Re: Toaster Oven dimmer ?


Sylvain Munaut wrote:
>
> Yes, I've seen that. Actually it's when I saw you successfully soldered
> BGA that I decided to try it by myself ;)
>
> I've just bought a oven, it's not quart element, just 2 heating resitors
> on the top and 2 heating resistors on the bottom. 1500W total power. The
> inside looked exactly like
> http://www.sparkfun.com/tutorial/ReflowToaster/reflow-toaster.htm
>
> To do a quick heat speed test, I placed a thermocouple inside. However,
> it was near the back panel, not really centered (it's a multimeter probe
> so i inserted it trhu a screw hole). And at posteriori the real inside
> temp must have been quite hotter than that.
>
> It heats at about 1-1.5 °C at the start and at 0.2 °C/s when above
> 200°C. However these measure might be flawed see what follows.
>
>
> As a quick test, I just took a PCB where the silk screen was failed and
> where I did some solder test. I took some pads where there was a solder
> "bubble" on the pad and applied flux, then some 0805 and 1206
> components. Then I turned on the oven till I read 130 °C, maintain that
> for 2 min, then heat up till 220°C and maintain that for 30 s. However
> the temperature in there must have been higher as the pcb itself kindof
> melted ;) (the different layers separting themselves, bubble appearing
> inside) Guess I have to get a better reading than that. The solders
> looks ok though, even if the components and the pcb are near burnt ;)
>
>
> Sylvain

I would say that you were way above 220 degrees C on the board that
seperated.

I have noticed that most of the heating takes place by infrared. If
the thermocoule was not in contact with the board, there could have
been large temperature differences. I saw a 50 C difference between a
piece of copperclad (very reflective of IR) and a board with green
soldermask in testing. I placed my thermocouple directly on top of the
board near the BGA.

Your heating speeds seem reasonable. Mine is about 2C/second at room
temperature and 0.5C/second at 200 C. Xilinx recommends ramping up to
the peak temperature at 2-3 degrees C per second if I remember
correctly. I believe I would be in that range with the second element
since the decrease in speed is probably due to the poor insulation of
the oven.

Darrell Harmon

.

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