Asymmetric Lead Frame Design for Resin Molding Balance
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Solution Overview
Problem
Conventional lead frames for multi-chip packages face challenges in supporting die pads in a balanced manner, leading to unbalanced forces during assembly, which results in resin molding defects such as package bending, voids, and wire disconnection due to Z-directional vertical variations.
Innovation Solution
A lead frame design where one die pad deviates from the resin molding area's center line, with the die pad connecting portion aligned opposite to the deviation, and suspension leads are shaped to maintain balance, reducing Z-directional vertical variations and preventing resin molding defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the die pad is deviated from the resin molding area center line to secure wire bonding region and reduce wire lengths, then the wire bonding area is improved, but the die pad support balance deteriorates causing Z-directional vertical variations
Solution Approach 1:
The patent applies asymmetry by intentionally deviating the die pad from the resin molding area center line to create an asymmetric layout. This asymmetric positioning secures adequate wire bonding area and reduces wire lengths while the die pad connecting portion is positioned on the opposite side to counterbalance the asymmetry, preventing Z-directional vertical variations.
2Strength
If the die pad connecting portion is aligned with the die pad to maintain structural integrity, then the structural support is improved, but the support balance deteriorates due to unbalanced arrangement
Solution Approach 1:
The patent applies the counterweight principle by positioning the die pad connecting portion on the opposite side of the die pad relative to the resin molding area center line. This creates a counterbalancing arrangement where the die pad and die pad connecting portion are offset from each other, maintaining structural integrity while achieving support balance and preventing unbalanced forces during assembly.
3Ease of manufacture
If conventional lead frame designs are used with unbalanced die pad arrangement, then the manufacturing simplicity is maintained, but resin molding defects occur due to Z-directional vertical variations
Solution Approach 1:
The patent maintains manufacturing simplicity by using a conventional lead frame structure with asymmetric positioning of the die pad and die pad connecting portion. This asymmetric arrangement deviates from conventional symmetric designs but prevents resin molding defects by balancing the support forces, thereby improving reliability without significantly complicating the manufacturing process.
Data Source
AI summary
A lead frame is provided. Although there is a die pad (2) located to deviate from a main plane center line of a resin molding area (10), a die pad connecting portion (6) is located to deviate from the main plane center line of the resin molding area in a direction opposite to the deviation direction of the deviated die pad (2), so that it is possible to reduce a Z-directional vertical variation of the die pad in processes. Accordingly, it is possible to prevent resin molding defects such as package bending, voids, failure of resin filling, wire disconnection, exposure of semiconductor chips, and exposure of die pads.