SMD beginner -- solder paste

People seem to prefer toaster ovens. I've seen web sites where people do BGAs in them.

It's not bad for modest jobs.

You can get a laser-cut mylar stencil for something like $25 these days. I saw one ad from a board house that includes one free with any batch of boards.

Same-day seems to work. Something like 4 hours is best. Depends on the flux.

John

Hop over to Sparkfun and take a look at their tutorials on this. They have some hints that may come in handy.

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Rich Webb     Norfolk, VA

Yeah, I saw the Sparkfun stuff.

John, you mentioned flux -- hate to sound like a moron but do you coat the board with some sort of flux BEFORE you apply the solder paste?

Only 4 hours work time? Not good. So you should reflow the solder the same day you're saying?

And the 256? Best stuff to use?

Sounds like it -- easy cleanup.

I'm about ready to trash all my leaded components and buy SMD.

The flux is mixed in with the paste. That's why it has the consistency of glue. It's basically tiny solder particles in flux. This makes it sticky, which is usually useful - SMT components tend to stay on the PCB (surface tension / stickiness) until you melt the solder at which point they are essentially welded on. I've seen PCB's turned upside down and the (as yet unmelted) solder paste kept the components on the board.

I've normally heard people say "use a tub of paste within 24 hours of opening". I'm not sure if it's because the solder oxidises or the flux loses solvents.

SMD is surprisingly easy to work with if you have a steady hand, and start with the larger devices like 1206. I use some x7 stereo glasses to help me see close up.

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Nemo

Thanks Nemo -- going to start stocking up on parts (1206 especially).

Will put some stereo glasses on my list as well -- any suggestions?

What paste do you like? Do you stencil or apply with syringe?

I'd like a popular paste and be able to buy at a size where it won't go bad.

250 -- 500 G?

An Optivisor 5 diopter (2.5x) is the usual recommendation for working. If you want or need more magnification there are higher diopter lenses available but you sacrifice some working distance. Not too expensive (about $30) but if you are tempted by the cheaper ones that are out there, be aware you'll probably be getting cast acrylic lenses in place of optical glass.

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Rich Webb     Norfolk, VA

something like this ?

I do have trouble with up close vision anyway -- wear reading glasses.

-- so 2.5x is fine?

actually, probably this one ?--

It's glass and for some reason, cheaper?

Amazon's pricing can be hard to understand. ;-)

I'd trust the acrylic lenses from OptiVisor. Where people get into trouble are the $4.95 look-alikes in the bargain-bin at the hardware store -- some probably really are bargains but many have density "waves" in the plastic with resulting distortions. The OptiVisor optical-grade acrylics might be lighter in weight than the glass, so it may come down to personal preference.

It's worth also getting the add-on loupe.

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Rich Webb     Norfolk, VA

Not really, some of the offerings are from Amazon "associates", so you have to shop carefully for the best deal.

I've had my OptiVisor for at least 30 years, still in regular use. My wife even uses it for fine needlework ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Jim Thompson wrote in news: snipped-for-privacy@4ax.com:

I use a clip-on binocular magnifier,it's plastic,2.25X magnification,focal length of 8-10". It works good,and allows me side vision and I don't need to flip it up out of the way. It only cost $5 on Ebay. They come in different magnifications.The stronger ones mean you have to get closer to the workpiece.

I also have a visor-style magnifier made by General,bought it at HD,but it was clunky to use,needing to be flipped up to return to normal vision.

--
Jim Yanik
jyanik
at
localnet
dot com

Do you answer the door on Halloween while wearing it?

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Greed is the root of all eBay.

Naaaah! The flashlight under the chin gimmick is quite adequate ;-) ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Just don't do it after 'drag' racing. You'll scare them to death. ;-)

--
Greed is the root of all eBay.

Come on, you know you don't need the flashlight. ;-)

My young daughters (40 years or so ago), learning new words they didn't yet quite comprehend, used to refer to me as "extinguished" ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Smart girl! ;-)

She had you confused with Jeorge, and left off the word 'FIRE'. ;-)

--
Greed is the root of all eBay.

I have several pair of disposable "reading glasses" with temple illuminators (when batteries die, its a good time to discard them! :> ). I prefer these to my optivisor as the latter tends to catch fumes up under the "bill" (not a problem with the glasses).

As you said, higher diopter forces you to hold the work closer. A 1.5D is usually a good compromise for me (2.0D tends to feel crowded).

The problem with the glasses is you have to learn to wear them "granny style" (tip of nose) else when you look *up*, the world spins! At least the optivisor can be readily flipped up and out of the way (though it feels and looks dorky -- though illuminated reading glasses are dorky, too! :> )

If I am doing any real work, I prefer my stereoscope as I can set the magnification (7-30X) I want, leave the piece under it and pull my head away whenever I need to consult documentation

*without* having to deal with glasses or the visor. Having to free up a hand to move glasses or flip up visor is just a PITA.

Unfortunately, it is rather large and bulky. Only suited to those cases where you can bring the work to the workstation (and not the other way around).