Vapour phase Soldering

[wraper]

Tombstones are just painful.  We get the odd ones happening in our reflow oven from time to time.

I know this is an old thread, but just out of curiosity: did you try the notched paste mask (see picture)?

IMDES is full of BS. Lower amount of paste can somewhat help but the main issue is that supposed temperature profile (with proper rise curve) on their website is totally fake. Just making my own crude controller in one evening, without any fine tuning reduced tombstoning by at least a factor of 10.

[mrpackethead]

I do use a notched stencil, like that, but the reason you use it, is NOT for tombstones!!!    Its there to help mid component balling..   ( tiny bits of solder that find their way off the pad and 'ball' up and sit mid way on the component.

Like Wraper,  the profile that a stock IMDES machie produces is just garbage.   

[SWR]

Thanks for the feedback. 
I'll propably have to roll my own controller then?
The following pieces comes to mind with the UI on the phone:
- ESP32: https://www.aliexpress.com/item/ESP32-WROOM-32-ESP32-WROOM-32D-ESP-WROOM-02-ESP-WROOM-02D-Module-Espressif-Original/32963147246.html?spm=a2g0s.9042311.0.0.27424c4do9R97H
- PSU: https://www.aliexpress.com/item/AC-DC-110V-220V-to-3-3V-700mA-2-3W-Switching-Switch-Power-Supply-Buck-Converter/32833671094.html?spm=a2g0s.9042311.0.0.27424c4dqlJOSB
- Temp: https://www.aliexpress.com/item/MAX6675-K-Type-Thermocouple-Temperature-Sensor-Converter-Board-For-Arduino-SPI-Interface-Module-For-Arduino-50mA/32834862835.html?spm=a2g0s.9042311.0.0.36474c4d2fRX9M
- Heat: https://www.aliexpress.com/item/SSR-25DA-DC-control-AC-SSR-white-shell-Single-phase-Solid-state-relay/32295725401.html?spm=a2g0s.9042311.0.0.27424c4dYBRlNf

Do you have a better solution?

[daedalus]

I have just reflowed my first batch of boards with vapour phase. I am very happy with the quality of soldering achieved. Currently i am using a cheap hotplate, and an asparagus steamer with approximately 200ml of Galden 230 in the bottom, and the pcb in a mesh tray above the fluid. I have a dual channel temperature meter, and am measuring temp in the fluid and temp 1" above it. I currently heat on full power until the galden hits 220 deg C, then i turn off the heat and let it coast until the board has seen 230 deg C for 40s. After that i quench the entire pot in a sink of cold water.

After doing this on 3 runs the galden remaining is appearing milky coloured, is this to be expected?

[mrpackethead]

The 'milky' appearnace will be flux that is now floating ( not disolved ) in the galden.
I'd seriously suggest that your profile woudl be pretty scary if you are just heating it full on.
Get a little bit of PID control.

( see my thread about my frying pan project ).

[Koen]

Yes. Filter it with coffee paper filters from time to time.

Don't waste your time and money complicating a process that works so easily.

[mrpackethead]

Yes. Filter it with coffee paper filters from time to time.

This works really well

[ebclr]

[helius]

The thermocouple should be attached to the board, not put in the boiling liquid; it's physically impossible for it to be anything other than 230°C, no information is gained.

[daedalus]

Thanks for the help, will run the lot through some filter paper and see if that helps. I just ran another batch, and getting some tombstoning, so probably will upgrade to a PID controller at some point soon.

RE the thermocouples, the one above the board is there so that i can be sure that the whole board has reached thermal equilibrium before this sensor hits 230. Regarding the other one, I start from cold with the board in place, so having a sensor that lets me know how long until the vapour cloud forms is useful as i am operating this manually.

[wraper]

Coffee filter will only help if you rapidly filter the fluid after reflow. Otherwise flux will just deposit on walls and galden will become clear again.