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Soldering Surface Mount Components
6

Soldering Surface Mount Components

Soldering Surface Mount Components

(OP)
I know most boards are now put together by robot but is there an elegant way to solder surface mount components by hand?
Special solder or flux?

I'm just referring to chips with a low connection count, typical 3 maximum of 8

Thanks
Roy

RE: Soldering Surface Mount Components

You need some sort of reflow solder and a reflow oven. Robots, or more precisely, pick&place machines, only place the chips on the board that already has solder paste on it. The boards then go through a reflow furnace, which is what actually does the soldering. People have gotten by with a modified IR oven, but you still need the solder paste.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Soldering Surface Mount Components

SMT can be assembled and soldered by hand, but depending upon the component size and the pitch of the IC leads it can require a bit of experience. Good soldering iron and fine tips are a must. A hand-held hot-air pencil is handy. I've worked with contract manufacturers that had skilled assemblers that would do, by hand, a dozen boards with 100 components each in just a few hours as a prototype run ahead of a formal pick-n-place program and solder stencil being made.

Lacking that, well, I have ways I do it that work with experience. A blunt tip, fresh de-solder wick, and good tweezers. Tack an IC down by one lead. Use tweezers to align as you re-heat the lead. Tack the corner pins. Have a go at the middle pins. Then use the de-solder wick to remove all of your mistakes taking care to only remove the majority of the solder with the wick.

RE: Soldering Surface Mount Components

I regularly hand solder SMT components down to 0201, but I need to use a microscope. No special solder other than eutectic and a quality iron with a fine tip. Flux is typically brought out when there's rework to be done, but the initial pass typically doesn't need it.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Soldering Surface Mount Components

This morning I had to hand solder two 12LGAs. That's 12 pins underneath a 2mm square package! 0.009" traces on 0.020" centers.

Was a royal pain.


Roy, I'll solder them for you if it gets to be too big a hassle.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

These were not accessible, but I hand soldered them since paste and a high-end hot-air gun just made it hard to find the 12LGAs over and over.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

Unless it's for power, 98% of the traces I work with are 3-4mils... try tacking a wire to THAT for debug purposes. Spools of thin magnet wire abound around here. Fixing a 4mil via with an annular ring <11mils is also a fun day. Thank God I spend most of my time designing and not fixing.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Soldering Surface Mount Components

E-gads! Even a fine tip soldering iron tip probably looks like a barn door held up to those traces.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

I don't have the most steady of hands, but our brain does an amazing job with feedback. If someone other than me were to look at my hands under the microscope, I have no doubt they would be wiggling in/out of the field of view at a relatively fast rate... but once I'm looking at them, the visual feedback reduces those jitters to a scale similar to that when seen only with the naked eye. In essence, most can work under the microscope on tiny objects with no more trouble than without one on similarly-scaled larger objects.

I just looked... when zoomed in fully using the scope on my desk, four quad-resistor packs (0804) sitting end to end barely fit the field of view. The scopes on the soldering benches are even high magnification. Our soldering tips are pretty fine, so there's still plenty of viewing area, even with an 0201.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Soldering Surface Mount Components

A good iron with a chisel tip, thin solder, good tweezers and good wick can go a long way. Concave tips can be good too for wipe soldering leads on an IC.

If I have a lot to do or any pads that aren't accessible I'll get a stencil from Polulu for about $50, squeegee some solder paste through it, then place components and put it in toaster oven.

Cheap stencils:
https://www.pololu.com/product/446

Oven that doesn't require mods:
http://www.bestbuy.ca/en-CA/product/panasonic-pana...

RE: Soldering Surface Mount Components

pololu for stencils, huh?

Try this place. I've ordered one from here at 3am and had it shipped at 5am. Blew my mind.

ohararp stencils
$25 - Highly recommended.

I get the Kapton ones. They last quite well. I've gotten Kapton ones to do a first few protos and ended up not needing any revs, and gone on to make a couple hundred boards with them.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

mud, you say that oven doesn't require mods... does it have a programmable temp profile? If so, that would be a dream for a reflow oven. I've often considered picking up an IR oven and making a controller, but other projects always seem to take priority.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Soldering Surface Mount Components

Man Dan.. All the toaster ovens I've used for reflow required substantial modding to get them capable of heating fast enough to get near typical profiles. Usually I have to add insulation on all sides and block holes you could march three roaches shoulder-to-shoulder thru.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

I've come across several decent DIY setups online, generally in the $300 range or so (that includes the oven). Insulation is rule #1. I'm working on a new LED project, and I will likely need something simple like that for quick prototyping. I may just break down and build one using COTS parts.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Soldering Surface Mount Components

Thanks for the recommendation itsmoked. ohararp stencils looks like a good site.

MacGyver, I use an oven similar to the one in the link and change temperature manually about once a minute. A controller and insulation would be a nice addition.

RE: Soldering Surface Mount Components

Thanks M&S. Manual. Yikes.

Dan you can use any old clapped-out toaster oven that is 1400W or so and has top AND bottom elements. You will want one with a single shelf that slides in and out without any herky-jerky. Throw away the rest of the shelves.

You will likely need to hack it to remove all signs of temp control. Wire it up so you plug it in and it heats up.

Then use something like this stuff:
McMaster Carr Semi-rigid insulation
to insulate the top, sides and back. Often the bottom doesn't matter much.

Grab a ramp-and-soak temp controller or use an Automation Direct cheap CLICK PLC with a TC module and a relay of some sort. Cycles are so mellow you can use a mech relay without issues.

You want a small gauge TC too. I use these:
24AWG or smaller Type J or K

You place the TC directly on one of the boards you're reflowing. You put it on a bare pad somewhere so it is measuring the actual board pad temps. You need it coming in from above so you can slide in the shelf with the boards then lift and set down, very much like a phonograph needle, the TC onto the selected board. You want the TC stiff enough to stay but not wrestling-match stiff so when you let go it sweeps across your parts going to where it wants to be.. (Been there.)

Then setting the control profile you typically have some initial long PWM to get the board up to about 80/90C and then dwell there for moisture reduction. Then more aggressive PWMing to get to about 80% of the melting point and once settled there you do a full-on bust-a-gut sprint up to the peak temp in about 30 seconds. (that's where you need the power and low heat loss). Then power down and let the whole thing cool down to just below the freezing point then you need to open the oven door about 30% to get the temp down pretty quick or you roast all your parts and the boards lose their flatness.

A PLC might make the most sense since no normal Ramp-and-soak deals well with the second based times and the fact that the oven will be fire-walled often to make the schedules. You will end up setting the Ramp and Soak to ridiculous values that will be changed before ever reaching them just to get close to the desired profile. A PLC could also open the door for you in a timely manner.. I've not noticed and 'browned' things. A PLC also could BEEP you that the cycle is over since you do NOT want this thing out-gassing in the same room you're in.

Oh OH You definitely want an oven with a see thru glass window as you'll need to watch the process frequently to troubleshoot and tweak.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

I considered that unit but delivery is fairly abysmal so I re-rolled my own.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

One thing that is somewhat unclear is support for different profiles. A comment or two I read suggested you had to reprogram the entire thing if you want a new profile, and those who used multiple profiles left it connected to a computer. With all of that power/storage, you would think they could have multiple profiles stored.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Soldering Surface Mount Components


Putting a servo in the hot air stream of the opened door seems wrong to me.

RE: Soldering Surface Mount Components

I believe that's correct Dan. On the other hand I don't see any point to different profiles. If you get one that works that's the only one you'll use. So unless you're doing completely different processes like actually drying parts or sintering some strange design you probably do not need multiple programs.

btrue; good point but there is really so little thermal mass in a toaster oven that the servo is 'toasted' for only about 2 minutes.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

I would imagine most of that hot air passes by the servo with minimal transference of heat... now if the servo was placed IN the oven, that might be a horse of another color...

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Soldering Surface Mount Components

I use a soldering gun for soldering SMBs. soldering SMb really require skill to do it. We can't just do it by having soldering experience with discrete components

RE: Soldering Surface Mount Components

I gave ohararp a try with my latest stencil order. Pololu is much better. They are faster, similar price when shipping to Canada, have better shipping options and better time/price options.

RE: Soldering Surface Mount Components

Feb 14: placed order
Feb 16: received email from ohararp saying it "was" shipped on Feb 17
Feb 20: shipper's tracking info did not say it had been picked up. I emailed ohararp asking for update.
Feb 21: tracking info still doesn't say it's been picked up and still no reply from ohararp.

RE: Soldering Surface Mount Components

Crap. After years of faithful service (as stated) he did the same thing to me the exact same times as a you.

After writing him saying essentially, 'you normally take a few hours to ship, here it is 15 days.. It appears you did the postage but never actually shipped it!'.

His response was abject apology, refunded all charges, did it again (or for the first time), shipped it priority USPS, and I got it two days later - 5 days after I got the boards..

Apparently he does this as moonlighting and he said his day job sent him off elsewhere for a week, (I gathered this was a first).

Sorry for your and (my) bad experiences.
I told him, "This is a big problem not knowing what the delivery is really going to be. Some jobs don't matter but some are critical, and if we could just know what the turnaround was going to be then we could go elsewhere when pressed for time."
I got no response.

I'll give Pololu a try next time.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

Sounds like he should hire someone. Or put a warning on the website. I like that Pololu lets you decide how many days it'll take. My boards usually take less than a week so I usually want fast stencils but it's nice to have the option of waiting a bit to save some money.

RE: Soldering Surface Mount Components

I had access to solder paste at my previous employer. That makes surface mount hand soldering much easier. Unfortunately I haven't found a vendor yet for purchasing small quantities (a tube or two) of solder paste yet.

Z

RE: Soldering Surface Mount Components

(OP)
Wow, lots of replies.
I can see where I would need a toaster oven to assemble a board with many components but my boards are single sided probably have about 10 on a board 1-1/2 square.
I have been soldering the surface mount components with just a regular fine tipped iron, typically LEDs or components with no more than 8 legs.
I tin the circuit board first with just a dab of high quality solder then hold the component in contact and just heat each pad with my iron to melt the solder, sometimes melt a dab of solder close to the component leg for good measure.

Crude I know!













RE: Soldering Surface Mount Components

Zappedagain: There are small syringes of solder paste on digikey.

Roydm: It's best if you just tin 1 pad per component before placing the component. If you only tin one pad then the component can be pushed down to contact the PCB while heating that 1 pad. That was required in avionic communications equipment for a few reasons:

Less chance of losing electrical conductivity when there is a bad solder joint, ex; cracked or cold.

Less chance of contaminant buildup causing short circuit, ex; dust buildup under floating capacitor.

It can reduce the stress on the component and the solder since the component is supported by the PCB instead of by solder.

RE: Soldering Surface Mount Components

Thanks Keith! It's been under my nose the whole time. My previous employer buys it in bulk and has to have it cold-transported and then stored at -40C. They end up throwing about 90% of it away at the expiration date.

Z

RE: Soldering Surface Mount Components

Ah zapped.. I once thought that too. I have since come to a different conclusion.

If you buy the paste I linked you to DKY will automatically ship it next day with an ice pack in an insulated bag. $$$$$$ painful!!!! After using more than ten of those syringes of paste over a couple of years we've found that if we leave the syringes capped and in the insulated bag with the ice pack when not actively using it. It is completely usable for about 3 months. We see no difference at all. After about three months of summer we start to see separation and it doesn't stencil as cleanly.

We simply try to keep its daily temp cycling to a minimum. If we aren't going to use it for a while we toss the bag into the bottom of a loaded (thermal mass) cabinet to keep it as cool as the office can provide in a place with the lowest likely thermal cycles.

We've actually used it out to probably 6 months.

That said I always, in the "checkout instructions", direct DKY to NOT elevate the shipping for the solder paste. The one time they did anyway a call got them to wipe all shipping charges.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

(OP)
Mudandsnow,
Thanks, I will try the one pad method.

The solder paste sounds like a royal pain!

RE: Soldering Surface Mount Components

Seeedstudio prototype pcb assembly service makes soldering easy, there's no need to soder by yourself.

RE: Soldering Surface Mount Components

We were just thinking of that. How's it work there in particular?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Soldering Surface Mount Components

Hi
I soldered smt components before,and alot,they made for prototypes,if you planning to do that for a product you sell at the market,then use robot or furnace for production

And yes it needs very skilled technician, even through hole solder may can't solder smd components

It needs heat gun if you solder blga ic's,and heater with very thin tip " the heater equipped with the heat gun is perfect use" if you sold a chip pins on the board surface the solder to be very thin and good quality,

I hope i helped,regards

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