Do I need a permission to show pictures of a printed circuit board of a device (consumer electronics) on my personal blog? I would like to show how certain modifications to the product can be made. I took some pictures during the process. Does sharing these pictures infringe any IP rights?
Yes, you may
The layout of the board and its appearance are not protected by copyright, because they are not expressions or any other type of copyrightable content. Even if they were (say if some protested art was displayed on the board) you are displaying this for instructional purposes, and not harming any market for the board, so fair use is likely to apply (in the U.S.).
The device could be protected by patent, but you are not copying or imitating the board, nor showing anyone how to do so, so that would not apply.
You are not selling or advertising the board, nor knock-offs of it, so trademark protection would not apply, even if a protected trademark is visible on th board. Just in case, be sure to make clear that your video is not authorized or endorsed by the maker of the board.