I am laying plans to start working with SMT for the first time. Would
0805 components be a suitable size for a beginner, or would another size be appropriate?
I have been a sometimes hobbyist for a long time, since the mid 70's when I was a teenager, but until now I have never ventured beyond through hole construction, mostly due to a combination of tooling and a complete lack of dexterity.
I have recently been convinced by someone that SMT has a much wider availability of components and the prices are generally much less than the equivalent THT components. The compactness of SMT construction is also very attractive.
I plan to start with a small hot air station and then move up to a more proper reflow setup if I ever get more ambitious.
My primary concern is the handling of components. The 0805 sized components seem to be very common and I strongly doubt I could ever go below that due to vision and dexterity issues.
However, is 0805 too small for a klutzy beginner? I'm not particularly ambitious at this point, but that could change, depending on my interests and level of success.
With the right equipment I would expect 0805 to be manageable, though obviously that depends on your ability which you are in a better position to assess than me.
Before you layout a PCB maybe you could buy some 0805 resistors and see how well you can handle them? Maybe print some actual size footprints on paper and see if you can place the components? perhaps not very realistic but should give you an idea of what you are getting into without the time and expense of laying out an actual PCB.
Personally I have found component density to be more of an issue than size, e.g replacing an 0402 with plenty of space around it would, for me, be easier than replacing an 0805 in the middle of tightly packed area, especially if it is a small component between two tall capacitors.
I'd suggest 0805 or 1206 to start with. Hot air isn't a slam dunk for assembly because it's easy to blow the components away--paste isn't very sticky. I suggest using an adjustable hotplate from a chem lab (which are cheap on ebay) with a _thick_ aluminum frying pan on top (also cheap).
For protos we use one of those plus a chunk of 1/2-inch aluminum jig plate from McMaster-Carr. You really need the aluminum to spread out the heat, or the board won't reflow uniformly. A thermocouple thermometer is pretty cheap as well, but you need to really squash the sensor against the hot plate, e.g. with a screw or a big binder clip.
Get some good lab glasses. If you were a teenager in the 1970s (as I was) you'll be needing bifocals. My lab glasses are +0.75 (comfortable for a desktop computer) and +2.25 for close work. Your reading correction plus 1.25 or 1.5 diopter is the ticket. I pay about $40 for a pair of those from Zenni Optical. Don't use drugstore ones unless you happen to have the matching interpupillary distance--even a millimetre of error makes a difference.
For small stuff, e.g. checking TSSOP packages for solder bridges, I use an original Mantis microscope ($1400 used) with 4x and 8x lenses. There are a lot of Chinese scopes on eBay for a few hundred bucks new.
Make sure you get a _stereo_ microscope and not just a _binocular_ one. Stereo scopes provide normal stereopsis, i.e. your eyes look at the field from different directions so that you get depth perception. It's cool and useful to be able to look around stuff, and the Mantis is great for that.
Also spend the money for decent stainless-steel tweezers, not the Chinese or (especially) Indian ones. You want pointy ends with not too skinny a taper, one pair straight and one pair curved. You'll use the curved ones the most. Get some alcohol to keep the tweezers clean, because otherwise flux will make them stick to the parts. Another tip is to make adjustable self-closing tweezers: Use a small binder clip sliding up and down the jaws of the tweezers to adjust the closing force. That really helps prevent losing parts when you change your grip on the tweezers.
You'll also need a jig for applying paste. You can get good solder stencils for cheap along with your Chinese PCBs, but you need to surround your board with other bits of board of the same thickness, or the stencil won't lie flat on the board and the paste will go everywhere.
The key is to get the paste right and then apply the parts with tweezers, resting the heel of your hand on the bench so only your small muscles have to coordinate. An adjustable-height chair and a fairly tall workbench (36 inches or so) are a huge help there too.
After that, start saving up for decent test equipment. ;)
Have a great time at it!
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
Way back when I did a "sampler" board to help answer this question, and found that I could do 0603, 0402, and maybe 0201, sized resistors by hand (soldering iron :). The 01005 was a bit too small, even with a microscope.
Project here in case you want to make one yourself:
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I typically use 0603 size, and 0.5mm pitch ICs, with a soldering iron (40 mil chisel). You learn how to design PCBs that are easy to solder parts onto ;-)
0805's are a good size. That's my preferred size for production boards, too.
Hand soldering isn't bad. People use kitchen convection ovens or hot plates, too.
You'll need some magnification, something with some working distance. I love my Mantis, but that may be too expensive for you just now. A desktop immuminated magnifier should be enough, 3x or so maybe.
1206's frightened me once. Now 0603s are fine, but I hate 0402s.
I make prototypes by Demeling copperclad FR4. Works great.
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Try surface mount. It's not bad at all.
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John Larkin Highland Technology, Inc
lunatic fringe electronics
I've seen the breadboarding via islands before, but I really hadn't thought much about dremeling a board for SMT, but that looks like it actually works quite well.
Due to handling issues I'm really starting to think in terms of 1206, at least until I gain some experience with tweezers and small objects. I would like to move to 0805 because I like the extra compactness.
One other thing I've recently discovered by working on some smaller items is that I need a raised work area, and that goes double if I'm going to do surface mount work of any sort. With strong glasses my focal length is just too short otherwise.
I've seen all sorts of articles on hot plates and different ways to customize them for SMT use. I've also seen some projects for converting toaster ovens for reflow use. One of those is probably the route I'll eventually take, $$$ are a strong concern. Most likely a hot plate approach as I think it quite unlikely I'll make more than one or two boards at a time, or week even.
I suppose I'm going to have to start ordering boards, too. I don't think my homebrew boards are going to survive this transition unless I move to photo developing boards.
An awful lot of considerations to move into light SMT work. I underestimated the amount of preparation I'm going to need to start, but I'm starting to really think I can do it AND enjoy it.
I prefer to use (inch) 0805 or larger, but can manage (inch) 0603 without too much invective. The metric coded 0603 parts are much smaller
- 0603 inch is 1608 in metric, and metric 0603 is inch 0201 (don't sneeze.)
That said I've been known to cruise sleazebay for surplus partial reels of 2512, 1210 and 1206 parts (while there are some intermediate sizes between those, they seem to be much less common, though I will search on them as well - 1008 also seems to be uncommon) looking for parts I might make use of at low cost in sizes that are easier to see/handle. Overkill, perhaps, and not as compact as possible, but I'm mostly making stuff on my own, not for production.
I use a soldering iron - Weller WTCPN/TC201 with a long pointy cone, (1/64" radius tip) that I mostly use the side of. I have other tips, but have not changed that one since I first started messing with surface mount. Many folks do think you need a fat chisel tip, but I find the versatility of the long point (if you grok using the side as well as the tip) is better for me.
I (now) have a rework station but only use it for desoldering, usually - messing about with applying paste has not found much appeal as yet. While there are supposed to be horrors from assembling SMT with a normal iron, I have yet to run into them personally, and thus weight the horror stories kinda low.
I got a set of "my normal prescription with 5 diopters added to it" glasses - that, and a lot of light, are helpful, though a fancier setup (microscope or the like) with a longer working distance might be nicer.
+1 puts your "infinity" at a meter, +2 is half a meter, +3 is 1/3 of a meter, +4 is 1/4 of a meter, and +5 is 1/5 of a meter, or roughly 8 inches from your eyeballs. Some folks use a USB microscope/camera and a monitor (the larger the better) as a different means of magnifying the work area with plenty of eye relief.
The parts I hate are the multi-pin packages with insanely small spacing. SOP seems quite comfortable by comparison with vast 1.27mm pin spacing. SSOPs and tighter tend to make me feel either grumpy or hopeless. I probably would hate BGAs if I was inclined to use any, but so far I've been spared that joy. I'll happily use DIPs when available.
Solder surface tension plays a big role in production assembly and soldermask is very important as a result, especially for the tight spacings - if you have the right amount of solder, a chip that's more or less in the right place will self-center when the solder melts. A hot tweezer gives you the fancy way to do this on a two-terminal device (or remove it easily) but you can often heat both ends with a single iron if you move quickly. Manageable packages are hold in place, tack a pin on one corner, tack a pin on the other corner, correct if needed, and then solder the rest of the pins. Unmanageable packages you have to solder them all at once and try to avoid bridges from too much solder.
--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.
You may also find it easier to find parts in 0805, depending on the part.
There are other methods, as I mentioned in my first reply (right about as you were writing this, I'd guess, so you wouldn't have seen them) - the camera-scope and screen is probably the most affordable of them, unless you find a handy source for cheap used microscopes and find a suitable one among those, or happen to have one. Trick being you need a scope that gives you room to work - dissection scopes are often as suitable (optically) as those sold as "assembly scopes."
Yes, cutting islands in copperclad is a very handy 1-off at-home technique with SMT. For some applications (not all, particularly high frequency ones) generic adapter boards to get back to DIP pin spacing are also handy/useful.
--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
From time to time I have wondered if a very narrow tip could be used for the larger SMT items. I've seen tutorials on how to do the SOP and SSOP packages with larger tips.. It doesn't look easy at all, but doable. I can't even wrap my head around trying one of the small packages, though. I have a decent Hakko 888D that seems to do everything I need. I already have a similar time to the one you described, maybe I should get it out of the package and use it! The only reason I hadn't is because I'm still doing THT work, but as you said, using the side as well may let me use it for normal work too.
I'm continually improving my technique with soldering, but I have an essential tremor that makes fine work difficult without having to brace the iron against something. I may be able to manage the 1206 packages with some work, but anything smaller I just don't think is within my abilities.
I've just ordered a set of bifocals with a higher diopter, I hope that will let me ditch the magnifier headband I have been using. It works well, but it throws shade over my work area if I'm not careful and lean in too close.
The number one problem I see in students (of all ages) learning to solder is getting them to actually (they've had the noises go in their ear and out the other, rather than hearing it, usually) relax and rest the tip of the iron on the work. Your hand can jiggle all over the place (or as JL says, you can arrange your workspace with some sort of wrist rest to reduce that motion) if the iron tip is on the place it needs to be.
As training, solder without any "grip" on the iron at all - let the handle lay on your flat, open palm - most folks start out with a death grip on it, and if I do that, I can't hold the tip still, either. I don't usually solder like that, but I have a very relaxed grip on it.
Even on SMT, I'm often using the side - on a well-designed pad, there's often more room to apply heat to the pad (and let heat and solder flow to the pin) than there is to apply heat to the pin. Given a desire to get in, get done, and get out quickly, the most effective (thus, largest area) transfer of heat is beneficial.
Under "modern approaches to work lighting" there are some stunningly bright, small, LED flashlights (US = UK torches), and you can strap one or two to your glasses or magnifier frame. (or purchase something where someone in China has done that for you, but usually the flashlights are inferior in that case.)
--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.
I suggest you drop $25 on a Swiss pair and see. ;)
Mainly the poorly-ground points that aren't reliably parallel, so that parts tend to squirt out like the way kids shoot cherry pits from their thumb and fist. Also they tend to be magnetic stainless, which is a pain with nickel end caps.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
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