Copper Powder Low-Temperature Sintering via Crystallite Control
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Solution Overview
Problem
Current copper powders for low-temperature sintering in conductive pastes face challenges in achieving sintering at even lower temperatures without affecting substrates or semiconductor devices, due to limitations in thermal stress and electrical characteristics.
Innovation Solution
A copper powder with a packed bulk density of 1.30 g/cm3 to 2.96 g/cm3 and a crystallite diameter to 50% particle diameter ratio (D/D50) of 0.060 or more, optimized through chemical reduction methods, enabling sintering at a lower temperature with improved electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copper powder is sintered at high temperature to achieve good sintering properties, then sintering strength is improved, but thermal stress damages substrates and semiconductor devices
Solution Approach 1:
The invention changes the physical and chemical parameters of copper powder by controlling crystallite size (D) to be 0.060 or more times the particle diameter (D50), and adjusting packed bulk density to 1.30-2.96 g/cm³. This parameter optimization enables sintering at lower temperatures (290°C or less) while maintaining adequate sintering strength, thus resolving the contradiction between sintering strength and thermal stress damage.
Solution Approach 2:
The invention performs preliminary preparation of copper powder with specific crystallite size and packed bulk density before sintering. By pre-optimizing these microstructural parameters, the copper powder achieves enhanced low-temperature sintering capability, allowing sintering to proceed at reduced temperatures that avoid thermal stress damage to substrates and semiconductor devices while still achieving required bond strength.
2Temperature
If copper powder particle size is reduced to enable low-temperature sintering, then sintering temperature is lowered, but sintering strength becomes insufficient
Solution Approach 1:
The invention optimizes two critical parameters simultaneously: crystallite size (D) and packed bulk density. By controlling D/D50 ratio to be 0.060 or more and packed bulk density to 1.30-2.96 g/cm³, the copper powder achieves a balance where fine particles enable low-temperature sintering (290°C or less) while the optimized density ensures adequate sintering strength through improved particle packing and contact area.
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 powder achieves sintering at a temperature of 290° C. or less, ensuring effective low-temperature sintering properties and maintaining electrical characteristics, while avoiding thermal stress issues.
Implementation Method 1
sintering-type pastes in which copper particles making up the copper powder are sintered by heating upon use
Implementation Method 2
a crystallite diameter D determined from a diffraction peak of a Cu (111) plane in an X-ray diffraction profile obtained by powder X-ray diffractometry of the copper powder using Scherrer's formula
Data Source
AI summary
A copper powder containing copper particles, wherein the copper powder has a packed bulk density of 1.30 g/cm3 to 2.96 g/cm3, and wherein a 50% particle diameter D50 when a cumulative frequency is 50% in a volume-based particle diameter histogram of the copper particles, and a crystallite diameter D determined from a diffraction peak of a Cu (111) plane in an X-ray diffraction profile obtained by powder X-ray diffractometry of the copper powder using Scherrer's formula satisfies D/D50≥0.060.