From: bill.sloman@ieee.org
On 18/01/2026 10:22 am, John R Walliker wrote:
> On 17/01/2026 04:58, Bill Sloman wrote:
>> On 17/01/2026 4:19 am, john larkin wrote:
>>> On Sat, 17 Jan 2026 03:59:00 +1100, Bill Sloman
>>> wrote:
>>>
>>>> On 16/01/2026 11:01 am, john larkin wrote:
>>>>> On Thu, 15 Jan 2026 23:01:38 +0000, John R Walliker
>>>>> wrote:
>>>>>
>>>>>> On 15/01/2026 18:15, john larkin wrote:
>>>>>>> On Thu, 15 Jan 2026 17:51:59 +0000, liz@poppyrecords.invalid.invalid
>>>>>>> (Liz Tuddenham) wrote:
>>>>>>>
>>>>>>>> john larkin wrote:
>>>>>>>>
>>>>>>>>> On Thu, 15 Jan 2026 15:18:31 +0000,
>>>>>>>>> liz@poppyrecords.invalid.invalid
>>>>>>>>> (Liz Tuddenham) wrote:
>>>>>>>>>
>>>>>>>>>> john larkin wrote:
>>>> MELF resistors may have more surface area to dissipate heat over the
>>>> long term but the peak short term power dissipation limit is strictly
>>>> determined by what is happening in the resistive track itself.
>>>
>>> But a MELF can have a longer and wider resistance track compared to a
>>> planar equivalent.
>>
>> But most resistors dissipate most of the heat they generate into the
>> printed circuit board on which they are mounted. Planar surface mount
>> resistors do that a lot better than MELFs.
>
> Do you have any data for that?
It's a broad generalisation, and only really applies to small surface
mount resistors, but they are the resistors that sell in the largest
numbers.
> In both cases the substrate is alumina
> which has a high thermal conductivity. MELFs have crimped on end caps
> which probably provide good thermal conduction into the pcb pads.
But not as good as the flat solder pads on planar resistors.
--
Bill Sloman, Sydney
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