While on the subject of MIL. SPEC. or Military Specification, it is generally not realised that Mil. Spec. chips are
basically the same as any other chip, however their AQL or Acceptable Quality Level is tightened right down and the
permissible errors in a sample batch of, say, 1,000 chips, 10% are tested first of all in the sample batch and if there are no errors or
there are virtually zero errors, that is to say, in say the sample batch of 100 chips, 99% passed with flying colours and 1% is a
"bit suss" and pass all basic functionality tests however they do not meet the 100% AQL and therefore can be safely sold as garden variety commercial chips.
How it works is simple, you have a run of parts, widgets, ICs, resistors or whatever mass produced product and you need to know what the error level is.
What is done is, let us visualise 100,000 ICs . You need to know if they pass or fail in any way. Out of this 100,000 ICs, there is a calculated formula for the
sample batch to be removed for testing. In that sample batch for testing, let us say a sample of 100 ICs are to be "Burn-In Tested".
These are fully tested with what is termed a "burn-in " test. That is to say, they are run at there very limit for several hours, days or weeks at their maximum voltage,
maximum switching frequencies to evaluate if any become problems. If no errors or failures appear, then the batch is put aside and another batch sample taked from
further down the "line", let us assume the batch is number 60,000 to 60,100 this batch. 100 taken out and tested.
The same testing is run over hours, days or weeks and if all is fine, anothe batch taken and so on.
Here is the interesting bit. If an error was discovered in the batch, it is noted, the batch is put aside and marked accordingly and the sample is widened to
include further numbers from various stages in the run.If that testing reveals further failures, then the sample is again widened to increase the posibility of finding further failures.
Once the sample batch has exceeded a set formula it is then deemed to be a faulty batch and rejected by Quality Control. Being that production techniques are so well
managed these days, high use of advanced clever photo-lithography, so the chances of it happening are so slim that one could almost take wagers on the full outcome of a batch.
There is a set down procedure for Quality Control on manufacturing best practices and is closely adhered to by manufacturers, whether it is for ICs, food or even toys.
Thankfully cars are not tested in this manner. ;-)
Having said that, one can purchase a batch of, say 500 pieces of NE-555 chips and test every single chip, one chip at a time for all
the correct parameters "per the data sheet". This will ensure that each and every chip is fully functional, have each chip "burned in"
at its maximum recommended supply voltage, perhaps overnight or a week, on a specific "test bed" and see how many pass or fail,
the passes "could" basically be classed as "Mil. Spec".
The strange thing is, if only 100 are tested from a batch of, say 500, this would perhaps strongly indicate a compliance to
the manufacturer's data sheet specifications or better. To do this, requires a great deal of precision test equipment, special
high stability power supplies and a host of test equipment costing thousands of dollars !
Also, having noted that, it would be safe to say that certain chips in that control batch of a mere 100 chips could actually perform a
small percentage better than others in the batch, it would be unreasonable not to expect this result from a quantity of only 100 pcs of
mass manufactured NE-555 chips or in fact any other type of semiconductor manufactured these days. It does not get any better than this !
This however dispels the myth and story that manufacturers make special chips, manufactured with extra bits or thicker substrate,
thicker attaching wires, increased substrate pads areas and so on, to special specifications, calling them MIL.SPEC. It simply is not so.
This is so different in contrast to Military specification equipment. Take for instance ruggedised laptops made for the Military. These are by their very nature built to a
strict guideline and stringent specifications whereas they can be dropped from a certain height, kicked, be blown up in a Army tank (only kidding here) and still boot up and survive.
Why does this occur ? They are designed from their inception to be the best of breed.
Panasonic has earned a great reputation for making very rugged laptops for use by the Military. They have earned their place in manufacturing durability,
reliability and performance, as have several others.