Bump Electrode Asperities for Semiconductor Mounting Reliability
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Solution Overview
Problem
The miniaturization of semiconductor devices poses challenges in narrowing the pitch of electrodes for surface-mounting, as the thermal expansion mismatch between copper bump structures and insulating resin layers leads to adhesion and connection reliability issues due to heat stress.
Innovation Solution
A device mounting board with an insulating resin layer, a wiring layer, and bump electrodes having asperities on their side surfaces with greater surface roughness than the top surface, enhancing adhesion and connection reliability through improved anchor effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper bump structures are used for electrode connections, then electrical conductivity is improved, but thermal expansion mismatch with insulating resin layer causes adhesion deterioration under heat stress
Solution Approach 1:
The bump electrode is designed with different surface roughness characteristics at different locations: the side surface has greater roughness to enhance adhesion with the insulating resin layer, while the top surface maintains lower roughness for reliable semiconductor device bonding. This local differentiation of surface properties resolves the contradiction between adhesion strength and connection reliability
Solution Approach 2:
Asperities are formed on the side surface of the bump electrode in advance, before the semiconductor device is mounted. This preliminary surface treatment ensures that when heat stress occurs during subsequent assembly or operation, the pre-formed asperities are already in place to prevent separation at the bump-insulating resin layer interface
2Length of moving object
If solder bumps are used for flip-chip mounting, then electrode pitch can be reduced, but the size of solder bump and bridge formation limit further pitch narrowing
Solution Approach 1:
The invention changes the geometric parameters of the bump electrode, specifically creating an aspect ratio where the height is greater than the diameter, and forming asperities on the side surface. This parameter modification allows the bump structure to maintain electrical connectivity while reducing the planar footprint, enabling narrower electrode pitch without relying solely on miniaturizing the bump diameter
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 separation of bump electrodes from the insulating resin layer under heat stress, enhancing connection reliability between the bump electrodes and semiconductor device electrodes, thereby improving the overall reliability of semiconductor modules.
Implementation Method 1
asperities are formed on a side surface of the bump electrode and the surface roughness of the side surface thereof is greater than that of a top surface thereof
Data Source
AI summary
A device mounting board includes: an insulating resin layer; a wiring layer provided on one main surface of the insulating resin layer; and a bump electrode, electrically connected to the wiring layer, which is protruded from the wiring layer toward the insulating resin layer. Asperities are formed on the side surface of the bump electrode and the surface roughness of the side surface of the bump electrode is greater than that of the top surface of the bump electrode.