I like MELFs for inboard components. Insert the component in a hole and solder to pads on the top and bottom of the board.
Otherwise, stick with 0805 or 1206 as you can hand assemble quite easily - unless you have the coffee jitters. 0603 and 0402 can be hand assembled, but tends to be a very unpleasant task.
-- Mark
Spehro Pefhany skrev:
absolutely, theres just too many variables; distance between eyes, strenght for each eye, etc...
I wear glasses (-3.5 or theres about) and I've tried to buy a pair of ultra cheap one size fits all just to have and extra pair and they are just about useless
-Lasse
Hello Lasse,
They are ok if the eyes just age normally. I can work just fine with the cheap ones and so does my wife. And our neighbors. Of course, if one eye develops worse than the other that's a different story. Then I'd get prescription glasses as well.
BTW a camera-TV setup is great for SMT but only for folks who can get used to looking into a different direction than where the work area is.
Regards, Joerg
When I worked for a while at one of the major computer manufacturers in the desktop systems engineering department I learned to solder SMT stuff rather well when reworking prototype motherboards. I could hand solder 0402 caps and resistors without much trouble. We did have a binocular microscope and fiber optic light and a good soldering iron though.
It looks really weird in the microscope when you bring the solder into view and it is a "giant" metal rod twice the diameter of the SMT part. Yup, I used plain old fine roll solder. Oh, and if something possesed me to put a drop of liquid flux on the part it looked like a big flood on the PCB. :-)
I got a pair of drugstore bifocals once, and I think the bi-parts were misaligned with my lines of sight - I got terrible eyestrain headaches after about 15 minutes. Now I have a 1.75 or so for the computer and a
2.0 for the crossword puzzle. I was kind of bothered when the other day I happened to look at my TV, which is at the foot of my bed, with my computer glasses, and it was crystal-clear. Damn! I don't want my eyes to get even lazier! )-;Cheers! Rich
You made me look. My solder is 0.020", so I'm all set unless I start using 0201's. Now I have a better idea of how SMALL those things are, too.
Here's my setup: Optivisor with 3.5x lens[1], Metcal STTC-043 tip (0.020" conical), and a Panavise model 333 board holder. Oh, and pointy-sharp tweezers. I've only gone down to 0805 so far, but that didn't seem that small.
[1]
He just said that he passed 40, but not how many miles back :-)
-- James T. White
(lol)
It's more the repeated blows to the head...the Krazy Glue helps keep the loose bits from falling off and inconveniencing passers-by.
I still want to see the pictures of that snap rectifier gizmo. Could make a very cute Pockels cell driver.
Cheers,
Phil Hobbs
I posted some pics of the mechanical assembly to a.b.s.e. If you like, I can privately send you schematics and stuff, and maybe even reveal the secret semiconductor we discovered. My original application, ripping atoms off samples in a 3d atom probe, has been replaced by femtosecond lasers. Oh well, I did get some shares of stock, which I am confident will buy me a bicycle in my retirement.
John
Being replaced by a fs laser isn't so bad...could have been a computer. ;)
Since I work for the Sirius Cybernetics Corporation, getting stuff like that is a little dicey for me, much as I appreciate the offer. Maybe you and I and perhaps one or two other people should write a book on circuits specifically for instruments. There's a _lot_ of cool tricks that ought to be preserved and transmitted, and not a lot of appropriate recipients graduating at the moment, more's the pity.
That way you'd at least get some useful advertising in exchange for all the trade secrets. Not that there are that many people who'd even be able to _build_ a circuit like that, even from a book, but we must live by hope.
(Maybe we can needle Jim T enough to get him off his duff with his book, which would be another good deed.)
Cheers,
Phil Hobbs
Don't worry Rich, the lenses won't make your eyes lazy.
General reading glasses' considerations:
They may bug you if the lenses' centers aren't spaced the same as your eyes are when converged on your work. If the lens is off-center with your pupil, prismatic distortion results, which displaces objects laterally from the position expected/predicted by the focusing effort now needed to focus on them. (The apparent displacement is also likely different for each eye.) Vertical displacement is disorienting, even nauseating.
The result is that your extra-ocular muscles clash from the conflicting cues--e.g. simultaneously trying to _converge_ to match the focusing effort, and _diverge_ to line up the images from the two eyes. Fighting each other is tiring, producing a headache ("eyestrain").
These difficulties can be avoided or fixed by 1) just practicing and getting used to the lenses, if the adjustment isn't too severe, 2) using weaker lenses and longer working distances, 3) getting lenses with the correct spacing (IP / "interpupillary distance"), or 4) using an optical aid with built-in prismatic correction, like the OptiVisor-style head-mounted magnifier (very nice, and not expensive). The latter, ideally, allows *you* to look straight ahead and focus at 'infinity' while the device focuses and redirects your line-of-sight to the workpiece, thus avoiding any strain at all.
The distortions and problems increase rapidly with stronger lenses, but, being ideally myopic, t'ain't a problem for me--I can usually get by with no lenses at all :-\\
If you're pre-presbyopic, e.g.
Sounds like fun. I'm in.
The advertising doesn't matter, but maybe we can peel off a few of Win's groupies.
Nah, only liberal weenies do stuff that's good for humanity.
John
Terrific. You write and I'll direct. ;) Let's think about some topics and exchange them.
BTW, all, please chime in with suggestions for things to include. No more than 20% pet peeves, please. (Well, maybe 60%--this is s.e.d, after all.)
Nonononono. Might catch the never-get-overs. Besides, they're mostly male and probably poorly groomed.
An excellent start.
Cheers,
Phil Hobbs
Because, like pens and pencils, I don't buy good ones because I lose them. I don't use them often enough to keep track of 'em and learned long ago the only way I'd have such things when I needed them was to saturate the area, so I'd have one whenever I needed one. I can't affort do saturate the area with Franklins. I *know* where they are, and they don't break when I sit on them.
I talked to an optometrist a while back. She even recommended the cheapies for occasional use, with weaker ones for slightly longer viewing.
-- Keith
I like being myopic. One of these years soon I think I'll get some new lenses, and I'm going to make sure the doctor leaves me this way. Being fixed-focused at infinity sounds like a real nuisance in my business.
John
[....]
On doing 0402s.
You need non-magnetic tweezers and good eyes to do 0402s. The other thing to have is a bunch of extras of each part. If you drop one its gone even if you drop it onto the PCB.
After you finish, turn the PCB upside down to let the lost parts fall off.
-- -- kensmith@rahul.net forging knowledge
-- -- kensmith@rahul.net forging knowledge
And totally clean tweezers, too. A bit of flux or even moist will make the part stick to the tweezers after you've released them.
Can be frustrating.
-- Siol ------------------------------------------------ Rather than a heartless beep Or a rude error message, See these simple words: "File not found."
I've got one myopic eye and one presbyopic eye. Strange, but it lets me read (and see smd parts) and yet also read street signs at a distance, both without glasses. It was annoying earlier in life to be basically blind in one eye for distances greater than 1m, particularly for sports in which stereo vision comes in handy, but has turned out to be quite useful.
-- Regards, Bob Monsen "I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection" -- Charles Darwin
Right - I'm not especially near-sighted, but enough so I can
*read* SMD markings that my barely-myopic s.o. can't even see!Not to worry...the doc can't change your eyes' optics, the source of your myopia, and can set your glasses to any working distance you specify.
(Lawfully, (s)he must, however, insist that you have at least one set of specs yielding 20/40 acuity (~=resolution) for driving, or caution you not to.)
Best, James
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