Browse Prior Art Database

Method of improving BGA joint yield and strength for SMD PCB pads

IP.com Disclosure Number: IPCOM000008472D
Publication Date: 2002-Jun-17
Document File: 6 page(s) / 334K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method of improving ball grid array (BGA) joint yield and strength for surface mounted device (SMD) printed circuit board (PCB) pads. Benefits include improved quality and improved reliability.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 77% of the total text.

Method of improving BGA joint yield and strength for SMD PCB pads

Disclosed is a method of improving ball grid array (BGA) joint yield and strength for surface mounted device (SMD) printed circuit board (PCB) pads. Benefits include improved quality and improved reliability.

Background

              Solder mask defined pads weaken the solder joint. The interface between the mask and the joint can initiate a crack. Yield issues occur from BGA opens created by solder paste gasses and flux that are trapped between the mask and the pad, causing voids and nonsolderable areas (see Figure 1). Increasing the pad diameter solves both problems.

              Large copper planes are required for power distribution. Solder mask-defined pads go hand-in-hand with these designs. BGA packages that require this type of plane on the PCB have a limit on package shrinkage because large diameter pads are required. This restriction hampers BGA package cost reduction efforts.

              In the conventional process, crater defects can occur with standard BGA pads in surface-mount technology (SMT) assembly (see Figure 2). In addition, solder mask-defined pads have reliability issues in thermal cycling.

Description

              The disclosed method is a design for pads on a copper plane. Special sprocket connections or multiple-sided recesses are applied to the copper. This result is partially defined metal pads or include vents that create stronger solder joints (see Figure 3). An alternative design illustrates the grid array (see Figure 4).

      Improved...