Solid sheet material especially useful for circuit boards

Abstract

A solid sheet which contains an nonwoven fabric made from short high tensile modulus fibers and a thermoplastic polymer having a low moisture absorption matrix resin that is useful as a substrate for circuit boards.

Description

[0001] This application claims the benefit of U.S. Provisional Application No. 60 / 315,890, filed Aug. 30, 2001.[0002] The field of invention relates to solid sheets comprising thermoplastic polymer having low moisture absorption and high tensile modulus fibers, in which the thermoplastic polymer is the matrix polymer, substrates for circuit boards made therefrom, and methods of making the foregoing.[0003] Circuit boards are important items of commerce, being used in virtually every electronic device. The "board" or supporting member of a circuit board or other electronic devices (such as the interposer in a flip-chip package) is an important component of such devices, and properties of the materials used to make such boards are important to the functioning of the electronic or electrical circuit.[0004] As electronic components have become more sophisticated, the demands placed upon the materials used for boards have increased. For example, for many applications it is preferred that ...

AI Technical Summary

Benefits of technology

[0046] While applying heat and pressure to form the first solid sheet, full or partial vacuum may also be applied to the single or multilayer structure to remove air or other gases dissolved in the materials of the single or multilayer structure or physically present in the structure, as between the HTMF and TP particulates. For example the single or multilayer structure may be placed in a vacuum bag or vacuum chamber and then heat and pressure applied. Using vacuum helps remove gases from the structure and avoid trapping gas bubbles (voids) in the first solid sheet. With any of the process variations described herein to consolidate the single or multilayer structure, use of vacuum is a preferred option.

[0051] Any TP which has a low moisture absorption, such as perfluorothermoplastics [for example, polytetrafluoroethylene; copolymers of tetrafluoroethylene with hexafluoropropylene, perfluoro(vinyl ethers) such as perfluoro(methyl vinyl ether)], or ethylene; poly(ether-ether-ketones); poly(ether-ketone-ketones); and poly(ether-ketones); polyesters such as poly(ethylene terephthalate, poly(ethylene 2,6-napthalate, and polyesters from bisphenol A and isophthalic / terephthalic acids; polycarbonates especially those having higher temperature glass transition temperatures; poly 4-methylpentene; poly(aryl sulfides); poly(ether-imides); poly(aryl ethers); and LCPs are useful. Preferred TPs are perfluoropolymers, particularly those mentioned above, and LCPs are especially preferred. Among the preferred properties for the TPs are very low moisture absorption, high melting point, low dielectric constant and low dielectric loss coefficient. LCPs have an excellent combination of such properties.

[0057] LCPs, and polyimide. When calculating the concentration of such fibers, the total of these types of fibers present will be used, for example the total of aramid and poly(phenylenebenzobisoxazole) fiber present. Among the preferred properties are high modulus, high melting point and / or glass transition temperature and low moisture absorption.

Problems solved by technology

These three factors are often adversely affected by the absorption of moisture by the board materials, which changes the dimensions of the board and / or changes the dielectric constant and / or dissipation factor of the board itself, and / or causes warpage.

However, fibers such as aramid fibers, and epoxy resins, absorb significant amounts of moisture, and so are sometimes unsuitable for use together in highly demanding circuit board uses.