[sdiy] pros and cons of SMT in DIY

Sun May 21 21:33:56 CEST 2017

convert it to m12
https://www.peauproductions.com/collections/playstation-eye-accessories
then you can use a wide variety of m12 lenses  there are some 3d
printable setups on thingiverse but they're not great.

i'd give you a specific one, but i use my ps3 eye for a different
setup, it is not really that hi res, but the frame rate is much better
640 x 480 at 60fps which i find better to work with than the slow usb
microscope cameras that are usually very laggy though with a higher
speed, i'll grab some pics and share of the quality once i'm finished
building these 500 pcbs ;)

cheers

On Sun, May 21, 2017 at 4:27 AM, cheater00 cheater00
<cheater00 at gmail.com> wrote:
> Yeah i know you can put th footprints on a board you'll populate with smd,
> that's the whole point. I posted about this here maybe 10 years ago already.
>
> Good to know about the experiences with magnet wire. Thanks.
>
> Charlie what lenses do you suggest for the ps eye? Do you have video demos?
>
>
> On Sat, 20 May 2017 18:59 charlie wallace, <charlie at finitemonkeys.com>
> wrote:
>>
>> a few of us are putting together 400 boards this week/end, it is
>> mostly smd 0805 with lqfp (which i personally dislike but i was
>> outvoted, i prefer qfn since it solders better)
>>
>> we have a stencil printer
>>
>> http://www.ebay.com/itm/332130477725?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
>> it is not great but once you get it dialed in it works, in the past we
>> just put hinges on a piece of MDF and the stencil, then cut out an
>> outline of the pcb to be made , and use those as guides
>>
>> the stencil comes from the pcb people or we laser cut or cnc one out,
>> these are generated from the tcream layer in eagle, with cheap ebay
>> 40w laser i use the engrave method rather than cut , it gives better
>> edges; if i cnc then i use brass shims, usually 3mil and i schrink the
>>  tcream a little first.
>>
>> the paste is applied using a thin spring steel metal scraper that i
>> used for clay sculpting, it works the best of anything i've found so
>> far, i use aim leaded water soluble solder the no clean stuff is no
>> good for these boards, and its a nightmare to clean if you have too
>>
>> then to a small pnp the neoden tm220a, though wish i'd gone for the
>> 240a at the time (bought by generating litecoins with old gpus a few
>> years ago) there is a nice ulp dp-tm220a.ulp that handles it, once its
>> up and running it does pretty good but not a lot of components can fit
>> it, we have a modified juki as well but its in storage.
>>
>> once as many parts as the pnp can place, the board goes into the
>> kitchen and the others place the few smd components, and then it goes
>> on to the madell hot plate, for a 170o cycle, after the thru hole
>> parts are added with the metal under either the amscope microscopes or
>> the mantis (all ebayed or bought from amscope directly during sales)
>>
>> then the board is de-briged if needed, usually the lqfp arm chips
>> since this time i let the board house do the stencil gerber and they
>> didn't shrink it.
>>
>> there are about 60 parts placed, the good thing about smd is that part
>> placement only has to be pretty close, the surface tension of the
>> solder will pull the parts in (usually)
>>
>> with two of us we can do about 10 boards an hour at a relaxed pace,
>>
>> qfn's i like since you can practically throw them onto the board and
>> they'll self right, and they tend not to bridge, we did a test where
>> we could see how lax the part could be placed and it'll still solder
>> in properly.
>>
>> smd size doesn't really matter if you're hot plating, once you get
>> down to like 0201 and such its all about magnification and a steady
>> hand, and if you don't have that then use a manual xy pick and place
>> tool, or an automatic one. manually soldering them is also straight
>> forward you can glue them in place then solder if you're not steady, a
>> small tipped iron with the right temperature it goes well , takes a
>> little bit of practice on how best to hold them and avoid tombstones
>> if not glued, again you can also use the xy tool to place and hold a
>> part while you hand solder it.
>>
>> we've taught 100s of people to smd aver the years, some have never
>> even picked up an iron before and they're placing chips, 0602s with no
>> bother , though occasionally people have soldered chips upside down
>> before ,another good argument for qfn
>>
>> basically you just need a good iron, good microscope (amscope rp type
>> is fine) i'd avoid most usb microscopes since too much lag so hard to
>> solder and stick to glass, but you can $5 a playstation eye , mod the
>> lense and and get an ok picture at 180fps, flux and a 10/5ml tube of
>> solder paste.
>>
>>
>>
>> On Sat, May 20, 2017 at 8:15 AM, Richie Burnett
>> <rburnett at richieburnett.co.uk> wrote:
>> > Paula, when you say "working with 0402", do you mean replacing the odd
>> > component here and there, or soldering 100s of SMT parts on?  And how
>> > are
>> > you actually doing the soldering?  With a fine tipped soldering iron and
>> > a
>> > steady hand?  ...heater tweezers?  ...or stencilling solder paste onto
>> > the
>> > board then placing components into the paste and ovening the board?
>> > Just
>> > curious what methods you're using, particularly to get consistent
>> > results
>> > with those tiny QFNs.
>> >
>> > I can also vouch for the structural integrity of super-gluing down
>> > wire-wrapping wire or polyurethane enamelled copper (magnet wire) for
>> > mods
>> > to PCBs.  Never seen one fail, and they're almost impossible to rip up
>> > if
>> > you need to.  I've never felt entirely happy with the fumes given off
>> > when
>> > someone has to solder in an area of the board polluted with dried
>> > Cyanoacrylate glue though.  I remember doing this once and leaping
>> > backwards
>> > with my eyes and nose stinging!  Can any of the chemists on this list
>> > comment on what vapours are liberated when a hot soldering iron touches
>> > cured Cyanoacrylate glue?  (I appreciate that I should already have been
>> > soldering in an area with positive airflow away from me, extraction to
>> > outdoors, etc...)
>> >
>> > -Richie,
>> >
>> > -----Original Message----- From: paula at synth.net
>> > Sent: Saturday, May 20, 2017 3:45 PM
>> > To: cheater00 cheater00
>> > Cc: Synth DIY
>> > Subject: Re: [sdiy] pros and cons of SMT in DIY
>> >
>> > On 2017-05-20 03:42, cheater00 cheater00 wrote:
>> >>
>> >> Yes, a TH pcb will be able to hold a daughter pcb just by the
>> >> through-holes, whereas SMD pads will not hold one. So you can easily
>> >> change topology using an extra pcb on a TH circuit but not on an SMT
>> >> circuit.
>> >
>> >
>> > You know you can use both SMT and through hole if you need?
>> > My current project for work has around 100 SMT parts, and 7 through
>> > hole, some of which are for PCB interconnect.
>> >
>> > At the end of the day, the choice is up to the designer.
>> > I'm really comfortable working with 0402 and QFN (3mm x 3mm) packages,
>> > and with modding them with mod wires if needed (for the record super
>> > gluing a mod wire makes it rock solid).
>> > I'm considering trying 0201 for some parts, just as a personal challenge
>> > :)
>> >
>> > So it's up to each person.
>> > There's no "right or wrong" or "this way is better", it's just
>> > different.
>> >
>> > Paula
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