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Square Shaped Pads for Land Grid Array Packages

IP.com Disclosure Number: IPCOM000083108D
Publication Date: 2005-Feb-28
Document File: 2 page(s) / 50K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses square shaped land grid array (LGA) pads to maximize the available mating area between the socket and the LGA package. Benefits include reducing the risk of electrical discontinuity.

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Square Shaped Pads for Land Grid Array Packages

Disclosed is a method that uses square shaped land grid array (LGA) pads to maximize the available mating area between the socket and the LGA package. Benefits include reducing the risk of electrical discontinuity.

Background

LGA pads on a package provide the electrical interface between the processor and the I/O socket. The tip of the contact of the socket touches the metal pad on the package and “wipes” across it during assembly. The area of the metal pad that is available for maintaining the electrical continuity is marginally reduced by the solder resist, which overlaps slightly with the metal pad (see Figures 1 and 2).

The LGA pads in use today are mostly circular in shape. Circular pads support multiple wipe directions because of their symmetry, but their available mating area is not large. Oval pads are suited only for a specific contact design. Once the contact “wipe” direction is finalized, the elongated side of the oval pad is oriented along that direction. Typically, the substrate design is not started until the wipe direction of the socket contact (and thus the orientation of the oval pad) is finalized. This results in a longer development time.

General Description

The disclosed method’s square-shaped pad for LGA packages is shown in Figure 3. The four corners of the LGA pad are rounded to minimize the concentration of the fringing fields which deteriorate signal integrity performance (i.e., high-speed res...