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Method for an alternate via for printed wire boards

IP.com Disclosure Number: IPCOM000007719D
Publication Date: 2002-Apr-16
Document File: 3 page(s) / 34K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an alternate via for printed wire boards (PWBs). Benefits include improved performance, reduced defects, and improved reliability.

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Method for an alternate via for printed wire boards

Disclosed is a method for an alternate via for printed wire boards (PWBs). Benefits include improved performance, reduced defects, and improved reliability.

Background

              Conventionally, via holes are drilled in the board, and pad art is registered to the vias. Then, everything is plated as one structure: the top pad, via barrel and bottom pad. The drill hole must intersect the pad so the connection between the conductive paths is minimized.

              Conductor coatings and via plugs are conventionally applied after the pad/via structure is manufactured. The plating process has good control for 2-sided pads, but results are less predictable as drill sizes decrease and padless vias are employed. This condition particularly occurs as pitches decrease down to .8 mm for technology that is not microvia technology.

              For a topside via-pad interface, pad/drill registration issues can make meeting tolerances for routing difficult in small pitch applications (see Figure 1).

              Padless via plating is not clean on the topside of the printed circuit board, leading to an inconsistent joint (see Figure 2).

Description

              The disclosed method uses a grommet in manufacturing a via structure for a PWB. This method can be used for creating specialized conductive features for press-fit connectors that require good tolerance in the hole diameter. Another use for this method is special ball-grid array (BGA) via structures, such as a via-in-pad that requires excellent drill-pad registration as BGA component pitches are reduced. The grommet forms the pad, if needed on the top and b...