Fluoropolymer-glass fabric for circuit substrates
View Patent ↗An improved circuit substrate is provided wherein glass cloth is completely embedded within fluoropolymer by thermocompression to form a composite structure, which when containing an adhesive agent such as the combination of functional groups and liquid crystal polymer is self-adhering to a metal layer such as of copper.
1. A composite structure comprising dimensionally stable glass cloth and melt-processible fluoropolymer, the entire thickness of said glass cloth being embedded in said fluoropolymer, and a cooper layer adhered to at least one surface of said glass cloth embedded in said fluoropolymer, said fluoropolymer containing an effective amount of adhesive agent to improve the adhesion of said glass cloth embedded in said fluoropolymer to said copper layer by at least 60% as compared to said glass cloth embedded in said fluoropolymer wherein said fluoropolymer contains no adhesive agent.
2. The composite structure of claim 1 wherein said glass cloth is embedded into said fluoropolymer by contacting at least one surface of said glass cloth with a sheet of said fluoropolymer and melting said sheet while compressing said glass cloth against said fluoropolymer sheet, thereby forcing said the entire thickness of said glass cloth into said fluoropolymer sheet.
3. The composite structure of claim 2 wherein both surfaces of said glass cloth are contacted by a sheet of said fluoropolymer and said melting and compressing forcing said glass cloth and each said fluoropolymer sheet together to embed the entire thickness of said glass cloth with fluoropolymer from said sheets thereof.
4. The composite structure of claim 1 containing two said glass cloths superimposed adjacent to one another, the entire thickness of both said glass cloths being embedded in said fluoropolymer.
5. The composite structure of claim 4 wherein said fluoropolymer is embedded into both said glass cloths by interposing a sheet of said fluoropolymer between said glass cloths and melting said sheet while compressing said glass clothe against said sheet, thereby forcing the entire thickness of each said glass cloth into said fluoropolymer sheet.
6. The composite structure of claim 1 wherein the peel strength between said copper layer and said glass cloth embedded in said fluoropolymer is at least 0.8 kg/cm.
7. The composite structure of claim 1 having a layer of copper adhered to both surfaces of said glass cloth embedded in said fluoropolymer.
8. The composite structure of claim 1 having a dielectric constant at a frequency of 10 GHz of no greater than 3.0 and a coefficient of linear expansion of no greater than 2.5×10 −5 /° C.
9. The composite structure of claim 1 wherein said adhesive agent comprises functional groups contained by said fluoropolymer and LCP contained within said fluoropolymer.
10. The composite structure of claim 9 wherein said LCP has orientation in the fibrous state within said fluoropolymer.
11. The composite structure of claim 9 wherein said LCP is contained within said fluoropolymer as particles.