There is a foreign substance on the LGA.
What should I do if it is removed or washed?
Can I wipe it off with IPA?
Intel Core i3-6100 Processor 3M Cache, 3.70 GHz
That doesn't look like it is a foreign substance; that looks like pin scratches on the pads. They likely won't have any effect of the operation of the processor. If you want, however, you can (carefully!) wipe the bottom of the processor using a clean, lint-free cloth and see if anything is removed. Do not attempt to wipe the pins within the socket itself; they're too delicate for this.
By the way, I found the following content on other pages.
What is the "Approved cleaning solvent" described here.
Please tell me. thank you.