[SI-LIST] Re: Thermal resistance values
- From: Pat Diao <Pat_Diao@xxxxxxxx>
- To: "'SRogers@xxxxxxxxxxxxx'" <SRogers@xxxxxxxxxxxxx>,nico.fleurinck@xxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Tue, 16 Sep 2003 10:02:26 -0700
Junction-to-Board thermal resistance is a clearly defined parameter by Jedec
(Theta-JB). The suggested measurement below doesn't tell you anything about
theta-JB.
Theta-JB is the thermal resistance from die-surface to a location on PCB
adjacent to the package (<1 mm from package edge). It includes two part of
resistance: die to package bottom and the section of PCB under the package.
Theta-JB can be obtained by either thermal modeling or measurement. In
either case, one needs to: 1. maintain heat dissipation only thru PCB; 2.
determine die temperature (usually using a diode on chip); 3. determine PCB
temperature at <1 mm from package; 4. determine power dissipation.
Theta-JB standard is available at at www.jedec.org (No.JESD51-8).
Pat Diao
ASAT Inc.
Fremont, CA
-----Original Message-----
From: Steve Rogers [mailto:SRogers@xxxxxxxxxxxxx]
Sent: Tuesday, September 16, 2003 8:34 AM
To: nico.fleurinck@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Thermal resistance values
Why not try a measurement! Do people still do this
What about you run one of your semiconductors on your board and measure =
how hot it gets. Now run one in free space and measure how hot it gets. =
I would think the difference between the temperatures would be a =
reasonable guide. Clearly you need some electrical connections to make =
the thing work but if you keep these to very thin wires that can take =
the current this approach may work. The alternative is to buy the book =
suggested and do some reading!
Good luck
Steve Rogers B.Eng (Hons) C.Eng IEE
RF Design Engineer
Micromill Electronics Limited
Leydene House
Waterberry Drive=20
Waterlooville Hampshire
PO7 7XX
Tel: +44 (0) 23 9236 6600
Fax: +44 (0) 23 9236 6673
Registered No. 1456922 (England). =20
Registered Office Brook Road
Wimborne, Dorset BH21 2BJ
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-----Original Message-----
From: Nico Fleurinck [mailto:nico.fleurinck@xxxxxxxxxxxx]
Sent: Tuesday, September 16, 2003 2:42 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Thermal resistance values
Dear expert,
I need to determine the "Junction to Board" thermal resistance of my
semiconductors that I use on my board.
I know the "Junction to case" values but I don't know how I can =
determine
the Junction to board values.
Can you help me with this?
Many thanks already,
best regards,
Nico
*******************************************
* Nico Fleurinck *
* Junior Design Engineer *
* VERHAERT Satellites & Platforms *
* Hogenakkerhoekstraat 21 *
* B-9150 Kruibeke *
* *
* Tel : +32 3 250.1984 *
* Fax : +32 3 254.1008 *
* e-mail : nico.fleurinck@xxxxxxxxxxxx *
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