SMD Soldering - do I need Hot Air Soldering Station?

Hello! I have to resolder some SMD resistors on my step-down transformer. Do I really need Hot Air station. Is there any method to resolder that using normal soldering iron?

Best regards, Overkiller

A hot-air rework station will help, however…

For small surface mount components its not hard to desolder the whole device
since they are smaller than the soldering iron bit - just tin the iron generously.

Its resoldering that’s tricky, but practice on some scrap board until you are
confident. Temperature control is important - too hot and you risk delaminating
the board after several attempts, and this is true for hot air too.

For removing SMD resistors and caps, I would suggest to use two soldering irons and simply pick up the part with each iron touching then lifting each end. From my experience, hot air blower is useful to remove smd ICs, but not for removing passive parts i.e it can blow unintended parts off the pcb in the directed area.

When soldering smd Rs and Cs, it is useful to have use a tweezer to hold the part in place and melt a drip of solder on the tip of the iron then solder one end first. Once one end is soldered and the part is fixed in place, the other end is easy.

overkiller: Is there any method to resolder that using normal soldering iron?

I've never worked with SMT parts, but from what I have gathered, the key things in order to use a "normal" soldering iron are:

  1. Temperature control
  2. A fine tip
  3. Flux - lots of flux (more for fine-pitch ICs than for discrete components, though)

I have an old Hakko soldering iron (909 or 911, can't remember) that has extremely fine soldering iron tips for SMT work, plus temperature control - so you want something like that; if you find yourself doing a lot of rework, hot-air works well for removal and reflow, but not so much for discrete components as the hot air will just blow them off (unless you anchor them in place on the pads with a drop of super-glue or something).

As for flux - it's important mainly for ICs with a lot of pins; you need liquid flux for this, and you basically want to flood the pins with flux, then run your solder over the pins (and you may still need to do some cleanup afterward with braid).

But again - this is just what I have read (and watched videos of) - I don't have any experience (haven't had the need yet). I would also second the recommendation of practising on something else first to get the hang of things.

You do not need a hot air station but they are very handy. I picked one up on eBay for $65. I use it frequently. http://www.ebay.com/itm/8508D-Hot-Air-Gun-Rework-Soldering-Repair-Station-SMD-ESD-PLCC-BGA-LED-Nozzles-/301011239971?pt=LH_DefaultDomain_0&hash=item4615ab0423

If this is more than a one shot operation, I would get the hot air gun.

Joe

Thank You all for anwsers! :)

Will rosin will strong enought? Or I need something stronger, something like soldering paste? And last thing - my soldering iron is 40W and does not have temperature control... I know that will be handy but for now I cannot buy new soldering iron. Should I try to solder without temperature control? Or wait until I'd get new iron?

If your soldering iron doesn't have temperature control, I would wait until you get a new one rather than taking the chance, having it be too hot and end up damaging the board. Better safe than sorry in my opinion. Also, practice a lot when you get the new station just to make sure you have the hang of it.

There are some cheaper temperature controlled stations out there (don't know what you budget is) but I have this one and I really like it. It's under $100, has great temperature control and from my research they are very durable so it will have a good long life. http://www.gotopac.com/Hakko_FX_888_Soldering_Station_s/3893.htm

Hope that helps! :D

Nice soldering station!

For now i’m looking for one. Could You help me choosing one?
I saw these(sorry for non-english shop):
http://sklep.avt.pl/cyfrowa-stacja-lutownicza-80w.html - SP-80D
http://sklep.avt.pl/stacja-lutownicza-zd-931-48w-24v-vtssc40.html - ZD-391

Are these good? Or should I look for something else? Or the one what kt245 proposed?

Temperature control is essential.

Make sure that you aren't buying an iron with variable -power- control.

Liquid flux will help, rosin flux is fine. Don't use plumber's soldering paste because it is usually an acid flux and may damage the board and/or parts.

Unless you get a "no clean" variety of liquid flux, you should clean the board off afterwards.

A really fine tip is actually a bit of a handicap when soldering surface mount, because it doesn't transfer heat very well from the heater to the tip, the round end doesn't transfer heat as well to the PCB and component, and because the solder tends to pull away from the tip. Unless you are soldering 0603 and smaller parts, a 1/16 inch screwdriver tip works well.

I have a dual soldering iron thing in sort of a tweezer configuration. If you get a cheap one, it may or may not work, and the expensive ones are over $200 USD. And they are only good for one thing, removing chip resistors and capacitors. So if you aren't trying to save the part that you are removing, a large tip with a lot of solder may be just what you need. Or two soldering irons. Be generous with the flux.

http://www.mcmelectronics.com/product/21-8230

polymorph,

I'm not going to rescue that part (it is an capacitor)and i want to replace it with the same part. I'll try using screwdriver trick. You said that Liquid flux will help. I can create flux dissolving rosin in spirit, will be that enough? I'm usually adding rosin until it stops dissolving.

If you're just removing a few parts you should consider ChipQuik. It's like a solder with a much lower melting point; it mixes with the existing solder and keeps everything molten longer so it's easier to remove.

"Screwdriver trick"? If you are referring to something I said, then I must clarify.

By "screwdriver tip", I meant a soldering iron tip that has two flat sides, similar to a screwdriver:

And not a conical tip, where there are no flat sides:

Nothing involving an actual screwdriver.

If you use a very large, flat tip that is large enough to bridge both sides of the chip capacitor, then you can flood it with plenty of solder and take it off that way.

Nothing involving an actual screwdriver. I apologize for any misunderstandings.

A lot of rosin fluxes, as I understand it, are just pine resin, aka colophony, dissolved in alcohol. I -think- usually ethanol (or denatured alcohol, which is ethanol with other things added to poison it).

Use the flux in rosin cored solder there is no need to use anything else.

Solder quickly and try to use as little solder as possible.

I was addressing the part about unsoldering.

When soldering, follow Grumpy_Mike's advice.

I saw this cool video on you tube, this guy makes it look so simple.

http://www.youtube.com/watch?v=SDr1khlbvPY

sensai: I saw this cool video on you tube, this guy makes it look so simple.

It's not hard, but don't follow this guy's example. You don't want to be running your tip on top of the legs like that; you should be at the corner between the legs and board so you get heat on the pads. What he did here is get all the solder on the legs and potentially nothing between the legs and board.

He's also clearly well off-center. Tack down the corners and make sure it's aligned properly before doing a whole row of pins. That's really the hardest part -- just getting the parts aligned right.

That's really the hardest part -- just getting the parts aligned right.

Yes strongly agree with that. You take more time over alignment than doing the actual soldering. The more pins on a device the longer it takes. Just solder one pin at first to get it aligined, once you solder that second pin you are comitted.

Thank you guys for help! :)

I'll borrow solder with temperature control, and if will have time show here the result of solder.

For now we can close the thread.