DIY Vapour Phase Frying Pan Project

[mrpackethead]

I've never tryed this, but it is an interesting idea.    Vapour phase removal of a BGA.    The lifting arm has a special high temp adhesive tape, that you use to stick it to the bga.   Into the oven, and when its hot enough the spring will lift it up.

Of course everthing else gets molten.. but.. non the less its one way to doing it.

[mikeselectricstuff]

Reworking aluminium PCBs sounds like a nightmare!

Quote from: mikeselectricstuff on Today at 07:53:07 pm

I have one of those - they are awesome for reworking aluminium PCBs.

With a hotplate it's a piece of cake - place the PCB on the plate, then push it down with a probe where you want to rework, to improve  thermal contact - then just pick off the old part, and drop on a (pre-fluxed) replacement.
If I was doing it a lot I'd make a rig with a hand-rest, but for thinks like replacing LEDs or popping mis-placed ones into place it's really quick & easy

[Kean]

With a hotplate it's a piece of cake - place the PCB on the plate, then push it down with a probe where you want to rework, to improve  thermal contact - then just pick off the old part, and drop on a (pre-fluxed) replacement.
If I was doing it a lot I'd make a rig with a hand-rest, but for thinks like replacing LEDs or popping mis-placed ones into place it's really quick & easy

I bought a 946D with the same thing in mind, so glad to hear it works for you. 
I think the 946D is basically the same as the C model, but also comes with clamps for doing phone screen repairs.

I also have a KADA 853A IR unit which I use for pre-heating for through hole rework & part salvage.

[trevwhite]

Quote from: trevwhite on Yesterday at 08:06:37 pm

Reworking aluminium PCBs sounds like a nightmare!

>Quote from: mikeselectricstuff on Today at 07:53:07 pm

I have one of those - they are awesome for reworking aluminium PCBs.

#smlt#/blockquote>

With a hotplate it's a piece of cake - place the PCB on the plate, then push it down with a probe where you want to rework, to improve  thermal contact - then just pick off the old part, and drop on a (pre-fluxed) replacement.
If I was doing it a lot I'd make a rig with a hand-rest, but for thinks like replacing LEDs or popping mis-placed ones into place it's really quick #smamp# easy

I take it you have to watch the clock when doing this. You cant have the components hot for too long else damage will be caused?

How long does it take to heat up the board? Can it actually be used for reflow or is it too slow?

Trev

[mrpackethead]

I spent a bit of time today, working out how i will describe the Reflow curve.  I've decided i'll represent it in JSON. This makes it very easy to tweak and change, and add additional curve points if required, without adjusting the main code.

Everything shoudl be pretty straight forward to undersand.  Looprate is in Hz.. This means we'll read the temp, and adjust the the PID settings 10times a second.     We'll interpolate the values between the stated points.

{
  "name": "SAC305_LS230",
  "description": "Reflow profile for Frying Pan"
  "looprate": 10,
  "heating_max_duty_cycle": 100,
  "cooling_min_ontime": 1
  "profile":
     {
     "p1": {
             "time": 120,
             "temp": 150
           }
     "p2": {
             "time": 180,
             "temp": 160
           }
     "p3": {
             "time": 220,
             "temp": 230
           }
     "p4": {
             "time": 260,
             "temp": 230
           }
     "p5": {
             "time": 240,
             "temp": 200,
           }
     "p5": {
             "time": 300,
             "temp": 80
           }
     "p6": {
             "time": 360,
             "temp": 40
           }      
   }
}

[mikeselectricstuff]

Quote from: trevwhite on Yesterday at 08:06:37 pm

Reworking aluminium PCBs sounds like a nightmare!

>Quote from: mikeselectricstuff on Today at 07:53:07 pm

I have one of those - they are awesome for reworking aluminium PCBs.

#smlt#/blockquote>

With a hotplate it's a piece of cake - place the PCB on the plate, then push it down with a probe where you want to rework, to improve  thermal contact - then just pick off the old part, and drop on a (pre-fluxed) replacement.
If I was doing it a lot I'd make a rig with a hand-rest, but for thinks like replacing LEDs or popping mis-placed ones into place it's really quick #smamp# easy

I take it you have to watch the clock when doing this. You cant have the components hot for too long else damage will be caused?

How long does it take to heat up the board? Can it actually be used for reflow or is it too slow?

Trev

For reworking Ali boards, it heats up quick enough that time isn't a big issue.
Probably a little slow for reflow (800W heater) but would probably work if you pre-heated it before putting the board on. if you wanted to do it a lot, I'd maybe look at adding an insulating lid to reduce heat loss

[mrpackethead]

I have attached some intial code, that demonstrates how we can read the reflow profile from the json file, interpolate it, and create the set point.

Adding pid and temp read to this wont' take much longer, and i will change the timing so it does not use delay. rather actual system times, as reading the temp, and seeting the new PID will take time.


The code is python3;

Useage

python vpfry.py profile

[mrpackethead]

THis is the box i'm going to use to mount everything in.  Since its got AC power this is something that you dont just tag together on the bench to test..  I will get a combo 20A Circuit breaker/RCD for it as well. 

I need to put an AC fan in the box i think.

All the bits ( including the control PCB ) will be able to be mounted on teh DIN rail.  The heatsinks for the SSRS' have a profile that lets you slide them onto the din rail, they are a bit of a loose fit though, so i'll have to do somethign to secure them down. 

Going to connectorise everything so its easy to swap things around.  Adds to teh cost, but as this is a prototype it makes it a LOT more flexible.

[mrpackethead]

Mm. so if you dont' have an reflow system, then how to do you reflow the board that you need for the controller?

Ran out of time to do this one today. Maybe tommorrow.

[mrpackethead]

Assembled three pcbs, and yes, these where reflowed with vapour.

Couple of wee issues, but nothing thats a big deal.. I had the wrong USB connectors, so had to panelbeat a coupel of connectors to fit. :-)     The USB bit stands up, and i can talk to the chip.  will have to read the datasheets now to reach teh other devices.

[mrpackethead]

This project has to be diyable. so ive been deliberate about picking things that are relatively easy to get.

For the cooling fan,  I've picked a low cost ( i got this for NZ$19 on special ) AC desk fan. (23cm).      I dont' need or want most of  it, just the motor and the fan blade.   It took a few minutes to disassemble, and got the motor out.     Differnet models are going to need a differnet approach to this.    I removed as much as i could of the osciallation unit, but have a good look at it, and dont' remove too much. In the case of this fan, i'm going to leave the plastic part attached, as while it did contain the gears for the oscillation, it also holds the rotor in place.

This is only a 30W fan.  It looks like it will provide enough useful air flow.

[trevwhite]

Can I ask what method you used to vapour reflow these prototype boards?

Trerv

[mrpackethead]

Can I ask what method you used to vapour reflow these prototype boards

I reflowed them in the frying pan, with galden.. and some 'human' logic.. and a thermocouple plugged into a multimeter.     

[trevwhite]

Would it be possible to give a bit more detail? I would like to do a few boards and your experiences would really help my initial trials

[tautech]

Would it be possible to give a bit more detail? I would like to do a few boards and your experiences would really help my initial trials

Read the first post and study the linked thread.

[trevwhite]

I think a Controleo3 might be able to control a setup. It seems to have some fancy profiling command set and also intelligent PID control. It seems very flexible and source code is open for any mods. Looks like a lot of work has gone into it. Anyone used one/can recommend?

https://www.whizoo.com/
Trev

[wraper]

I think a Controleo3 might be able to control a setup. It seems to have some fancy profiling command set and also intelligent PID control. It seems very flexible and source code is open for any mods. Looks like a lot of work has gone into it. Anyone used one/can recommend?

https://www.whizoo.com/
Trev

Unless you write your own firmware, it won't work properly with vapor phase. It's nothing like controlling usual reflow oven. Simply slapping PID won't do the job. Given that you want proper temperature ramp. Not 100^oC PCB temperature and after 20 seconds solder already melted.

[trevwhite]

Hi, Wraper. Could you give a bit more detail on why it wont work? I know it's buried in the other thread but is there a link to the ideal profile for vapour phase?

I moticed the controleo even has a servo out. Might be possible to automate lifting the board up to help with cooling.

[wraper]

Hi, Wraper. Could you give a bit more detail on why it wont work? I know it's buried in the other thread but is there a link to the ideal profile for vapour phase?

I moticed the controleo even has a servo out. Might be possible to automate lifting the board up to help with cooling.

Because you basically need to regulate height of vapor phase, not it's temperature.

[trevwhite]

So once vapour reaches the right height then its just about dropping power delivery to maintain the height or temperature. So I think that can be scripted in the controleo3. Phase 1 would be to heat it up and then once it reaches above a temperature, phase 2 would implement a second pid control specifically to maintain the temperature which would reduce the power delivery dramatically.

The last thing is how to cool the board down quick enough.

[wraper]

As of ideal profile, generally you should preheat PCB by some other means and then move PCB into chamber with vapor phase. What I've done and what this thread is about is making workaround by slowly rising vapor phase to preheat PCB by air and small amount of vapor above vapor phase. The issue is that when liquid reaches boiling point, vapor phase rises extremely fast and has a lot of heat capacity. But before it reaches boiling point PCB simply stays cool.

[wraper]

So once vapour reaches the right height then its just about dropping power delivery to maintain the height or temperature.

It's will be somewhat controllable that way only if you place multiple temperature sensors at different heights. Also control is extremely laggy. It's not like you stop heating and vapor will stop to rise.

phase 2 would implement a second pid control specifically to maintain the temperature which would reduce the power delivery dramatically.

The problem with PID is that by time when it adjusts itself, solder is already melted. Basically you need to shut down heating even before vapor rises. Unless you want to heat with extremely small power extending reflow profile to unreasonably long time.

Here is what I've done with my oven

RTD position was lowered by about 5mm but it still reads lower than temp on the PCB, and there is significant inertia. Right now it works like this (PID would be useless in this case):
1. Start heating
2. Once reached 80^oC, stop heating, wait 25s (after this PCB will be about 150-160^oC hot)
3. Heat 14s, likely a little bit more would be better, like 18s.
4. Stop heating, wait 25s (after this PCB will be about 180-190^oC hot)
5. Start heating
6. Once 195^oC is reached, stop heating and turn on cooling.

Here is profile. In volts, not temperature units but you get the idea. Not perfect but order of magnitude better than it was originally. As you see, I start cooling fans way before 230^o C reflow temperature is reached. Because I know that once I add a bit more heating, PCB temperature will shoot to max.

[trevwhite]

Thanks for the information. How long does the board sit at 230 or 240C? I think the paste profiles like it to be for at least 45 seconds.

[wraper]

Thanks for the information. How long does the board sit at 230 or 240C? I think the paste profiles like it to be for at least 45 seconds.

There is no issue not staying long enough above melting point. The problem is cooling fast enough. Also with vapor phase you don't need to keep it under max temperature for long. All of the solder melts basically instantly everywhere. There is no such thing as heavier parts or large copper planes taking significantly more time.

[trevwhite]

I emailed Peter a bit who designed and makes the Controleo3. He has indicated that the profile language he created means that timers, wait for temp to be reached and ramp control can all be sequenced with his product. It seems the Controleo3 is not the typical reflow oven controller.

So based on Wraper's profile, is there much variation depending on the board size? I am thinking there must be some but maybe the vapour cloud has so much energy in it that there is capacity and one profile would do all boards.

Also cooling has been raised as important. Are fans blowing air at the pan proving good enough?