Production method for copper/ceramic joined body, production method for insulated circuit board, copper/ceramic joined body, and insulated circuit board
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Solution Overview
Problem
Existing methods for bonding copper and ceramic substrates in insulating circuit boards face issues with crystal grain coarsening and non-uniformity, leading to inaccurate ultrasonic inspections and potential thermal resistance and peeling problems during temperature cycles.
Innovation Solution
A method involving copper members with specific impurity content and crystal grain size control, where the copper member has a purity of 99.96% or more, limited P, Se, and Te content, and a controlled pressing load and heating process to suppress crystal grain growth and ensure uniform bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copper plates are directly bonded to ceramic substrate at high temperature (800°C or higher), then bonding strength is improved, but crystal grains of copper plates become coarse
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of copper plates (adding specific amounts of S: 0.003-0.03 wt%, Se: 0.003-0.03 wt%, Te: 0.003-0.03 wt%) to modify the material properties. This compositional adjustment enables the copper to maintain fine crystal grains even at high bonding temperatures (800-850°C), resolving the contradiction between achieving strong bonding and preventing grain coarsening.
2Manufacturing precision
If S content is increased to suppress crystal grain growth, then crystal grain size is controlled, but local coarsening occurs and ultrasonic inspection accuracy deteriorates
Solution Approach 1:
The patent applies local quality by creating a balanced compositional structure where S, Se, and Te are distributed in specific proportions (each 0.003-0.03 wt%) rather than relying on excessive S alone. This balanced distribution ensures uniform crystal grain refinement throughout the copper plate without localized coarsening, maintaining both grain size control and ultrasonic inspection accuracy.
3Manufacturing precision
If copper plates with fine crystal grains are used before bonding, then appearance quality is improved, but crystal grains coarsen during high-temperature bonding process
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the chemical composition of the copper plates before bonding (adding S, Se, and Te in specific amounts). This preliminary compositional modification creates a material that is inherently resistant to grain coarsening during the subsequent high-temperature bonding process, ensuring both fine initial grains and stability throughout bonding.
4Reliability
If high bonding temperature (800°C or higher) is applied, then bonding reliability is improved, but surface undulations occur during temperature cycling
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of copper (adding S, Se, and Te) to suppress crystal grain growth. This results in finer and more uniform crystal grains that maintain surface smoothness even after high-temperature bonding and subsequent temperature cycling, resolving the contradiction between bonding reliability and surface smoothness.
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 method effectively prevents crystal grain coarsening and non-uniformity, allowing for accurate bonding state evaluation and maintaining surface smoothness even under temperature cycles, enhancing the reliability of copper/ceramic bonded bodies and insulating circuit boards.
Implementation Method 1
a bonding step of bonding the copper member and the ceramic member laminated to each other by pressing the laminated copper member and ceramic member in a laminating direction and heating
Implementation Method 2
there is concern that a part of crystal grains of the copper plates may become coarse during bonding
Data Source
AI summary
A method of producing a copper/ceramic bonded body, the copper member having a composition having a Cu purity of 99.96 mass % or more, a balance of inevitable impurities, a P content of 2 mass ppm or less, and a total content of Pb, Se and Te of 10 mass ppm or less, the method includes bonding the laminated copper member and the ceramic member by pressing and heating, wherein an average crystal grain size of the copper member before bonding is 10 μm or more, an aspect ratio is 2 or less, and a pressing load is 0.05 MPa or more and 1.5 MPa or less, a heating temperature is 800° C. or higher and 850° C. or lower, and a holding time at the heating temperature is 10 minutes or longer and 90 minutes or shorter.