Leadframe Panel Grooves for Burr Control
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Solution Overview
Problem
The fabrication of leadframe-based semiconductor packages often results in excess conductive material, such as burrs, which interferes with testing and can cause shorting due to improper contact with test probes, and affects wirebonding stability, especially in larger modules.
Innovation Solution
Incorporating grooves in the connecting bars of leadframe panels, formed through etching, to reduce the incidence of excess conductive material and maintain wirebonding stability by limiting the thinnest portions of the panel to regions adjacent to leads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sawing is used to separate leadframe modules, then productivity is improved, but excess conductive material (burs) is generated causing testing interference and potential shorting
Solution Approach 1:
The patent applies preliminary action by forming grooves in the connecting bars before the singulation process. These grooves are created in advance to control where the saw blade will cut and to provide a pathway for burr removal. The grooves are positioned and dimensioned so that during subsequent sawing operations, excess conductive material is directed into these pre-formed channels, preventing it from interfering with testing or causing shorting.
2Loss of substance
If bar thickness is reduced to minimize material, then loss of substance is improved, but wirebonding stability deteriorates
Solution Approach 1:
The patent applies local quality by varying the thickness of the connecting bars along their length. The bars have a non-uniform cross-section with thicker regions positioned at critical locations where wirebonding stability is required, and thinner regions in areas where material reduction is beneficial. This localized variation in thickness allows the structure to maintain necessary mechanical stability while minimizing overall material consumption.
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
Significantly reduces the risk of excess conductive material and maintains acceptable wirebonding stability, even for larger leadframe modules, by allowing for precise separation and minimizing burr formation during the singulation process.
Implementation Method 1
Incorporating grooves in the connecting bars of leadframe panels, formed through etching
Data Source
AI summary
According to an exemplary implementation, a method includes utilizing a leadframe panel comprising a plurality of leadframe modules, each of the plurality of leadframe modules having a leadframe pad. The leadframe panel has a plurality of bars each having a plurality of grooves, where the plurality of bars connect the plurality of leadframe modules. The method further includes attaching a device to the leadframe pad. The method also includes molding the leadframe panel while leaving a bottom of the leadframe pad exposed. Furthermore, the method includes sawing through the plurality of grooves of the plurality of bars to singulate the plurality of leadframe modules into separate packaged modules.