Wiring Substrate Surface Metal Layer Plating Adhesion
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Solution Overview
Problem
The challenge is that when using molybdenum (Mo) as a high-melting point metallic material for the surface metal layer in wiring substrates, the plating layer is not easily plated and tends to peel off due to the migration of copper (Cu) from the surface metal layer during firing, affecting the heat dissipation characteristics.
Innovation Solution
A wiring substrate design featuring an insulating base with a heat dissipation member containing Cu, a surface metal layer with Mo as the main component, and a plating layer where Cu from the heat dissipation member and surface metal layer are bonded, allowing for effective plating and improved adhesion of the plating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If CuW is used as the material of the heat dissipation member and the surface metal layer, then the thermal expansion coefficient matches that of alumina ceramics and co-firing is enabled, but Cu of the surface metal layer moves to the heat dissipation member during firing, causing the surface metal layer to not sinter properly
Solution Approach 1:
The surface metal layer is segmented into multiple functional layers: a lower layer containing Mo and Cu (where Cu provides bonding to the heat dissipation member), and an upper layer containing Mo as the main component (which prevents Cu migration and provides plating functionality). This segmentation allows each layer to perform its specific function without interfering with others.
Solution Approach 2:
Different regions of the surface metal layer have different compositions tailored to local requirements: the lower layer near the heat dissipation member has higher Cu content for bonding, while the upper layer has higher Mo content for preventing Cu migration and enabling plating. This local quality differentiation resolves the contradiction between bonding strength and sintering quality.
2Manufacturing precision
If Mo is used as the high-melting point metallic material of the surface metal layer, then the sintering temperature issue is resolved, but the plating layer is not easily plated on the surface and may peel off
Solution Approach 1:
The surface metal layer has different compositions at different depths: the upper layer has high Mo content for high-temperature stability and sintering compatibility, while the lower layer has Cu added to provide good plating properties. This local quality variation allows the surface to resist Cu migration while the subsurface provides plating functionality.
Solution Approach 2:
The surface metal layer is a composite material combining Mo and Cu in specific proportions and distributions. Mo provides the high-temperature stability and sintering resistance, while Cu provides the bonding capability and plating processability. The composite structure allows both materials to contribute their advantageous properties simultaneously.
3Strength
If Cu is present in the surface metal layer for bonding, then adhesion to the heat dissipation member is improved, but Cu migrates to the heat dissipation member during firing, causing sintering defects
Solution Approach 1:
The surface metal layer is divided into functional zones: a lower bonding layer with Cu for adhesion to the heat dissipation member, and an upper protective layer with Mo to prevent Cu migration during firing. This segmentation isolates the Cu to where it is needed for bonding while preventing its harmful migration to the surface.
Solution Approach 2:
Mo acts as an intermediary barrier between the Cu-containing lower layer and the heat dissipation member. It allows thermal contact and bonding while preventing direct Cu migration to the heat dissipation member during high-temperature firing, thus mediating between the need for Cu bonding and the need to prevent Cu migration.
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 configuration enables reliable plating and suppresses peeling of the plating layer, enhancing thermal conductivity and heat dissipation characteristics by bonding Cu from both the heat dissipation member and surface metal layer, thereby improving the performance of electronic devices.
Implementation Method 1
Cu contained in the heat dissipation member and Cu contained in the surface portion are bonded to each other
Implementation Method 2
a heat dissipation member disposed in the insulating base, the heat dissipation member partially exposed from the insulating base, the heat dissipation member containing Cu
Data Source
AI summary
A wiring substrate in which a plating layer is sufficiently plated on a surface metal layer and which has an excellent reliability is provided. A wiring substrate includes an insulating base; a heat dissipation member disposed in the insulating base, the heat dissipation member partially exposed from the insulating base, the heat dissipation member containing Cu; a surface metal layer disposed on a surface of the insulating base, the surface metal layer contacting and covering the heat dissipation member, the surface metal layer containing Mo as a main component, the surface metal layer including a surface portion containing Cu; and a plating layer disposed on the surface metal layer, wherein Cu contained in the heat dissipation member and Cu contained in the surface portion are bonded to each other.