Instructables
Picture of T962A SMD Reflow Oven Fix/Hack
I've recently purchased a popular T962A SMD reflow oven. The reviews are split on this oven - some find it to be quite acceptable, while others find it completely useless. After much researching, I decided to give it a try.

(Feel free to skip this part if you already have the oven.)

T962A is an inexpensive IR (infrared) SMD reflow oven. It has a microcontroller to control temperature and timing (profile), so you can basically put populated PCBs in, push the button and simply wait for a few minutes. Then the PCBs are done.

There are some issues with this oven, but my experience is rather positive overall. For my purpose this oven works well.

However the problems are:

1. The oven produces horrendous smell.
I'm not taking about the smell of solder paste melting. The oven itself produces the smell even without anything in it.

2. The heat distribution is not very even.
This is not an issue with leaded solder, but becomes a major problem with lead-free solder. As lead-free solder requires much higher temperature to reflow, the extra temperature needed to ensure the solder reflow on all parts of PCBs can burn the parts in the hot spots. Even though I'm lucky enough to not fry any PCBs with this oven, some parts did come out looking burned.

I want to share what I did to improve on those issues.
 
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Gerhard562 days ago

Hi,

maybe it is worth to think about an new Controller instead of a hack. New Controller, USB, so no nasty Buttons, cause the KBD is ... and have easier way to select/create profiles and control the fan/heater ...

With best regards

Gerhard

ketchopi1 month ago

You made my day, I was ready to give up, it didn't work with lead-free paste.
I have the little one (T-962), and there is no SSR in this model, but the card seems to be the same. I control now the fan as you do, by putting 0V (through a 1k resistor) to the pin #2 of the optocoupler and I read the state of the heater at the same place as you do.


Tests still in progress but turn the fan on at slow speed during the entire process seems to be better than turn it on only when the heater is on (in my case anyway).

KirAsh41 month ago

So I made this mod to my T-962 oven and it all works as expected. The problem I'm having is that it's affecting the profile way too much. After all it's sucking in cold air. I've slowed down the fan as much as I could but it's still too much. When the fan is running on PWM, the oven can't reach the required temperature and when it does get within 10 degrees, which automatically shuts off the heating elements and therefore also the fan, the temperature will always overshoot the target. I did a quick plot of a profile on an empty run and you can see it here: http://imgur.com/9SMPlkw (the Heat, Fan, and PWM Fan plots are simply on/off indicators, not like the temperature ones.) You can see, during ramp up, how every time the heating elements shut off (and therefore the fan as well), the temperature will raise and overshoot the target temperature.

So my next step now is trying to figure out a way to not suck in cold air in, but somehow recirculate the hot air that's already in the oven. I'm not sure how well it would work if I close the intake vent during the ramp up, and open it up again during the cool down phase. Maybe I need to find a third fan to install somewhere inside the oven so it only recirculates the hot air that's already inside, as opposed to using the cooling fan to recirculate the air.

chinmay.das made it!4 months ago

I did the modification nearly a year ago, but lost the images somewhere. Anyways it works good. I used a Freeduino for FAN control, but Now I am thinking about replacing it with 555 timer circuit. :)

oven_before.JPGoven_after.JPG
fdavison4 months ago

Thanks for the info about the masking tape. Man, did that stink!

pcoyle4 months ago

Worked Perfectly with the Digispark USB Dev. Also had to change LED = 1 for rev 4 board. The pullup resistor is a must of course, but now I need to do proper calculations for the timer been off. On a PCB In the center of the lamps (T962) im getting a max temp of 293 which is seriously bad for component life. Thanks LEDartist

brettjones4 months ago

I have the T962 and like dzak, the arduino worked for the fan. However, the fan doesn't go on during cool down mode anymore. It works with the arduino controlling it but no longer with the stock controller. Any hints? Worst case I can always add a switch to the circuit to manually turn it on.

ledartist (author)  brettjones4 months ago

Do you have a 1k ohm resistor in series in the fan control line? You need one.

(see 5th photo under step 2)

colorado_rob made it!6 months ago

Very nice! I purchased a T-962 (the smaller sibling of the T-962A) and the Arduino hacks works there too. I ripped out the masking tape and replaced it with kapton tape. I used a tiny, cheap Digispark (which uses an ATTINY85) instead of an Arduino Uno for the fan control. A little shrink wrap to insulate the USB connector and a little more hot glue to hold it in place (who is going to notice a little more in there, eh?) and it works like a charm. I had to change the LED pin to "led = 1" for the Digispark. Everything else just worked.

Digispark_T-962.JPG

I was wondering Colorado_rob, How is that ATTINY85 working out for you in the system regarding the Main intake fan at the back regarding the even temperatures and temp profiles. I have the exact the same version of reflow oven and I find the temps seriously crazy. On Profile 1 with fluke DMM temp sensor I reach up to 277 degress (C) (LCD screen thinks it's doing a great temp job with false readings)

which is crazy, although it doesn't burn the boards, I am worried about the lifetime of the components attached to the PCB over the heat madness. There is another problem about hot, and cold spots, will this mod actually help it ?

Thanks for your reply Rob..

petrockblog7 months ago
Thanks a lot for your instructions - helped me a lot!

Recently I also finished a review about the T-962a - maybe you are interested in it: http://blog.petrockblock.com/2014/01/10/reflow-oven-t-962a-a-review/
dzak28 months ago
thanks for the info; i have ordered a T962 ; which in fact is only 800W ; this model is NOT using the solid state relay to power the lamps, but is in fact using a BT139 triac to power on/off the heaters. the board is the same as your just that the empty spot on your board is filled with the BT139 and some resistors
ledartist (author)  dzak28 months ago
Good to know. Thanks!
dzak2 ledartist8 months ago
I can confirm that the hack works fine also with the T962 version; there is just a little space problem to put the ardunio board ; i glued it to the top and protected top & back with some kaptop tape.

Mine also had masktape underneath the isolation instead of just on top; stripping that solved the horrible smell aswell!

thanks for the nice mod, and your code! it's simpel but effective!
frankav9 months ago
Nice article. Just received mine and sure enough, masking tape inside. Have Kapton tape already on order for another project, not arrived yet though. Anyway, need to add one very important thing: Safety. I checked mine and suspect all will be the same. The panels are coated with paint which acts as a good insulator. An earthing check showed the earth tag to not be connected to the back panel chassis. Having fixed that, there was also no continuity from the back panel to the rest of the case. This was fixed by grinding away the paint under a couple of screws each which go attach the back to the bottom and top chassis halves respectively.
dcms410 months ago
I was wondering what width and approximately how much Kapton tape you needed for this modification?
ledartist (author)  dcms410 months ago
I used wide tape (about 6 inch wide), but narrow tape should work just fine. Not too much tape is needed. I'm guessing about a yard.
I think you'll have to buy a roll anyway right?
dcms4 ledartist10 months ago
Yeah, I was just trying to figure out how much of a roll, based on the width and length.

You posted in May, is it still working well for you? How often do you use it? What's the largest thing you've baked?

Thanks.
Don
ledartist (author)  dcms410 months ago
It's working pretty well. Once the temp profile is tuned in, this oven produces pretty reliable results.
I only use it once or twice a week on average. The largest PCB I've done is about 5 x 5 inches, two of them together.
budgetcomputer11 months ago
i need some information for t962a

We are a computer and mobile phone repair shop and we repair laptop and mobile phone motherboards, for example GPU on the laptop main-board we fix by applying certain heat by hot air gun and applying flux on it reflowing process, and liquid damaged mobile phone main-board we do ultrasonic cleaning and then heat the main-board to reflow.

My understanding of this machine is that while doing the reflow manually we can just put the laptop mother board in this oven set the right time and heat setting and it will reflow the soldering on the ic and chips? am i right? if this is correct i will buy the machine and is it compatible with voltage in new zealand?

hoping to hear from you soon?
ledartist (author)  budgetcomputer11 months ago
There is a lot of information about this oven - just google T962. My experience is that if you limit the use to lead-tin solder and avoid large components like USB jacks, this oven works well.

I'd look for a better oven for what you are trying to do personally...

gbmhunter1 year ago
Thanks for this teardown of the T962A! I am looking at getting one, this is better than any review I have found!
Hey I just post my reply to this post, but It just got vanished somewhere, so I am reposting my comments.
I got you. But I can say the IR heating part is doing there work quite well, because I use an additional set up for Temperature Measurement using an Industrial Thermocouple+ Arduin+LCD display. What I found the heating element is actually working w.r.t Temperature increment resolution (Which is 1-3 degree C rise in temp per Sec) which is required for reflow process. All issue comes with Uneven heat distribution. Yah you are right , I will try out your Fan trick, n find if it solves the heating issue. Thanks for your support.

Oh yes I will ask her to leave comment or query on your blog , in fact your blog is the best resource to know about your work.. :)
Is it.. Did you set up your own temp profile? Have you tested it? I hope Customized profile does not show up That time difference. I tried to bake two WiFi board using this oven, but due to this time difference the whole process ran over time , as result WiFi modules pop out n module got dead :( . Then I learn for this reflow process timing is very imp factor, even if you bake little more just for 2-3 secs components get damage seriously. So please share your results on the customized temp profile. :) And yes I am A Fan of your Led Art work. I showed your work to one of my Friend , who is an Interior Designer, and she totally blown away. She asked me if you would like to share your art work process from your blog.
ledartist (author)  chinmay.das1 year ago
I did set up custom profile, but the preset one worked pretty well for lead-tin solder. I just wanted to see if I can improve it.

The built in timer is simply slow. It's the same when you use custom profile as well, so you can simply treat each 10 sec step as 15 sec step in creating your profile.

I also did not find the timing to be too critical. With lead-free solder, I tweaked the profile to keep the peak temperature time as short as possible, but temperature accuracy (which I don't have the tool to verify) and heat distribution are more important.

I'd attribute your problem of burning parts to uneven heat distribution (hot spots), and temperature error. This oven can be running much higher temp than what it's telling you.
Also taller parts get too much heat because they are closer to the heater. My fan trick might help a bit.

Thanks for showing my work to your friend! Please have her email me or leave comments on my website, and I will answer her questions.



Hello Akimitsu Sadoi. good to know you have found a solution of that nasty smell. I bought the same model oven few months back. But during running this oven I found a serious defect in heating process. As per the profile configured for re-flow soldering the complete process should be completed in 7-8mins, but when I ran the process It took nearly 12 mins in actual .And a very strange thing is you can actually monitor that time delay error on its GLCD screen. I did some test running to monitor the re-flow graph , and I found this delay was happening through out the process.I hv more detail information regarding this issue n wud like to share . But you have also found way to improve heat distribution. I will try it on my system, hence will update you if dat solve that delay problem.
and All the best for your Maker Faire trip. :)
ledartist (author)  chinmay.das1 year ago
Thanks for your comment.
The timer is indeed very off - takes about 1.5 times what the panel says. So I took that into account in creating my temp profile.

I think it's an usable enough machine to be worth the price, but could be a lot better.

Please let me know more about your experience.

Aki

kbaudio1 year ago
muy didactico muy buen trabajo te felicito!!!!!