I have grown so accustomed to using metal film resistors for 
'everyday' applications that carbon film doesn't usually feature in my 
thinking.

A Taiwanese manufacturer has asked whether they can substitute carbon 
film for metal film in a design. They claim that cf costs are far 
lower. Volumes are only moderate (1,000 - 10,000 products per year at 
most). Most resistors are operated at far below their power and 
voltage ratings.

My initial reaction is that whereas most resistors could technically 
be changed to CF, the cost savings would be minimal compared to other 
costs and that sacrificing the reliability of metal film would not be 
worthwhile. I'm also dubious about the merits of allowing CF as they 
would almost certainly be Chinese* sourced with unknown (indeed 
non-existent) provenance and aimed at bottom of the market, 
quality-irrelevant applications. (I've little doubt that there is a 
reason that they are cheap).

Thoughts? - or recent experiences with modern CF resistors.
Am I too prejudiced against a new 'mature' technology?



        Russell McMahon

* I've no doubt that when it makes sense to do so China can produce 
products of superb quality. But I also have little doubt that the 
burgeoning market / what the market will bear / caveat emptor / take 
no thought for the morrow ... / aspects of the present market 
explosion mean that quality will often be, at best, only as good as it 
has to be. 

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