Lead Frame Depressed Portion Cutting to Prevent QFN Burrs
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Solution Overview
Problem
Burr formation on the bottom face of depressed portions in lead frames during the manufacturing of semiconductor devices can lead to variations in mounting height, flatness, and reduced mounting strength due to the softness of copper lead frames, which affects the reliability and performance of QFN-type semiconductor devices.
Innovation Solution
A method involving resin sealing, partial removal of resin material using laser light, and controlled cutting to inhibit burr formation, where a part of the resin material remains in the depressed portion to prevent burrs from occurring during the cutting process, ensuring consistent mounting and improved strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the resin material in the depressed portion is entirely removed by laser light irradiation, then the depressed portion is completely exposed, but burrs easily occur on the bottom face of the depressed portion during cutting due to the softness of copper lead frames
Solution Approach 1:
The patent applies partial removal of resin material instead of complete removal. The laser light irradiation step is controlled to remove only a portion of the resin material in the depressed portion, leaving some resin remaining. This partial action prevents burr formation during cutting while still achieving sufficient exposure of the depressed portion for subsequent plating and electrode formation, thereby resolving the contradiction between exposure precision and burr prevention.
2Reliability
If the lead frame is made of copper for good electrical conductivity, then electrical performance is improved, but burrs vary in height and cause mounting issues due to copper's softness
Solution Approach 1:
The patent applies preliminary action by leaving resin material in the depressed portion before the cutting step. This remaining resin acts as a protective cushion during cutting, preventing burr formation on the copper lead frame's bottom face. By preparing this protective condition in advance, the patent maintains copper's excellent electrical conductivity while preventing the mounting height variations and flatness issues that would otherwise result from burr formation.
3Ease of manufacture
If complete resin removal is performed to expose the depressed portion, then plating can be applied directly, but cutting produces burrs that reduce mounting strength
Solution Approach 1:
The patent applies partial resin removal that balances two manufacturing requirements: sufficient exposure of the depressed portion for plating application and retention of enough resin to prevent burr formation during cutting. This partial action approach maintains mounting strength by preventing burrs while still enabling effective plating, thereby resolving the contradiction between ease of manufacture and mounting strength.
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 effectively inhibits burr formation, reducing variations in mounting height and flatness, and enhancing the mounting strength of semiconductor devices by maintaining a consistent resin-metal interface during the cutting process.
Implementation Method 1
a laser light irradiation step for irradiating the depressed portion with laser light to remove the resin material in the depressed portion by the laser light so that a part of the resin material remains in the depressed portion
Data Source
AI summary
A method for manufacturing a semiconductor device includes a resin sealing step for sealing a semiconductor chip with a resin material in a state where the semiconductor chip is bonded on a lead frame in which a depressed portion is formed, a laser light irradiation step for irradiating the depressed portion with laser light to remove the resin material in the depressed portion by the laser light so that a part of the resin material remains in the depressed portion, and a cutting step for cutting a bottom face of the depressed portion in the lead frame together with the part of the resin material in the depressed portion.