Sourcing IC's and other components

Hi all! New member here so here goes with my first post!! Please be gentle with me!!

Ive been messing around with electronics for years now but I'm finding I'm designing and planning more and more these days. I have always stuck to using the big name suppliers (I'm sure you all know who I mean!) for IC's and other components but with the advent of the internet and auction sites I keep coming across companies that sell IC's in bulk. Some of these companies are in the far east and advertize on everyones favorite auction site as well as elsewhere. Now I have heard more than a few horror stories of people unwittingly buying counterfeit parts and companies printing part numbers on duff chips and passing them off as the real thing. Is this problem rife with far eastern suppliers? I wouldn't have thought so and it seems unfair to lump all of these companies in with the bad eggs. Has anyone any experience of bulk buying IC's for these big companies (wherever in the world they are!)? I'm aware that some DIP package devices are starting to be withdrawn and I'm looking to get my stocks up before they disappear for ever. Any help would be greatly appreciated.

Thanks, Bunk.

To be certain of the source you will have to stick to the ISO certified suppliers who have traceability back to source. Some suppliers from that auction site are OK but I'm vary cautious of dealing with some far eastern companies. Although some seem to be large stockists they are often working from a back room at home and themselves dealing in whatever they can get their hands on. I've had a few LCD modules that were definitely out of specification and I've bought LEDs that despite being branded by a major manufacturer were visibly much dimmer than the same types purchased for a legitimate distributor. Your mileage may vary. Many of the suppliers are good and honest and even if they are dealing with counterfeits may not be aware of it but there are also rogues who knowingly sell rejects or remarked goods. The trouble is telling them apart, especially when they change trading name almost daily!

Brian.

Why would you want to stock up on obsolete components? Do you have a specific list of parts you are looking for? Most companies clinging on to obsolete parts do so for good reasons such as re-approval if the product design is changed or high cost of re-design for a low volume product.

Keith

Hi Guys! Thank you for your speedy replies! Brian, that was pretty much what I thought. I've seen other people saying similar things. Sorry to hear of your experiences but thanks for sharing them with us. Keith, I didn't realise these companies only carried obsolete parts. I thought they also supplied new components to industry etc. alongside the big boys such as RS etc. There are a few obsoletes I wouldn't mind getting hold of but obviously not for new designs. My interest is mostly in the audio/synth/fx area although recently I have been teaching myself PIC programming (which has been a bit of a learning curve!) so as an example I want to get some stock of the venerable LM/JRD13700/13600/NE5517 transconductance op amp. Its a building block of so many designs but I feel the writing might soon be on the wall for the DIP variants. The SOIC versions are less than half the price at some distributors and I can't see Texas keeping production running to satisfy the DIY market? I know On Semi and New Japan Radio are currently producing them in DIP packaging; is this what's meant by 'second sourcing'? If so do second source suppliers tend to extend the life of the DIP format or do they eventually phase out old packages too? I know that's a pretty wide ranging question but it's something that pre-occupies me in these days of miniaturization and having seen several DIP parts go to the wall. Excuse my ignorance but I don't work in electronics, I'm a humble common or garden Electrician!

Thanks again,

Bunk.

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I think you should 'bite the bullet' and use surface mount, even for DIY projects. Availability of through hole is not going to improve although I know quite a number of Chinese manufacturers don't do SM yet. As long as you can avoid QFN style chips, hand soldering is not that difficult with practice.

Keith

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Just to add, if you do end up with a situation with PCBs wanting through hole parts you can always use adaptor PCBs. Not ideal, but very handy on occasions.

Cheers Keith. I'll have to do some research on the techniques required..not to mention the extra strong glasses I'll need! I have been thinking that would be the way to go but as a last resort really. The basic PCB software I'm running supports SMT so that shouldnt be too big a deal. Would you advocate using SMT resistors/caps etc too or just sub the through hole parts I can't avoid using such as IC's?

Bunk.

Use SM for everything - parts are dirt cheap. You can use ceramic capacitors almost everywhere which I don't think you will find in through hole for large values. If you go for 0805 for the capacitors/resistors they are pretty easy (they look quite chunky to me - I use 0603 unless space it tight in which case it is 0402). I use a large magnifying lamp which I spend a lot of time looking through - I even need it to probe PCBs with an oscilloscope probe when parts are small - so buying a good one is a worthwhile investment.

Keith

Really helpful advice Keith, thanks. I almost bought a big illuminated jewelers loupe in Lidl the other week! I knew it was fate! Great advice on the other parts too. Ill have to feed the hamster in my ancient laptop that's running PCB Express and have a look in their libraries. SM will be beneficial as I'll be able to fit some 'larger' designs on the limited board size offered by PCB Express...While I'm at it I'll give myself 10/10 for stating the obvious! Any other advice regarding the optimum part family for other components such as IC's, transistors etc would be greatly appreciated bearing in mind I'm a SM beginner. Another ridiculously obvious question..Is there a specific type of glue used to hold the parts for soldering or is that not the done thing? I don't want to melt my little SM friends!

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I've just got a big box of mixed SM/TH components and connectors off an auction site that I need to go through. It cost me next to nothing so it was worth a punt. If there is a *** I'll find some Curtis/SSM chips lurking in the bottom!!

No, you don't normally glue parts - that was really for putting surface mount parts through through hole wave machines without the parts falling off! I tack one corner of an IC carefully then the diagonally opposite corner then solder the rest. Have a look on the PCB ... Section of this forum - there are lots of discussions about how to solder SM parts.

Keith

I bought 200 MOSFETs on EBay from China. Got the parts and tested the on resistance. The part IRLB3034 was marked and even shipped in tubes labeled from International Rectifier. The spec is 0.020 ohm with 4.5 volts on the gate. The parts I got were 0.064 ohm. May not sound like a big deal but passing 40 amps the MOSFET will overheat when the real one stays cool. I tested a "real" part with the same test setup and it was 0.017 ohm.

Like someone stated, stick with ISO suppliers.