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Stacked Package QFBGA with Bi-Metal

IP.com Disclosure Number: IPCOM000074585D
Publication Date: 2005-Feb-23
Document File: 3 page(s) / 215K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that allows the stacking of lead frame packages over a ball grid array (BGA) package. Benefits include decreasing space on the board and increasing solder joint reliability (SJR) on the BGA.

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Stacked Package QFBGA with Bi-Metal

Disclosed is a method that allows the stacking of lead frame packages over a ball grid array (BGA) package. Benefits include decreasing space on the board and increasing solder joint reliability (SJR) on the BGA.

Background

Currently, there is a need to increase BGA SJR, and to solve limited space issues. These problems are currently solved by shrinking the size of packages; however, small packages lead to a smaller pitch and smaller balls. These solutions increase board assembly costs and increase reliability concerns, due to the smaller balls. Also, substituting a lead frame package with a BGA which has a smaller size increases the cost of the package. Figure 1 shows the current state of the art, where a BGA is assembled near a gull wing QFP. This configuration takes up a large amount of space on the board.

General Description

The disclosed method consists of a lead frame package stacked on top of a BGA. An interface material is used to connect both packages. In addition to saving space on the board, the lead frame package acts as a guard for the BGA during temperature cycles and shock. Figure 2 and 3 show the disclosed method with two different lead frame packages: a gull wing package stacked on a BGA, and a J lead package stacked on BGA.

The lead frame package and the BGA are manufactured with a standard process. The lead frame device is added to the top of the BGA using an interface material (e.g. epoxy). A special fixture is used to...