×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

resistor power dissipation

resistor power dissipation

resistor power dissipation

(OP)
I have datasheets from two different manufacturers (Dale/Vishay and Panasonic) that claim their resistors in the 2512 package have a thermal resistance of 65-66 C/W.  A colleague said 200C/W is more like it and just proved it by putting 1W through a 2512 resistor and watching the solder melt off the leads after about 30 seconds.  

How do they spec this?  The Dale data sheet says they use EN140401-802 for packages under 1206 but leaves the larger packages undetermined.  This shows 220C/W for the 1206.  

I can ask the manufacturers, but the tech support for passives isn't very strong these days so I thought I'd post it here first.  

Z
 

RE: resistor power dissipation

It depends upon what the 2512 is soldered to.

I recently used 2512 on a circuit board, and verified the heating by using a DC supply and thermocouple on one of my PCBs and found around 70 to 80 C/W rise.

BUT - my PCB uses 4 oz copper with 100 mil traces to the resistor! In the actual design I'm only using them for 1/2W.

RE: resistor power dissipation

It does indeed depend on what they're soldered to.

One time we had a high value resistor in series with a fairly high voltage supply (and its load), and it was melting the solder in its PCB.

The fix was heat sinks on the resistor leads; ~1/2" square x .02" thick fins, pierced in the center and soldered on the leads adjacent the resistor body.  Brass would have been fine, but we made them out of copper because the dominant alleged EE couldn't/ wouldn't understand the basics of convective heat transfer.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: resistor power dissipation

(OP)
IR - That's a great link!  I see that they take a lot of the PCB effects into account to get their low numbers.  

Thanks for the replies, all!  

John D
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources