Hello everyone,

I have been doing my research about SMD. They are very small and are useful when you need to make a very small circuit. I am having trouble finding a site to buy small quantities of SMD components. I found a source on eBay for SMD capacitors and resistors. (good deal)

Does anyone know where I could buy general purpose SMD parts such as simple IC, LEDs, etc. I tried Digikey and Jameco (very difficult to navigate the site to find what you are looking for).

Also, in the SMD world was is the basic PNP and NPN transistor. The 2N3094's and the 2N3906's of the big world.


I am mainly looking for the following basic components:

LM55
LM556
LM324
LM386
LM741
LM339
:wink:

I would really appreciate some help,

thanks,

George L.

 

what country are you located in George?

I recently bough LM556 in an SO8 package from bgmicro.com - very cheap

I also picked up 100x 2222A npn's in the SOT-23 package from the same place.

BG Micro is in the USA

you might want to check www.futurlec.com (based in China) - they ship internationally for very low rates

 

you can buy 2n3904's and 2n3906's in surface-mount form at jameco and most other places. Remember, even in a much larger through-hole component, the actual chip in the package is very small, so most often you can buy the SAME part in a surface-mount version. For all SMD resistors, capacitors, etc. I pretty much exclusively order from digikey.

I suggest you order yourself a digikey catalog, it makes finding discrete parts much easier... and spend some time getting used to their search system, I don't usually have too much trouble with it.

Probably the most important thing you need to do in order to start looking for surface-mount parts is find a list of IC package names and diagrams of each... you should know that things like SSOP, SOIC, SOT, TSSOP are surface-mount IC packages of various sizes, and things like 0604, 0805, 1206 are SMD resistor/cap packages. Usually that's the only way to tell SMD parts apart from regular ones at places like digikey, short of actually scouring the datasheet of every part. If you know what package you want, and what part, you can narrow it down pretty quick at the digikey search with the filters. for instance, if you search for "lm339" and filter it to 14-soic, you immediately get a nice list of usable parts.

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EEgeek.net

 

thanks for the awsome help and very quick response time.

I live in the USA, Northern NJ.

Does anyone know of a good site to teach the basics of SMD technology, I am not sure of the exact size difference betwen the 0604, 0805, 1206.

thanks for all the help,

thanks,

George L.

 

The catalog is a great resource for that

Mouser and Digi-key catalogs have a diagram of the part, with H, W, D measurements, and sometimes a scale comparison.

I believe, but I'm not 100% certain, the numbers like 0805 are measurements, in tenths of a milimeter

so a 0805 resistor is 0.8 mm long by 0.5 mm wide.

Another handy tool I made for myself, and suggest you make one - is a size comparison chart. Using the Cadsoft Eagle pcb cad program, I went into their refrence library and copied a whole bunch of different SMT packages into a pcb layout (like 0603, 0805, 1206, 1210, SOT-23, SOT-223, etc...) and then labeled each one - then I printed that out, and I now have a sheet showing the different pieces, in the proper scale, along with what their pin configurations look like.

Sometimes an eagle library isn't 100% accurate on the layout for a package, and its recommended you check the actual part to the layout if you're going to actually make a PCB

 

I thought the SMD for res and caps (0402,0603,0805,1206) were the measurments in mills ie millionth of an inch not millimeters

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Nothing is impossible.
Once a problem is realised, the rest is just details

 

I find Mouser.com far easier to navigate than Digikey. Things like voltage regulators are grouped together, while with the Digikey catalogue it's spread over 100 to 200 pages. I never seem to get the Digikey filter to work properly and I find their labeling system arbitrary. Sometimes they will label 3.3v sometimes 3.3volt, or just 3.3, and I've seen mistakes in the labels as well.

I know it's not universal, but I generally find Mouser.com far cheaper as well. 0805 led's can be had for 11cents each...

I try to get everything SMD now. far easier to work with.

__________________
Mark Higgins

 

indeed, mouser is cheaper in many areas, like resistors, transistors, and apparently LEDs ... they're more expensive for ICs in general, and have a small selection on some things - I also find they (mouser) don't ship as fast, dispite both claiming "same day" shipping.

drilling holes in home-made PCBs sucks - I try to go SMD whenever I can!

 

Isn't a mill one thousandth of an inch?

 

Here's a link to a page which has a table listing the dimensions of various sizes of surface mount resistors:
http://www.practicalcomponents.com/d...mr-drawing.htm
JB

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Nothing is impossible for the man who doesn't have to do it himself - Weiler's Law

 

You won't find LM741 in surface mount, NObody wants to use that old dog!

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see my website: www.geocities.com/russlk

 

apparently someone is still buying them

http://www.mouser.com/index.cfm?hand..._pcodeid=51123

741 op-amp, in SO8 package

 

Thanks for all the helpful tips everyone, I am ordering my SMD parts from Mouser, much easier to navigate than Digikey or Jameco.

I'm just wondering, do they make tiny SMD photo-resistors, I couldn't locate any on Mouser, also, I couldn't find an SMD diode, its got to be there, its the most basic part!

Does anyone know about these two parts I couldn't locate, It would be very helpful.

thanks,

George L.

 

just about anything that's made in the semiconductor industry is available first as a smd part and through-hole parts come later, if at all

of course, if the part is ancient or mechanical in nature, through hole still dominates, but the latter is changing thanks to electrically conductive epoxies replacing solder

mouser's website is easy to browse if you don't know what you're looking for, but hard to search ... I easily found 100's of options for surface mount diodes with a quick query in the digikey search

surface mount LDRs are out there, might be easiest to find them with a catalog size I doubt they use any type of standard smt package

another thing to remember, any part can be surface mounted, for things with leads it usually involves trimming the leads as short as possible and putting a 90° bend on the end, for it to rest on the pads. of course, the mechanical aspects of that are risky, so it depends on your application.

 

You're looking for a photo-transistor or photo-detectors. They are listed under Optoelectronics -> Opto Components in the catalogue. Example: Page 85 has the everlight phototransistors.

Diodes are listed under Semiconductors -> Discrete Semiconductors in the catalogue.

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Mark Higgins