Semiconductor Package Ground Bar Segmentation for Noise Reduction
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Solution Overview
Problem
Conventional leadframe semiconductor packages with ground bridge bars suffer from ground coupling noise and poor bonding strength due to random bonding of analog and digital ground wires, and are vulnerable to moisture penetration and delamination, leading to reliability issues.
Innovation Solution
A semiconductor package design with separate ground bars for digital and analog signals, connected by distinct bonding wires and tie bars, and a molding compound encapsulating the die pad and leads to reduce delamination and moisture ingress, while etched grooves and steps enhance interlock and bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ground bridge bar is used for both digital and analog ground wires, then the structure is simpler, but ground coupling noise and water wave effects occur
Solution Approach 1:
The ground bridge bar is divided into multiple separate ground bars, with each ground bar dedicated to a specific type of ground wire (digital or analog). This segmentation prevents digital and analog ground wires from randomly bonding together, eliminating ground coupling noise and water wave effects while maintaining structural organization.
2Ease of manufacture
If ground wires are directly bonded to the die pad surface, then the bonding process is simpler, but moisture penetration and delamination occur
Solution Approach 1:
The ground bridge bar serves as an intermediary structure between the die pad and the ground wires. Instead of bonding ground wires directly to the die pad surface, they are bonded to the ground bridge bar, which is itself connected to the die pad. This intermediate structure prevents moisture penetration and delamination while maintaining electrical connectivity.
3Strength
If the ground bridge bar is supported by tie bars, then the structural support is provided, but the ground bridge bar becomes vulnerable to twist and deform
Solution Approach 1:
The single ground bridge bar supported by tie bars is segmented into multiple separate ground bars, each with its own support structure. This segmentation reduces the vulnerability to twist and deformation by distributing mechanical stresses across multiple smaller, more stable structures rather than one large vulnerable bar.
4Temperature
If the die pad bottom surface is exposed, then heat dissipation efficiency is improved, but moisture attacks increase
Solution Approach 1:
The ground bridge bar acts as an intermediary that allows the die pad bottom surface to remain exposed for heat dissipation while providing a protected bonding path for ground wires. The exposed die pad surface maintains thermal contact with the PCB for heat sinking, while the ground bridge bar prevents moisture-related reliability issues by providing a sealed bonding interface.
Data Source
AI summary
A semiconductor package includes a die pad; a semiconductor die mounted on the die pad; a plurality of leads in a first horizontal plane disposed along peripheral edges of the die pad; a ground bar downset from the first horizontal plane to a second horizontal plane between the leads and the die pad; a plurality of downset tie bars connecting the ground bar with the die pad; a plurality of ground wires bonding to both of the ground bar and the die pad; and a molding compound at least partially encapsulating the die pad, inner ends of the leads such that bottom surface of the die pad is exposed within the molding compound.