I'm setting up my first profile for a Heller oven.(Heller 1707) I'm using Kester's NXG33 solder paste, 4 layer, .062" PCB. I have the profile matching the spec. very well. My only question/concern is shocking the board with too much heat as it hits the zone in my oven. Is there a rule of thumb for a decent *Celcius/second. I want to say I read 3*C/s but I can't find where I read that. Does anyone with more experience able to shed some light?
I take a board at room temp and place it in a cold oven. Set the temp for max and watch the solder. At about 5 to 8 minutes the solder paste at the edges of the board turn from gray to silver. Then the solder in the center of the board flows. I watch the large components in the center of the board because they are last to flow. Then I open up the door and turn off the power. Don't bump the board until the solder sets up!!!