Wiring Substrate Through Electrode Asymmetric Design
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Solution Overview
Problem
The existing through electrodes in semiconductor chip packages have a reduced reliability due to a smaller contact area between the pad electrode and the conductive body, leading to decreased electrical and mechanical connection reliability, especially under heat stress, and risk of damage during the formation process.
Innovation Solution
A wiring substrate configuration with a first insulating layer and a second insulating layer of different thicknesses and materials, where the through electrode has a smaller diameter at the connection section and overlaps with the insulating layers in the peripheral area, reducing stress and increasing joint strength, and the second insulating layer is formed in an L shape to enhance mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the through electrode has a smaller diameter at the connection section, then the stress on the pad electrode is reduced, but the contact area between the pad electrode and conductive body is reduced
Solution Approach 1:
The through electrode is designed with an asymmetric diameter distribution along its length, being smaller at the connection section with the pad electrode and larger at other sections. This asymmetric configuration reduces stress concentration at the critical connection interface while maintaining adequate contact area through the enlarged diameter at other portions, thereby simultaneously improving joint strength and electrical connection reliability.
Solution Approach 2:
Different sections of the through electrode are given different diameters according to their specific functional requirements. The connection section has a smaller diameter to reduce stress on the pad electrode, while other sections have a larger diameter to ensure adequate mechanical strength and electrical contact. This local differentiation of geometric properties optimizes both stress distribution and electrical connection.
2Ease of manufacture
If the pad electrode is exposed to the through hole side during formation, then the through electrode can be formed, but damage occurs in the pad electrode
Solution Approach 1:
The through electrode formation process is designed to preliminarily protect the pad electrode from damage during the etching and filling operations. By controlling the exposure extent and providing protective measures during the formation process, the pad electrode integrity is maintained while still allowing the through electrode to be successfully formed with adequate contact area.
3Strength
If the first insulating layer thickness is reduced in the overlapping area, then the stress from thermal expansion mismatch is reduced, but the insulation performance may be compromised
Solution Approach 1:
The first insulating layer is designed with spatially varying thickness, being thinner in the overlapping area where thermal expansion stress occurs and thicker in other areas where insulation is critical. This local differentiation allows stress reduction at the critical interface while maintaining adequate insulation performance in regions where electrical isolation is the primary concern.
Data Source
AI summary
A method of manufacturing a wiring substrate including a step of forming a through hole that includes forming a first concave portion in a substrate that extends from a second surface to a first insulating layer without passing through the first insulating layer; forming a second insulating layer at least within the first concave portion; and forming a second concave portion through the second insulating layer and the first insulating layer to expose a surface of a pad electrode, wherein the second concave portion is formed within the first concave portion; and filling the first concave portion and the second concave portion with a conductive body or forming the conductive body to coat inner walls of the first concave portion and the second concave portion, and forming the through electrode such that it is connected to the pad electrode.