Yes they are CHEAP, But these Overseas Parts don't always meet full specifications.
That is true. There are the following categories, in my experience:
(1) Rip-offs: We all know about rip-offs and it is simply not advisable to buy that category of component except from the manufacturer or a trusted source: batteries, big electrolytic capacitors, medium and high power RF transistors, audiophile transistors. safety critical items
(2) Factory rejects: this may not be as bad as it sounds, apart from item1 category components, from a home builder point of view. It may be a that a batch sampling criteria has not been fully met or the case is not formed correctly or even that the component paperwork is not in order or has been lost.
(3) Second tier manufacture: is a full spec product but the manufacturer is second tier and does not fully comply with the very best manufacturing and quality standards
(4) New old stock: many components fall into this category, especially the old favorites, NE555, LM358, etc. I bought some Motorola chips a few years ago with a date code from the 1980s.
(5) Full spec: a high proportion of components fall into this category. There are mountains of perfectly good components that are simply surplus to requirements, which are either trashed or sold to component brokers. And if vendors buy directly from the manufacturers, in any volume, the cost of most semiconductors is ridiculously low. Bear in mind that a billion 555 timer chips are manufactured ever year.
At the company where I worked we had a small production line making marine radars and the stuff they chucked out would make you cry. At the end of each batch of radars they simply put all remaining components in a skip (dumpster). When I tackled them about it, they said that they could not use old components on a new batch of radars and, besides which, the cost of sorting and storing the old components would be more than the components were worth. Old in this case being 6 months. The main input capacitors on the radar were computer grade GE 6,800uF. Guess what value capacitors my audio amps had in them.
As a matter of interest, I recently batch checked about a thousand 2%, 250mW, metal film, resistors. They were well made, indistinguishable from the real thing, and all the resistance values ranging from 10R to 1M were in spec. Total cost £4UK including PP from Hong Kong.
I suggest that, with caution, you can get some bargains from the low-cost vendors if you are careful and selective in what you buy.
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