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Method for solder pad and test point definition by adaptive vision-assisted laser removal

IP.com Disclosure Number: IPCOM000022117D
Publication Date: 2004-Feb-25
Document File: 3 page(s) / 55K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for solder pad and test point definition by adaptive vision-assisted laser removal. Benefits include improved density, routability, and improved performance.

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Method for solder pad and test point definition by adaptive vision-assisted laser removal

Disclosed is a method for solder pad and test point definition by adaptive vision-assisted laser removal. Benefits include improved density, routability, and improved performance.

Background

         Solder-mask misregistration occurs to conductive-surface features due to material movement, circuit definition tolerances, and photo imaging tolerances. They limit the assembly of small pitch packages and devices because of spacing limitations between surface features. The resulting defects include shorting and solder-joint failure.

         Conventionally, this problem is solved by defining solder mask openings by using photo-imaging techniques. A photosensitive mask is applied and exposed with ultraviolet (UV) light. The mask is then chemically developed and cured. The pattern registration is dependent on the alignment of a phototool to an etched circuit on the board. The conventional registration capability is +/- 2 mils (see Figures 1 and 2).

         Laser removal (ablation) is conventionally used on epoxy-based materials for microvia drilling applications. Charged coupled device (CCD) cameras are commonly used in surface mount technology (SMT) assembly for the placement of components, the alignment of screen printing, and other applications. CCD cameras are also used in automated optical inspection to detect the boundaries of etched copper features.

General description

         The disclosed method is the removal of a solder mask from printed circuit board (PCB) surface pad features with critical tolerance registration by adaptive vision-assisted laser. The method enables the design, assembly, and test of small-pitch packages and devices.

         The disclosed method enabl...