Regulation temperature peaks in reflow temperature (at least at the probe)

[babysitter]

Hey everybody,

employing a induction cooker and a tall asparagus cooking pot I made a setup to solder prototypes.
I am trying to approximate the VPS process as recommended by the solder paste maker, leaning towards using JEDEC J-STD-020 as guideline a bit now. The vapour medium used is Galden LS 230 and I realize the profile basically by observing a stop watch and thermometer to change the power setting of the induction cooker.

Attached you find the temperatures I logged with a K-type probe "sitting" on top of a bare PCB during one trial, the other records look similar. (Dont care for the cooling, I am not there yet.)

During the ramp-up phase you see that I got large temperature swings which I explain to myself by on-off-regulator action. These swings are much more than the JEDEC recommendation of 3 K/second.

Do they look dangerous or will these be low pass filtered by the parts on the PCB? The K-Type probe has a low mass to heat and is sitting on top of the board dry while the parts will already swim in a mix of flux and metal balls, coupled to the PCB and its "thermal inertia."

Does anyone have experience with this or how to measure better? I want to prevent the need to immerse the probe in paste with preparation, desoldering and cleaning each time, and with boards to populate there is not a lot of space for it besides a "touchdown area". (Actually I would like to have the probe "flying" over the board and consider that I first verify that the profile will be reproduced each time at board+part level and then I can go to measure the temp of the flying probe only to confirm that the board is exposed to the right profile.)

Best regards

[babysitter]

Forgotten attachment syndrome