Ceramic Substrate Terminal Contact Layer Adhesion
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Solution Overview
Problem
Ceramic substrates for mounting LEDs face issues with corrosion at the connecting terminal portions when used in high-temperature and high-humidity environments, leading to open failures due to the poor adhesion properties of copper layers with ceramic substrates and corrosion from soldering flux compositions.
Innovation Solution
A ceramic substrate design featuring a contact layer made of nickel-chromium alloy, chromium, molybdenum, or palladium between the ceramic substrate and the copper layer, set back from the copper layer's side surface, with a coating metal layer to enhance adhesion and corrosion resistance, and a protection layer to prevent etching corrosion, ensuring reliable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper layer is used in the connecting terminal portion, then electrical conductivity is improved, but adhesion property to the ceramic layer deteriorates
Solution Approach 1:
The patent introduces a contact layer as an intermediary between the copper layer and the ceramic substrate. This contact layer (made of nickel, chromium, molybdenum, or palladium) serves as a mediator that provides both good adhesion to the ceramic substrate and compatible electrical conductivity with the copper layer, thereby resolving the adhesion problem while maintaining electrical conductivity.
Solution Approach 2:
The connecting terminal portion is designed as a composite structure with multiple layers: a contact layer and a copper layer. This composite material approach combines the advantages of different materials - the contact layer provides adhesion to the ceramic substrate, while the copper layer provides high electrical conductivity, thus resolving the contradiction between adhesion and conductivity.
2Reliability
If a copper layer is used in the connecting terminal portion, then electrical conductivity is improved, but corrosion resistance from soldering flux composition deteriorates
Solution Approach 1:
The contact layer acts as a protective intermediary between the copper layer and the soldering flux composition. It shields the copper layer from direct contact with corrosive flux, thereby preventing corrosion while allowing the copper layer to maintain its electrical conductivity function.
Solution Approach 2:
The contact layer is applied in advance to the copper layer before soldering operations. This preliminary protective layer prevents the harmful action of soldering flux composition from reaching and corroding the copper layer, thus preserving both the electrical conductivity and corrosion resistance of the connecting terminal portion.
3Strength
If the contact layer is set back from the copper layer side surface, then adhesion property is improved, but manufacturing precision requirements increase
Solution Approach 1:
The contact layer is formed first on the ceramic substrate, and then the copper layer is formed on top of it. This preliminary action of forming the contact layer first provides a stable base that improves adhesion, while the subsequent copper layer formation can be done with standard precision requirements, thus reducing the overall manufacturing precision burden.
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 prevents corrosion and open failures at the connecting terminal portions, enhancing the connection reliability and durability of the ceramic substrate even in harsh environments, as demonstrated by the resistance and adhesion tests.
Implementation Method 1
The contact layer includes one of a nickel-chromium alloy, chromium, molybdenum and palladium, and is set back from a side surface of the copper layer in a substrate plane direction
Data Source
AI summary
A ceramic substrate is provided that includes a ceramic substrate main body having a principal surface, and a connecting terminal portion disposed on the principal surface of the ceramic substrate main body that is capable of being connected to another component via solder. The connecting terminal portion includes a copper layer and a coating metal layer covering a surface of the copper layer. The ceramic substrate includes a contact layer disposed between the ceramic substrate main body and the copper layer. The contact layer includes one of a nickel-chromium alloy, chromium, molybdenum, and palladium, and is set back from a side surface of the copper layer in a substrate plane direction.