You will need to add the following entry into the manifest.xml
DeploymentTarget The depoloyment target is location where the assembly will be copied to and can ether be the bin folder of the WebApplication or it could be the GlobalAssemblyCache (GAC)Location The location of the assembly within the cabinet file. SafeControl A SafeControl element entry as described at the beginning of the post.
Using this method, your assembly will be correctly deployed the servers in the farm as well as added to the safe controls of the web application. Again any new server added to the farm will automatically get all the solution packages deployed.