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QFP Lead Frame Power Bar Structure Improvement

IP.com Disclosure Number: IPCOM000236215D
Publication Date: 2014-Apr-11
Document File: 4 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Abstract

In current advanced packaging for high density packages, it has become more and more challenging for die designer to maximize the usage of the pin output for each package especially if there is a large amount of power/ground pins required for thermal and electrical performance. Hence, the designer often has to accommodate at least two leads to support the power bar with one of the leads serving as a dummy (in some occasion) while maintaining the case outline/pitch of the package. With the conventional power bar design the lead width will have narrow to accommodate the dummy lead supporting the lead frame structure. This kind of power bar design may potentially have lead bouncing issues when performing stitch wire bonding depending on the number of dummy leads supporting the structure and the length of the power bar. Overall, current design package pin count is limited by its geometry. In this paper, we introduce a method to improve the lead frame power bar structure by maintaining the connection between the power bar and die flag in the lead frame formation.

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TITLE

QFP Lead Frame Power Bar Structure Improvement

ABSTRACT

In current advanced packaging for high density packages, it has become more and more challenging for die designer to maximize the usage of the pin output for each package especially if there is a large amount of power/ground pins required for thermal and electrical performance.  Hence, the designer often has to accommodate at least two leads to support the power bar with one of the leads serving as a dummy (in some occasion) while maintaining the case outline/pitch of the package. With the conventional power bar design the lead width will have narrow to accommodate the dummy lead supporting the lead frame structure. This kind of power bar design may potentially have lead bouncing issues when performing stitch wire bonding depending on the number of dummy leads supporting the structure and the length of the power bar. Overall, current design package pin count is limited by its geometry.  In this paper, we introduce a method to improve the lead frame power bar structure by maintaining the connection between the power bar and die flag in the lead frame formation.

CONTENT

A method to improve the lead frame power bar design structure by reducing the space needed to strengthen the power bar structure as compared to the conventional lead frame design is provided.  Thus, increasing the lead width and pitch can potentially increase the number of the stitch bonds that can be bonded onto the lead fingers. Also, the power bar design provided here will not make use of lead space but rather just the die flag so it will increase the number of available package pins.

Figure 1 shows a power bar design structure that has a down-set similar to the die flag that will be exposed after molding. With this design, it enables more power bars to be formed...