Porous Metal-Solder Joining Layer Without Pressurized Sintering
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Solution Overview
Problem
Conventional joining methods using metal nanoparticles require pressurization control during sintering, which is challenging due to thermal expansion, leading to expensive equipment and laborious maintenance, and complicates mass production of multiple joined structures.
Innovation Solution
A joining method where spacers are melted or decomposed before solvent evaporation, allowing for precise thickness control of joining layers without pressurization, using a nanometal paste with metal nanoparticles and a solvent, and heating to sinter the metal nanoparticles without pressurization, eliminating the need for pressurization control equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pressurization treatment is applied during sintering to form rigid joining layers, then joining strength is improved, but equipment complexity and maintenance cost increase due to need for pressurization control during high-temperature heating
Solution Approach 1:
The patent extracts the pressurization function from the sintering process by introducing spacers that provide mechanical support independently. The spacers are placed between the substrate and mounting board to maintain spacing without requiring pressurization control during heating, thereby eliminating the need for complex pressurization equipment while still achieving rigid joining layers through sintering alone.
Solution Approach 2:
The spacers act as intermediary elements between the substrate and mounting board. These spacers (made of glass fiber reinforced resin or ceramic) mediate the spacing and support functions, allowing the sintering process to proceed without pressurization control. The spacers are removed after sintering, having fulfilled their intermediary role during the joining process.
2Stability of the object's composition
If pressurization control is implemented during high-temperature sintering, then joining layer rigidity is improved, but manufacturing cost and maintenance labor increase
Solution Approach 1:
The pressurization control function is extracted from the sintering process and replaced by spacers that provide mechanical support during heating. This eliminates the need for expensive pressurization control equipment and reduces maintenance labor, while still achieving rigid joining layers through the sintering of metal nanoparticles alone.
Solution Approach 2:
The spacers are disposable components that are placed temporarily during the sintering process to provide spacing and support. After serving their purpose during heating, they are removed by etching or other means. These inexpensive, temporary components replace the need for expensive, maintenance-intensive pressurization control systems.
3Manufacturing precision
If pressurization treatment is used during sintering to ensure precision, then joining layer thickness precision is improved, but productivity decreases due to inability to process multiple structures simultaneously
Solution Approach 1:
The pressurization control step is extracted from the sintering process and replaced by spacers that provide mechanical support during heating. This allows multiple semiconductor devices to be sintered simultaneously in a furnace without requiring individual pressurization control, thereby maintaining thickness precision while significantly improving productivity through batch processing.
4Manufacturing precision
If spacers are used to maintain spacing during solvent evaporation, then volumetric shrinkage compensation is achieved, but spacer material selection is constrained by melting point requirements
Solution Approach 1:
The patent specifies that spacer materials must have melting points lower than the solvent boiling point but higher than the sintering temperature. This parameter constraint enables the use of materials like glass fiber reinforced resin and ceramic that can withstand sintering temperatures while melting before solvent evaporation. This parameter change allows spacers to be removed easily after serving their spacing function, achieving thickness precision without overly restricting material options.
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 method achieves high-precision thickness of joining layers, reduces production costs, and enables simultaneous sintering of multiple structures in a high-temperature furnace, improving productivity and thermal conductivity by filling pores with resolidified spacers, while preventing remelting of the joining material.
Implementation Method 1
the resulting products are preheated to certain temperatures (e.g. 100-150° C.) in high-temperature furnaces, thereby causing solvents in the nanometal pastes to evaporate
Implementation Method 2
the products are heated to sintering temperatures (e.g. 200-300° C.) to progress the sintering process, thereby forming joining layers
Implementation Method 3
heating a product obtained in Step (ii) at a temperature equal to or lower than a temperature where the solvent in the nanometal paste is evaporated, to cause the spacer to melt or decompose
Data Source
AI summary
A joined structure includes: a first member; and a second member that faces the first member and that is joined to the first member via a joining layer. The joining layer includes a metal material and a solder material, apart of the metal material has at least one pore, and the solder material is located in a part of an internal area of the at least one pore. Also disclosed is a joining method that makes it possible to produce the joined structure. Further disclosed is a joining material used in the joining method. The joining method makes it possible to achieve non-pressurization sintering processes while maintaining high precise thickness of a joining layer between the first layer and the second layer based on the spacer.