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Tear-Drop BGA Pad and Solder Design

IP.com Disclosure Number: IPCOM000034122D
Publication Date: 2005-Jan-17
Document File: 3 page(s) / 342K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses tear-drop shaped pads and solder balls to better withstand the compression applied to the BGA solder ball joints. Benefits include reducing the propagation of cracks and opens in the BGA process.

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Tear-Drop BGA Pad and Solder Design

Disclosed is a method that uses tear-drop shaped pads and solder balls to better withstand the compression applied to the BGA solder ball joints. Benefits include reducing the propagation of cracks and opens in the BGA process.

Background

Currently, BGA solder ball damage is usually caused by uneven surfaces between the PCB and package during assembly, handling, or testing. When the strain or stress exceeds the solder joint tension limit, the BGA solder balls start to crack or open. The crack or open usually occurs at the perimeter of the package, especially at the corners of the BGA where the balls form the weakest links within the entire BGA ball design; the crack begins.  In addition, the crack at the outer joint surface would propagate to the center of the BGA package. Figure 1 shows the current state of the art.

The following measures are currently taken to solve this problem:

§         BGA ball attachments at the package corners are de-populated to prevent open ball joint issues. Another package routes the non-critical signal to the perimeter/corner of the BGA package to minimize the impact of ball damage.

§         In the manufacturing front-end process, reflow and wave solder are optimized.

§         In the manufacturing back-end process, a manufacturing and assembly specification (MAS) is used to ensure proper handling and testing processes are followed.

General Description

The disclosed method uses tear-drop shaped pads and solder balls to better withstand the compression applied to the BGA solder ball joints. During reflow, the ends of the balls bulge due to the IC weight compression; this bulging helps distr...