SMTA International Conference Proceedings

Reliability Improvement Of Array QFN Package

Author: You-Chye How
Company: Texas Instruments Electronics Malaysia Sdn. Bhd.
Date Published: 10/13/2013   Conference: SMTA International

Abstract: Array QFN, or other acronyms trademarked by IC manufacturers, is an enhanced version of conventional QFN with multi-row of terminals featuring miniaturization at high I/O density. This package technology has unlimited design flexibility for designer to easily move around leads and die paddles within the package to meet customer layout requirement because it doesn’t require tie bar or lead dambar to hold the leads and die paddle. Recently, this package had gained strong popularity among IC manufacturers to develop such technology internally or leveraged external subcontractors, mainly for its superior thermal, electrical, component level reliability performances and miniaturized package size. Array QFN also known by its superior board level drop test reliability because of the protruded leads as a result of etched back technology which enables this package to have higher stand-off after SMT process. Despite the advantages of Array QFN, it possesses various challenges in package design, material selection, assemblies and SMT processes.

In this paper, Array QFN assembly process was introduced. Component level and board level reliability tests failures on Array QFN were investigated and analyzed on failure root causes for resolution. Meticulous selection of mold compound base on its critical properties helps reduce wire sweep percentage. Stencil design for SMT process was planned and experimentally conducted to achieve optimum barrel solder joints formation for better board level drop test reliability. Lead frame with different anchor design also plays important roles to improve board level drop test reliability in conjunction with optimum stencil design.

Key Words: 

Etched back, anchor design, reliability, Array QFN, wire sweep, stencil design.

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