Sherman Banks wrote:

> Hi Folks,
>
> We've got an engineer who wants to stack 1206 resistors 3 high in order to
> achieve a larger power rating. While it is intuitively obvious to us that
> this is NOT the way to go, we are at a loss to find any published documents
> that caution or forbid the practice.
>
> Can anyone cite a published source that can give more specific "rules or
> guidelines" on this subject.
>
> We've searched, J-STD-001, SM-780, SM-782, A-610, and R-700
>
> Help!!!!!
>
> REGARDS
> Sherman Banks
> [log in to unmask]
> 408/481-6047

I would look into wether or not stacking the components actually
increases the power ratings as much as the engineer thinks it does.

The surface area of a 1206 resistor stacked 3 high is only 70%
more than that of a single 1206. The other part of the power rating
of a component is conduction and I doubt that stacking the parts
would change this number much. Depending on the board layout
you might see an increase of less than 50%.

All told, using a 1210 would seem to be a much better idea.

---------------------------------------------------------------------
| Dr. Kevin Dale Kirmse
| PhD Electrical Engineer
|
| King of Prussia, PA 19406
| [log in to unmask]
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