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Thin, Quad Flat Leaded Package

IP.com Disclosure Number: IPCOM000237150D
Publication Date: 2014-Jun-05
Document File: 4 page(s) / 742K

Publishing Venue

The IP.com Prior Art Database

Abstract

Common quad flat leaded packages (QFP) have external leads or terminals formed in a shape of J or a gull wing. For the former, the leads are folded towards the package body whereas for the latter, the leads are shaped away from the package body. These two types of leaded packages are common and can be seen in many electronic devices. They have been widely used and accepted by the industry for many years. The other version of leaded package is the quad flat non leaded (QFN) packages in which the leads are flush with the bottom and/or sides of the package body. The configuration of this package allows it to be thinner than conventional QFP because it is molded on only one side. The disadvantage of QFN package is the limitation in the ability to view the solder joint after board mount. This poses a challenge as we will not be able to know if there is sufficient solder coverage under the leads or terminals unless we do a destructive test such as cross section or rip the package from the board. This will not only damage the package but also the expensive board. Thus, although QFN provides the benefit of a thinner package than QFP, ease to view the amount of solder coverage on the leads remains a big challenge.

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TITLE

Thin, Quad Flat Leaded Package

ABSTRACT

Common quad flat leaded packages (QFP) have external leads or terminals formed in a shape of J or a gull wing. For the former, the leads are folded towards the package body whereas for the latter, the leads are shaped away from the package body. These two types of leaded packages are common and can be seen in many electronic devices. They have been widely used and accepted by the industry for many years. The other version of leaded package is the quad flat non leaded (QFN) packages in which the leads are flush with the bottom and/or sides of the package body. The configuration of this package allows it to be thinner than conventional QFP because it is molded on only one side. The disadvantage of QFN package is the limitation in the ability to view the solder joint after board mount. This poses a challenge as we will not be able to know if there is sufficient solder coverage under the leads or terminals unless we do a destructive test such as cross section or rip the package from the board. This will not only damage the package but also the expensive board.  Thus, although QFN provides the benefit of a  thinner package than QFP, ease to view the amount of solder coverage on the leads remains a big challenge. 

CONTENT

The packaging concept is a thin, quad flat leaded package. This package is different from conventional QFN package in terms of the terminal layout. Conventional QFN have the terminals located at the peripheral and within the outline of the package itself.  Here we propose the terminals protrude out of the package, similar to a QFP package. The construction of this package also allows the package to be thinner than the current QFP with 2 sided mold caps. Figure 1 gives a pictorial view on the method of assembly.

Figure 1 Steps in the fabrication a thin, flat quad leaded package

The end assembled package has Gull wing lead configuration. The leads are formed away from the package body. They can be easily viewed from the top and side of the package. Th...