PCBs: HASL, Lead-free HASL or ENIG finish?

[grufti]

It's just like everything else in my experience. You get better at it the more you do it.

Good tweezers are important and I can't stress chipquik flux enough. I sometimes tape the tiniest parts in place with little bits of masking tape when I solder them with an iron. Surface tension will take care of the alignment when you use a hot air station. Bring the general area up to temperature first, then get the paste to do its job.

You're going to be just fine. Start with the resistors to get a feel for the process. I try to avoid having to use solder wick except as a very last resort. Don't smother your small parts in solder because solder wick will cure it all. That's not my experience.

[Paul Birkeland]

The hot plate method looked pretty attractive to me as well, especially if you aren't doing a ton of boards.

[Deke609]

Many thanks all. I've got some good pin tip tweezers. I'll order a flux pen. Just watched some videos of people soldering tiny pitch parts with a soldering iron and it looks doable. But I've ordered a stencil just in case.

cheers, Derek

[grufti]

Magnification is essential. You can do what you can see. Surgeons, who work on eyes or infant's hands, and dentists who care about their work, could not do what they are doing without magnification.

[Deke609]

Many thanks. Good there too. I only solder with magnification.

[2wo]

For the multi plan SMD's I pre tin the pads on the board then I have some really nifty flux I got in a SMD rework kit from Digakey. It comes in a syringe with a fine needle so you can get it just where you need it and it is sticky enough to hold your part in position. Then I add a very little soldier to a standard 2mm tip and very lightly run it down the row, the solder on tip is to transfer the heat, the pre tin is enough to make the connection. If it is a big chip. I tack a corner or two to help keep it in position...John

[Deke609]

Thanks John. That's precisely the method I saw in a video today, and the one I plan to try.

cheers, Derek

[diynewbie]

You  might to spend a little money and try a smd practice board like: https://www.amazon.com/Gikfun-Welding-Practice-Soldering-Training/dp/B00Y20JYTM .  This one goes down to a form factor smaller than you will need for the intended project.

If your tweezers are magnetic, I would recommend getting a non-magnetic one.  As already recommended, you will want liquid flux.  Also, purchase extra small parts.  You sneeze or cough and a 603 resistor will be gone for good.  Use a magnifying glass while shining a light from the back side of the board to make sure none of the IC legs are connected by solder.

[Deke609]

More good advice. Much appreciated!

.... try a smd practice board

I plan to test my smd-soldering mettle by trying to desolder and then resolder a bunch of parts on a pcb that came out of my DAC as part of an upgrade. I've read/watched about the the difficulties of desoldering those millipede iC's, so this should be "fun".  Liberal use of a heat gun may be involved (for desoldering).  What I lack in skill I make up for with dogged determination (aka stubbornness), so I am weakly confident that I'll figure it out.   

Also, purchase extra small parts.  You sneeze or cough and a 603 resistor will be gone for good. 

That already happens to me with parts that are an order of magnitude larger! Although usually not from sneezing. So I've ordered enough of the small cheap parts (wow are smd parts cheap compared to through-hole!) to populate 10 boards and enough of the more expensive ICs to complete 5. I've ordered the min 5 boards, but only need 1. So with luck I'll have a surplus of spare parts and have enough left over to complete at least 1 or 2 of the other boards.

cheers and thanks, Derek

[grufti]

Just one more hint from me. I've discovered that taking a high resolution photo in good light is sometimes the only way that I can tell whether or not all the legs of a millipede have made proper contact. They often do even when I'm not fully convinced while soldering. It becomes difficult to judge when it's just a small [correct] amount of solder.

[2wo]

The desoldering is actually harder, you need a heat gun or the kit I got has some busmith based solder like stuff that when you apply it to the row of legs melts the joints and stays molten for an uncanny amount of time.

I learned the basics on cheap DAC kits off eBay...John