Winter 1990
Optimizing Dry Film Photoresist Lamination
As the density of a printed circuit board increases, circuit line
defects that were only viewed as slight irregularities with coarser
boards, become functional problems which can lead to decrease
in manufacturing yields. The defects on etched innerlayers
include open and nicked circuits. These defects can be caused by
interfacial voids: tiny pockets of air which become trapped
between the copper foil and the dry film photoresist during
lamination. Modifying the lamination pressure, speed, or roll
temperature, increasing the dry film thickness, or preheating the
boards can eliminate or greatly reduce the yield losses
encountered when manufacturing fine line innerlayers.
Brian Grundy, DuPont Electronics, Ltd., UK
