Composite Film for High Frequency PCBs with Low Thermal Expansion
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Solution Overview
Problem
Current composite films for electronic devices using high-frequency band signals face challenges in achieving low dielectric tangent, excellent embedding properties, surface smoothness, and high adhesion to plated copper, while also requiring compatibility with low thermal expansion and minimal melt viscosity.
Innovation Solution
A composite film with specific layer configurations, including a layer A with a minimum melt viscosity of 100 to 4,000 Pa·s at 80 to 150°C and a layer B with a minimum melt viscosity of 50,000 Pa·s or more at the same temperature, containing polyimide compounds, inorganic fillers, and a conjugated diene-based elastomer, is used to address these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an inorganic filler is highly filled in the build-up layer to reduce thermal expansion, then thermal expansion is reduced, but surface flatness and adhesion to plated copper deteriorate
Solution Approach 1:
The patent uses a composite resin composition combining polyimide resin with specific inorganic fillers (silica, alumina, or barium sulfate) to achieve both low thermal expansion and good surface flatness. The composite structure allows the material to maintain dimensional stability while providing a smooth surface that embeds circuit patterns effectively.
Solution Approach 2:
The patent specifies precise parameter ranges for the resin composition: inorganic filler content of 30-70 parts by mass per 100 parts of polyimide resin, and minimum melt viscosity of 100-4000 Pa·s at 80-150°C. These controlled parameter changes enable the material to achieve both low thermal expansion and excellent embedding properties simultaneously.
2Stability of the object's composition
If an inorganic filler is highly filled in the build-up layer to reduce thermal expansion, then thermal expansion is reduced, but adhesion to plated copper deteriorates
Solution Approach 1:
The patent employs a composite system where polyimide resin serves as the base material providing adhesion, while inorganic fillers (silica, alumina, or barium sulfate) are added in controlled amounts (30-70 parts by mass per 100 parts of resin) to reduce thermal expansion. This composite approach maintains both adhesion and dimensional stability.
Solution Approach 2:
The patent controls the filler content parameter within 30-70 parts by mass per 100 parts of polyimide resin and maintains minimum melt viscosity between 100-4000 Pa·s at 80-150°C. These parameter optimizations ensure sufficient adhesion to plated copper while achieving low thermal expansion properties.
3Loss of energy
If materials with low dielectric constant and dielectric tangent are used for high-frequency signals, then transmission loss is suppressed, but embedding properties and surface smoothness deteriorate
Solution Approach 1:
The patent optimizes the resin composition parameters: polyimide resin with minimum melt viscosity of 100-4000 Pa·s at 80-150°C, and inorganic filler content of 30-70 parts by mass per 100 parts of resin. These parameter changes enable the material to achieve low dielectric tangent (≤0.005 at 5 GHz) while maintaining excellent embedding properties and surface smoothness.
Data Source
AI summary
A composite film for electronic device using high frequency band signals, which is low in dielectric tangent, excellent in embedding properties relative to unevenness of a circuit, etc., and excellent in surface smoothness, and has high adhesion to plated copper is provided; and a printed wiring board containing a cured material of the composite film for electronic device and a method of producing the printed wiring board are also provided. Specifically, the composite film for electronic device is a composite film for electronic device using high frequency band signals, including a layer A having a minimum melt viscosity at 80 to 150° C. of 100 to 4,000 Pa·s; and a layer B having a minimum melt viscosity at 80 to 150° C. of 50,000 Pa·s or more. The composite film for electronic device is low in thermal expansion properties and excellent in handling properties of film.