Hi All - these are good, sensible tips easily added to my BOMs.  Thanks.
J


Vitaliy wrote:
> Mike Hord wrote:
>> As for the rest of the input, it sounds like most of you are in the same
>> frame of mind I was- I have one part (the assembled board) that I buy
>> from my CM.  They manage a list of parts that they are allowed to use
>> (for instance, multiple manufacturers of *3904 transistors) to fill a
>> given
>> order.
>
> We allow our CM even more freedom: we don't give them a list of parts that
> they are allowed to use, we only tell them which parts they must use as
> specified. Most of the time it's OK to assume that a jellybean 3904 will
> behave like a 3904, and that a generic 1k 0402 will have a resistance in the
> 950-1050 ohm range.
>
>
>> We used to do it in a far more complex manner, involving an individual
>> part number under ECO control for every component (down to resistors)
>> on every circuit board (of course, parts may be used on multiple boards).
>> Having to do an ECO to add a new vendor to the list of approved 1%
>> 0402 1k resistors seems like a REALLY big waste of money to me, and
>> fortunately we've moved away from that.
>
> That does sound like overkill. The notes at the bottom of our BOM read:
>
> - OK to substitute equivalent parts, unless marked with "No" in Sub column.
> - Resistors:
>      - If power dissipation (W) is not specified, assume it's not critical.
>      - If tolerance (%) is not specified, assume 5%. OK to substitute 1%
> parts as long as value remains within range.
> - Capacitors:
>      - If minimum voltage rating (V) is not specified, assume 6V.
>      - If tolerance (%) is not specified, assume 20%.
>
> We also get FAs so worst case, if a component does not behave as expected,
> we can tell the CM to substitute it before starting production.
>
> Vitaliy
>
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