The present invention relates to methods for making multilayer circuit boards, and more particularly relates to methods for making flush surface laminates for constructing multilayer circuit boards, such as printed circuit boards used in computers and other such equipment.
In the manufacture of multilayer printed circuit boards for certain applications there is a need to make a more compact, higher speed board without sacrificing circuit density on the board. This can be accomplished using power core and/or signal core laminates to make a multilayer circuit board having an electrical resistance between layers of approximately 50 ohms rather than 80 ohms as provided with conventional circuit boards. However, using conventional printed circuit board manufacturing techniques, it is difficult, if not impossible to achieve this relatively low resistance circuit board structure within desired tolerances.
Also, conventional printed circuit board manufacturing techniques normally require chemical processing steps, such as applying photoresist, additively plating circuit lines or the like, and flash etching, which result in a "wet" process. However, for environmental and safety reasons, it is preferable to make circuit boards using "dry" processes, that is processes, such as plasma gas treatment and mechanical drilling, which do not involve chemical processing steps of the type associated with wet processes.
Thus, it is highly desirable to manufacture a multilayer circuit board, for use in a computer or other such equipment, having a relatively low resistance between layers of the circuit board. Also, it is even more desirable to manufacture such a multilayer circuit board using dry processes.