I need to back up a non responsive iPhone 7 to my computer

Well, the answer depends on exactly what "non-responsive" means.

If you can, plug your iPhone into iTunes (12.7 or later) on your computer and start the backup.

How to back up your iPhone, iPad, and iPod touch - Apple Support

If the iPhone is too "non-responsive" to perform this operation, then try:

If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

Finally if that does not solve it, then it's too late to perform a backup. Backups must occur before catastrophes. After a catastrophe has occurred, it's too late.

If the device is unresponsive, it's a bit late for that. You need to back it up before something goes wrong, not after.