Anyone want to collaborate on this?
I was thinking, rather than use a temp sensor, point a pyrometer at the PCB to get an accurate temperature of the board itself. I'm not the only one thinking of this, I found a few links.
I have a Harbor Freight noncontact pyrometer that is good to 250C, which should be high enough with leaded solder paste. I opened it and found it had a row of pads along the edge labeled. Someone already did the the work of figuring it out here:
http://dbearsblog.blogspot.com/2011/04/harbor-freight-infrared-thermometer.html
A comment on it says:
http://www.meas-spec.com/downloads/TSEV01C_rev2.pdf
.. is described, that the thermometer uses an I2C BUS. EXAMPLE: For reading object temperature send: 0xB6
Return values i.e.: Byte(0) = 0x0E, Byte(1) = 0xAA
Temperature Tobj = (256 * Byte(0) + Byte(1)) / 100 = (256 * 14 + 170) / 100 = 37,54°C
I want to cut a hole in the top of my toaster oven to look through. However, I need a glass window that will pass IR. Standard glass will not do so. I did a bit of Googling but the sources I found were wholesale with huge minimums, albeit low prices per square cm. If I have to, I figure I can break apart an IR heater bulb and use a chunk of that glass. The right silicone will stand up to over 300C. A fan in the sensor compartment should keep it cool.
Some good literature on reflow soldering temps:
http://www.altera.com/literature/an/an353.pdf
I'm thinking of a triac with phase control via an Arduino. I want it to have a 128x64 pixel monochrome screen and be able to save multiple temperature profiles. My intention is to also use it to cure pigmented inkjet ink for directly printing resist onto blank PCBs with an Epson R200. Settable parameters would be max delta Temp, target temps, and hold times.
So, anyone want to collaborate on this?
Steve Greenfield AE7HD
aka Polymorph
This could end up as a Kickstarter/IndieGoGo project.
I don't have a burning desire for a reflow oven. Keith (who could actually use one daily) has talked building one several times.
My random thoughts:
- Sounds like you are making a scientific instrument quality oven. Does the process require such precision? It is recommended, but what are the possible side effects of Doing It All Wrong: with hot air or process control or a airtemp thermocouple in a non-calibrated oven?
- Asking for a sample of the glass from a sales rep or a business/.edu front might yield a piece big enought to work with.
- I like the idea of an oven window, period.
- Brief Googling shows lead-free paste melt points in the 240-260C range, so it's probably doable.
For temps, I'm going by published temperature profiles. This sensor is at the top end of what is required.
As far as overbuilding, that is what I do.
Actually, curing the ink does seem to be rather picky. Although most seem to just watch it and judge by the copper turning purple.
I've seen quite a few Youtube videos where someone has just placed their board on an electric skillet, just manually shutting off the power after all joints have melted.
But where's the fun in that?
I know you have done some research, but:
- this guy is smart + pretty good at documenting
- I haven't seen a "George Foreman"-type grill used for this before.
http://jeelabs.net/projects/cafe/wiki/POF_04_Reflow_controller
The more I think about it, the more I worry that a pyrometer will give me false readings just because it gets a component with a different emissivity placed beneath it.
I want to use this for more than just reflow soldering. Curing inkjet resist, drying out electronics, etc. I'm thinking a thermocouple will do.
meh the toaster at work does a good enough job reflowing hp printer nics... an cooks a fine frozen pizza.