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Author Topic: How to pick surface mount components  (Read 992 times)
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I need to order some 10uf capacitors and various resistors for a circuit I am working on. The components need to be fairly small, as the circuit will be flexible (it will be an extension of what I posted here: http://arduino.cc/forum/index.php/topic,66649.0.html). However, I am hand soldering them, so they cant be microscopic...

Now when looking at parts at digikey, for every itam I am looking at there are ~100+ very similar itams to choose from. So similar that I find it hard to chose the right one.

Can you give me any generall recommendations on how to chose the right surface mount component? Maybe you could even point me to a specific brand/formfactor that you are comfortable using.

The circuit will be partly arduino powered at 5 volts and ~200milliamps and partly use external power with 9V and ~400milliamps.

If you have any suggestions, they will be very much apreceated.

Cheers

p.
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I think people generally consider 1206 components to be easy to solder, 0805 to be generally OK, but many people start to complain about having to solder 0603 components or smaller. It is definitely doable, but one benefits from having some kind of magnifier. With a powerful enough magnifier I have even soldered 0402 components by hand but it is not fun (the biggest problem is losing the components because they are so small).

Why not get an assortment of resistors in various sizes (they are really cheap) and find out what your tolerance is (no pun intended).

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Look for parts like these.

Resistor, 10K, R0805   R1      P10.0KCCT-ND
Resistor, 1K, R0805   R4      P1.00KCCT-ND
Capacitor, 100nF, C080RND   C1    08053G104ZAT2A   478-1423-1-ND
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Keep in mind that ceramics aren't really meant to be hand soldered.  So you have to make a tradeoff between being big enough to solder and small enough that the entire SMD heats up evenly.  When I was new to soldering SMD I did 1206.  At this point, I am comfortable with 0805.  If I am using lead(Pb) solder, I'll go down to 0603.  (Lower melting points.)

For narrowing down the selection...  pick the package size, pick the voltage (give yourself headroom... remember ceramics have a voltage coefficient), select your Capacitance, click the "In-Stock" option, and sort by price.
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  This is a handy thread, I wish we could have some sticky threads like this.


Thanks guys,
Mark
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Ok, I have finally compiled my shopping list:
(all will be used on circuits with 5v and maximum draw of ~200mA, except for the 110ohm resistor which will be in a 12v circuit)

Resistor – 10k
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10.0KCTR-ND


resistor 110 ohm
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P110ACT-ND


resistor 180 ohm
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P180ACT-ND

capacitor 0.1uF
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=478-1423-1-ND


LED Green
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=475-1406-1-ND

LED Yellow
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=475-2555-1-ND

LED Red
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=475-2510-1-ND

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Problem: I cant seem to find IR leds on digikey - when searching there is not even an option for selecting the wavelength I need (900 - 910nm). Any Ideas?

Also, the LEDs I selected require 2mA Is that enough for a LED to be well visible at daylight?

EDIT: found them. they are called "IR Emitters" and not "IR LEDs"

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=846-1023-1-ND

I am fairly confident about the other components (i tried to have no dimensions under 1mm and only pick popular itams) but if anyone could take a look and tell me if I selected anything dodgy I would apreceate thet.

Thanks

P.



« Last Edit: July 19, 2011, 03:27:15 pm by fkeel » Logged


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You will want to change the 10k resistor to the cut tape version
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P10.0KCCT-ND

When looking on Digi-Key, be on the lookout for the minimum order quantity. For a tape and reel it will generally be in the thousands of pieces. Cut tape refers to a reel where they cut the tape and can sell you just 1 piece or more.

Also your 10k is a 1% resistor and your other two are 5%. Not sure if that is important to you, but just so you are aware of it. BTW, lower percentage numbers are more accurate.
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darn. i just ordered.

oh well - i will give it a try and report back how they are.
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Quote
the LEDs I selected require 2mA Is that enough for a LED to be well visible at daylight?

I wouldn't think so. Even if they are high-efficiency.  2mA is very low.

Smaller LEDs take less current for the same perceived brightness - its the current-density on the die that matters.  Still daylight is bright...
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