Cheap Reflow Oven

[kurra]

I am looking for a cheap reflow oven. It seems the Puhui T-962 model has the low cost reflow oven market all sewn up. 

I have read many critical reviews of this model, including all the suggested mods and community firmware, but a lot of these reviews were quite old. Is it too much to hope that Puhui has heeded these issues and fixed them?
I just can't get excited about buying something and then having to do a bunch of mods 
Has anyone bought one of these ovens in 2020?  I see them referring to '2020 model' but the main difference I can see is provision to attach an exhaust duct. Duh!
Are there any other alternatives in the < $US500 range that I haven't found?

[48X24X48X]

At least what they told me they have now replaced the masking tape with kapton tape and even told me masking tape is dangerous. LMAO. That's a start. 🤭

[Mangozac]

We have one and did all the mods. It's fine for small boards (let's say less than 70x70mm) but anything larger has too much variation in temperature across various areas of the board. The solution to this is just higher reflow temperatures but you end up with a bit of browning or melting of plastic connectors. Unless it's just a single board being reflowed we typically fire up the 6-zone reflow oven these days, even for prototypes. Yes, it sucks a lot more power but we know the soldering will be perfect.

Bottom line: for hobbyist and one-off reflows of non-critical boards it's fine. Anything more than that I would steer clear.

[asmi]

I used modified T-962 for years, until recently purchased ZB2520HL as I needed to work with larger boards. So far I'm quite happy with the purchase, it works great with no modifications at all, so far the largest board I reflowed in it is 200x117 mm. New oven doesn't seem to affect plastics as bad as previous one did, for example Mini-Circuits ADP-2-1+ parts stayed mostly white after reflow in the new oven, while they became noticeably more dark after old one.
So give it a try if you're OK with other parameters.

[TimNJ]

How many boards and how consistent do you need it? Do you need it for engineering prototyping, or is this for small commercial production need?

A normal toaster oven with no modifications has worked way better than I expected, for prototyping. We use leaded solder paste which is a little more forgiving, and makes it less likely to scorch your board. Only had issues when trying to reflow a 3oz copper board, took too long to heat the increased thermal mass, PCB delaminated/bulged.

Other than that one occaision, we just did an initial calibration with thermocouple (attached to an "typical" PCB) and datalogger to understand maximum allowable time (after it's switched on) to keep the temperature under control. Often, we visually wait for the solder to begin melting, then wait about 10 more seconds, then shut off the heating element, slightly crack the toaster oven door to bring the temperature down slowly.

We always use soft-termination ceramic capacitors for prototyping so that might give us some resilience to iffy solder profile. I'm not sure.

But, we've now done lots and lots of boards this way, many different occasions, with good success. If you're looking for a production-ready machine, then absolutely do not do this! But, for quick prototyping, seems okay to me.

[fourfathom]

How many boards and how consistent do you need it? Do you need it for engineering prototyping, or is this for small commercial production need?

A normal toaster oven with no modifications has worked way better than I expected, for prototyping.[...]

Yes, for prototyping I also use an un-modified toaster oven and it works very well.  I did put together an arduino-style controller that uses a thermocouple sensor on a small scrap of circuit board, and an external solid state relay to control the oven.  With this I can get pretty close to the recommended thermal profiles, the only difference being a slower cool-down ramp if I neglect to open the oven door once the reflow is completed.  My controller beeps at me to remind me to open the door, but it doesn't seem to matter if I don't.  I am also using tin/lead solder paste so the temperatures are a bit more forgiving.

This definitely isn't a solution for more than a few small boards at a time.

[kurra]

Thanks for the comments.  I want it for prototyping and small production runs (10-20 boards).
I hadn't come across the ZB offerings and I am now thinking the ZB2520 might be the go. A little more than I had in mind to spend, but ...

[48X24X48X]

I used modified T-962 for years, until recently purchased ZB2520HL as I needed to work with larger boards. So far I'm quite happy with the purchase, it works great with no modifications at all, so far the largest board I reflowed in it is 200x117 mm. New oven doesn't seem to affect plastics as bad as previous one did, for example Mini-Circuits ADP-2-1+ parts stayed mostly white after reflow in the new oven, while they became noticeably more dark after old one.
So give it a try if you're OK with other parameters.

How long does a reflow cycle takes from room temperature to peak (around 245 degree Celsius) for a lead-free profile? The only video made by a fellow forumer here on YouTube showed it is 15 minutes which is too long! Their curve shape looks way off compare to the Puhui ones.

[jmelson]

Thanks for the comments.  I want it for prototyping and small production runs (10-20 boards).
I hadn't come across the ZB offerings and I am now thinking the ZB2520 might be the go. A little more than I had in mind to spend, but ...

I've been using a GE toaster oven with a thermocouple controller since 2007 with excellent results.  The trick is to poke a micro-sized thermocouple into a plated through hole in the board.  I got a ramp-and-soak thermocouple controller on eBay, this allows you to program temperature ramps, holds and additional ramps to do the reflow temperature profile.

I often do six boards at one time and have had quite good results.  I do almost all lead-free now, but did use it for leaded solder in the past.  Temperature is not perfectly uniform, but I ramp to 235 for the peak temperature, and all the boards reflow fine with GC10 solder paste.

Jon

[jmelson]

How long does a reflow cycle takes from room temperature to peak (around 245 degree Celsius) for a lead-free profile? The only video made by a fellow forumer here on YouTube showed it is 15 minutes which is too long! Their curve shape looks way off compare to the Puhui ones.

It is about 10 minutes, including the cool-down.  I use about 1 minute to 180 C, hold at 180 for 1 minute, ramp to 235 C for one minute, hold at 235 C for one minute, and cool to room temp in 2 minutes.  (The program gets way ahead of the oven during the cooldown, but I open the door at about 150 C and take the boards out when below 100 C.

Jon

[TimNJ]

Thanks for the comments.  I want it for prototyping and small production runs (10-20 boards).
I hadn't come across the ZB offerings and I am now thinking the ZB2520 might be the go. A little more than I had in mind to spend, but ...

I've been using a GE toaster oven with a thermocouple controller since 2007 with excellent results.  The trick is to poke a micro-sized thermocouple into a plated through hole in the board.  I got a ramp-and-soak thermocouple controller on eBay, this allows you to program temperature ramps, holds and additional ramps to do the reflow temperature profile.

I often do six boards at one time and have had quite good results.  I do almost all lead-free now, but did use it for leaded solder in the past.  Temperature is not perfectly uniform, but I ramp to 235 for the peak temperature, and all the boards reflow fine with GC10 solder paste.

Jon

How long does a reflow cycle takes from room temperature to peak (around 245 degree Celsius) for a lead-free profile? The only video made by a fellow forumer here on YouTube showed it is 15 minutes which is too long! Their curve shape looks way off compare to the Puhui ones.

It is about 10 minutes, including the cool-down.  I use about 1 minute to 180 C, hold at 180 for 1 minute, ramp to 235 C for one minute, hold at 235 C for one minute, and cool to room temp in 2 minutes.  (The program gets way ahead of the oven during the cooldown, but I open the door at about 150 C and take the boards out when below 100 C.

Jon

Can you link to the controller you are using, for reference? It is using an SSR? Ordinary toaster oven?

Thanks.

[jmelson]

Can you link to the controller you are using, for reference? It is using an SSR? Ordinary toaster oven?

The controller is an Omega CN4801-F1-AL2-RAMP.  I got it on eBay for about 1/10th the list price.
It has proportional 4-20 mA output, which I really didn't need.  I also got a spool of micro thermocouple wire to go with it.
I have an external SSR on a small heat sink wired in series with the thermostat built into the oven.
Yes, it was the largest toaster oven in the WalMart store when I went looking in 2007.  It has a convection motor/fan, but I have not found that that feature actually does any good at evening out temperatures.  This oven has two heating elements above the rack, and two below.

Jon

[Rat_Patrol]

I use a Contoleo converted toaster oven with great results on 100x200mm 4 layer PCBs. Extremely consistent, reliable results. Once I got my profiles tuned, perfect results every time. Total cost was around $300.

I'm actually planning on building 2 more. My PnP machine outruns my reflow oven 2:1, so if I build 2 more, I'll be able to have enough reflow capacity to be running at 100%+ capacity of the PnP.

For about $1k, I'll have all the reflow capacity I'll need for the foreseeable future.