Elimination of Localized Passivated Nets
Original Publication Date: 1988-Mar-01
Included in the Prior Art Database: 2005-Feb-15
In the manufacture of a particular type of printed circuit board, circuitization is accomplished by electroless plating of copper in exposed and developed photoresist line channels which contain seeded epoxy laminate. These seeded epoxy laminate line channels (nets), when plated, will constitute the circuitry of the board and are electrically isolated from each other. A result of this electrical isolation of lines is that under certain conditions these circuit lines, sometimes as close as 2 mils apart, will plate to drastically different heights. This problem constitutes a defect where the copper thickness is below the requirement and is detected by an electrical tester which tests the resistance per unit length of each circuit on the board.