An implantable medical device includes an enclosure having a sidewall and a welded seam in the sidewall, the seam extends along a perimeter of the enclosure. A thermoform is located adjacent a surface of the enclosure and is secured in place within the enclosure. A metalized surface is located adjacent an interior surface of the enclosure sidewall and is secured in place by the thermoform. The metalized surface extends along a perimeter of the enclosure and is configured to obstruct laser energy during a weld seam process. The metalized surface may be provided as a separate backup band component or may be integrated in a perimeter sidewall of the thermoform.