Semiconductor Capacitor Pad Layout for Void-Free Reflow Joints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The junction reliability of thin film capacitors in semiconductor packages is compromised due to the formation of large voids during the reflow process, caused by flux gas vaporization from solder paste, which affects the integrity of the capacitor joints.
Innovation Solution
The semiconductor package design incorporates capacitor pads with via patterns eccentric from the center line and a small diameter, allowing flux gas to escape easily, thereby preventing large void formation and enhancing junction reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder paste is used to mount the capacitor during reflow process, then the capacitor can be securely attached to the substrate, but flux gas vaporization forms large voids in the joint that deteriorate connection reliability
Solution Approach 1:
The via pattern is positioned eccentrically (off-center) relative to the capacitor pad, creating an asymmetric configuration. This asymmetry provides an escape path for flux gas during reflow, preventing gas accumulation and large void formation in the joint, thereby resolving the contradiction between secure attachment and void-free bonding
Solution Approach 2:
The via pattern acts as an intermediary structure between the capacitor pad and the substrate. It serves dual functions: providing electrical connection and creating a controlled pathway for flux gas escape, thus mediating between the bonding process requirements and the void formation problem
2Reliability
If the via pattern is positioned at the center of the capacitor pad, then the electrical connection is optimized, but flux gas gets trapped and forms large voids
Solution Approach 1:
The via pattern is deliberately positioned asymmetrically (eccentrically) rather than at the center of the capacitor pad. This asymmetric positioning creates an escape route for flux gas during reflow, preventing gas trapping and large void formation while maintaining adequate electrical connection through the via
3Reliability
If a large diameter via pattern is used, then the electrical connection area is increased, but the flux gas escape path is blocked leading to void formation
Solution Approach 1:
The via pattern uses a controlled diameter that is optimized to balance electrical connection requirements with flux gas escape needs. The eccentric positioning ensures that even with a substantial via diameter for good electrical connection, there remains sufficient space around the via for flux gas to escape, preventing void growth
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 design effectively mitigates void growth and improves the reliability of capacitor joints by allowing flux gas to escape, ensuring better electrical connections and package integrity.
Implementation Method 1
The via pattern may be eccentric by a distance from a center line of the pad pattern... allowing flux gas to escape easily, thereby preventing large void formation and enhancing junction reliability
Data Source
AI summary
A semiconductor package including a core substrate, a semiconductor chip in the core substrate and having chip pads, a redistribution wiring layer covering a lower surface of the core substrate and including redistribution wirings electrically connected to the chip pads and a pair of capacitor pads exposed from an outer surface of the redistribution wiring layer, conductive pastes on the capacitor pads, respectively, and a capacitor via the conductive pastes and having first and second outer electrodes on the capacitor pads, respectively, may be provided. Each of the capacitor pads includes a pad pattern exposed from the outer surface of the redistribution wiring layer, and at least one via pattern at a lower portion of the pad pattern and electrically connected to at least one of the redistribution wirings. The via pattern is eccentric by a distance from a center line of the pad pattern.