An implantable medical device and methods of manufacture are provided for implantation in a body. The device includes a device housing having an interior cavity and electronic circuitry located in the interior cavity of the device housing. The electronic circuitry detects a physiologic condition of the body and delivers a therapy to the body. The device further includes a feed-through assembly having a feed-through housing that is joined to the device housing. The feed-through assembly includes conductors held in the feed-through housing and electronically connected to the electronic circuitry. A back-fill member is joined to the feed-through housing. The back-fill member has an opening there through communicating with the interior cavity of the device housing. A sealing element is hermetically secured in the opening through the back-fill member. The sealing element and back-fill member are formed of different first and second materials, respectively. The second material is generally harder than the first material. For example, the sealing element may constitute a titanium ball configured to be deformed when pressed into the opening in the back-fill member, where the first and second materials constitute titanium and a titanium alloy, respectively. The back-fill member is dimensioned relative to a support tool to permit the back-fill member to self-align during an initial sealing operation by shifting and/or tilting relative to a support tool.