So the last thing I need to do before I start diving into gEDA and designing boards is acquire parts kits for the more common SMD devices. I guess I would rather prototype in SMD because it makes stuff smaller, and also means less drilling (since I'll be etching my own boards in most cases).
I can get some resistor and capacitor kits from the local altronics for not TOO much, but what about other components? are there similar kits anywhere for, say, transistors, diodes etc?
I live in Australia but I am willing to order from overseas.
This is for my own personal use so waste of time isn't really an issue :)
Mick.
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Both Altronics and Jaycar sell "some" ICs, transistors, diodes, etc., but, in general, a fairly small (but useful) selection. Farnell and RS will also have some selection - I don't know because I generally don't use their services.
I tend to do all my prototyping using standard components and then change to surface mount for the production. And where possible I try and use components which I already use in other products and which I have stock of.
Sometimes it's almost impossible to get certain components without hitting the "minimum order quantity" barrier, which, for some parts, can be in the hundreds or thousands, even for ICs. On the other hand some manufacturers will sell you one or two parts. Others won't but will quite happily send you a couple of free samples - good idea if you're only building a one-off for yourself.
E-bay can also be a source of some parts, occasionally in ones, but quite often larger quantities.
Otherwise use Google and hunt around!
Good luck
Alan
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If those kits existed, and perhaps they do, they always contain the wrong choice of transistors. IMO, you better make a small list of general purpose transistors, fets, diodes, and order a hundred of each. And some regulators and opamps too.
You can also search on ebay.com for 'transistor kit' etc.
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If you find a SMD kit, let us know. In the meantime it's not hard or expensive to get a good start by electing and ordering from DigiKey, etc. The first clue is the happy fact that for most of the common parts we've come to know over the years, there exist SMD versions which incorporate the original number in the new part number, making it easy to search for them. For example. consider the 2n3904 npn transistor. For common-place SMD (as opposed to sub-sub- miniature) you'll want a SOT-23 package version. They're called mmbt3904 and are available from many manufacturers. Or you can get smbt3904 by Infineon (the s is for Siemens), pbmt3904 by Philips, or mmbt3904LT1 by ON Semi, with the LT1 to distinguish themselves from the rest of the crowd, since their old m prefix (for Motorola) no longer does so.
Second, these parts are really cheap. DigiKey's lowest price is from MCC (Micro Commercial Co.), order p/n MMBT3904TPMSCT-ND * priced at 7.5 cents quantity 10, ** or only six cents quantity 100. Order 10 for 75 cents, 20 for $1.50, or 100 for $6 and have a lifetime supply.
You can get 20 of this and 20 of that, until you exceed $25 to avoid the $5 handling fee, and have a pretty nice customized SMD collection to get started. DigiKey haa a $6 international handling fee, plus you've got extra shipping to Australia, so you may want to find a local distributor.
Notice how the rule is followed, the smaller the part, the longer the part number. 2n3904 for the large part, MMBT3904TPMSCT for the small one.
** You can order just one part from DigiKey, their p/n 568-1741-1-ND, which is the Philips PMBT3904, 8 cents. That one part will cost you $5.08 plus shipping. :-)
BTW, the cheapest sot-23 mmbt3904 transistors are only 1.7 cents in a standard 3000-piece roll, or 1.36 cents for 7 rolls from DigiKey, probably even less elsewhere.
Beyond resistors and caps, a decent selection of chokes and general inductors is a good idea. Coilcraft has a developers kit (I have never bought it, but it's quite complete from the specs).
As others have mentioned, it's quite easy to get samples from most of the major IC mfrs, although some will only give you those if they believe they have the prospect of selling a lot of them (maybe a thousand or so up to hundreds of thousands).
I agree with prototyping at SMD for some things as the board characteristics change dramatically between through-hole parts and SMD (not so much of an issue at low speeds, of course) although it can be an issue with high quality audio, I am told. As an example, a lot of SMD caps have microphonic effects best avoided for very high end stuff (others here know far more on this subject than I).
The best advice I can give is to try and use 'standard' parts rather than the high drool factor new chips that will probably not be multi-sourced. Some parts won't be, of course, but if they are common enough in distribution at least you can get them from Farnell, RS, Digikey, Mouser etc.
Part numbers are not only confusing, they also cover a huge range of price. If you have the Farnell catalogue, you can see the same nominal part from different manufacturers with price variations of 5:1 with, of course, their wildly varying part numbers.
I was pricing a MAX 3243E (now second sourced from TI); from Maxim it was $3.11 and from TI $0.74 - this was direct from the mfrs web pages, incidentally.
The same goes for even commodity (but high performance) parts such as the OP-xx and OP-xxx series op-amps, incidentally. Look carefully at the base part numbers and compare the prices by mfr.
But as to parts - stock up on some simple FETs as well. They work very nicely as switches. Sometimes a bipolar such as the xx3904/xx3906 is best, other times a FET does the job better (no gate current is a nice thing in a static situation for low power designs). My BOMs regularly include the 2N7002 (which is, oddly enough a SOT23 part. Most 2N parts are through hole) for N-channel and TP0610T/K for P-channel.
For higher (but still fairly low) currents, the PMV45EN from Philips (notwithstanding Philips semi is now a 'new' entity) is easily vailable from distribution and works well as a power switch for loads up to about 1A.
Some diodes as well - the ubiquitous 1N914 (once known as the 1N4148) and now renamed (back) to the BT914 in SOT23 is a great general purpose and signal diode. For schottkys (which are now widely available and no more expensive than their conventional counterparts) I use the MMDL770 and MBRM series from On Semi a *lot*.
Power FETs are not quite as transposable, but if you get them in the SO-8 package then the footprints will be the same - just pay attention to the spec if it's part of a SMPS - Vishay (siliconix), IR and others make a number of high performance devices in this footprint.
When there are differing specs, my rule is to at least have a common footprint :)
I'm finding SMD a lot more pleasant to prototype with than thru-hole components.
If the price is right, that's not a problem. A few weeks ago I accidentaly 'clicked' 250 pieces into the basket instead of 50. When I wanted to change that I noticed 50 pieces cost 3 euro and 250 pieces on a small reel cost 2.5 euro.
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Get the free Skyworks diode-varicap kit. I think Agilent has some nice RF transistor-diode kits, also free. Make up an impressive company name and applications.
And just buy a bunch of vanilla SMT transistors, like BCX70, BCX71,
2N7002, and maybe some BAV99 dual diodes and a couple of voltage regulators.
Email me a list from Mouser or Digikey, and I'll buy them and ship them to you. They have nice kits, too.
I doubt the really good capacitors like polystyrene or polycarbonate are available in surface mount.
Something odd I learned related to SMD is that certain JEDEC devices spec both the device characteristics and the package. For instance, there isn't a SMD version of the 1n4148 since it must be sold in the glass seal package. Now you can get similar SMD devices, but there would be no 4148 in the number.
Oh well. It didn't exist when I was specing the parts. What was bad was at the time sot23 packaging was in short supply, so putting a cheesy diode in one was not high on the list as it was probably the lowest return on investment.
If you're going to make up a company name and some applications, you can get 10-12 samples of just about anything you desire from most of the major manufacturers (TI, National, AD, Maxim, On Semi, Freescale, IR, Vishay, Coilcraft, Cooper Coiltronics [host of others] and even Intel if you do it right :)
That way you can get an impressive stock of parts - and that's exactly how I stocked up my skunkworks lab for little inhouse projects where I need 1 of this, 2 of that etc. When the FAEs come calling (and they will call) you can always tell them the project fell through but you may be interested in their stuff in a few months ;)
With some (TI, On, IR and National) I tell the FAEs I am making some inhouse stuff and if it works I *might* use it in a product. They seem happy enough to get me the parts anyway.
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