Lead Frame Mold Locking Structure to Prevent Package Cracking
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Solution Overview
Problem
Packaged electronic devices often experience cracking due to mold bar peeling or separation from the lead frame during fabrication, which can lead to damage or degradation of the semiconductor die and electrical interconnections.
Innovation Solution
A method of fabricating electronic devices that involves mounting a semiconductor die on a lead frame, electrically connecting it, and performing a molding process to form a molded package structure that extends under a mold locking structure, preventing separation from the lead frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the molded package structure is formed without a mold locking structure, then the fabrication process is simpler, but the molded package structure separates from the lead frame causing cracks
Solution Approach 1:
The mold locking structure is formed on the lead frame before the molding process begins. This preliminary action creates a locking mechanism that prevents the molded package structure from separating from the lead frame during subsequent fabrication steps, thereby maintaining package integrity without complicating the overall manufacturing process
Solution Approach 2:
The mold locking structure acts as an intermediary element between the lead frame and the molded package structure. It provides a mechanical interface that ensures proper adhesion and prevents separation, resolving the contradiction between simple fabrication and reliable package integrity
2Reliability
If the molded package structure extends under the mold locking structure, then separation is prevented, but the molding process becomes more complex
Solution Approach 1:
The mold locking structure extends in the vertical dimension (z-direction) above the lead frame plane, creating a three-dimensional locking feature. This dimensional extension allows the molded package structure to be locked in place without requiring complex lateral or planar features, thereby preventing separation while maintaining relatively simple molding processes
Data Source
AI summary
A method of fabricating an electronic device includes: mounting a semiconductor die in a unit area of a lead frame; electrically connecting the semiconductor die to a conductive feature in the unit area of the lead frame; performing a molding process to form a molded package structure that extends through multiple unit areas of the lead frame along a first column of the lead frame and extends under a mold locking structure in a side portion of the lead frame at an end of the first column to oppose separation of the molded package structure from the side portion of the lead frame; separating the first column from an adjacent second column of the lead frame; separating an electronic device of the unit area from the lead frame; and separating the side portion from the first column of the lead frame.