Construction differences of same value resistors in same package but different power ratings

[terranigma]

In the attached diagram, 1/2 and 1/4 watt resistors have the same package size.

I wonder that what are the construction differences of same value resistors with same dimensions but different power ratings? How they managed a higher power rating in the same housing?

Are they differ in spiral turn count? Which one has less spiral turn (which is less inductive), higher wattage or lower wattage?

Are they differ in film material thickness?

Thanks.

 

[arjen6t8]

Can you give a link to the datasheet? Searching the net for the types given doesn't show results to me.

Normally, resistors of low wattage (<1W) are metal film, not wire wound.

 

[terranigma]

It is not a wirewound resistor. A regular metal/carbon film resistor. I mean "engraved spiral turn" of film layer, not the wire turns of a wirewound resistor.

Here is the document that I'm referring to (a domestic manufacturer that is not in the business anymore):
http://www.alpelektronik.com.tr/?page=direnc

 

[arjen6t8]

My guess is a thicker yet lesser wide carbon film, for the higher wattage rating in the same housing size.

Is this your own scraping work? If so, get two of the same resistance, one at 1/4 W and another 1/2 W and do the scraping, and compare number of turns.

 

[terranigma]

Is this your own scraping work?

No, I found it on Google.

I'm just trying to figure out its construction benefits before ordering them. This ALP (not "ALPS") resistor factory was producing their resistors in Japanese standards in Turkey. Their 1/2 watt resistor size is small comparing other brands (Yageo, Cinetech etc.).

 

[wg_ski]

The smaller case size will have a higher temperature rise at a given wattage. They may be able to take the higher temperature, but you also have to consider resistance temperature coefficient. There will be a larger R change, and you have to decide whether to live with it.

 

[MarcelvdG]

This is a link to the datasheet of ranges of metal film resistors with the same peculiarity: the miniature resistors can handle more power for a given size than the general resistors. Except for the power rating and the maximum voltage rating of the MFS60 type, everything else appears to be the same for a given size, including stability over time at maximum dissipation, failure rate, the temperature at which the maximum power dissipation is specified and the temperature to which the power has to be derated (which would normally be the maximum body temperature).

I have no idea what the contruction or production test differences may be. Given the different power ratings and apparently equal maximum body temperatures, it seems that the miniature resistors are better cooled at a given size (more power for a given temperature increase).

https://mfrelectronics.com/wp-content/uploads/2024/07/METAL-FILM-RESISTORS-01.07.2024-1.pdf

 

[Mark Tillotson]

One point: Resistor leads can be tinned steel (cheaper), or tinned copper. The latter can conduct much more heat away.

 

[VivaVee]

The body could contain an alumina powder mix which conducts heat away from the core better. Philips made the MRS16T resistor in the 1980s that was rated for 0.5W but fitted on a 2e spacing compared to their standard MRS25 0.6W resistors that required a 4e spacing. In this case, e = 0.1" or 2.54mm

 

[VivaVee]

My memory failed. Power rating was 0.4W.

compared to the more usually sized 0.6W MRS25: