Surface mount components

[[527]phil]

I've recently started using surface mounted components for my circuits. But I'm having a hard time differentiating between capacitors and resistors, I've googled it but none of the pictures we're of any help. Does anyone else use surface mount electronics, and can help me?

[Mike AA]

Originally Posted by [527]phil

I've recently started using surface mounted components for my circuits. But I'm having a hard time differentiating between capacitors and resistors, I've googled it but none of the pictures we're of any help. Does anyone else use surface mount electronics, and can help me?

I have worked with and have a ton of SMC's. I cant remember exactly the difference, but I want to say resisters are black and capacitors are a brown or dark orange. Did you need to know how they looked because you have a pile of them or to dissect another circuit?

-Mike

[Eldarion]

Originally Posted by Mike AA

I have worked with and have a ton of SMC's. I cant remember exactly the difference, but I want to say resisters are black and capacitors are a brown or dark orange. Did you need to know how they looked because you have a pile of them or to dissect another circuit?

-Mike

Capacitors also come in light tan. Sometimes you will get lucky and the resistors will have a code printed on them in white.

[lupjohn]

Originally Posted by [527]phil

I've recently started using surface mounted components for my circuits. But I'm having a hard time differentiating between capacitors and resistors, I've googled it but none of the pictures we're of any help. Does anyone else use surface mount electronics, and can help me?

Just finished a nice learning kit on SMC from Chaney electronics. Their quote is that all smc resistors are marked with the resistance. Capacitors are unmarked but may have one pole marked for polarity( forgot the polarity right now). If you can find this kit online it sells for a little over $20.00USD and has a small practice circuit board and lots of chips to practice identifying and then soldering to the board using the methods outlined in the lesson plan. After completing the practice placing and soldering there is a second small funtional circuit that flashes two LED's. I haven't finished it yet but with the help of a magnifier light from Harbor Freight it is a complete intro to using SMC mount components for circuit development. LRU.

The kit is their Delux SMC soldering kit. Try this link:
http://www.chaneyelectronics.com/
The Chaney site has many kits there for intro training (for First Team members just starting out). Best wishes.

[[527]phil]

Thank you. I've been soldering circuit boards to use the parts for almost 8 years now (cheaper than buying new ones from radio shack). But i always seemed to think that those really tiny parts we're too small to use so i overlooked them and often threw them out. But i recently was flipping through a magazine i found at work for hobby electronics and i saw a SMT kit. So i researched it a little and found out that resistors and capacitors look the same. But thanks a lot for your help, I'm looking at a small circuit board i had lying around and i can see that only the black ones are labeled for resistance. And sitting right in the middle of the thing is a PIC16C56A . I've also been looking for websites that sell SMT parts, the best so far is www.goldmine-elec.com . they have tons of SMT stuff including LED's.

[KenWittlief]

sometimes resistors are not marked, but they are almost always black on one side and white on the other. If you see a white part, its a resistor placed upside down.

Surface mount inductors are usually dark grey and unmarked.

The secret to soldering surface mount parts is to get a tube of solder paste. (note: solder paste is not the same thing as flux paste). It comes in a syring with a metal needle, and you need to buy the handle to squeeze it out of the tube. (expensive$$$). The solder paste is tiny little balls of solder mixed with solder flux. It has the consistancy of peanut butter.

You hold the component with tweezers on the clean pads, put a dab of solder paste on one end of the part, then touch it for a second or two with an iron. The solder melts and wells up so nice on the part and the pad. Then you do the other end.

To use wire solder correctly you need to hold the part on the pads, heat the pad with the iron and apply the solder at the same time. Unless you have three hands its impossible.

I also recommend you get a pair of 2.5X reading glasses. They have them in drug stores and places like BJs or Sams club pretty cheap ($16 for 3 pairs). The other thing is: you cant solder a moving target, so you need a vice or something to hold the board still while you solder parts to it.

[[527]phil]

http://www.speleogroup.org/SMT-boards-sg.pdf

The link above shows a method of holding components in place while soldering, it's on one of the last pages. And yes, if your going to do this but a pair of magnifying glasses. i have a magnifying visor that goes up to 4 times magnification. I don't use solder paste, i just heat up some solder until i get a small bead on my soldering iron tip. then i touch it to the part to be soldered (very carefully)

[Mike AA]

Originally Posted by [527]phil

Thank you. I've been soldering circuit boards to use the parts for almost 8 years now (cheaper than buying new ones from radio shack). But i always seemed to think that those really tiny parts we're too small to use so i overlooked them and often threw them out. But i recently was flipping through a magazine i found at work for hobby electronics and i saw a SMT kit. So i researched it a little and found out that resistors and capacitors look the same. But thanks a lot for your help, I'm looking at a small circuit board i had lying around and i can see that only the black ones are labeled for resistance. And sitting right in the middle of the thing is a PIC16C56A . I've also been looking for websites that sell SMT parts, the best so far is www.goldmine-elec.com . they have tons of SMT stuff including LED's.

I got a large box of SMDs/SMTs, off ebay for only about $10-15 In the box I found over a hundred rolls of SMDs, most of these rolls had 100+ components on them. I have made some circuits but not had time to do a lot of work. If you just want a whole assortment of components this would be a good idea, in my opinion.

-Mike

[Mike Betts]

Originally Posted by [527]phil

... I don't use solder paste, i just heat up some solder until i get a small bead on my soldering iron tip. then i touch it to the part to be soldered (very carefully)

Phil,

I strongly suggest that you put a very small glop of solder flux under the pads if you are going to use this method. The flux core solder you use to create the small ball of solder on your iron will be "flux free" after heating and will not do its job of cleaning the oxidation from the component and board pads.

Without the flux (or a very complicated cleaning under inert gas process), you run a good chance of the solder not flowing completely under the pad.

JMHO,

Mike

[KenWittlief]

what Mike said^

one thing that is frustrating with surface mount parts, esp 0603 or smaller, is when a circuits not working.

I use a 30X stereoscopic microscope with a bright light to inspect the boards for assembly errors, and its really amazing how parts can be almost soldered - the solder is about 0.1mm away from the part. Its really hard to spot without an expensive microscope.

thats why you need to solder SMD carefully - its also very easy to cook the parts with the iron and have them crack or separate from their end caps.

SMDs were not designed to be hand assembled.