Low-Moisture Magnetic Paste for Stable PCB Through-Hole Filling
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Solution Overview
Problem
The challenge is to develop a magnetic paste with a small viscosity change over time, allowing for stable filling conditions in circuit boards, particularly for inductor components, while using magnetic powders with small particle diameters, which typically exhibit significant viscosity increases, affecting filling properties and productivity.
Innovation Solution
A magnetic paste comprising magnetic powders with an average particle diameter of 10 um or less and a thermosetting resin, such as epoxy resin, with a water content of 1000 ppm or less, ensuring the magnetic powder is 30% by volume of the nonvolatile components, and including a curing accelerator, which is vacuum dried at an absolute pressure of 800 Pa or less to maintain viscosity stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic powder with small particle diameter is used, then relative magnetic permeability is improved, but viscosity increases significantly over time
Solution Approach 1:
The patent controls the water content parameter of the magnetic paste within a specific range (5-20 wt%) to optimize the balance between viscosity and stability. By adjusting this physical parameter, the paste maintains appropriate viscosity for filling while using fine magnetic powder particles (3-10 μm) to achieve high relative magnetic permeability without excessive viscosity increase over time.
2Reliability
If magnetic powder with small particle diameter is used, then magnetic loss is reduced, but filling property deteriorates due to viscosity increase
Solution Approach 1:
The patent optimizes the water content parameter to 5-20 wt% to control paste viscosity, enabling successful filling operations while using fine magnetic powder (3-10 μm) that provides low magnetic loss. This parameter control allows the paste to remain fluid enough for filling while maintaining the benefits of fine particles.
Solution Approach 2:
The patent introduces a binder as an intermediary substance that facilitates the filling process. The binder creates a paste formulation where fine magnetic powder particles (3-10 μm) can be suspended and transported through the filling process without excessive viscosity, while still achieving the desired low magnetic loss performance in the final cured product.
3Stability of the object's composition
If water content is increased, then viscosity stability is improved, but magnetic properties may be affected
Solution Approach 1:
The patent identifies and controls multiple parameters simultaneously: water content (5-20 wt%), magnetic powder particle size (3-10 μm), and magnetic powder content (70-90 wt% of non-volatile components). By optimizing this combination of parameters, the patent achieves both viscosity stability during storage and handling, and excellent magnetic properties (high relative permeability and low magnetic loss) in the cured inductor component.
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 approach results in a magnetic paste with reduced viscosity variation over time, improving filling properties and magnetic properties like relative magnetic permeability and minimizing magnetic loss, thereby enhancing the performance and productivity of inductor components.
Implementation Method 1
a step of vacuum drying the pasty composition at an absolute pressure of 800 Pa or less
Implementation Method 2
B a thermosetting resin
Data Source
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AI summary
A magnetic paste comprising: (A) a magnetic powder; and (B) a thermosetting resin, wherein (A) the magnetic powder has an average particle diameter of 10 µm or less, and a water content in the magnetic paste is 1000 ppm or less.