Copper Powder Paste Laminate Adhesion via Silane Intermediary
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Solution Overview
Problem
The challenge is to achieve strong adhesion between a sintered copper powder body and a ceramic substrate across a wide temperature range, as the thermal expansion difference between them can lead to separation during the firing process.
Innovation Solution
A laminate structure is developed where the copper powder paste sintered body is laminated on a ceramic layer, with elements such as Si, Ti, and Zr from the copper powder surface treatment agent present in a thickness range of 5 to 15 nm at the boundaries, enhancing adhesion through a thin amorphous layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper powder is used as electrode material instead of silver powder or nickel, then cost is reduced and electrical resistance is improved, but adhesion between the fired electrode and ceramic substrate deteriorates due to thermal expansion difference
Solution Approach 1:
A silane coupling agent is introduced as an intermediary substance between the copper powder and ceramic substrate. The coupling agent forms a thin layer (5-15 nm) containing Si, Ti, and Zr elements that chemically bonds to both the copper powder surface and the ceramic particles, acting as a mediator that bridges the thermal expansion difference and prevents separation during firing.
Solution Approach 2:
The electrode paste is formulated as a composite material system comprising copper powder, ceramic particles, glass frit, and silane coupling agent. This composite structure allows the electrode to exhibit both the electrical properties of copper and the thermal compatibility of ceramic, resolving the adhesion problem caused by thermal expansion mismatch.
2Reliability
If the number of layers is increased to increase capacitance per part, then capacitance is improved, but the paste must be applied thinner which requires finer printing pitch without disconnection
Solution Approach 1:
The paste formulation parameters are optimized by adjusting the ratio of copper powder to ceramic particles, the type and concentration of silane coupling agent, and the binder composition. These parameter changes enable the paste to maintain structural integrity at thinner applications, allowing finer printing pitch while preventing disconnection during firing.
Solution Approach 2:
The silane coupling agent is specifically concentrated at the boundary regions between copper powder particles and ceramic substrate, creating local reinforcement zones that prevent disconnection. This localized quality enhancement at critical interfaces allows the overall paste layer to be applied thinner without compromising connectivity.
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 improves the adhesion between the sintered body and the ceramic substrate, resulting in better performance in tape peeling tests and specific resistance, making it suitable for applications like MLCC and LTCC.
Implementation Method 1
strong adhesion between the fired body and the ceramic substrate is required so that the fired body and the ceramic substrate are not separated
Implementation Method 2
elements selected from Si, Ti and Zr derived from a copper powder surface treatment agent are together present with a thickness in a range of from 5 to 15 nm in boundaries
Implementation Method 3
a thermal expansion coefficient of the metal is higher than that of ceramic which is a substrate, and a difference in expansion and contraction is generated during the firing process
Data Source
AI summary
Provided is a laminate of a sintered body produced by sintering a copper powder paste and a ceramic substrate, which has improved adhesion between the sintered body and the ceramic substrate. A laminate with a copper powder paste sintered body laminated on a ceramic layer, the laminate comprising portions where one or more elements selected from Si, Ti and Zr derived from a copper powder surface treatment agent are together present with a thickness in a range of from 5 to 15 nm in boundaries between the copper powder paste sintered body and the ceramic layer, when observing the boundaries by scanning the laminate with STEM over 100 nm across the boundaries in a thickness direction of the laminate.