Reflow soldering at home, hot plate vs oven

[NaxFM]

Hi everyone, I'm looking for a way to perform reflow soldering at home, but I don't know which is the best approach.
Can you tell me your experience with the two methods? I really don't know if I should invest in an hot plate or an hobbyst oven like the T-962.
From what I've seen both looks almost equivalent, maybe with the hot plate is a bit easier to get good results.

[jmelson]

I do small-scale production reflow in a GE toaster oven with a thermocouple temperature controller.  I poke a micro-sized thermocouple junction into a plated through-hole in the board, and program the temperature ramps into the ramp-and-soak controller.  Even though the oven does not keep perfectly even temperatures over the whole area, it works amazingly well.  The ramp-and-soak controller allows you to set several time-temperature ramps and hold times.  Having the thermocouple ina through-hole in the board means the controller is actually controlling board temperature.  When I did not do that, it burned the boards, as the air did not pick up IR like the board did.
This GE oven has two linear heating elements above the board, running left-right, and two below.  I have run well over 2000 boards with this system.
Jon

[rstofer]

I use both...

For the hotplate, I put the board on a cold plate, turn the knob to High and wait for the solder to flow.  Then I use tweezers to remove the board, placing it on a heat resistant surface (usually the kitchen counter tile) and that's it.  Oh, don't forget to turn off the hotplate.  Hotplates with seriously voided top plates (big opening) don't work as well.  Some people overcome this by using a circular saw blade as a heat spreader.

Note that there isn't even an attempt to match a proper soldering temperature profile.

For the oven, I modified a Black and Decker InfraWave oven - no longer in production.  The big change is stuffing the void between the inner and outer sheet metal with high temperature insulation.  I used an earlier version of this controller:

https://www.rocketscream.com/blog/product/tiny-reflow-controller-v2/

At least this makes an attempt at a proper profile.

I usually build my projects with MiniBoards from ExpressPCB (3.8" x 2.5") so the hotplate works well.

[Skashkash]

I've used both a hot plate (946C style) and a small home conversion toaster oven (older Controleo).
 
    I get more consistent results running a known profile (non ROHS) in the oven.
    You can also start a reflow cycle in the oven and not have to continually watch it the whole time.

    I do like having the hotplate around for doing rework.

     

     
   

[fourfathom]

I started out using an electric skillet, but even with the small boards I was building I wasn't seeing uniform heating.  Using an IR camera I could see that the skillet had significant temperature differences across the heating surface. 

Other people have used sand or a metal plate to even out the heat, but I decided to try a toaster oven.  I built my own controller, and used a thermocouple attached to a scrap of PC board to monitor the oven temperature.  I didn't add any insulation to the oven, and control both upper and lower heating elements with a SSR on the power cord.  The board being reflowed and my thermocouple board sit on a thin aluminum shelf mid-oven (the shelf is the drip-tray that came with the oven.)  With my controller I can get quite close to the published multi-stage temperature profile as long as I open the oven door after reaching the target temperature.  The oven works quite well.

[wizard69]

Mostly I come from the repair side so from that standpoint a hot plate can be useful to have.   As to how useful they are for reflowing a board you will have to ask others.   In any event having one isn't a mistake in my mind.

Now when it comes to temperature control there is nothing like ovens.   We use a variety of process ovens at work (entirely different industry) and frankly they are some of the better pieces of equipment you can have.   Properly designed and built ones are very reliable.   Go the DIY route the controls are simple or can be more complex.   YOU can buy a ramp / soak controller or consider one of the DIY projects, in the end you can closely duplicate commercial cycles .   You probably can get by without any fancy control at first, it would be crude but not impossible.

The reality is toaster ovens can be had dirt cheap if you take the time to look.   Given this I would say resist the desire to limit yourself to one solution and plan on having both tools.   Do realize I'm a tool junky and have mroe tools than I know what to do with.   In this case though I don't see where having both tools is a problem.



Considering how cheap toaster ovens can be

[twospoons]

I use a cheap BGA rework station bought off Aliexpress.  The preheater plate + hot air works great for reflow.  And of course you can also use it for rework and repair.
https://www.aliexpress.com/item/32983502787.html?spm=a2g0o.productlist.0.0.f0c778fbXhp8qG&algo_pvid=6c84595d-9675-415e-9abe-9073e66e6b80&algo_exp_id=6c84595d-9675-415e-9abe-9073e66e6b80-0&pdp_ext_f=%7B%22sku_id%22%3A%2267166031114%22%7D&pdp_npi=2%40dis%21NZD%21216.81%21112.74%21%21%21%21%21%40210318be16616336770861493e1527%2167166031114%21sea&curPageLogUid=xxBMfw5RdiJV

[tggzzz]

Halfway house: saucepan with glass lid and something to keep the PCB off the saucepan bottom.

I have had success with a saucepan with a thin layer of sand on the bottom, on a gas hob. The sand spreads the heat so hotspots at reduced, and acts as a buffer making the PCB temperature more controllable.

[Jackster]

A reflow oven with a good temperature control will be best in terms of reflowing correctly. Especially if you have larger components that suck up the heat on the board.
Getting everything at an equal temperature will prevent stress and failed solder joints.

That being said. If I have a one off prototype. I'll shove it on our hotplate rather than my T-962 reflow oven.

That and it doubles up as a hotplate for rework obviously.

We have the 946-1010
https://amzn.to/3wAHogl

They make them in larger sizes as well.

Personally I would skip using a toaster oven and get the hotplate. I started off with a toaster oven and while they are fine and you can get good results (I have boards working today that I made in a toaster oven nearly 8 years ago), they are just not that good enough to beat out a hotplate with a single set temperature.

We all start somewhere but IMHO, toaster ovens are really naff. After all the costs to retrofit them, hotplate from AliExpress is cheaper and better.

[tooki]

A well selected toaster oven can do a really good job, especially if it’s got a good reflow controller driving it. At work, despite the fact that we have an actual conveyor belt reflow oven, we actually use a toaster oven with a commercially-sold reflow controller for most of our boards. It really does a fantastic job.

The thing about hot plates is that a) they cannot be used to assemble boards with components on both sides, b) for reworking boards with any components or component legs on the bottom, and c) they struggle with components that suck away heat, like large inductors.

[fourfathom]

toaster ovens are really naff. After all the costs to retrofit them, hotplate from AliExpress is cheaper and better.

The only mod I did on my toaster oven was to drill a tiny hole in the back for my thermocouple lead.  And for a long time I just ran the lead through the front door crack.  My arduino-style controller, thermocouple interface, and SSR are the rest of the package, all outside of the oven.  A Chinese hotplate is probably cheaper and useful, but At least for me, a zero-mod toaster oven delivers the desired thermal profile at a very reasonable price.

One thing I realized when characterizing the oven behavior was that I *didn't* want to use a PID algorithm.  Knowing the thermal inertia and heater on-off lag time, it was easier to fit the temperature profile by using on-off heat control, and temperature/time control points.  My algorithm can self-calibrate by doing a couple of test runs, but unless the ambient temperature changes dramatically (I have my lab in the garage) recalibration isn't necessary.

[rooppoorali]

I think hot air rework station will be good.

[David Hess]

I do small-scale production reflow in a GE toaster oven with a thermocouple temperature controller.  I poke a micro-sized thermocouple junction into a plated through-hole in the board, and program the temperature ramps into the ramp-and-soak controller.  Even though the oven does not keep perfectly even temperatures over the whole area, it works amazingly well.  The ramp-and-soak controller allows you to set several time-temperature ramps and hold times.  Having the thermocouple ina through-hole in the board means the controller is actually controlling board temperature.  When I did not do that, it burned the boards, as the air did not pick up IR like the board did.
This GE oven has two linear heating elements above the board, running left-right, and two below.  I have run well over 2000 boards with this system.

I like that idea.  I wonder if a convection toaster oven would work better.

[fourfathom]

I like that idea.  I wonder if a convection toaster oven would work better.

Some people have added a fan inside the oven chamber to stir the hot air.  The motor is outside the chamber and the motor shaft goes through a hole into the chamber where it spins the fan.  I don't know if this is really necessary -- my thermocouple is attached to a probe-board much like jmelson described, and I'm getting even reflow without the fan (on admittedly small boards, so far no bigger than 3" x 4".)

[MathWizard]

There's some nice videos/pages on converting toaster ovens. I have 1 and it seems to heat up fine. Some day when I learn some more microcontroller stuff, and get some expensive parts, I might try modding it.

In the meantime if I had some insulation it would do better as a pre-heater.

[fourfathom]

In the meantime if I had some insulation it would do better as a pre-heater.

Why do you say this?  Using thermocouple feedback and simple duty-cycle control of the heating elements I can maintain any temperature between ambient and 250C within a few degrees in my un-modified oven.  I don't use duty-cycle control when doing reflow because all-on and all-off control gets me the temperature ramp I need. 

Here's a plot of the reflow profile I am using.  I would like to have the cool-down be a bit quicker.  I can do that using a fan to blow ambient air into the oven when the door is open, but what I have now is close enough that I don't bother.

Also, a plot of the oven in duty-cycle mode.  I think I was using a 20% duty-cycle, without any temperature feedback for this test.  I was using a Bresenham pulse-density algorithm, with a 1Hz clock rate.

[djsb]

Which hotplate would people recommend NOW that can be bought online in the UK. I'm considering the miniware MHP30 but would ideally like a bigger area. Thanks.

[RoGeorge]

Or a halogen lamp (garden lights):



or a car light bulb, or a ceiling spot bulb:
https://www.eevblog.com/forum/reviews/ir-hand-soldering-iron/

[Jackster]

Which hotplate would people recommend NOW that can be bought online in the UK. I'm considering the miniware MHP30 but would ideally like a bigger area. Thanks.

I have used the cheap ones with great success over the past year.

The 100*100mm is out of stock but the 200*200mm is in stock on Amazon.
https://amzn.to/3UbIbyH

[MathWizard]

Or a halogen lamp (garden lights):



or a car light bulb, or a ceiling spot bulb:
https://www.eevblog.com/forum/reviews/ir-hand-soldering-iron/

So is that a controller hooked up to the lamp ? WHat would it be, something controlling an SCR thing ? I have lamps like that, but I've never tried to use them as a heater yet.

I have a GPU that I'm sure I broke solder balls connections on, and my hotair station couldn't remove a ram chip.

1 of my next projects will be to convert my toaster oven to a reflow oven w/ controller. But for an under heater, outside the oven, a light might be good for me.


Something like this is pretty good too

[RoGeorge]

is that a controller hooked up to the lamp ? WHat would it be, something controlling an SCR thing ? I have lamps like that, but I've never tried to use them as a heater yet.

I have a GPU that I'm sure I broke solder balls connections on, and my hotair station couldn't remove a ram chip.

Yes and yes.

If the hot air station is to weak for a BGA GPU, try adding a preheater underneath.  A halogen lamp underneath that GPU might be good enough as a preheater even without a temperature controller.  Just don't close it too much too fast, so you won't desolder by accident any small SMD parts underneath the BGA.  Add plenty of flux on the BGA side.

Always use a preheater when reworking big chips.  The preheater makes a big difference.

[Gyro]

Full project details (Halogen floodlight oven) here...  https://www.therandomlab.com/2017/07/halogen-floodlight-smt-reflow.html