[sdiy] SMD soldering technique

Thu Mar 23 17:27:26 CET 2017

congrats of going SMD, but I have to say I find your technique overly
complex.

what I do for 0603/0805 and SOT/SO parts:

1) apply solder (0.35mm, lead free Felder ISOCORE, 3.5% flux, no clean)
to one pad, or diagonal pads if a larger IC

2) pick part with tweezers, reheat the pad with the solder and place the
part

3) solder the other pad(s)

4) done.

for smaller ICs like TSSOP I add some Edsyn FL22 flux to the pads, then
solder them with the same 0.35mm solder and tip as above, using a $200
stereo microscope (Amscope SE 400-Z, 10X)

On 23.03.2017 09:00, cheater00 cheater00 wrote:
> Hi,
> I have recently bought an SMD learning kit to try out some techniques.
> I've had some really good results that were stunning for a person who
> tried real SMD soldering for the first time, so I thought I'd share
> what I did and what I used.
> 
> I got one that looks like this, but I think I got mine on Amazon:
> 
> https://www.aliexpress.com/item/DIYmall-SMT-SMD-Component-Welding-Practice-Board-Soldering-DIY-Kit-Resitor-Diode-Transistor-By-start-Learning/32776255634.html
> 
> The 1206 were easy, as were the 0805 and 0603. Too bad they didn't
> have smaller ones. I didn't have to use a microscope but I wear
> contact lenses so my vision is OK. Good lighting was crucial (see by
> the end of the email), as my eyes couldn't resolve the detail without
> it. With the light the work was really comfortable.
> 
> I've used my Hakko-clone soldering station Aoyue Int2903 with this
> Hakko-clone T12 tip type JL-02:
> 
> https://www.aliexpress.com/store/product/Hot-Hakko-T12-Soldering-Tips-T12-JL02-Series-Iron-Solder-Tip-For-Hakko-Fx-951-high/1486111_32574864414.html
> 
> The tip I used worked pretty good.
> 
> I used AmTech Tacky Flux, model NC-559-V2-TF. I bought it from Insat
> on http://www.bga-reworking.co.uk/. They have other good soldering
> stuff so check them out. I made enough of an order that they sent me a
> set of tweezers and cutters. The tweezers are ESD and very precise,
> the cutters have really nice blades but the spring shifts around which
> is annoying.
> 
> It's important to buy the flux from an authorized distributor listed
> on this page:
> 
> http://www.inventecusa.com/reps---distributors.html
> 
> You can find AmTech knockoffs nearly everywhere and obviously they're
> not going to have the same chemical composition as the original.
> Amazon has the knockoff, so does eBay. The flux is really important.
> 
> I first put the board in a "helping hand" stand, although I am
> awaiting the delivery of an inexpensive pcb holder vise. Does anyone
> know where to get aligator clips for the helping hand that don't have
> the teeth? Much rather rubber jaws or no teeth at all? That would be
> so much better. I might put some heat shrink on these.
> 
> I start soldering by applying a tiny amount of the flux to the board.
> Then I'd add some Stannol SN60Pb39Cu1 to the pads. I have a 1.00mm
> diameter 500g spool that'll last me, my children, and my children's
> children a lifetime. I could use some finer solder though, maybe
> 0.2mm, because 1mm really applies very quickly. I'm holding my
> soldering iron in my right hand.
> 
> Next I'll take a pair of ESD tweezers and, holding the tape in my
> right hand, I'll pry it open with the tweezers and pick out the part.
> I'll put it on the board and apply heat to the top pad with the
> soldering iron, then to the other pad. The part will not have settled
> yet, so once it's held securely by the joints I'll let go with the
> tweezer and heat both pads alternating between them until the part
> settles. If it needs pushing in place I'll use the tweezer or a
> spudger. I'm going to buy a magnetic knife holder thing for my
> tweezers and spudgers which should make the process easier.
> 
> At this point the resistor pads will have gratuitous balls of solder
> on them, so I'll remove nearly all of it with Pollin 1mm wick, order #
> 840 030:
> 
> http://www.pollin.de/shop/dt/OTY5OTUxOTk-/Werkstatt/Loettechnik/Entloetgeraete/Entloetlitze_1_0_mm_1_5_m.html
> 
> it comes out of the spool condensed so I twist it around until it
> separates into a mesh. This way it'll absorb much more solder for the
> same length.
> 
> At this point I might have to realign the resistor so I'll use some
> heat and a spudger. I use these spudgers:
> 
> https://www.aliexpress.com/item/6Pcs-Hand-Tool-Professional-Steel-Solder-Assist-Electronic-Components-Repair-Welding-Auxiliary-Tools-Set-FULI/32780051115.html
> 
> or at least ones that look the same. I don't know where I bought them
> any more. ("Welding" is Aliexpress for "Soldering" and "Auxiliary
> tool" is for "accessory", useful when searching for something)
> 
> The flux makes all the difference. I did the first resistor with the
> flux, and it worked well. I did the neighbouring one without applying
> flux, I just used flux from the previous one, and that was pretty good
> too. I tried the third pad watching out not to apply any flux, and the
> results were really bad. As soon as I applied a little flux the joints
> cleaned up, and the resistor applied well. The flux also smells really
> nice. I later cleaned it off with some 70% ethanol and normal q-tips.
> 
> I don't have a good light set up yet so during the process I used the
> Black Diamond Revolt head-mounted lamp which I bought several years
> ago, use all the time, and it remains like new.
> 
> http://blackdiamondequipment.com/en_US/headlamps-and-lanterns/revolt-BD620613_cfg.html
> 
> It has an adjustable angle mount which was very important for soldering.
> 
> The nice thing about this soldering technique is that it gave me
> really perfect results without much of a fight. I might still have to
> practice to leave more solder on the pads, but the initial results are
> very promising.
> 
> The one improvement I'd like is a different tweezer. A sideways
> tweezer would be better, where the jaws curve in on themselves out of
> the plane of the sheet metal the tweezer is made of. I haven't been
> able to find one with a nice angle (say 75 degrees) and a fine tip and
> ESD coating. If anyone has a suggestion, I'd love to hear about it.
> 
> After cleaning with 70% ethanol, the board still seems to have a bit
> of a film on it, so if someone has a suggestion for a better solvent
> for the AmTek flux, let me know please.
> 
> Hope this helps someone. If not, at least I had fun documenting what I
> did in case I forget in the future :)
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