What size SMD resistors and capacitors? - Page 1
Forum section: electronics / beginners

author: jgalak
author_rank: Regular Contributor
timestamp: January 24, 2018, 02:23:15 pm
content: I'm just starting to get into SMD designs, and wondering what size SMD components to try to aim for. In the past, I always used PTH passives, doing hand-soldered SMDs only when for chips that weren't available in PTH, but want to move away from that.I've done one set of boards with stencil, paste, and oven, and definitely planning to continue that way. On those boards, I chose 0402 passive (for no real reason, just happened to be what I picked) and found them to be annoyingly small. Even without soldering, just getting them positioned was a PITA. So I'm wondering what folks prefer, especially for this sort of soldering tech - stencil, hand place, oven (or hot-air station).I have no need for machine assembly, nothing I ever do will likely be mass produced. I'm mostly working on things like balloon trackers, so while size/weight is important, I don't think the difference between a 1206 and a 0402 will matter much.I've also seen it mentioned that 0402 should be used for RF. Is that just to reduce lead impedance? Does it really matter that much? (My interests are mostly in vhf and uhf amateur bands)My initial thought after dealing with the 0402 annoyance was to go as big as possible, straight to 1206, but perhaps that's overkill....

author: bd139
author_rank: Super Contributor
timestamp: January 24, 2018, 02:48:08 pm
content: I can't speak for UHF but I've built a VHF receiver (2m) with TH parts that is reliable and have a half built spectrum analyser which is all TH and that has an LO which spans 145-300MHz. Also don't forget that a lot of the older higher bandwidth scopes such as Tek 475 / 485's were all TH as well. In fact the resistor between the attenuator and the front end buffer on a Tek 475 (200MHz bandwidth) is a standard carbon film TH part no better than the crap you get from China now.I wouldn't consider using anything smaller than 0805 myself. I can work those by hand easily without magnification. If I pushed into UHF I'd be more concerned about what happens between the parts i.e. transmission lines etc. A few nH of stray lead inductance there from bad routing or accidentally turning something into a filter has some really noticeable effects. I'm slightly scared of anything above about 300MHz though if I'm honest

author: tszaboo
author_rank: Super Contributor
timestamp: January 24, 2018, 03:33:16 pm
content: I use 0603 as my go-to component, everything else needs some explanation"This is bigger, because power dissipation""This is smaller, because power supply for BGA chip"I can hand solder 0603, but it takes some effort, and not everyone can.But 0805 should be perfectly placeable and solderable by hand.

author: AndyC_772
author_rank: Super Contributor
timestamp: January 24, 2018, 03:50:31 pm
content: Same here, 0603 by default.0402 if there's a good reason, such as the board having to be tiny, or on a very high speed design where trace lengths need to be kept to a minimum. I generally avoid them on any board I'll be soldering myself by hand, because they're really fiddly to handle, but on a machine placed board the size is a complete non-issue.0805 and bigger if I need the power dissipation or voltage rating.

author: phil from seattle
author_rank: Super Contributor
timestamp: January 24, 2018, 05:50:10 pm
content: For hand assembly and hand solder, I use 805s and 1206s. For reflow, 603s and 805s. I infrequently use TH Rs and Cs when I want to have as much copper plane as possible for a heat spreader. I've gotten to the point where I really hate having to bend, mount, solder and cut a TH part. What a huge amount of work vs an SMD. I am always a bit amused by people that avoid SMDs - almost none of the good stuff comes in TH anymore. With cheap & fast PCB vendors and prototyping adapters, it's pretty easy to use SMDs. Of course TH connectors have their place.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 24, 2018, 05:59:06 pm
content: I usually use 0805 is no special needs. 0603 is still possible to had solder, but it gets difficult to route a line beneath.Using SMT passives is really easy, once used to it I do not like THT resistors and caps anymore - though I still like THT chips and sockets.

author: kostasb
author_rank: Newbie
timestamp: January 24, 2018, 06:03:01 pm
content: I don't know about UHF and VHF.My iron is a Antex CS18 with 1107 tip because was the cheaper solution for low temperature and 0.2mm tip as I can say.I'm using solder 2% Ag (Sn62Pb36Ag2 0.5mm) because of the lower melting point.The 0402 parts break up with this combination, so I'm using 0603 that can handle the temperature.Reasonable size easy handled.

author: phil from seattle
author_rank: Super Contributor
timestamp: January 24, 2018, 06:10:16 pm
content: Quote from: Kleinstein on January 24, 2018, 05:59:06 pmHand soldering SOICs, QFP, TSOPs and similar is easy. Lots of tutorials on techniques for doing it. Anything with a lead sticking out is hand solderable. Solder wick is your friend! It's the LGAs, BGAs and such that are a challenge. If you do many projects, moving to reflow is pretty natural and worth the effort to learn.

author: bd139
author_rank: Super Contributor
timestamp: January 24, 2018, 06:14:33 pm
content: To be honest with some of the parts you can glue them upside down and run bodge wires easy enough. I did this with a Si570 recently. Also easier to replace if you blow them up, which I also did recently

author: phil from seattle
author_rank: Super Contributor
timestamp: January 24, 2018, 06:33:51 pm
content: Bodge wires - hadn't heard that term before but knew what it meant instantly! I've done a number of dead-bugs. Great for when you don't have the right adapter in your stock.

author: nanofrog
author_rank: Super Contributor
timestamp: January 24, 2018, 08:10:12 pm
content: Wire Wrap Wire is excellent for bodge wires, and it's very inexpensive ($4.75 for 1000ft forexample).For SMD passives, I prefer 0805 as it fits the spacing on DIY Protoboard, is easy to solder by hand, and not all that expensive. 0603 is cheaper though if you're having boards made.FWIW, I can do smaller using a microscope and micro iron if I need to (done 0201 by hand). It's just a PITA for me due to tremors in my hands.Of course I've hot air too, which does make life a bit easier at times.

author: tox3
author_rank: Contributor
timestamp: January 25, 2018, 11:05:24 am
content: 0603 is my default - easy to handle and low cost

author: JohnPen
author_rank: Regular Contributor
timestamp: January 26, 2018, 08:56:10 am
content: I started with 0805s when building Scotties Spectrum analyser and stayed with that size. Hand soldering , with a magnifier to cope with old age, is not too bad although I find inductors particularly difficult. Having a large stock of TH components I still use them for AF designs where generally space is plentiful. It seems sad to throw away all those large TH components and convert to SMDs after years of collecting.

author: max_torque
author_rank: Super Contributor
timestamp: January 26, 2018, 10:10:33 am
content: For hand assembled projects, on 2 or 4 layer pcbs, with no space concerns, i use 0805. massive choice, easy to handle, not too picky about either the precise footprint or, more critically, how much solder paste they have. They are big enough to not tombstone too much either, especially when you've just quickly blobbed out some solder paste by hand from a syringe etc. They also don't get blown around by hot air too much, making hand mods/repairs/assys easy too.If i want a smaller form factor, then i swap to 0603. Slightly harder to place, more critical to get the paste right, but significant space saving.Smaller than that, just isn't worth the hassle for a DIYer unless you have very specific circumstances, especially as you'll also have to start moving to a 4,6, or even 8 layer pcb to leverage that extra space.

author: bd139
author_rank: Super Contributor
timestamp: January 26, 2018, 10:29:47 am
content: I think this is actually proportional to age:16-24 -> 040224-38 -> 060338-50 -> 0805 (I'm in that one)50-65 -> 120665-dead -> 3W wirewounds.

author: Dubbie
author_rank: Unknown
timestamp: January 26, 2018, 05:23:33 pm
content: I like 0805s for prototypes because they fit nicely between 0.1” header pins.For most boards 0603 is the perfect balance between real estate and ease of assembly.My current project is all 0402 due to extreme space constraints, which is not too bad although I have to assemble under the microscope.

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2018, 08:43:55 pm
content: I use 0603 generally, it's small enough to get nice compact layouts and large enough that I can see the parts and don't have too much trouble with them blowing away if I breathe on them. 0402 is doable but why? Unless you're just showing off or really don't have the room it's just a pain.0805 is a good choice for SMT beginners, 1206 stuff looks gigantic to me.

author: whalphen
author_rank: Regular Contributor
timestamp: January 27, 2018, 05:20:42 am
content: Started using 0805. Still use that for test circuits where I'll be replacing parts and sticking probes and soldering in test wires while tweaking the design. Switched to 0603 for everything else. I work under a lighted magnifier lens. Use the microscope for checking results. It's best when I work early in the day and avoid coffee. (According to the chart above, I should be using 1206).

author: JohnPen
author_rank: Regular Contributor
timestamp: January 27, 2018, 11:49:20 am
content: Great despite successfully using 0805, albeit with a magnifier, I have been consigned to 3 watt resistors!!

author: lapm
author_rank: Frequent Contributor
timestamp: January 27, 2018, 12:02:10 pm
content: Personally i can go 0603 with hand solder pads with some magnification and not struggle. Im 43 and need reading glasses now days.

author: james_s
author_rank: Super Contributor
timestamp: January 27, 2018, 08:33:02 pm
content: Quote from: JohnPen on January 27, 2018, 11:49:20 amAt least you can keep on building stuff with them after you're dead, according to that chart.

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 29, 2018, 12:37:20 am
content: I use 1206 only because when everything started heading that way I thought that I needed to jump on the bandwagon. I bought lots of new kit and purchased kits from China of resisters, capacitors, diodes and other stuff. I had no idea what size to go for either but just picked 1206. Now I have a comprehensive collection of 1206 I'm sort of stuck in that size although I do have quite a few components in other sizes growing.... I think 0805 and 0603?..... not sure. I can quite easily hand solder 1206 and 0805 even with my eye sight. It's a lot about technique and using the right equipment for the task. Lots of flux and different soldering irons for individual components/IC legs/IC leg flowing etc. Watch some youtube videos. If I were starting again I'd probably go with 0805 but any of them are quite small.

author: Wimberleytech
author_rank: Super Contributor
timestamp: January 29, 2018, 02:46:22 am
content: Damn that was brilliant. Sadly approaching wirewounds!!

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 29, 2018, 09:33:24 am
content: Quote from: Wimberleytech on January 29, 2018, 02:46:22 amThat is what binocular microscopes are for.

author: westfw
author_rank: Super Contributor
timestamp: January 29, 2018, 10:03:17 am
content: I bought a bunch of 1206, but have found them annoyingly large on a pcb - about the same area as a vertically mounted resistor... now designing with 0805s.

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 29, 2018, 10:13:27 am
content: Quote from: westfw on January 29, 2018, 10:03:17 amI was looking last night at how much it would cost to buy another SMD parts container or three and get the parts to switch. I might get 0603 parts as well. They are so cheap in kits and it’s handy to have various sizes for repairs anyway. The smallest ones are insanely small though.

author: IconicPCB
author_rank: Super Contributor
timestamp: January 29, 2018, 11:20:42 am
content: 0603 does not give you that much advantage over 0805 in terms of packing density.0603 can be a challenge to productive assembly by handA good engineering compromise would be 0805

author: cowasaki
author_rank: Frequent Contributor
timestamp: January 29, 2018, 11:40:54 am
content: Quote from: IconicPCB on January 29, 2018, 11:20:42 amYes, I agree. The 0805 should be about the best size to use. But for under £10 I can get a kit of 0603 for repair spares or those boards that you want to make very small :-) I bought a great little case for storing small SMD components and just managed to find a company selling them in multiples. I think another 3-4 should do it :-)

author: schmitt trigger
author_rank: Super Contributor
timestamp: January 29, 2018, 03:26:47 pm
content: I agree with blueskull; one can do some very minute work but is a PAIN in the REAR END!Takes out all the fun of assembling a board.Plus if you have to troubleshoot and re-work it is even tougher still.For me, (in my mid-60s) 0805 and the occasional 0603 are the norm.BTW, back in my teenage days, when I assembled some vacuum-tube circuits, I did use 3, 5 and 10 watt wirewounds. Soldered with a solder gun like these:

author: IconicPCB
author_rank: Super Contributor
timestamp: January 29, 2018, 07:55:46 pm
content: A small secret....Before You get a bunch of 0402s get a heart attack. Seriously.And survive it.You will be prescribed a beta blocker which will help steady the body. No shakes no worries when it comes to soldering grains of sand.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 29, 2018, 08:01:24 pm
content: Quote from: bd139 on January 26, 2018, 10:29:47 amI think this shows a valid trend, though I am in the last category and would recommend 0805. Another limit that is a little soft is around the 0603/0805 boundary it gets really hard to make your own boards. Even with the really cheap board vendors I like making my own since I am a slave to instant gratification.

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2018, 08:13:35 pm
content: I use toner transfer to etch my own boards occasionally. Not so often anymore but I still do it now and then. If I'm not sure it will work, only want one of them, or I want to build one today then I'll etch it myself. Otherwise I send 20 bucks to China and wait a few weeks.

author: ferdieCX
author_rank: Regular Contributor
timestamp: January 29, 2018, 08:21:41 pm
content: Altough I wear glasses since I was 9, I can solder 0805 by hand using a lighted magnifier lens without problems.I prefer to use only passive components and diodes in SMD. According to the list, I should be using 1206.

author: Kremmen
author_rank: Super Contributor
timestamp: January 29, 2018, 08:44:38 pm
content: I am in the official 3W category but in practice 0201 is no big deal. Did some just now with no issues. Actually, the biggest obstacle is the tweezers. Mine work nicely down to 0603 but for 0201 i really need something sharper.IconicPCB has a good hintWhile my ticker is doing all right so far, i do have a bit of blood pressure and as part of the medication for that i take beta blockers. Hands are steady as bedrockNo problem whatsoever to position the miniscule grains.That said i do prefer 0603 and when needed, one size up and down.

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2018, 09:41:58 pm
content: My problem with stuff smaller than 0603 is not so much working with them but keeping track of the parts. It's very easy to breath too hard and blow them around the board, or try to pick one up and have it shoot out of the tweezers never to be seen again.

author: nanofrog
author_rank: Super Contributor
timestamp: February 06, 2018, 02:40:37 pm
content: Quote from: blueskull on January 29, 2018, 10:56:44 pmFWIW, liquid or paste/gel flux will do the same thing IME. Fortunately, rinsing tweezers frequently can minimize or even avoid this issue.

author: jgalak
author_rank: Regular Contributor
timestamp: February 06, 2018, 02:51:42 pm
content: Thanks everyone. I ended up standardizing on 0805 and bought some assortment kits (resistors, capacitors, inductors). I'll get other sizes as/when necessary.

author: phil from seattle
author_rank: Super Contributor
timestamp: February 06, 2018, 08:28:06 pm
content: Quote from: bd139 on January 26, 2018, 10:29:47 amFunny. I'm weeks away from 65 and have no problem doing 805s. 603s with a bunch of swearing. But, I'm still building a manual PnP machine...

author: IconicPCB
author_rank: Super Contributor
timestamp: February 06, 2018, 10:51:51 pm
content: 0805 is the new 1206

author: nanofrog
author_rank: Super Contributor
timestamp: February 07, 2018, 06:50:45 pm
content: Small may work most of the time, but there are instances where the smaller packages can't handle the power requirements (i.e. 1/8W for 0805, though 1218 or 2512 can handle 1W).FWIW, I'm also fond of MELF where low inductance, low noise, and high stability are required (up to 1W in a 2.2mm diameter x 5.8mm long cylinder).