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Extend QFPSO Leads Count with Oblique Leads Design

IP.com Disclosure Number: IPCOM000240127D
Publication Date: 2015-Jan-05
Document File: 3 page(s) / 413K

Publishing Venue

The IP.com Prior Art Database

Abstract

QFP/SO package has a limited lead count. If the lead count needs to be increased, then the package body size must be enlarged. Further, some customers do not like too fine pitch package because the SMT process control is more complex, which leads to high failure solder bridge issues. In this paper, we present a way to increase the number of QFP/SO lead counts without increasing the package body size.

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Extend QFPSO Leads Count with Oblique Leads Design

Abstract: 

QFP/SO package has a limited lead count.  If the lead count needs to be increased, then the package body size must be enlarged. Further, some customers do not like too fine pitch package because the SMT process control is more complex, which leads to high failure solder bridge issues.   In this paper, we present a way to increase the number of QFP/SO lead counts without increasing the package body size.  

Body:   

We have developed a package with a high lead count but small body size.  More specifically, the package is a QFP/SO package with oblique leads.  The package maintains lead pitch and achieves higher density advantages. Since lead pitch is not reduced, there is no solder bridge concern.

Claim :

1.     Oblique leads design to increase lead count via lead pitch exiting package edge is smaller than final PCB SMT lead pitch.

2.      Radial ray leads shape

L/F drawing comparison: Current QFP leads are all straight design, if we apply oblique design,

it will increase leads count with same body size. L/F design is no impact for mold process.

•          Manufacturability / Feasibility analysis:

  1. Base on current trim/form tooling, just need do fine tune for Dambar width. Before it is 0.5 pitch, now it is 0.4 pitch.
  2.  Process flow needn’t do any change.