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Topic: Reflow Oven for Beginner (Read 377 times) previous topic - next topic

czu001

I have been doing hobby electronics for a few years now, and I'm wanting to step up my SMT game by purchasing a reflow oven.

I've seen a few on Amazon, but I was wondering if anyone had suggestions on a hobbyist reflow oven.  I only reflow small boards in small quantities, and I only do it every so often.  Any suggestions?  Thanks.

larryd

#1
Jan 22, 2020, 05:19 am Last Edit: Jan 22, 2020, 05:31 am by larryd
There are a few examples on YouTube.
Some people use a hot plate. Frying pan with aluminum insert.

I believe user CrossRoads just watches the solder flow thru the window.



>>>>-------->          Where are you CrossRoads.




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Wawa

#2
Jan 22, 2020, 06:03 am Last Edit: Jan 22, 2020, 06:05 am by Wawa
small boards in small quantities, and I only do it every so often.  Any suggestions?
Then forget about an oven and buy a hot-plate (for smd soldering).
And a rework station (hot air), which you need anyway.
I set the hot-plate usually to ~160C, and spot-reflow after ~5 minutes with the hot air wand.

I also have an oven, but only use it for the larger projects.
Leo..

larryd

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Wawa

You get a 'cleaner' result when pre-heating (~160C) with the hot-plate and soldering with hot air (~220C).
Using hot air is also easier with large items, like USB sockets, SD card holders and inductors.
Leo..

larryd

You get a 'cleaner' result when pre-heating (~160C) with the hot-plate and soldering with hot air (~220C).
Using hot air is also easier with large items, like USB sockets, SD card holders and inductors.
Leo..
That makes sense.


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MarkT

I have a slightly modified sandwich toaster - very cheap.  I just moved the bottom element to the top so there are two heating elements at the top now.  The existing temp control is rough and ready, a bit of experimentation to calibrate it is needed, then I just use two settings, one for soak, one for full heat, and watch for the solder paste to reflow (very obvious if you point a bright light source at it through the window).

Cost minimal.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

xl97

I just use a generic toaster oven from my local wal-mart..  (cost my $17.00)

Same process I told CrossRoads about years back...

I posted about an article that also allows you to use a vinyl cutter and gerber files to make your own solder masks as well

lay down the stencil
smear your solder paste
remove stencil
populate board with components..
throw it in a cheap toaster over @ around 200+ degrees...  and wait for 3-5 minutes.. waiting for the paste to re-flow.

The solder will get 'dry' looking...  right before it melts and gets shiny.


Good reads:

http://dangerousprototypes.com/blog/2013/05/17/cutting-stencil-using-a-silhouette-cameo/

http://hackaday.com/2012/12/27/diy-smd-stencils-made-with-a-craft-cutter/
http://www.idleloop.com/robotics/cutter/
This script/project is by: Peter Monta
http://pmonta.com/blog/2012/12/25/smt-stencil-cutting/

http://dangerousprototypes.com/2013/05/17/cutting-stencil-using-a-silhouette-cameo/

https://www.dmstudios.net/?page_id=14

https://forum.arduino.cc/index.php?topic=365863.0

(ie: shrinking pads:  first couple lines)
http://dorkbotpdx.org/blog/travis_s/making_kapton_stencils_at_adx_portland_using_eagle_pcb)


Boards made using the above gerber2graphtec approach.. and a $17 toaster oven:




Stencil:












ShermanP

I did a hot plate project for U.S. makers using the $10 Walmart hotplate and a circular saw blade.

But I have to point out that when you go from hand soldering of SMD parts to an oven or hot plate, you then have to deal with solder paste.  It's difficult to avoid putting on too much paste, and the way to avoid that is to use a stencil.  In many cases, by the time you order a stencil, work up a system to mount it, order solder paste (which has a limited lifespan even if refrigerated), and then place all the parts, it may end up being more trouble than just hand soldering.  Of course for some parts you don't have a choice, but it may be that specifying packages that are easy to solder by hand works well enough.

Anyway, here's the hot plate and saw blade.  It's based on the idea of turning the element on, then off, then on again for specific times, which turns out to be very forgiving.  That's  as opposed to trying to measure temperature with a thermocouple, which can be a bit tricky and lead to scorching.

https://www.youtube.com/watch?v=hqwbDlXcs_I


wvmarle

I order stencils with the PCBs. If more than one PCB at a time I'll try to get one stencil for all of them, usually no problem size wise. Saves serious cost :-)

Applying solder paste is a matter of minutes including placing PCB and aligning stencil.

For the actual soldering I've used a basic reflow oven or hot air; the first works a lot better but requires me to travel to my local makerspace. Looking into the hot plates, they're pretty cheap. Very interesting as my volume doesn't warrant a reflow oven (it's simply too bulky) but a small hot plate is really interesting.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

ShermanP

For the actual soldering I've used a basic reflow oven or hot air; the first works a lot better but requires me to travel to my local makerspace. Looking into the hot plates, they're pretty cheap. Very interesting as my volume doesn't warrant a reflow oven (it's simply too bulky) but a small hot plate is really interesting.
The thing that's unique about a hotplate is that the temperature response is very much delayed with respect to turning the power on and off.  (See attached chart.)  You turn on the power, and it takes a while before the surface starts to heat up.  You turn off the power, but the surface temperature continues to increase for quite a while.  So there's really no way to control the temperature in real time.  You have to figure out in advance what on/off pattern produces the right temperature profile, and then follow that timing each session.  Or, if you don't want to bother about soak periods and such, you can just turn on the hot plate, then remove the board (not just turn off the power) when the reflow has finished.

wvmarle

I'm aware of that, but it's a great way to pre-heat the board and finish off with a heat gun. Or manually increase the heat. The few minutes it takes is fast enough not to damage anything by heating too long.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

MarkT

And with a hotplate you can't do components on both sides.  When I need this with an oven I do one side (typically bottom) first, then reverse the board and push into scrumpled aluminium foil to hold them in place during the second side reflow.   I often find the underside is useful for decoupling caps for instance, freeing up topside for signal routing.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Wawa

And with a hotplate you can't do components on both sides.
I do that all the time.
Because I only pre-heat on the hotplate.
Leo..

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