Crushed Silica Resin Composition for Hybrid Circuit Boards
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Solution Overview
Problem
The high cost and specific production methods of spherical inorganic fillers like silica and alumina limit their use in producing substrates and circuit boards with excellent adhesion to metal and high thermal conductivity, prompting the need for a more affordable and effective inorganic filler solution.
Innovation Solution
A resin composition comprising a curable epoxy resin with a phenol novolak resin curing agent and inorganic fillers with specific particle size distributions, including coarse and fine powders of crystalline silicon dioxide, is used to create a resin-cured product with enhanced adhesion and thermal conductivity, suitable for hybrid integrated circuits and circuit boards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spherical inorganic fillers (silica or alumina) are used to achieve high thermal conductivity and excellent adhesion, then the substrate and circuit board exhibit excellent properties, but the production cost increases significantly due to specific production methods like flame fusion
Solution Approach 1:
The patent replaces expensive spherical inorganic fillers produced by flame fusion with inexpensive crushed inorganic filler materials. This substitution maintains the functional requirements for thermal conductivity and adhesion while dramatically reducing production costs by using readily available crushed materials instead of specially manufactured spherical particles.
Solution Approach 2:
The patent changes the particle size parameters of the inorganic filler from uniform spherical particles to a specific bimodal distribution consisting of coarse powder (5-20 μm average, 50-70 vol%) and fine powder (0.2-1.5 μm average, 30-60 vol%). This parameter change in particle size distribution enables both high thermal conductivity and excellent adhesion properties while using cheap crushed materials.
2Ease of manufacture
If crushed inorganic filler is used to reduce production cost, then manufacturing becomes more economical, but the adhesion to metal plate and thermal conductivity may be insufficient
Solution Approach 1:
The patent segments the inorganic filler into two distinct size categories: coarse powder (5-20 μm average particle size) and fine powder (0.2-1.5 μm average particle size). The coarse particles provide structural framework and thermal conduction pathways, while the fine particles fill gaps and enhance adhesion to the metal plate surface, achieving both cost-effectiveness and high reliability.
Solution Approach 2:
The patent creates a composite filler system by combining coarse and fine crushed inorganic powders in specific proportions (coarse powder 50-70 vol%, fine powder 30-60 vol%). This composite structure leverages the advantages of both particle sizes: coarse particles for thermal conductivity and fine particles for adhesion, achieving performance comparable to expensive spherical fillers at lower cost.
3Reliability
If high filling amount of inorganic filler is used to achieve high thermal conductivity, then thermal dissipation improves, but the resin composition may become difficult to process and exhibit poor adhesion
Solution Approach 1:
The patent applies local quality by assigning different functions to different particle sizes within the filler system. Coarse particles (5-20 μm) are distributed to create thermal conduction pathways, while fine particles (0.2-1.5 μm) are concentrated at the resin-filler interface and metal plate contact areas to enhance adhesion and fill voids, enabling high filling amounts without compromising processability.
Solution Approach 2:
The patent transitions from considering only the total filling amount to considering the three-dimensional particle size distribution. By introducing a bimodal size distribution with coarse and fine particles, the patent optimizes the spatial arrangement of filler particles, allowing high overall filling content while maintaining resin flowability and adhesion through proper particle packing.
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 resin composition achieves excellent adhesion to metal, high thermal conductivity, and electrical insulation, making it suitable for heat-dissipating materials in electronic components, while preventing bubble formation during production and ensuring reliable hybrid integrated circuits with improved heat resistance and moisture resistance.
Implementation Method 1
a curable resin comprising an epoxy resin and a curing agent for the epoxy resin; wherein the curing agent comprises a phenol novolak resin
Implementation Method 2
the inorganic filler comprises a coarse powder containing particles having an average particle size of 5 to 20 μm... and a fine powder containing particles having an average particle size of 0.2 to 1.5 μm... the resin-cured product... having a thermal conductivity of 1.5 to 5.0 W/mK
Data Source
AI summary
A substrate, a circuit board and a multilayer circuit board are provided which, although being made of an inorganic filler as a crushed product, are capable of providing a highly reliable hybrid integrated circuit because of having excellent adhesion to a metal plate or metal foil and exhibiting a high thermal conductivity. A resin composition comprising a curable resin comprising an epoxy resin and a curing agent for the epoxy resin; and an inorganic filler filled in the curable agent; wherein the curing agent comprises a phenol novolak resin, and wherein the inorganic filler comprises a coarse powder containing particles having an average particle size of 5 to 20 µm, preferably particles having a maximum particle size of 100 µm or below and a particle size of 5 to 50 µm in an amount of 50 vol% or above; and a fine powder containing particles having an average particle size of 0.2 to 1.5 µm, preferably particles having a particle size of 2.0 µm or below in an amount of 70 vol% or above. A substrate for a hybrid integrated circuit, a circuit board and a multilayer circuit board, which use the resin composition.