Angled Encapsulant Guides on Leadframe Leads
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Solution Overview
Problem
The increasing miniaturization of leadframes in semiconductor packages makes them more susceptible to displacement during encapsulation, leading to defective packages due to mold flash and improper lead positioning, as the inner leads are weaker and more prone to being covered by the encapsulant.
Innovation Solution
The formation of encapsulant guides on the inner leads, which are angled to prevent displacement by pushing the leads outward as the encapsulant flows past, ensuring they remain in their proper positions and are exposed on the package surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If leadframe size is reduced to achieve miniaturization, then package size and cost are improved, but lead strength and stability deteriorate, causing displacement during encapsulation
Solution Approach 1:
The patent applies preliminary action by forming protrusions on the leads before the encapsulation process. These protrusions are created during leadframe fabrication as preventive measures to stop lead displacement before it occurs during molding. The protrusions act as pre-positioned mechanical stops that will interact with the encapsulant to maintain lead positioning throughout the encapsulation process.
2Volume of moving object
If leadframe size is reduced to achieve miniaturization, then package size and cost are improved, but manufacturing precision deteriorates due to mold flash and improper lead exposure
Solution Approach 1:
The protrusions are formed in advance on the leads to prevent displacement during encapsulation, ensuring that leads maintain their correct positions and remain properly exposed on the package surface, thereby preventing mold flash and improving manufacturing precision.
Solution Approach 2:
The patent converts the potentially harmful effect of encapsulant pressure, which would normally cause lead displacement and mold flash, into a beneficial force. The angled protrusions are designed to interact with the flowing encapsulant, using the encapsulant's own pressure to push leads outward and maintain their proper positioning, thereby preventing defects.
3Quantity of substance
If inner leads are made thinner to increase lead density, then lead count is improved, but lead robustness and resistance to displacement worsen
Solution Approach 1:
The protrusions are formed on the thin inner leads before encapsulation to provide mechanical support and prevent displacement. This preliminary structural modification allows the leads to remain thin for high density while gaining the strength needed to resist encapsulant pressure.
Solution Approach 2:
The patent applies local quality by adding protrusions only at specific locations on the leads where they are most vulnerable to displacement during encapsulation. This localized modification provides targeted reinforcement without increasing the overall lead thickness, maintaining high lead density while improving robustness at critical points.
Data Source
AI summary
A method for fabricating a leadframe with encapsulant guide is provided, including forming a die attach paddle. Leads are formed around at least portions of the die attach paddle, and encapsulant guides are formed angled on a plurality of the leads to push the leads outwardly when an encapsulant flows therepast.