QFN Package Singulation via Segmented Mold Cutting
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Solution Overview
Problem
In QFN package production, the existing dicing process generates metal burrs that can cause short-circuit issues and poor planarization, leading to assembly problems due to the close clearance between leads and protrusions from the bottom surface.
Innovation Solution
A method involving a support tape with conductive pads of equal height to the dies, surrounded by mold compound, which are wire-bonded and then singulated by cutting only the plastic material, avoiding the generation of burrs by not severing integrally connected leads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the dicing device cuts through leads and resin simultaneously using a rotating blade, then singulation is achieved, but metal burrs are generated causing short-circuit issues and poor planarization
Solution Approach 1:
The cutting process is segmented into two distinct steps: first cutting only the mold compound to expose the leads, then separately cutting the leads. This segmentation prevents simultaneous cutting that generates metal burrs, thereby eliminating short-circuit issues while maintaining production efficiency
Solution Approach 2:
The mold compound acts as an intermediary layer that is removed first to expose the leads for subsequent cutting. This intermediate step allows the leads to be cut without generating burrs that would cause short circuits, solving the harmful effect while preserving the benefits of automated dicing
2Productivity
If leads are cut simultaneously with resin using a rotating blade, then singulation is completed, but planarization becomes poor due to protrusions from the bottom surface
Solution Approach 1:
The singulation process is divided into sequential steps: first cutting the mold compound, then cutting the exposed leads. This segmentation ensures that leads are cut cleanly without generating burrs or protrusions, achieving excellent planarization quality while maintaining high productivity through automated processing
Solution Approach 2:
The mold compound is cut and removed in advance to expose the leads before lead cutting begins. This preliminary action allows for precise lead cutting without generating protrusions, ensuring poor planarization is eliminated while preserving fast singulation
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 prevents short-circuit issues and improves the flatness of QFN packages, ensuring better connections to the wiring substrate by eliminating burrs and maintaining the structural integrity of the package.
Implementation Method 1
Mold compound is positioned between the first and second planes in voids between the conductive pads and the dies
Data Source
AI summary
A quad flat no lead (“QFN”) package that includes a die having an active side positioned substantially in a first plane and a backside positioned substantially in a second plane parallel to the first plane; a plurality of separate conductive pads each having a first side positioned substantially in the first plane and a second side positioned substantially in the second plane; and mold compound positioned between the first and second planes in voids between the conductive pads and the dies. Also a method of producing a plurality of QFN packages includes forming a strip of plastic material having embedded therein a plurality of dies and a plurality of conductive pads that are wire bonded to the dies and singulating the strip into a plurality of QFN packages by cutting through only the plastic material.