mounting Considerations For Power Semiconductors) pdf has a graph showing heat-sink rating against pad area for one pcb example.

More useful files at http://www.onsemi.com/site/support/l...otes_0,00.html

cunningham · 28th July 2004, 10:10 PM

True that copper is more dense and a better conductor than aluminum, electricity and heat. But copper has one major drawback, it corrodes. Unless you plate the copper with something to stop this.

28th July 2004, 08:51 AM	#1
metebalci diyAudio Member Join Date: Feb 2004 Location: Istanbul/TURKEY	copper area size Hi, How do you calculate the required copper area to be used as a heatsink for components e.g. rectifier diodes ? (I think this area is called Thermal Territory) Regards, MB

28th July 2004, 09:14 AM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	3 things. Tube diodes (except possible high power specialty types) do not use, nor need heatsinks; SS diodes (except zeners) do not dissipate enough power to bother; and heatsinks are rarely copper. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

28th July 2004, 12:31 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	metebalci, to eliminate confusion (and maybe help you get an answer more quickly), I've moved this over to Solid State. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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28th July 2004, 11:17 AM	#3
metebalci diyAudio Member Join Date: Feb 2004 Location: Istanbul/TURKEY	OK. First of all, I am talking about SS diodes. For example, SB560 (package: DO-201AD) has theta-ja 25C/W. Assuming 3W dissipation (it is rated at 5W), its temperature rises to ambient + 75C. That seems too much and must be taken into consideration. Only thing can be done is to mount diode in vertical direction and leave a copper area. This is mentioned in ON Semiconductors - Rectifier Applications Handbook - Chapter 2.

28th July 2004, 12:37 PM	#5
tubetvr diyAudio Member Join Date: Jan 2003 Location: Now back in Sweden	The SB560 has a voltage drop of 0.67V so if you have 3W dissipation you have a current of ~4.5A which is very close to max rating. I would never use a diode in this package for 3W dissipation, If I needed 4.5A I would select a TO 220 package and screw it to the chassis, it is very bad engineering practice to be so close to device limit as you indicate in this case. I would never exceed more than half the max rating for a rectifier diode, it is easy to find diodes for higher ratings so there is no need to be so close. Regards Hans

28th July 2004, 05:18 PM	#6
metebalci diyAudio Member Join Date: Feb 2004 Location: Istanbul/TURKEY	SY, Thanks... tubetvr, OK. I got it...

28th July 2004, 10:10 PM	#8
cunningham diyAudio Member Join Date: Jun 2004 Location: Knoxville	True that copper is more dense and a better conductor than aluminum, electricity and heat. But copper has one major drawback, it corrodes. Unless you plate the copper with something to stop this.

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