Rework with Scotle IR-PRO-SC

[N3Star]

Hello,
I'm having major trouble with rework on this station. I (since most likely it's profile problem) keep killing or at least damaging chips. For now I'm using 3 TCs, 2x0.127 and one 0.25, all omegas, all are within 3 degrees from each other, I try to keep the TC end on the substrate and motherboard. GPU usually moves at ~225-230C on TC, so it's more less accurate. I mainly rework old GPUs and Xbox 360 on it. I have modded it to use variable bottom temp with P-soft, bottom max temp is 260C, realistically on thinner PCB I get 200 degrees, ramp is +60C from the profile (set like that so that top heater keeps up on 5-20% power up to ~180C). Top heater is about 4cm above flip chip. My profile is:
r1:0.38 L1:130 d:1 ---> on this step it ramps very slowly up to ~ 150C and then goes to:
r2:0.5 L2:220 d:200 ---> I never need to go higher or longer than that
Whole process takes ~ 9-10min, which is long, but profile I made from an extended SAC305 reflow profile killed every chip I tried.
(5mins till GPU comes off, but back then I tried to keep the GPU at 220-221C max;
r1:0.78 L1:100 d1:20 ---> ramps up to 150, slowly goes to 180, then:
r2:0.8 L2:220 d1:200)
On this at least I don't see solder balls coming from under the flip chip, though reflow usually leads to artifacts or black screen, so no short, but also not working. If it matters flux I'm using is either Amtech NC-218 or NC-559.

[diif]

Your top heater max temp looks low 200c max ?
Bottom heat lower, top heat higher.

[N3Star]

No, 200C was test only, I wanted to see what temp I would get without top heater (real bottom temperature). As I said on a regular profile I can take off the chip at ~225-230C.

[diif]

You have your bottom at 260c and your top at ?

[N3Star]

All my profiles go up to 220C, but due to thermal inertia it's higher, I never saw any temp higher than 230 on TC though.

[diif]

I have 200 on my bottom and I think 230 on the top.

[N3Star]

OK, how does Your profile look? I mean the slope, I think as long as it's made for IR upper heater I'll be able to replicate and try it. I also drew a rough sketch of how my profile looks like.

[diif]

I can't give you the exact settings at the moment but my top heater profile looks like a standard reflow profile. https://duckduckgo.com/?q=reflow+pro...e_17451(2).jpg

My bottom heater heats the whole board to around 100c and the top heater does most of the work. I have my heater closer. It's an Elstein element.

[N3Star]

OK, if You do anything later then please do take a picture of the slope. I'll also try on my own to more or less replicate that profile.
BTW, while we're at it, do Your boards get yellowed? Mine after 5min profile are in immaculate condition, but those after 10min one are kinda yellowed.

[N3Star]

Earlier today I did a test of how quickly this machine (100% power bottom heater only) can get a Xbox 360 mobo up to 200C, results in picture. I tried to make a profile out of it, it's about 300 seconds long (not included bottom heater initial phase of getting these +60 degrees), suitable for 70-90% power of bottom heater, I also upped the top heater temperature to 225C.

[diif]

I don't really have a slope, more a shape I showed earlier.
It rises at a couple of different rates and holds then rises to finish for the last bit before turning off, then I engage the fans.
It was a while since it was set up and I have no idea where the laptop is that we used to set the profile.

[N3Star]

For *some* reason I just cannot solder with rss profile, it has to be more of rts shape. Though I like leaving a bit of time for the PCB at 130-170C to soak this temperature.
Don't sweat it, but do You remember temperature rise rate for the final step? Since You have IR plates at 120C it's likely that our stations differ quite a bit, because mine doesn't have bottom HR component, it's all dark IR. This also seem to differ with other knowledge I got (bottom should do most of the work, top only for the last step), but then again everybodys profiles are like 5-6 minutes and mine is almost 9min long.

[diif]

I soak at about 200/210 before the final push, I think we have near identical stations. Apart from my upgraded top heater.
I will be able to get more precise details of the profile in a few days.