On Fri, 13 Dec 2002, Spehro Pefhany wrote:

*>At 09:53 PM 12/13/02 +0200, you wrote:
*>>On Thu, 12 Dec 2002, Spehro Pefhany wrote:
*>>
*>>*>We're still using Imperial measurements for PCBs, but I find that many or
*>>*>even most components and virtually all *new* component footprints are now
*>>*>hard metric. It takes more digits and is less accurate generally to enter a
*>>*>metric measurement in Imperial units than the other way around (because
*>>*>2.54 is exact and 1/2.54 is a repeating number). But, if they are within a
*>>*>mil (thou) that's good enough, usually.
*>>
*>>Imho the reason is that China, the main manufacturer of consumer
*>>grade components , is a METRIC country.
*>
*>Assuming you are talking about mainland China, I don't think she has yet
*>originated standards in many, if any, components- they are virtually all
*>originally Japanese with some SE Asian.

China, ex-USSR and all former coutries that used to belong to COCOM used
metric versions of all parts that you care to think of for MANY years.
This includes metric versions of nearly all TTL chips (Russian made ones I
know of)  (using 2.5 mm instead of 2.54mm as modulus). Maybe some of the
guys in those areas can comment.

As to standards, one produces what the market asks for. Since many
products leave mainland China ready assembled they can well be metric
inside. This is probably more of a historical thing now but it used to be
so that you had to bend pins to get a 2.5mm MCU susbstitute to fit a
2.54mm modulus board design ... fortunately only chips with relatively few
pins were made that way (with 2.5mm modulus) afaik.

Peter

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