LTCC Wiring Substrate with Inorganic Reflecting Layer
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Solution Overview
Problem
Low temperature co-fired ceramics (LTCC) substrates used in light emitting devices face issues with silver conductive layers, where the glass layer provided to prevent corrosion is inadequate in suppressing discoloration and maintaining light extraction efficiency.
Innovation Solution
A wiring substrate design featuring ceramic layers with a conductive member that includes an upper conductive layer, internal conductive layer, lower conductive layer, vias, and a covering layer with an inorganic reflecting layer and glass layer, where the upper conductive layer has an exposed region for mounting the light emitting element, enhancing heat dissipation and reducing discoloration by using a stacked structure of inorganic reflecting and glass layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a glass layer is provided on the conductive layer to prevent corrosion, then corrosion resistance is improved, but discoloration suppression is insufficient
Solution Approach 1:
The patent applies a composite covering layer structure consisting of a glass layer and an inorganic reflecting layer. The glass layer provides corrosion resistance by forming a protective barrier, while the inorganic reflecting layer suppresses discoloration by reflecting light and preventing silver migration to the surface. This composite structure simultaneously addresses both corrosion protection and discoloration prevention that a single glass layer cannot achieve.
Solution Approach 2:
The inorganic reflecting layer acts as an intermediary between the silver conductive layer and the external environment. It prevents direct interaction between silver atoms and light/oxygen that causes discoloration, while the glass layer serves as an additional intermediary protective barrier. This dual-intermediary approach effectively suppresses both corrosion and discoloration mechanisms.
2Temperature
If the upper surface of the element mount region is made higher than the covered portion, then heat dissipation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating a raised surface structure specifically at the element mount region while keeping other areas covered. This localized elevation improves heat dissipation from the light emitting element by increasing surface area and enhancing thermal coupling with the substrate, without adding complexity to the entire device structure. The selective application of the raising feature minimizes overall complexity while achieving the thermal management benefit where needed.
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
The solution effectively reduces discoloration and improves light extraction efficiency by using a stacked inorganic reflecting and glass layer covering structure, while maintaining excellent heat dissipation properties and corrosion resistance.
Implementation Method 1
The covering layer has an inorganic reflecting layer and a glass layer, and the inorganic reflecting layer reflects light
Implementation Method 2
the covering layer covers a portion of the upper conductive layer... the inorganic reflecting layer and a glass layer, where the upper conductive layer has an exposed region
Implementation Method 3
The vias electrically connect the upper conductive layer, the internal conductive layer, and the lower connective layer
Implementation Method 4
The wiring substrate includes ceramic layers and a conductive member... maintaining excellent heat dissipation properties
Data Source
AI summary
A wiring substrate includes ceramic layers and a conductive member. The ceramic layers have an uppermost ceramic layer and a lowermost ceramic layer. The conductive member includes an upper conductive layer, an internal conductive layer, a lower conductive layer, vias, and a covering layer. The upper conductive layer is disposed on an upper surface of the uppermost ceramic layer. The internal conductive layer is interposed between the ceramic layers. The lower conductive layer is disposed on a lower surface of the lowermost ceramic layer. The vias connect the upper conductive layer, the internal conductive layer, and the lower connective layer. The covering layer covers a portion of the upper conductive layer. The upper conductive layer includes a covered region covered with the covering layer and an element mount region. An upper surface of the element mount region is higher than an upper surface of the covered portion.