Author Topic: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven  (Read 36610 times)

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Offline peter.mitchell

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #25 on: December 21, 2013, 02:29:20 am »
Just wondering, whats the go with using SSRs in these things, compared to using TRIACS? Is it primarily just heat dissipation.
A SSR is typically just either a triac or a pair of back-to-back MOSFETS, plus isolation etc. in the same package.
I think some use photovoltaic isolators to drive MOSFETS, which probably reduces losses- a triac drops typically 0.8V, so produces a fair amount of heat when switching heavy loads.
SSRs also have stuff like isolation & approvals taken care of.

BTW I didn't like how it looked like that low-voltage wire could touch the fuseholder.

I just queried it because often in these kinds of things it seems like they switch the load slowly, but quite hard, so i don't expect the elements(or whatever else is being switched) to last long - though I have no idea if they do or not. I understand why they do it (the loop is quite slow so the switching speed is fairly inconsequential), it just seems kinda wrong when you could use some triacs and run the elements more "proportionally". (I hope you understand what I mean)

The point about isolation and approvals though is fair enough in itself.

Is there some other reason to use MOSFETS, I mean at 10A you need a MOSFET with 80 mOhm on-resistance (and 300+ volt capability) which is quite expensive, just to compete with the 0.8 V drop in the triac?
I don't know if it is just me, but I do generally think of SSRs as back to back MOSFETS (even though i know there is a lot of variety amongst them), rather than TRIACS because of their performance when used with DC. To me, the "relay" part of SSR implies isolated, switching of anything, be it AC, DC, pulsed DC, AC with DC offset ect.

 

Offline mikeselectricstuff

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #26 on: December 21, 2013, 02:29:54 am »
If they'd have used a transformer with a primary center tap and a back panel voltage selector switch, or to save money, just a jumper on the PCB, they could have easily made it 230/115V.

..except the SSR would need to handle twice the current for the same wattage
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Offline TorqueRanger

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #27 on: December 21, 2013, 02:59:55 am »
Those boards look absolutely beautiful, aside from the silkscreen, such a letdown. however.... if you dont use silkscreen on your products, 10/10!

Yeah, just the poor silkscreen, bummer.
Ever think about selling the boards as a limited edition???
 

Offline Bored@Work

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #28 on: December 21, 2013, 03:02:31 am »
Hi
Has anyone here tried a small infrared reflow oven such as  http://www.ebay.com/itm/T962-INFRARED-IC-HEATER-REFLOW-OVEN-SMD-BGA-T-962-d-/260799459468?pt=LH_DefaultDomain_0&hash=item3cb8dbf08c

For $245 USD it is about the same cost as this thermal controller+toaster.

Google T962. That thing is horrible trash.
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Offline jancumps

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #29 on: December 21, 2013, 03:10:58 am »
Nice video of the home (small business) reflow owen, especially showing the process and the traps there are (calibration, metal grill etc)..

I wonder though, if you should mentioned a bit more clear that you didn't actually purchase the owen and controller (was gifted), and that the entire set (including materials, delivery etc) would have cost close or over 300 Euros.
it must have been mentioned somewhere. I'm too lazy to run through the whole 1 hour video to find out where though;)
 

Offline zapta

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #30 on: December 21, 2013, 03:37:26 am »
Convection can make all the difference. The first run failed being undertemp, but notice the parts that didn't reflow were directly above the metal of the tray.

.. and here the the proof using my grandma's E4:

Drain the swamp.
 

Offline DarkPrince

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #31 on: December 21, 2013, 04:22:21 am »
Looks like 1500W is holding up pretty well for you. I noticed that after calibration the high temperature measurement was off. The controller thinks there was only a 6°C overshoot where as there was an 11°C one according to your reference (Agilent). Not a thermal conductivity/mass issue either as it also tapered off. I'd presume that is an issue where more than expected (beyond the thermocouple) non-linear relationship occurred. So before it was calibrated I wonder what the offset between true and measured temperature was at high temperatures (200°C+).

I'm looking forward to using a reflow oven. Tired of the hot-air rework which is a PITA with varying sized parts.

Thanks for the morning video!
 

Offline BravoV

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #32 on: December 21, 2013, 04:35:06 am »
Just curious if using that kind of PID controller + a mounted hot air gun + an enclosure with some creative mod to circulate the hot air inside that spreads or circulates the air evenly without blowing off the board/components, will yield better result ?  Has anyone ever seen or tried similar setup ?

« Last Edit: December 21, 2013, 05:01:05 am by BravoV »
 

Offline Anks

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #33 on: December 21, 2013, 06:34:37 am »
So can I have a uCurrent olive gold
 

Offline thereza

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #34 on: December 21, 2013, 06:44:28 am »
I feel the need to chime in here.  I've been making prototype boards in toasters since '01.  I have made very complicated boards with all sorts of components including BGAs and mostly 0402 components.  In the past 12 years, I've had 1 board failure - it was a BGA that I didn't align properly.   The secret it to use an IR toaster - I have this one - http://www.amazon.com/Panasonic-NB-G100P-7-2-Quart-1300-Watt-Infrared/dp/B000063UZV (has been discontinued and they came out with a newer model; not sure what changed).  There is a black & decker one too but that one catches fire a lot. 

To reflow - put the board in the oven - turn it on full heat, watch it waiting for it to reflow (3-4 minutes), give it another 5-10 seconds to make sure that the undersides of the components reflow (thermal packages, etc)  open door and turn off.  DONE. 

Never measured the heating profile, never had a problem with the full-on approach.   Only failure was due to a misaligned BGA once. 

I use lead free solder from these guys - unrefriderated shelf life of ~3-4 years from my experience http://www.zeph.com/zephpaste.htm
make sure to get their nice plunger.  I also use their BGA flux for bga stuff.  everything else they sell is horrible.   And use the smallest tips (red ones).

If its complicated, I cut out a stencil using my silhouette stencil cutter.  cheap, works great.   Else just use the syringe to spread some paste on the pads.

 

Offline Chipguy

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #35 on: December 21, 2013, 06:57:58 am »
Regarding the stencil, they definetly screwed that one up.
I just got a panel like yours from PCB pool some weeks ago and before I ordered that I actually called them and asked.
Their answer was clearly : "If you order a panel you will get a stencil for the panel".

It's not the first time they screwed that up. That was the reason I actually called them, because I was not sure.
Where is that smoke coming from?
 

Offline woox2k

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #36 on: December 21, 2013, 07:08:04 am »
1. Would it be possible to use some blank PCB as a tray to avoid uneven temperatures on the board?

2. Considering that the temperature sensor fault is not linear, i think it would be best to set the offset while on maximum temperature to avoid any unexpected overheats (or underheat for that matter). The whole point would be to make it reflow nicely while not damaging the components. Wrong temperature reading on room temp is not important at all.
 

Offline Alana

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #37 on: December 21, 2013, 07:15:09 am »
Have anyone used such oven to fix a laptop motherboard with chipset soldering fault?
 

Offline mtdoc

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #38 on: December 21, 2013, 07:36:15 am »
1. Would it be possible to use some blank PCB as a tray to avoid uneven temperatures on the board?l.

How about using a small, toaster over pizza stone like THIS

It has some good thermal mass and works well to evenly heat a pizza crust ....
 

Offline mikeselectricstuff

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #39 on: December 21, 2013, 08:07:49 am »
1. Would it be possible to use some blank PCB as a tray to avoid uneven temperatures on the board?
PCB is not ideal as it will not withstand repeated reflow cycles - a thin metal plate would be better
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Offline MatthiasBerlin

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« Reply #40 on: December 21, 2013, 08:35:23 am »
Severin, the maker of the oven, is a German family enterprise that manufactures smaller household devices. Their stuff is usually more at the lower end of the price range, but OK for the money.
Most of the products are not made in Germany, but in China. So most probably Dave's oven has been traveling around the world quite a bit yet ;) .
The company claims world-wide availability of their products, but seem not to be present in the Americas and Australia, just roughly Europe, Middle East, parts of Asia and Africa. So you were right about (regular) availability in Australia, it seems. See http://www.severin.com/gb for English home page.

That mixture of English and German everywhere around the kit, including the control software, is funny :) .
 

Offline JOERGG

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #41 on: December 21, 2013, 09:05:41 am »
At 11:55 in the video did i spot a unsoldered capacitor ?
And the long screw above the yellow connector looks misplaced, what is it used for?
If i write funny things, because english is not my native language, feel free to laugh. It is not always easy to find the right expression.
 

Offline Pat Pending

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #42 on: December 21, 2013, 09:15:15 am »
Don't use convection air if the oven is started from cold.

While the top surface of my PCBs (leaded paste) reached 230C, the underside 5cm lower was just getting to 200C.
I found it was better not to wire oven such that convection was always on.

After testing a layer of baking foil on the inside of the ovens glass door, the thermal ramp-up was much faster than without.
Aluminum flashing worked too and had a great appearance when installed. The thermal ramp-up was Ok, but the foil worked best even though it was crinkled.

I tried ceramic insulation between the oven and outer shell but this made cool down too long.
 

Offline EEVblog

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #43 on: December 21, 2013, 09:15:55 am »
Looks like 1500W is holding up pretty well for you. I noticed that after calibration the high temperature measurement was off. The controller thinks there was only a 6°C overshoot where as there was an 11°C one according to your reference (Agilent).

I was getting that sort of difference between the Agilent and Fluke probes at high moving temps also. So there are likely several variable at play here. That's proabbly the best matching that can be expected with such ovens.
 

Offline EEVblog

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #44 on: December 21, 2013, 09:18:05 am »
Regarding the stencil, they definetly screwed that one up.
I just got a panel like yours from PCB pool some weeks ago and before I ordered that I actually called them and asked.
Their answer was clearly : "If you order a panel you will get a stencil for the panel".

Yes, they just admitted they screwed that up, you usually get the full panel.
They have also said the silkscreen should have been better than that, and they would have offered a replacement in this case.
The EEVblog review curse strikes again!
 

Offline SPRX

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #45 on: December 21, 2013, 09:52:36 am »

Please check below Dangerous Prototypes' video on a reflow oven. I found it very useful too:

http://dangerousprototypes.com/2013/02/14/workshop-video-55-infrared-reflow-oven-qinsi-qs-5100/

 

Offline jesuscf

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #46 on: December 21, 2013, 10:18:37 am »
I have solder hundreds of boards using a cheapo B&D toaster oven with a homemade oven controller.  I also tested different toaster ovens with similar results.  A few things I have learned:

0) Nowadays you can cut your own high quality stencils using a craft cutter like the Silhouette Cameo.  All the juicy details can be found here:

http://dangerousprototypes.com/forum/viewtopic.php?f=68&t=5341

1) A LOT of heat escapes through the toaster oven window.  Covering the window inside with aluminum foil makes a huge difference.  If you need to see the solder paste re flowing cut an small hole into the aluminum foil!  Even with the aluminum foil there are two cold spots at the front on each side of the oven.

2) Put the temperature sensor directly on the board being re flowed.  Even better, put it closer to the highest thermal mass component that is closer to the window.

3) The convection fan doesn't help at all.  Actually, it makes things worst.  A 1500W toaster oven is capable of 1 oC/s.   Turn the fan on and you'll be lucky to get 0.5 oC/s.

4) PID controllers work quite nicely if they are tuned.   Change oven, ambient temperature, move the board around, etc. and the constants need to be adjusted.  I had much better results with a simple state machine that uses the code below.   The variables 'soak_temp', 'Soak_PWM', 'soak_time',  'reflow_temp', 'Reflow_PWM', and 'reflow_time',  are all adjustable using a keypad and LCD.  I adjust them depending on the solder paste used, the PCB manufacturer, and the profile of the components.  Attached is a screen capture of the temperature using the state machine controller.

5) Fumes.  Re flow in a well ventilated area.


switch (state)
{
    case 0: // Flux activation
        pwm=100;
        if (t_oven>=soak_temp)
        {
             state_time=0;
             state=1;
        }
        break;
               
     case 1: // Soak
         pwm=Soak_PWM;
         if (state_time>soak_time)
        {
             state_time=0;
             state=2;
         }
         break;
               
      case 2: // Ramp up
          pwm=100;
          if (t_oven>=reflow_temp)
         {
              state_time=0;
              state=3;
          }
          break;
               
      case 3: // Reflow
          pwm=Reflow_PWM;
          if (state_time>reflow_time) // Done.
         {
               pwm=0;
               state=4;
          }
          break;
               
      case 4: // Cool down
           pwm=0;
           if (t_oven<60) return;
           break;
}
« Last Edit: December 21, 2013, 10:51:04 am by jesuscf »
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Offline ShawnD

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #47 on: December 21, 2013, 10:26:55 am »

..except the SSR would need to handle twice the current for the same wattage
[/quote]

Since the standard North American outlet is 120V 15A the existing 16A SSR will do fine.  Most appliances are 1500W or lower. 
 

Offline jwm

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #48 on: December 21, 2013, 10:41:36 am »
Yeah that metal grill def caused an issue on the first attempt. Maybe some FR4 or similar as a baseplate to give more even thermals.

I was curious to see what a big piece of copper clad board would do acting as a heat shield and heat sink...

I have used a large sheet of solid copper on the tray between the board and the heating element to give signifigantly better results in a similar setup. Aluminum also worked and was cheaper but didn't develop nearly as pretty of a patina as copper did when heated. :)

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Offline HackedFridgeMagnet

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Re: EEVblog #558 - Beta Layout DIY SMD Thermal Reflow Oven
« Reply #49 on: December 21, 2013, 11:20:30 am »
I thought I saw the metal tip of the thermocouple touching the pcb copper in the video.
If it was touching would this have effected the reading of the temperature, by being a 3rd dissimilar metal?
 


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