Re: [neonixie-l] OT: Lateral thinking: Cheap SMT reflow oven...

[Mike Harrison]

On Mon, 14 Aug 2017 13:17:28 -0400, you wrote:

>> Is anyone here doing their own reflow-based SMT assembly ?
>
>I'm seriously considering it.  More and more parts are only available in SMT, 
>and it would be nice to do quick turn PCB assembly by milling a PCB then 
>assembling it.  Some parts are impractical to solder, while I haven't run into 
>much call for BGA parts, I do use a lot of things with thermal pads under them 
>that are tricky to hand-solder.

Even for bog-standard parts, if you have a lot of them ( maybe 50+)  reflow is 
easily way quicker.
Using a foot-operated vacuum pen, you can pick parts directly out of tape - 
particularly useful for
polarised parts so you don't have to check polarity of every one you pick from 
a random scattering
of loose parts.. 
For placing multiple parts from the same tape you can get down to 2-3 seconds 
per part.
The end result also looks nicer (assuming you stay on the right side of the 
line between "reflow"
and "incinerate".

Obviously use leaded paste, as the reflow/incinerate margin is much wider. 
If you have access to a lasercutter or vinyl cutter you can cut stencils, which 
saves even more
time, though a foot-operated dispener can be pretty qiuck - 1-2 dots per second 
once you get into a
rythm, and for stuff like SO packages you can just do a line long the pads. 
Even for fine-pitch
stuff, it;s often quicker to do a line then braid or drag-solder off the shorts 
it afterwards, or
just drag-solder them first


I did a video a while ago about this :
https://www.youtube.com/watch?v=pdGSFc7VjBE

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Re: [neonixie-l] OT: Lateral thinking: Cheap SMT reflow oven...

[John Rehwinkel]

> Is anyone here doing their own reflow-based SMT assembly ?

I'm seriously considering it.  More and more parts are only available in SMT, 
and it would be nice to do quick turn PCB assembly by milling a PCB then 
assembling it.  Some parts are impractical to solder, while I haven't run into 
much call for BGA parts, I do use a lot of things with thermal pads under them 
that are tricky to hand-solder.

> Every so often I see an intriguing BGA device, but I wont design with it 
> because I have no way to solder, rework, test, or inspect them.
> Despite my age and worsening eyesight, I'm still able to hand-solder 0.5mm 
> pitch QFP devices, so unless someone has thoroughly wrung-out SMT assembly in 
> their garage and is willing to provide some tips, I'm sticking with 
> hand-soldered.

I am so far, my binocular microscope and good lighting help a lot.

However, putting down a bunch of paste dots and parts and soldering them all at 
once is attractive.  I'm looking at both hot plate soldering and a reflow oven. 
 There seem to be two camps of DIY reflow ovens, one is to buy a cheap Chinese 
purpose-built reflow oven like a T962 and upgrade it, the other is to buy an 
even cheaper toaster oven and modify it (whizoo.com  offers 
controllers, parts, kits, and instructions).

However, I'm still in the "thinking about it" stage, nowhere near "thoroughly 
wrung-out".  However, I'll share my experiences once I have some.

> For those of you who are unsure about hand-soldering SMT parts, the typical 
> 0805 package is very easy to solder with a good pair of tweezers and a 
> fine-tip soldering iron.

True.  This can be done with flux and old fashioned solder wire, or solder 
paste.  It can also be done with a hot air gun.  I find a decent board holder 
is a big help, and a simple toothpick is a handy tool.  Bigger 1206 parts are 
no problem, and I've managed 0603 without too much pain.  SOIC and 5050 parts 
are easy, and the various QFP packages are generally possible.

> The parts are so much cheaper, take-up less PCB area, and require far-less 
> storage space that I avoid thru-hole parts wherever possible.

Back when I made my own boards, I would have been thrilled about SMT.  My 
absolute least favourite part of board making is drilling holes.

- John

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