Multi-Layer Conductive Pad Structure for Corrosion Prevention
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Solution Overview
Problem
In electro-optical devices, the decreasing pitch of conductive patterns due to increased pixels or reduced pixel pitch leads to corrosion issues when exposed to air or water, and existing methods like resin coating are imprecise, making it difficult to accurately mount test pads on small ICs.
Innovation Solution
A mounting structure with a three-layered conductive pattern structure (first conductive layer, insulating layer, and third conductive layer) for mounting pads and a two-layered structure for lead portions, using materials like Ta, TaOx, Cr, and ITO, with the insulating layer as the outermost layer to prevent corrosion and allow precise patterning, enabling test probe contact even with small ICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resin coating is used to cover conductive patterns, then corrosion prevention is improved, but mounting pad coverage and precision deteriorate
Solution Approach 1:
The conductive pattern is segmented into multiple functional portions: mounting pads for IC connection, test pads for testing, and lead portions for signal transmission. Each portion receives different protective treatments appropriate to its function, avoiding blanket resin coating that would cover mounting pads.
Solution Approach 2:
Different portions of the conductive pattern have different structural configurations. Mounting pads have a three-layer structure (first conductive layer, insulating layer, third conductive layer) while lead portions have a two-layer structure (first conductive layer and insulating layer). This local differentiation allows precise protection without covering mounting pads with insulating material.
2Ease of operation
If test pads are arranged to overlap IC in plan view, then testing is enabled, but mounting precision deteriorates for small ICs
Solution Approach 1:
Test pads are positioned in the Y-direction adjacent to mounting pads rather than overlapping in the X-direction. This spatial reconfiguration in a different dimension allows test probe access without interfering with IC mounting precision, especially for small ICs.
3Productivity
If conductive pattern pitch is reduced to increase pixels, then device integration is improved, but corrosion resistance deteriorates
Solution Approach 1:
The conductive pattern uses a composite multi-layer structure combining conductive materials (first and third conductive layers) with insulating material (insulating layer). This composite structure provides both electrical conductivity and corrosion protection, enabling reduced pitch while maintaining reliability.
Data Source
AI summary
A mounting structure includes a mounting substrate on which a plurality of mounting pads each constituting a portion of a conductive pattern extending in a Y direction are arranged in an X direction, the X direction and the Y direction being two directions orthogonal to each other, and a member that is mounted on the mounting substrate so as to be electrically connected to the mounting pads. In the mounting structure, a first conductive layer, an insulating layer, a second conductive layer, and a third conductive layer are formed on the mounting substrate in this order from a lower side to an upper side. In addition, each conductive pattern includes the mounting pad that has a three-layered structure formed by laminating the first conductive layer, the insulating layer, and the third conductive layer, which is an outermost layer, in this order, a test pad that is positioned adjacent to a region where the mounting pad is formed, outside a region where the member is mounted, and that has the three-layered structure formed by laminating the first conductive layer, the insulating layer, and the third conductive layer, which is the outermost layer, in this order, and a lead portion that extends from the test pad, and that has a two-layered structure of the first conductive layer and the insulating layer, which is an outermost layer.