I never use Fahrenheit and I did could use +-10 degrees because in theoretical 200 degrees that represent a 10% of variation. There are no inconsistencies in the argument, please post exactly where you found any, maybe I'm expressing badly in english, sorry.
I repeat, IPC standards define a MAXIMUM temperature with a thin margin, not the solder exact temperature at any time. Please, post the IPC text where they "dictates" that the component would be solder at this exact temperature and not less or more.
And a common sense question.... Why Metcal sell three series of tips at different temperatures that all guarantees IPC standard? Why All the solder stations that comply with IPC standards allow freely change the temperature?
I answer it for you. Please read this IPC standard (I took the first that google sugest to me)
http://www.ipc.org/4.0_Knowledge/4.1_Standards/test/2.4.36b.pdfIf you read with attention the condition of +-6 degrees (I use always centigrade!) in 4.1 it's to stablish the accurate of the solder station that you use in the test. BUT IPC say's that the experiment can be done using three different temperatures 260,315 and 371 centigrade degrees...WHAT?
In point 5.4 IPC affirm "If the solder connection cannot be formed within five seconds using the specified method the test shall be repeated using the subsequent method. This deviation shall be noted in the test report". That is that IPC asumes that if the thermal transfer it's not sufficient (by the pad mass or tip) you need to use a temperature 50 degrees high!!!!
But if this text it's not enough in point 6.2 affirms that if you use a solder station with fix temperature tips like Metcal you can use for the 260 c degrees option the 500 series that have a max temperature of 302 degrees!!!! IPC asumes that you CAN solder at 260 degrees or 300 and it's the same experiment and both are equivalent!!!!!!!
IPC SAYS (not me!) that it's EQUIVALENT use 260 degrees or 300 degrees, 40 degrees of difference, a rough 15% upper of the "recommended" temperatureBy the way, in the same 6.2 point 315 c option recommends 600 series with max temp of 357 c and for 371 option you can use the 700 series with 412 degrees!!! (
https://www.wsbenelux.nl/wp-content/uploads/2014/11/metcal-tip-temperatures.pdf). In all cases IPC assumes that a difference of 40 degrees ITS EQUIVALENT AND ADMISIBLE
The specification of +-6 degrees it's only for repetibility of test between stations, to compare results, but in the same point (4.1) affirms without doubt that same solder station can be replaced by a metcal with 40 degrees more in each option!!!
But let's me read that some other big companies talk about this point. JBC recommends 300 to 350 c degrees (depends on component size) for a lead free solder that IPC marks a max of 260 C degrees and melt at 220 c degrees. (
https://www.jbctools.com/blog/correct-temperature-soldering/)
AGAIN, a 40 c degrees difference seems to be ok!!!!
When you solder EVERY day, which temperature selects in your station?