Plastic encapsulated semiconductor devices are susceptible to moisture due to the permeability of molding compounds. Devices may be baked until dry before being shipped to the customer to reduce the risk of cracking. To retain this dry condition, devices are packaged and shipped in dry-packs. A vacuum seal indicator (18) for flexible material enables a user to determine the integrity of a vacuum seal. The seal indicator has a quick recognition pattern composed of either negative (22) or positive (24) features or a combination thereof, and is placed inside a dry-pack bag (30) which is vacuum sealed prior to shipping. The integrity of the vacuum seal can be determined by looking at the dry-pack bag to see whether the recognition pattern is sharply defined against the bag or not. The vacuum seal indicator can be used in conjunction with any shipping media (28) as long as the outer bag is flexible.