SU959644A3 - Support for printed circuit boards - Google Patents

Abstract

1486372 Metal-clad fibrous webs MINNESOTA MINING & MFG CO 6 Jan 1975 [7 Jan 1974] 455/75 Heading B5N [Also in Divisions D1 and H1] Metal-clad dielectric sheeting for printed circuitry comprises an electrically-conductive metallic layer adhered to a non-woven web of a blend of different staple fibres substantially all of softening point above 230‹ C. which are compacted and bonded by a film-forming polymeric material, preferably present in amount 15-75 wt. per cent of the web; of the fibres (i) at least 5 wt. per cent resist distortion after 10 seconds' exposure to a 260‹ C. solder bath, (ii) at least 30 wt. per cent have a tenacity of at least 3À5 gm./denier and preferably a tensile elongation to break of at least 50% and (iii) at least 40 wt. per cent absorb less than 3% moisture at 65% RH and 21‹ C. for 1 day. Preferably the fibres are present in amount at least 10 kg./ream and the binder resists distortion after 10 seconds' exposure to a 260‹ C. solder bath. The fibres (i) may be of aromatic polyamides, e.g. phenylene phthalamides, acrylonitrile polymers, or glass. The fibres (ii) may be of drawn polyester or of aromatic polyamides as above. Suitable blends comprise 30-95 wt. per cent polyester, 5-60 wt. per cent polyamide and 0-70 wt. per cent acrylics. The web may be formed by air-laying the blend, impregnating with the binder by roller and drying and compacting. The binder may be a crosslinkable emulsion of (meth)acrylic ester-(meth)- acrylic acid coploymer or a vinyl chloride polymer. The cladding may be a Cu, Al, Ni, Ag or Au foil which is bonded by adhesive to the web, a suitable epoxy resin adhesive is described which is applied by dip-coating and B-staged, the foil then being applied with heat and pressure.

Description

(5) Substrate for PCB

The invention relates to metallized non-woven fiber substrate for printed circuit boards and can be used in electronic equipment.

A known substrate for printed circuit boards containing an electrically conductive layer and a dielectric layer comprising polyethylene terephthalate fibers bonded with a film-forming polymer binder Cl.

The nonwoven fibrous web in this metallized plate is composed of fibers that soften when heated during the manufacture of the web.

However, this substrate shrinks during etching.

The purpose of the invention is to increase the dimensional stability.

Claims (1)

This goal is achieved in that in a substrate for printed circuit boards containing an electrically conductive layer and a dielectric layer comprising polyethylene terephthalate fibers bonded with a film-forming polymer binder, as a film-forming polymer binder, a substance is taken, the fiber softening point is above 230 ° C fibers of aromatic polyamide are additionally introduced into the dielectric layer with the following content of components, weight: Polyethylene fibers 10, lenterephthalate 30-95 Fibers of aromatic polyamide 5-60 Pl nkoobrazuyuschee zuyu15 polymeric binding agent present, the softening point of the fibers which rest as film-forming polymeric binder ispol20 zuyuts resistant high temperature materials which react, providing a condition of mutual bonding or thermal stability. Such substances are reactive resins based on acrylic derivatives, mainly resins containing copolymers having most of the lower acrylics (usually 1 to 8 carbon atoms), acrylic or methacrylic acid, such as ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, and a smaller part of acrylic or methacrylic acid. Other suitable binders are thermoplastic polymers, such as vinyl chloride-based polymers (e.g., Vinyon resin, manufactured by Union Carbide). Binders should not absorb moisture, i.e. films from them should not absorb more than 3 moisture when exposed to an environment with a relative humidity at 21 ° C for one day (after bonding with the fibers, if the binder material is reactive). In addition, when heated to 230, the binder must resist the rapid degradation of its polymer structure. The binder is usually contained in an amount of 15-75 wt., Preferably less than 35 wt. .. The substrate for printed circuit boards is usually 0.5 mm thick. It is covered with a continuous electrically conductive metal layer, on one or two sides, preferably by gluing a previously prepared metal plate or foil with the aid of a binding substance, 50-250 microns thick. For bonding, the foil substrate is passed through press rolls and a furnace. Copper, aluminum, nickel, silver, and gold are used as the metal plate or foil. Example. Polyethylene terephthalate fibers (6 denierXl, 5 in. (3.8 cm), fibers of the type Celanese 9 Round too) tO wt.% ,. Dromatic polyamide fibers (poly / t-vysophthalamide) SS, 5 in. (3.8 cm) Nomex, du Pant;) 20 wt.%, polymeric binder (3 denier x 1-; 1/2 inch (3.8 cm) pow-Badesche Type 500) kQ wt.%. The prepared substrate was subjected to tests that showed the following changes in geometric dimensions,%: after etching 0.1; after 30 min of heating at 121 ° C 0.2; after 10 sec of heating at 2 ° C; 0.3; no swelling. Formula of the Invention A substrate for printed circuit boards containing an electrically conductive layer and a dielectric layer, including polyethylene terephthalic fibers bonded with film-forming polymer binder, which THAT, in order to increase dimensional stability, aromatic fibers are additionally introduced as a film-forming polymer binder, softening point, fibers above 230 ° C, as film-forming polymer binder polyamide in the following ratio of components, weight: Polyethylene terephthalate fiber 30-95 Aromatic polyamide fiber Film-forming polymeric binder, softening point of fibers which is higher than the standard. Sources of information taken into account during the examination 1. US Patent No. 3 bZb9V, Cl, 161-186, 1969 (prototype).