Lead-Frame Package Exposed Edge Solder-Resistant Layer
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Solution Overview
Problem
Current semiconductor packaging technologies face challenges in balancing manufacturing ease and efficiency with performance drawbacks, such as solder shorts and increased costs, particularly in lead-frame based packages and ball grid array (BGA) packages, which require improved reliability and reduced footprint sizes.
Innovation Solution
The method involves forming a lead-frame with a die attach paddle and contact pad connected by a link, mounting an integrated circuit die, molding a package body with exposed portions of the paddle and pad, etching to create an exposed edge, and applying a solder-resistant layer on the edge to prevent solder creeping and shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lead-frame based packages are used to facilitate packaging and singulation, then manufacturing ease and efficiency are improved, but solder contact reliability deteriorates due to solder shorts from close proximity of contacts
Solution Approach 1:
The link connecting the contact pad to the die attach paddle is divided into two segments: a first portion covered by the package body and a second portion exposed as a protrusion. This segmentation allows the exposed portion to be protected with solder-resistant material while maintaining the structural integrity and manufacturing efficiency of the lead-frame package.
Solution Approach 2:
Solder-resistant material is applied selectively only to the exposed second portion of the link, not the entire link structure. This local application prevents solder shorts at the critical exposed edge while maintaining solderability where needed, resolving the contradiction between manufacturing efficiency and contact reliability.
2Area of stationary object
If BGA packages are used to reduce footprint size, then area is improved, but manufacturing cost and efficiency deteriorate due to laminate substrates
Solution Approach 1:
The lead-frame structure is designed to serve multiple functions: it provides the mechanical support and electrical connections typical of lead-frame packages, while also enabling a reduced footprint configuration similar to BGA packages. The exposed link portion acts as both a structural connector and a protected contact element, allowing the package to achieve compact dimensions without sacrificing manufacturing efficiency.
3Quantity of substance
If high density of contact connections is implemented, then I/O pin count is improved, but manufacturing precision requirements worsen to prevent inadvertent solder connections
Solution Approach 1:
Solder-resistant material is applied in advance to the exposed second portion of the link before the soldering process. This preliminary protective action prevents inadvertent solder connections between adjacent high-density I/O pins, allowing higher pin counts to be implemented without requiring proportionally higher manufacturing precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances contact reliability, reduces rework risks, and allows for higher density and precision in contact connections, addressing the need for cost-effective and efficient packaging solutions with improved performance.
Implementation Method 1
depositing a solder-resistant layer on the exposed edge
Implementation Method 2
forming an exposed edge by etching away the link between the contact pad and the die attach paddle
Implementation Method 3
molding a package body on the lead-frame and the integrated circuit die including leaving portions of the die attach paddle, the contact pad, and the link exposed from the package body
Data Source
AI summary
A method of manufacture of an integrated circuit packaging system includes: forming a lead-frame having a die attach paddle and a contact pad connected by a link; mounting an integrated circuit die over the die attach paddle; molding a package body on the lead-frame and the integrated circuit die including leaving portions of the die attach paddle, the contact pad, and the link exposed from the package body; forming an exposed edge by etching away the link between the contact pad, and the die attach paddle; and depositing a solder-resistant layer on the exposed edge.