Glass fabric produced with zero-twist yarn

Details Glass fabric produced with zero-twist yarn Glass fabric produced with zero-twist yarn

1996-03-18

1997-09-02

Bell, James J.

Fabric (woven, knitted, or nonwoven textile or cloth, etc.)

Woven fabric

Including strand which is of specific structural definition

139 11, 139420C, 139426TW, 428902, 428219, 428220, 442203, 442208, D03D 300

Patent

active

056629907

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a glass fabric produced with zero-twist yarn, its use in the manufacture of printed circuits and in numerous other industrial applications, as well as to a process for the manufacture hereof.


BACKGROUND OF THE INVENTION

Glass fabric is used today with success in the most varied applications. The most important include those relating to advanced structural composites for the aeronautical and ship-building industries and dielectric composites for the electrical and electronics industry.
In particular, the Applicant is interested in the manufacture of glass fabrics for use in the electrical and electronics industry, preferably the construction of laminates for printed circuits and the manufacture of fabrics and gauzes used as a reinforcement in numerous industrial applications.
Printed circuits nowadays represent the most widespread and effective support medium for electronic equipment, ensuring both the mechanical anchoring and electrical connection of the associated components, and it is not possible to foresee any other connecting systems capable of replacing them in the medium or short term.
Consequently the laminates required for their construction have an important role and it is expected that their production volume will steadily increase for many years to come.
The printed circuits and the laminates used for their construction are required to have increasingly superior characteristics as a result of the evolution of microelectronics technology which enables an increasingly large number of logic circuits to be concentrated on the chips or on the physical support components.
The miniaturization of electronics devices has given rise to various assembly problems including the increased concentration of tracks on the printed circuits and hence the need to make them thinner.
As a result the amount of copper adhering to the laminate must be reduced. Under the impetus of this requirement, the thickness of the copper lamina of the printed circuits has been reduced, in a few years, from 70 microns to 35 and 18 microns, and the tendency is to reduce it still further to 12, or even 9 microns.
This innovative process has not radically affected the production criteria for laminates, but has made it necessary to use glass fabrics which are much more refined than those currently used.
In particular, textile manufacturers are being required to find, with increasing urgency, solutions to the problems associated with the surface of the fabrics which must always be flat and smooth and as far as possible free from loose strands and textile defects in general. In fact any filaments of the glass yarn present on the surface of the laminate penetrate into the copper during the pressing process, while rougher surfaces diminish the adhesion of the copper lamina to the support base of the epoxy-glass laminate.


State of the Art

The requisites for the supporting glass fabrics in laminates for printed circuits are closely linked to the performance required of the latter.
The laminate which is currently most widespread--called FR--4--has the characteristics shown in the table below:


TABLE ______________________________________ Technical characteristics of the laminate FR-4 ______________________________________ .epsilon. 4 Tg (.degree.C.) 140 HPCT (hours) 2 VO (pass/fail) Pass C.sub.u (N/mm) 2 .alpha..sub.z (ppm/.degree.K.) 200 P(t) (.mu.m) 5 D stab (ppm) 400 ______________________________________ .epsilon. = Dielectric constant Tg = Glass transition temperature HPCT = High Pressure Cooker Test VO = Selfextinguishing characteristics (in accordance with UL 94) C.sub.u = Bonding strength (copper to epoxyglass laminate) .alpha..sub.z = Heat expansion coefficient on Z axis P(t) = Surface profile D stab = Dimensional stability
The parameters Tg, VO, C.sub.u are influenced mainly by the characteristics of the resin used in the laminates, while the parameters .epsilon., .alpha..sub.z, P(t) and D stab are directly influenced by the characteristi

REFERENCES:
patent: 4543113 (1985-09-01), Forester et al.

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