[sdiy] SMD soldering technique

charlie wallace charlie at finitemonkeys.com
Sat Mar 25 19:02:10 CET 2017


i have 2x, 4x, 6x and 10x objectives, usually the 4x and 10x are on,
4x for assembly and 10x for inspection, beyond that i'd switch to the
amscope boom

the mantis is great because its "3d" you can look around the part
without moving the board around. but i have found it is a love/hate
relationship with people who've used it so always good to try one
first.

they're often on ebay for silly sums of cash and with no objectives,
but you can luck out and get them for a few hundred

On Thu, Mar 23, 2017 at 9:53 PM, cheater00 cheater00
<cheater00 at gmail.com> wrote:
> What sort of magnification do you use when soldering under the mantis? What
> about smd inspection?
>
>
> On Fri, 24 Mar 2017 04:34 charlie wallace, <charlie at finitemonkeys.com>
> wrote:
>>
>> i use solder paste with a water soluble flux, personally for me no
>> clean is a pita especially if people have to handle the boards
>> afterwards.
>>
>> drop the paste on the pad, drop the part on the paste, solder it with
>> an iron, hot gun, or hot plate, use an  under-board heater to help
>> with thermal shock and it makes a lot easier to work with too.
>>
>> i fill up a small syringe with a metal luer lock every so often, use
>> that up and put the rest in the fridge.
>>
>> we use the amscopes that are around  $100 or under (they're often on
>> sale), the R-P type,,though i have the trionocular boom one for when
>> lots of work, and an ebay'd mantis which is awesome.
>>
>>
>> On Thu, Mar 23, 2017 at 5:25 PM, cheater00 cheater00
>> <cheater00 at gmail.com> wrote:
>> > Thanks, I'll check out that flux.
>> >
>> > So you don't use any flux for the smaller parts? Does that work well at
>> > all?
>> >
>> >
>> > On Thu, 23 Mar 2017 17:31 Vladimir Pantelic, <vladoman at gmail.com> wrote:
>> >>
>> >> 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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>> >> >
>> >>
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