Electronics > Beginners
Manual (dumb) toaster-oven reflow parts recommendations?
RL_Tracksuit_Electro:
I want to do very low volume hobby smd reflow, been doing with hot air station and want to try oven.
I want to dip my toe in the water with the "watch it through the glass & thermocouple" approach, i.e. no microcontroller running a profile.
Basically, all I'm willing to invest in now is:
1. cheap toaster oven
2. multimeter with thermocouple I'll just wedge in through gap in the door mounted to a bare pcb or something with capton tape.
If you're doing it this way (or used to), would appreciate the amazon links to toaster oven & meter/couple you're using. Trying to avoid guessing and finding e.g. the door has no gap to run in a couple wire, etc. Otherwise I'll just guess. Really looking to keep this under $50 US. Thanks.
jmelson:
--- Quote from: RL_Tracksuit_Electro on January 19, 2020, 05:52:37 pm ---I want to do very low volume hobby smd reflow, been doing with hot air station and want to try oven.
I want to dip my toe in the water with the "watch it through the glass & thermocouple" approach, i.e. no microcontroller running a profile.
Basically, all I'm willing to invest in now is:
1. cheap toaster oven
2. multimeter with thermocouple I'll just wedge in through gap in the door mounted to a bare pcb or something with capton tape.
If you're doing it this way (or used to), would appreciate the amazon links to toaster oven & meter/couple you're using. Trying to avoid guessing and finding e.g. the door has no gap to run in a couple wire, etc. Otherwise I'll just guess. Really looking to keep this under $50 US. Thanks.
--- End quote ---
I use a cheap (WalMart) GE brand toaster oven with 4 heating elements. These are straight rods about 1/4" diameter that run horizontally, left to right. Two above and two below the rack. It has a thermostat that is outside the chamber, and so must work by self-heating due to the current.
I bought a ramp and soak thermocouple controller, that allows a thermal profile to be entered -- heat to 180 C, hold for 1 minute, heat to 245 C, hold for 1 minute, cool to ambient in 2 minutes. I lucked into a lifetime supply of micro-size thermocouple extension wire. I poke the thermocouple into a
plated-through hole in the PC board, thus the controller is monitoring the true temperature of the board.
I have done over 2000 boards with this setup, and it works great. Don't forget to put the thermocouple in the hole in the board, or the boards will
go up in smoke. Apparently, the PC board material and the ICs are great IR absorbers, and the thermocouple just hanging in the air is NOT!
I made that mistake ONCE, only.
I can do 4, 6 or 8 boards at one time, depending on size.
Jon
Peabody:
An alternative you might want to consider is a hot plate. I did a hot plate project which consists of the $10 Walmart hot plate, a $5 circular saw blade, and three screws, total cost about $20. Instead of measuring temperature with a thermocouple, you simply turn it on for a certain period, then off for another period, then back on for the last period, and it's the same for pretty much any board size. So instead of a thermocouple and its mounting issues, you just need a watch, or a previoudly-recorded audio tape that tells you when to turn it on and off.
There's a related video and a Github repo:
https://github.com/gbhug5a/Reflow-Hot-Plate-and-Controller
I donated mine to my local maker space, and they report it works fine. Leaded solder paste, of course. When I was testing it, I found it to be very forgiving, with no scorching of anything.
rstofer:
For small boards, I use a hot plate. I put the board on the plate, turn the knob fully on and watch for the solder to flow. I remove the board with tweezers, trying hard not to dislodge any parts, and set it aside to cool. Then I turn off the hotplate.
Toaster oven: Mine is automated so no help there. I did fill the cavity between the inner and outer wall with high temperature matting (McMaster-Carr) because the heat loss was so high I really couldn't get up to temperature anywhere near fast enough.
If you think you can see the solder flow, manual control may be enough. The thing is, I don't think you will be able to see the solder everywhere on the board.
RL_Tracksuit_Electro:
Thanks for the tip, I want to try this but you seem to imply leaded paste is necessary...
I have lead free but advertised as "low temp", the tube says melting point 137C/278F.
https://www.amazon.com/gp/product/B017RSGPI8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Is there something special about the leaded paste or did you just mean shorthand for melting point?
Any idea if the paste I have is within the range the hotplate approach can do?
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