[TowerTalk] 31 mix variability Re: AES SK

[jimlux]

On 7/9/16 1:21 AM, Ian White wrote:
> Several good points there, about the variability of ferrite cores.
>
> Ferrites are, quite literally, "bakery products". Just like bread and
> cakes, the properties of ferrites depend on the correct ingredients
> measured out in precise quantities, on the precise manner in which those
> ingredients are mixed, and also - most critically - on the
> temperature/time profile of the baking and cooling.
>
> Just like baking, the manufacture of ferrite materials is a complex
> blend of science and know-how. Once a specific product has been
> developed, consistency can only be achieved by repeating exactly the
> same processes for every batch.
>
> It is very easy to see how QC problems could appear from outsourcing
> those critical processes to an offshore company that lacks the original
> manufacturer's in-house know-how, with a language barrier that prevents
> that information being accurately transferred.
>
>

It doesn't even have to be offshore. Not all ovens are the same either 
in temperature profile or internal distribution, and there's a lot of 
other aspects.

There's more than one instance of a company "losing the recipe" even in 
the same plant, but also when moving manufacturing operations.  When 
Microsemi bought Symmetricom, they moved the Chip Scale Atomic Clock 
(CSAC) manufacturing (entirely within US and carrying over some of the 
same people), and lost the recipe somewhere, adversely affecting the 
operating temperature range.