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Preheat temp setting duration when using AOYUE (etc.) 853A rework pre-heater

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Need to handle a small reflow task (this isn't a repair task, but this kind of requirement probably comes up during repair so thought i'd start here.)

I'm going to use an Aoyue (etc.) 853A rework pre-heating unit before hot air soldering.

Any guidance available on what temperature preset and pre-heat duration I should use?

Any guidance available on what workpiece temperature I should measure before using hot air to reflow?

Would a Flir-type IR imager be sufficient to measure temp of the workpiece?

Solder will be either 63/37 PbSn or 57Bi42Sn1Ag paste. The workpiece is small FR4 PCB.

Thanks  for any advice (or pointers to information on this topic.)

Don't bother measuring the temperature, you don't need rocket science precision here.
I preheat to 125°C on lead free PCB and then spot-heat the areas of interest with hot air set to 360.
If you used Bismuth tin, you'll need to drop the temperature to 90 plate /145 air.

Don't throw the PCB on the already heated hot plate, start with a cold(ish) plate to reduce thermal stress.

Hello BreakingOhmsLaw, that is very much helpful!

1. I will begin from cold start on device, with workpiece already placed.

2. Shall I set pre-heat machine temperature (it's set-point for radiated heat) to 125C? For this pre-heat machine, there is ~2cm distance from thermal element (below) to workpiece (above), suspended by metal structure to keep PCB away from thermal element.

3. How long should I wait (once pre-heat machine reaches set point, until workpiece reaches OK temperature?

Thank you again!

I have a YIHUA 853A preheat unit. To get the PCB to 100°C, I need to set the heater temperature to 250°C. The safest thing is to measure the temperature of the PCB with a thermocouple!

That (preheat setting) was what I was completely uncertain about.

What do you use for a thermocouple, and how do you apply it for this purpose?



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