Effect of water contained in bond ply on MLB fabrication

The vaporization of retained moisture in bond ply is shown to be a major cause of the formation of blisters during MLB fabrication. In order to limit exposure of the bond ply to moisture as much as possible, the bond ply should be heat sealed in a polyethylene bag containing a dessicant. Dessication in the sealed chamber containing CaSO4 for a minimum of 24 hours and controlled storage are shown to give a 2- to 4-fold decrease in retained moisture. Portable dehumidifiers are found to be effective in storage areas.