OT: Lateral thinking: Cheap SMT reflow oven...

[Nick]

http://therandomlab.blogspot.ae/2017/07/halogen-floodlight-smt-reflow.html 

Genuine "outside the box" thinking...

Nick

[gregebert]

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

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.

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. 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.

[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

[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

[Paul Andrews]

I've done some hot plate reflow. Discrete components down to 0603 are straightfoward and easy to touch up with a soldering iron. Chips, on the other hand... I recently burned through three boards with a ESP8285 and a CP2102N on it. Never did get them to work.The main problem is not being able to figure out why afterward. I don't know if there were shorts or opens or if I heated them too long or if they exceeded their MSL rating or if my design was bad. For chips that don't have pads that extend up the sides, there is just no knowing if it worked or not, unless you break everything out so you can check for shorts and opens.

My successes (apart from discrete components and any chips that have legs, which are all pretty easy) include a LIS3DH (which is why I started with the reflow), USB micro connectors and a few others. Having pads on the PCB that extend out past the chip body gives some ability to visually inspect the joints and touch up with a soldering iron if necessary (as in, separating shorts - adding solder not so much!).

Some kind of binocular magnifier is pretty much essential, and I use a pin to apply paste and a loupe afterward to inspect the results as far as I can.

I'm wondering if getting solder masks made would be a good idea, but I'm not sure my ability to apply the paste would improve much.

So for now I think I will restrict myself to smaller breakout boards for the really difficult chips until I get better yields!

[ZY]

Almost all my projects are now SMT, mainly because I feel it saves so much time and money (smaller board size) compared to through hole components. It's way faster for me to place the parts than to manually solder each through hole component.

I currently use mostly 0603 parts and I recommend oshstencils for cheap plastic stencils. Whenever I send parts to oshpark I simultaneously do an oshstencil order.

I use the hot plate method to do my soldering. It's not entirely recommended because a hot plate gets pretty variable in temps, but if you just sit beside it for a few minutes and take the board off when you start seeing the solder melt it should be fine. I mark the spot on my dial where the temperatures are usually the best for me. However I'm currently working on a project to convert an old toaster oven to do the reflow automatically. I'm trying to get the temperature display to be nixie tube based.

[Tomasz Kowalczyk]

For me, 0805 parts are easier to solder than through hole. The board can lay flat and resistors aren't running away from their spots, there is no wire bending to lock them in place before soldering. SMD soldering is tidier. Plus, when I'm making my prototype PCBs at home, SMD = less drilling.
I recently learned how to solder QFN parts with a hot air gun and I'm happy with my results, these parts take very little space and behave better thermally than QFP because of the pad. However, I think it would be impossible to solder it with no short circuits on a homemade PCB - soldermask helps alot.

[Nick]

On Monday, 14 August 2017 20:47:26 UTC+4, gregebert wrote:

Is anyone here doing their own reflow-based SMT assembly 

Been doing this for a few years - I have my PCBs made at PCBway - madly cheap & good quality - they are the manufacturer, i.e. it's a direct sale, not just a reseller of services - I've had several 100 boards made by them with nothing but good results.

Recently, they added full SMT stencils starting at USD 15 for 37x47cm (19x29cm usable) - they will also cut both front & rear stencils on the same sheet if you want.

Nick

[Mitch]

I built a ControlLeo reflow oven from a kit, and I just ordered their new upgrade with a new touch screen controller. I tell my wife that it’s insulting to call it a toaster oven, but she persists. It works great. I just finished a few ESP32 DevKitC compatible micro controllers with 100% success.

I too use pcbway.com and I order stencils without the frame.

[Nick]

Hmmm. I had been considering a ControlLeo3. My current oven is not great.

How do you find it to use?

Nick

[Mitch]

Nick, it is very easy to use. Once the profile is set for the paste you are using, just press start. I use a standard profile that I have never touched.

[Nick]

On Wednesday, 16 August 2017 11:54:51 UTC+4, Mitch wrote:

Nick, it is very easy to use. Once the profile is set for the paste you are using, just press start. I use a standard profile that I have never touched.

What's the quality of the boards like? Consistent? Any burns etc.?

Thanks

Nick 

[Mitch]

Never. I’ve used it about twenty times and it’s always worked perfectly each time.

[Robert L]

Another ControlLeo user here. Have built two of them... one for home use, one on a bench at work.

Achieving excellent results with only a small sensitivity to placement of the temp sense thermistor. I use lead free paste for reflow, leaded solder for re-work.

Toying with upgrading my controller to the model 3, but not a compelling reason to do so. As I said, getting fine results with the rev 2 controller and a stock profile. The money saved will offset the cost of the ultrafine Metcal wands and tips I recently added :-)

B

[5-ht]

I've been using the Zallus Oven Controller for a while. It has worked quite well but it appears that it's no longer being sold.
See:  http://www.zallus.com/zallus-oven-controller/

Mark

[Nick]

Looking like a ControlLeo3 kit for me too then :) 

I got the UF bits for my Metcal 5200 about a month or so ago - love them - just so precise...

Nick