Soldering SMT Components

It's easy to solder most surface-mount parts by hand; just practise a bit.

And it's OK to use rosin-flux leaded (63/37) solder, even to solder lead-free parts. Better in fact.

As far as I know, nothing prevents whiskers, not even coatings. Except lead, of course.

John

[Sure is handy to have somebody else pre-filter the googlegroupers that are whitelist-able. Thanks, John! ;-) ]

And for the OP ... there are scads of how-to pages out there. The tutorials at (scroll way down for the surface mount stuff) have pretty good info for the enthusiast/hobbyist, including video clips.

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Rich Webb     Norfolk, VA

There are even people doing BGAs in toaster ovens.

We used to send our BGAs out to assembly houses, out of pure fear. Then we tried some in-house. We bought a bunch of inspection and rework gear, which we've mostly never used. Our yield so far is

100.0%.

John

What are you using for an oven?

Are you doing 1 or 2, or small batches like 10 or 20?

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I do surface mount assembly with an ordinary Metcal soldering station. I solder Rs and Cs using a small tip cartridge, and fine-pitch devices by drag-soldering with a mini-hoof cartridge.

Leon

Lead free toast, yum

martin

We have an Essemtec (Swiss) reflow oven, which has pretty good profile control. Batches are typically in the 5-10 range, but we sometimes do one or two protos. We have two Essemtec semi-auto p&p machines, so we really can't load a lot of boards in one day. If we get 50 or so, we'll often send them out to a board stuffer house.

John

Recently I posted to a similar thread:

Dimiter

------------------------------------------------------ Dimiter Popoff Transgalactic Instruments

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Metcal, ordinary? Those are the Mercedes-Benzes of solder stations. They are great but the ones I have used at clients were well north of $500.

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Regards, Joerg

http://www.analogconsultants.com/

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Tin whiskers do not grow from lead-free solders, where did you get that crazy idea? Tin whiskers grow from tin plating and only tin plating.

Lead does not prevent tin whiskers any better than any other means of pinning dislocations in tin, such as any of the alloys used as lead-free solders. No one has ever been able to show me believable evidence that so much as a single tin whisker has ever grown from any currently used lead-free solder alloy, and I doubt they ever will, it is simply not a valid reliability issue.

Complaining about problems with lead-free these days makes as much sense as still worrying about the Y2K bug. Forget about it, the conversion is over and done with for all but the smallest manufacturers, and reliability of the assembled circuits has continued to increase.

Lead is in fact not a very good means of preventing tin whiskers, due to well know problem of poor fatigue strength of tin-lead solders. All high-rel applications which need to withstand shock and vibration will be converting to lead-free; not the lowest cost SAC alloy but high performance lead-free alloys which are now being qualified (a lengthy process) but which clearly blow the socks off tin-lead in strength, ductility, shock resistance and fatigue life; all of the properties important for reliability except processing temperature are greatly improved and the processing temp for these alloys is only slightly higher than tin-lead. See for instance:

The down sides to lead-free are slightly higher cost and far higher complexity of specifying the optimum alloy, flux, and processing parameters, plus a need for tighter process controls.

This is not a reasonable forum for learning about soldering or PCB assembly in general, the issue is too complex and almost no one here is interested in it enough to have read up on the subject. Read the trade rags like SMT and Printed Circuit Design and Fab for a decent introduction to the subject.

The easiest way I've found to do SMT is drop a little bit of solder on the pads, then lay part on top and touch iron to the lead from the part and let it melt the solder.

I imagine with lead free this might not work so well but it works fine with rosin core.

I've given up on these posh tips for fine-pitch. My ancient Weller with a 2mm tip works as well once you've got the knack. Occasional cleanup with solderwick afterwards, but the posh ones sometimes need that too.

Metcal has a cheap iron for about $180 (PS-800). Tips are about $8 or $9. I use the 650 deg 0.016" tips for most of my work (0402 size and

0.5mm pitch parts). I like the small footprint of the station. has pretty good pricing.

For soldering those pesky ICs with the heat slug under the part, I use a waffle iron. The waffle iron I have has dual purpose plates, one side for making waffles, the other side is flat for, I'm guessing, grilled cheese and soldering.

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Mark

I got one of the older STSS power units cheap on Ebay. It can be used with the current MX-500 handpieces and cartridges.

The whole system cost me about 120 GBP, less than a new Weller system.

Leon

Thanks! That seems like a good place to buy tools. They've got good pricing on Hakko as well. So I bookmarked them. But I can't use a fixed temperature iron here in the lab because as a consultant I have to deal with widely different technology.

My wife would not approve and I might not get waffles anymore ;-)

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Regards, Joerg

http://www.analogconsultants.com/

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It's weird, I looked and indeed, Farnell charges you guys an arm and a leg. It was the same when I bought a new scope. Came from Farnell-UK (with a UK power cord!) yet cost me a whole lot less via Newark. Same for irons:

$127 for a WES51 station is a darn good deal. Maybe it's the RoHS compliance why they have you guys over the barrel.

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Regards, Joerg

http://www.analogconsultants.com/

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You Americans(?) are so lucky... here in the UK we have none of these "toaster ovens" or "waffle irons" which seem to be so essential for the serious constructor.

I mean, how can we be expected to do serious electronics without the correct tools for the job?

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John Devereux

I bought a small toaster oven from Argos for 20 GBP.

Leon

The temperature is determined by the cartridge, you just need different cartridges for different jobs. No calibration is required, which is a big advantage in a production environment.

Leon