We have two components (Component A & Component B). Component A has a link to Component B in a RTF field. When Component B is unpublished it causes Component A to be unpublished as well. We expected only the link to not resolve when Component B is unpublished. Is it possible to change this behavior? If yes, how?
Per my knowledge, this is the default behaviour that Tridion provides. You can write custom codes to achieve what you want. Below are few option in the order of their recommendations
Option 1: Write a Custom Resolver - You can get fair idea of custom resolver on the internet and one good link is here
Option 2: Tweaking through Event System on the Un-publishing event - Search Internet for samples
Option 3: Tweaking through Deployer Extension - Search internet for sample (Least recommended)
You can handle disabling Linking Propagation when un-publish. Check the following link to get an idea of the code you have to put in place in case you choose the Event System option (In your case you have to handle that in the un-publish events instead than in the publish events)