Softened Copper Column for Ceramic Substrate Joint
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Solution Overview
Problem
Conventional copper columns are too hard and cannot absorb the heat stress between ceramic and glass epoxy substrates, leading to cracks and fractures at the joints in ceramic column grid arrays (CGA).
Innovation Solution
A copper column with a Vickers hardness of 55 HV or less is achieved by work-hardening a copper wire through wiredrawing, cutting, and annealing at 600°C or higher for 60 minutes, followed by surface treatment and plating to absorb thermal expansion differences and enhance joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional copper wire is used for the copper column, then the column has high strength, but the column is too hard and cannot absorb heat stress, causing cracks and fractures at joints
Solution Approach 1:
The patent applies annealing treatment to change the physical parameters of the copper column, specifically reducing its Vickers hardness from conventional levels down to 55 HV or less. This parameter change allows the column to absorb heat stress through elastic deformation while maintaining sufficient structural strength, thereby preventing joint cracks and fractures.
2Reliability
If the copper column is made softer to absorb heat stress, then joint reliability improves, but the column strength decreases
Solution Approach 1:
Through controlled annealing, the patent achieves an optimal hardness parameter range of 55 HV or less, which balances the competing requirements of joint reliability and column strength. This precise parameter control allows the column to be soft enough to absorb thermal expansion differences while remaining strong enough to support mechanical loads.
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 copper column effectively absorbs heat stress, preventing cracks and fractures at the joints between ceramic and glass epoxy substrates, ensuring reliable connections in CGA applications.
Implementation Method 1
an annealing step for annealing the copper wire, which has been cut in the cutting step, as a copper column body section by maintaining the copper wire at 600° C. or higher in a heating temperature for a period of 60 minutes or longer
Implementation Method 2
the ceramic substrate and the glass epoxy substrate are expanded. When the voltage applied to the CBGA is removed, the ceramic substrate and glass epoxy substrate are shrunken
Implementation Method 3
a thermal expansion difference between the ceramic substrate and the glass epoxy substrate causes heat stress in the ceramic substrate and the glass epoxy substrate
Data Source
AI summary
To prevent the breakage of the joint between a ceramic substrate and a glass epoxy substrate. The copper column is formed by a wiredrawing step for drawing a copper wire formed linearly to a predetermined diameter; a cutting step for cutting the copper wire, which has been drawn in the wire drawing step, in a predetermined length; a pressing step for pressing one end of the copper wire, which has been cut in the cutting step, in a longitudinal direction to form a copper column member; and an annealing step for annealing the copper column member, which has been formed in the pressing step, by maintaining a heating period of 60 minutes or longer at 600° C. or higher. Thereby, the Vickers hardness of the copper column becomes is 55 HV or less and the copper column is softened. Therefore, when joining the ceramic substrate and the glass epoxy substrate through the copper column, heat stress caused by a difference between the thermal expansion of the ceramic substrate and the thermal expansion of the glass epoxy substrate can be absorbed by the copper member. As a result, the breakage of the joint between the ceramic substrate and the glass epoxy substrate can be prevented.