After the inner layer is exposed on both sides it will be processed through a develop/etch/strip line. A DES line is typically a horizontal conveyorized machine approximately 75 feet long. The developer is the first step, the sole purpose of developing is to remove the unpolymerized dryfilm exposing the base copper. The next step is the etcher which dissolves the unprotected copper. The last step is the stripper which removes the polymerized resist using a high pH solution.

Inner layers are typically inspected by AOI machines. The AOI machine will scan both sides of an inner layer one side at a time, the total process will take several minutes. After scanning each side, the operator can review each of the flagged locations to verify if there is an issue. Once the inner layer has been accepted it is sent to the lamination department.

Prior to lamination the inner layers are processed through an oxide process which alters the copper surface topography in order to increase the bond strength of the prepreg to the copper. The layers are assembled into a stack with prepreg used as bonding sheets and then laminated. The lamination process consists of the panels being bonded together in a vacuum at high pressure and high temperature. Each material has its own unique rheology that requires specific lamination parameters. The key parameters are heat rise, cure temperature, cure time and pressure.