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

  • Thread starter Thread starter Deke609
  • Start date Start date
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
 
Thanks John. That's precisely the method I saw in a video today, and the one I plan to try.

cheers, Derek
 
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.
 
More good advice. Much appreciated!

diynewbie said:
.... try a smd practice board
Click to expand...

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.  ;D

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

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
 
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.
 
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
 
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