Hi, by law you have to take care of your apartment (gott skick). This should be reflected in the bylaws.
By law you are also not allowed to disturb your neighbours (störning). So you should petition the board that they should demand that your upstairs neighbour fixes their floor so that it is done properly by code (fackmannamässigt). Ie he needs to make sure his floor is in "gott skick".
This is all based on that the squeaking noise is considered a "störning", (I doubt that but I'm not involved so it doesn't matter). And you need to prove that this is not the way you build floors. You need to find someone that can back your claim and submit that with your demand.
Send this to the board and they have to process it.
All this costs very little. If you don't get the response you seek claim that you will file a complaint with the environmental agency (miljöförvaltningen). That will force their hand and it will cost the brf around 10k.
If you have a "störnings jour" you could call them if you know there will be alot of disturbing noises for a while. At least you can file lots of reports but don't actually call anyone out to your apartment.
So this is might be a long process and you need to be patient for the board to act. They are probably as knowledgeable as you in these types of matter. But my advice is keep a nice tone, refer to the logic of the law and if that doesn't work keep adding threats to incur costs for the brf. Actually executing on the threats needs careful thoughts, it might just be better to move .