cde 334 Posted October 15, 2010 Share Posted October 15, 2010 Numbers are misleading. What you may think is big (or small) enough in your head, might not be the right size. Visuals help. Edit: Update Below. Clockwise from top: DIP 8pin IC (100 mil Lead spacing) Sot-23 3pin Transistor (50 mil Lead Spacing, due to 3 pin configuration, pin 1 and 3 are 100 mils apart) 0805 Capacitor Soic(Wide) 28pin IC (50 mil Lead Spacing) 2pin 100x100 mil Header 1206 Capacitor On a 2010 Penny for the size reference. The 1206 and Sot23 cover the date exactly. The 0805 isn't big enough to do that. The 0805's solder pads fit on the Soic's 50 mil spaced leads exactly. If you don't want to dedicate a pad to a decoupling 0805, just solder it straight onto the pins (if you ever find an IC with V+ and Gnd right next to each other that is). Same goes for the 1206 and the DIP's 100 mil spaced leads. You can even use a 2pin header to make a smd to through-hole adapter if you don't have the needed through-hole version. Both the 1206 and the 0805 (barely) can be done. Even the Sot-23, if you use 3 inline header pins and a bit of wire. Sot-23 has the same spacing as a Soic package ic. With the 3-pin parts, the middle pin of one side is removed, while the outer two pins on the other side are removed as well, so it has a 100 mil spacing on the side with 2 pins. The 4-pin version has 3 pins on one side, with an extra big pin on the other side (heat dissipation purposes normally). The 5-pin version has all 3 pins on one side and the 2 outer pins on the other side. The 6-pin version has a full set of pins on both sides. Even though sot-23 and soic have the same pin spacing and sizes, Soic chips, having a bigger body, are easier to handle. Even sop/ssop/tssop parts, with 25 mil spaced pins, are easier to handle than sot-23 6 pin imho. Lesson is really, stick to through hole for prototyping till you are ready to beta. Sot23 is hella tiny, and I would have not gone with it for the transistors I bought if I had known (The standard to-92 versions were the same price, and have higher watt ratings to boot). Ha. --- It happened again. I was expecting a decent sized QFP chip. I got: A 3mm x 3mm package QFN with pin spacing smaller than tssop, in a reflow only package. Oh vey. bluehash and jsolarski 2 Quote Link to post Share on other sites
gatesphere 45 Posted October 15, 2010 Share Posted October 15, 2010 Nice reference picture and explanation. I haven't gotten into SMD stuff, as I have terrible soldering skills... but still nice info. Thanks for the writeup! Oh, and that sucks for your transistors, but hey, you live, you learn. Also, gives you a chance to get some practice with small-pitch parts! Quote Link to post Share on other sites
cde 334 Posted October 15, 2010 Author Share Posted October 15, 2010 Oh, its not a loss, though its just a bit annoying. 3pin sot-23 isn't too challenging once you get it held down properly. I've done tssop with individual strands of solid core cat-5 cable once. It's just since I always breadboard, I have to break out the soldering iron to dead bug anything smd. I just recently picked up a pcb etching kit (1.97 for 6oz of ferric chloride, 5oz of resist solvent, 2 3x4.5 inch dual sided copper boards, and a drill. Radioshack clearance ftw) so I might make some proper boards. SMD is great for saving space, but a chore for breadboarding. Quote Link to post Share on other sites
gatesphere 45 Posted October 15, 2010 Share Posted October 15, 2010 NICE price on the kit. RadioShack? I'm headed there soon to see if I can pick one up Quote Link to post Share on other sites
cde 334 Posted October 16, 2010 Author Share Posted October 16, 2010 Radioshack Sku 276-1576. Closeout. Won't be restocked. Hit or Miss. If you don't see it (Small blue & white box, size of a Nintendo Wii Power Brick) ask them to check the district stock tool. Quote Link to post Share on other sites
NJC 17 Posted October 27, 2010 Share Posted October 27, 2010 I just recently picked up a pcb etching kit (1.97 for 6oz of ferric chloride, 5oz of resist solvent, 2 3x4.5 inch dual sided copper boards, and a drill. Radioshack clearance ftw) so I might make some proper boards. I highly recommended the iron on PCB etching method. I used it years ago, and it was amazing. I was able to get most SMT boards I designed made in a few hours with the exception of a few VERY small pitch components. The downside, you need a laser printer. Back in the day my aunt donated an old one that she wasn't using anymore. It had terrible resolution for normal printing, but more than enough for PCBs. http://www.dipmicro.com/store/PNPB This is the blue paper that you use to print the designs on. If anyone ends up wanting a tutorial or hints on this, I'll try to find the CD its backed up to, I wrote up an article almost 10 years ago. :-P I personally like surface mount, once I'm done breadboarding, I go right to SMT PCB designs. What's frustrating is trying to prototype with SMT only devices (like some of TI's op-amp's). Quote Link to post Share on other sites
cde 334 Posted October 27, 2010 Author Share Posted October 27, 2010 Laser printer is easy. Just hit up your local library. And I'll be printing on photo paper/magazine paper. Most I'll be doing is dip adapters, so should be easy enough that I don't need to spend more. Quote Link to post Share on other sites
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