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Fillet Joint on the Ball Grid Array Package

IP.com Disclosure Number: IPCOM000034129D
Publication Date: 2005-Jan-17
Document File: 2 page(s) / 64K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that strengthens ball grid array (BGA) packages during assembly by creating fillet joints at all or some of the outrigger joints. Benefits include a solution that increases the reliability of packages during shock, bend, vibration, and temperature cycles.

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Fillet Joint on the Ball Grid Array Package

Disclosed is a method that strengthens ball grid array (BGA) packages during assembly by creating fillet joints at all or some of the outrigger joints. Benefits include a solution that increases the reliability of packages during shock, bend, vibration, and temperature cycles.

Background

Currently, the size and pitch of packages are becoming smaller. As a result, smaller pads and solder bumps are used for the second level interconnect; however, this causes the solder joint of the second level interconnect to become unreliable (see Figure 1). This occurs because the standoff height between the package and the board becomes smaller than on the larger ball components. This smaller standoff reduces the flexibility of the solder joint during temperature cycle loading, resulting in solder joint cracks sooner in its lifecycle. In order to increase reliability, some packages use larger ball sizes; however, these are difficult to assemble in fine pitch. Other packages use underfill epoxy between the second level interfaces, but this increases assembly costs.

General Description

The disclosed method can be used for any BGA or CSP package, or direct die attach. It allows the solder to create a fillet joint on the package or the chip sides, after reflow and anchor the package to the board. This increases the cross section area that resists shear forces during temperature cycles. Also, it improves the solder joint reliability of the second leve...